_ L 1 B R A R Y. 7L KING'S College LONDON 0[Affd QLr Top Library /fa & To MY ftiYfe 9 1 201001021 6 KInPsCOLLEGE LONDON LONDON : MARCHANT, rRINTER, ING RAM-COURT* ft . THE " CYCLOPAEDIA OF ANATOMY and PHYSIOLOGY. EDITED BY ROBERT B. TODD, M.D. PROFESSOR OF PHYSIOLOGY AND OF GENERAL AND MORBID ANATOMY IN KING'S COLLEGE, LONDON J PHYSICIAN TO THE WESTERN DISPENSARY', AND TO THE ROYAL INFIRMARY FOR CHILDREN, ETC. ETC. VOL. L A D E A. LONDON : SHERWOOD, GILBERT, AND PIPER, PATERNOSTER- ROW. 1836. CONTRIBUTORS. ROBERT ADAMS, Esq. Surgeon to the Richmond Hospital, and Lecturer on Anatomy and Surgery, Dublin. B. ALCOCK, M.B. Dublin. W. P. ALISON, M.D. F.R.S.E. Professor of the Institutes of Medicine in the Univer- sity of Edinburgh, &c. J. APJOHN, M.D. M.R.I.A. Professor of Chemistry to the Royal College of Sur- geons in Ireland. VICTOR AUDOUIN, M.D. Paris. Professeur-Administrateur au Musee d'Histoire Na- turelle. B. G. BABINGTON, M.D. F.R.S. THOMAS BELL, Esq. F.R.S. Lecturer on Comparative Anatomy, Guy's Hospital. CHARLES BENSON, M.D. M.R.I.A. Professor of Medicine to the Royal College of Sur- geons, Ireland, &c. JOHN BOSTOCK, M.D. V.P.R.S. London. W. T. BRANDE, F.R.S. Professor of Chemistry to the Royal Institution, &c. J. E. BRENAN, M.D. Lecturer on Anatomy and Physiology, Dublin. G. BRESCHET, M.D. Surgeon to the Hotel-Dieu, Paris. JOHN COLDSTREAM, M.D. Leith. Member of the Wernerian Natural History Society of Edinburgh, &c. &c. DAVID CRAIGIE, M.D. F.R.S.E. Fellow of the RoyalCollege of'Physicians.Edinburgh.&c. J. BLIZARD CURLING, Esq. Assistant Surgeon to the London Hospital, and Lec- turer on Morbid Anatomy. G. P. DESHAYES, M.D. Paris. A. T. S. DODD, Esq. Surgeon to the Infirmary, Chichester, and late Demon- strator of Anatomy at (Juy's Hospital. II. DUTROCHET, M.D. Member of the Institute ol France, I'aiis. W.F.EDWARDS, M.D. F.R.S. Member of the Institute of France, Paris. H. MILNE EDWARDS, M.D. Professor of Natural History to the College of Henry IV., and to the Central School of Arts and Manu- factures, Paris. R. D. GRAINGER, Esq. Lecturer on Anatomy and Physiology at the Webb- Street School of Anatomy. R. E. GRANT, M.D. F.R.S.E. Fellow of the Royal College of Physicians, Edinburgh, and Professor of Comparative Anatomy and Zoology in the London University, &c. &c. JOHN HART, M.D. M.R.I.A. Lecturer on Anatomy and Physiology, Dublin. MARSHALL HALL, M.D. F.R.S. L. & E. London. ROBERT HARRISON, M.D. Professor of Anatomy and Physiology to the Royal College of Surgeons in Ireland. ISID. GEOFFROY ST. H1LAIRE, M.D. Member of the Institute of France, Paris. ARTHUR JACOB, M.D. M.R.I.A. Professor of Anatomy and Physiology to the Royal College ol Surgeons in Ireland. T. RYMER JONES, Esq. Professor of Comparative Anatomy, in King's College, London. F. KIERNAN, F.R.S. London. R. KNOX, M.D. F.R.S.E. Edinburgh. SAMUEL LANE, Esq. Lecturer on Anatomy, St. George's Hospilal, London , JOHN MALYN, Esq. Surgeon to the Western Dispensary, and Lecturer on Anatomy at the Westminster School ol Medicine. W. F. MONTGOMERY, M.D. M.R.I.A. Fellow and Professor of Midwifery to the King and Queen's College of Physicians in Ireland. R. OWEN, F.R.S. London. Professor of Comparative Anatomy and Physiology to the Royal College of Surgeons in London. RICHARD PARTRIDGE, Esq. Professor of Descriptive and Surgical Anatomy inKing's College, London. BENJAMIN PHILLIPS, F.R.S. London. J. C. PRICHARD, M.D. F.R.S. Corresponding Member of the Institute of France, Member of the Royal Academy of Medicine of Paris, and Senior Physician to the Bristol Infirmary. W. II. PORTER, Esq. Lecturer on Anatomy and Surgery, and Surgeon to the Meath Hospital, Dublin. RICHARD QUA1N, Esq. Surgeon to the North London Hospital, and Pro- fessor of Descriptive Anatomy in the London University. J. REID, M.D. Edinburgh. HENRY SEARLE, Esq. London. E. R. A. SERRES, M.D. Physician to the Hospital of La Pitie, &c. &.C. Paris. W. SHARPEY, M.D. F.R.S.E. Professor of Anatomy and Physiology in the London University. J. Y. SIMPSON, M.D. Edinburgh. J. A. SYMONDS, M.D. Physician to the Bristol General Hospital and Dispen- sary, and Lecturer on Forensic Medicine at the Bristol Medical School. ALLEN THOMPSON, M.D. Fellow of the Royal College of Surgeons, and Lecturer on the Institutions of Medicine, Edinburgh. C. WHEATSTONE, Esq. Professor of Natural Philosophy in King's College, London. REV. G.WILLIS, F.R.S. F.G.S. Cambridge. R. WILLIS, M.D. London. W. YARRELL, F.L.S. F.Z.S. Digitized by the Internet Archive in 2015 https://archive.org/details/b2130046x_0001 CONTENTS OF THE FIRST VOLUME. Page Abdomen Dr. Todd 1 Absorption Dr. Bostock .... 20 Acalculias Dr. Coldstream . . 35 Acids, Animal W. T.Br and e, Esq. 47 Acrita R. Owen, Esq. . . 47 Adhesion B. Phillips, Esq. . 49 Adipocere W.T. Brande, Esq. 55 Adipose Tissue Dr. Craigie 50 Age Dr. Symonds .... 64 Albino Dr.Bostock 83 Albumen W.T. Brande, Esq. 88 Amphibia T. Bell, Esq 90 Animal Kingdom .... Dr. Grant 107 Animal Dr. Willis 118 Ankle, Region of the. . Dr. Brenan 147 Ankle, Joint of the . . Dr. Brenan 151 Ankle-joint Abnormal ) fi> MamS} Egq_ _# ]54 Condition of the . . ' Annelida Dr. Milne Edioards 164 Anus R. Harrison, Esq. 178 Aorta Dr. Hart 187 Arachnida Dr. Andouin .... 198 Arm Dr. Hart 216 Arm, Muscles of the. . Dr. Hart 219 Artery Dr. Hart 220 Artery, Pathological l WJL Porter> Esq. 226 Conditions of . . . . ' Articulata R. Owen, Esq. . . 244 Articulation Dr. Todd 246 Asphyxia..... Dr. Alison 257 Aves R. Owen, Esq. .. 265 Axilla Dr. Benson 358 Axillary Artery Dr. Hart 363 Azygos Dr. Harrison .... 364 Back Dr. Benson 367 Bile W.T. Brande, Esq. 374 Bladder, Normal Ana- ) jyr jjarri tomy Bladder, Abnormal } B pMlUVs, Esq. . Anatomy ' Blood Dr. Milne Edivards Blood, Morbid Condi- )n D ,. . ' \ Dr. Babington . . tions of the ' Bone, Normal Anatomy Dr. Benson Bone, Pathological j W R Egq Conditions of » Brachial Artery .... Dr. Hart Bursae Mucosa; Dr. Brenan Carnivora T. Bell, Esq Carotid Artery Dr. Hart Cartilage Dr. Benson Cavity Dr. Todd Cellular Tissue R.D.Grainger,Esq. Cephalopoda R. Owen, Esq. .. Cerumen W.T. Brande, Esq. Cetacea Mons. F. Cuvier . . Cheiroptera T. Bell, Esq Chyliferous System .. Dr. Grant Cicatrix A. T. S. Dodd, Esq. Cilia Dr. Sharpey .... Circulation Dr. Allen Thomson Cirrhopoda Dr. Coldstream . . Cirronosis Dr. Todd Conchifera M. Deshayes .... Contractility Dr. Aliso7i Cranium J. Malyn, Esq. . . Cranium, Regions and } pr Muscles of the. . . . ' Crustacea Dr. Milne EJivards Cyst B. Phillips, Esq. . Death Dr. Symonds .... Analytical Index Page 376 389 404 415 4X0 438 465 467 470 482 495 500 509 517 562 562 594 600 602 606 638 683 694 694 716 724 746 750 787 791 809 THE EDITOR takes advantage of the opportunity afforded by the publication of the first Part of THE CYCLOPEDIA OF ANATOMY AND PHYSIOLOGY, to state more fully than can be done in a title-page the precise object and extent of the work. It is intended to embrace the whole of the sciences of Anatomy and Physiology, those terms being used in their largest sense as far as regards the Animal Kingdom. The anatomy of Man will form a considerable portion of the Work ; and this will com- prise not only the healthy or normal condition of his oeconomy, but likewise the abnor- mal states of the several organs and tissues, involving congenital aberrations from the natural formation as well as those changes which are the result and evidence of Disease ; thus affording a complete system of Human Anatomy, — general, descriptive, surgical and morbid. But the anatomical portion of the Work will further comprehend the anatomy of the inferior animals, contained in a series of articles to which the names of the several subregna and classes of the Animal Kingdom are prefixed ; and when to these are added dissertations on certain particular organs, or on the modi- fications which the systems of organs experience in the different gradations of the Animal series, a system of Comparative Anatomy will be formed, novel in its plan, and which it is presumed will prove of much greater utility to the Naturalist than if it were limited to the arrangement hitherto generally adopted. In the composition of the Zootomical articles, it was found advisable to introduce much that relates to the arrange- ment and subdivision of the several classes, and much likewise respecting the habits and peculiarities of the animals composing them, and thus a general outline of Zoology will be found included in those articles. But, as the Anatomist is not contented merely with what the scalpel presents to him, but has recourse to chemical analysis to obtain still further insight into the nature of animal substances, it would be a serious omission did not Animal Chemistry likewise obtain its due share of attention. In Physiology, which has been of late so much elucidated and advanced by the extended researches of the Comparative Anatomist, it is intended that this Work shall afford full information as to the state of science up to the present day, the articles in this Department being placed under the heads of the principal functions which are found throughout the whole or nearly the whole Animal Kingdom, as well as under those of some functions peculiar to certain classes. In conclusion, in referring to the list of eminent scientific men who have kindly engaged to contribute to this Work, the Editor trusts that it is not too much to say that there will be found in that list no inconsiderable security for the manner in which the great object of the Work will be accomplished. The Editor has to acknowledge himself much indebted, in the department of Comparative Anatomy and Zoology, to Professor Grant, whose numerous engagements have prevented his more intimate association in the Work as co-Editor, according to the original intention. To his talented and able friend Mr. Owen he is likewise under especial obligations for many valuable suggestions in the same Department, and he looks forward with pleasure to a continuance of the same valuable assistance in the progress of the Work. 26, Parliament- Street, May, 1835. OF ANATOMY AND PHYSIOLOGY. ABDOMEN, (in anatomy,) with which the terms venter and alvus are sometimes used synonymously. Gr. yao-Tyg- Germ, bauch, un- terleib, hinterleib. Ital. ventre", pancia, 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 ubdi et tegi soleat, aut quod alimenta in eo abdantur, aut intestina ibi sint abdita."* 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 liridgewatei' 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. B 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 interiorly 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 state 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, lience, 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 xualls 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 maybe 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 ala? 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 lamellre and tendinous ap- oneuroses, the cingulum abdominis musculoso- 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 fit 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 sci'obiculus cordis, (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 mom 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 depressions into smaller 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 lumbarspinous 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 conlrac- * Gcrtly, Anatomic dcs Formes Extericures, p. 189. The aliove engraving is reduced from the folio plates 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 reciprocally, 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 a line 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 CYCLOPEDIA 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 : (£7ri,upon, over ; yucrrrig, 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, p/ov^o;, 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 hi/pogastrium, (viro, beneath, yxarvj^, the stomach). This region is li- mited below in the centre by the pubis, and on each side it communicates with the upper part of the thigh. It is subdivided into the iliac regions on each side, and the proper hypo- gastric or pubic region in the centre. The two former constitute the upper or abdominal portion of the great region of the groin, which is completed inferiorly by the upper part of the anterior surface of the thigh. These regions afford peculiar interest to the surgical ana- tomist, in consequence of the occurrence in them of (the most common forms of hernia.*' (See Groin, Region of the.) The structures which enter into the com- position of the abdominal parietes, or their elements, (as the term has been lately applied,) are — 1. the skin : 2. the subcutaneous tissue or superficial fascia : 3. muscles and their aponeurotic expansions : 4. a particular fibrous expansion, or fascia : 5. a thin and 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 xone to the primary regions included between the horizontal lines. — Anat. Chirurg. t. ii. ABDOMEN. *3 In and between these several structures ramify the various arteries, veins, lymphatics, and nerves, which constitute the vascular and ner- vous supply to the abdominal parietes. 1. The skin on the anterior^hd. lateral parts of the abdomen is thin and ^HjAqth, 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 daring 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 fatus and placenta. In very fat persons, the depth of the depression is often very much increased by reason of the great thickness of the abdomi- nal parietes, and in some instances its form assumes that of a slit, and sometimes, instead of a depression, there is a greater or Jess pro- minence of the integument. In the lumbar region the skin is thicker and firmer than in the others; and we generally find it in a state of congestion after death, in consequence of the position of the body. 2. The subcutaneous cellular tissue on the anterior surface of the abdomen has obtained especial attention from anatomists, particularly that portion of it which is found in the hypo- gastric regions. It is denominated the superficial fascia,\ and is merely an expanse of cellular tissue possessing the same general characters * Winslow's Anatomy, by Douglas, v. ii. p. 160. t The application of the term fascia to the sub- cutaneous cellular investment in various parts of the body has occasioned no small degree of confusion among anatomists. A singular degree of confusion exists in Velpeau's description of this fascia : he observes in one place that the deep layers of the subcutaneous cellular tissue constitute the super- ficial fascia, and in the next page states that " the superficial fascia is nothing else than the cellular tissue condensed, whose laminas 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 suhcutaneous 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 Beclardf that it presents almost all the characters of an aponeurosis, inasmuch as it differs from an aponeurosis in wanting the shining and regular surface, and in possessing a degree of elasticity which never belongs to aponeurotic expansions. The elasticity of the superficial fascia is remarkable, and is by some compared to the elastic expansion over the abdomen of the larger quadrupeds ;J the comparison, however, is inaccurate, inasmuch as they are two distinct tissues, the former being cellular, and the latter the aponeurosis of the oblique muscles, which in some degree 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 (balluns 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. X Vid. Blandin, Anat. Topog. B 2 4* ABDOMEN. below and carrying it upwards; the expansion will then appear to arise from Poupa'rt's liga- ment, and spread over the subjacent aponeuro- sis. In some subjects it is so thin as to appear to be little more than the proper cellular cover- ing of the muscle and its aponeurosis, but in others it assumes a considerable degree of density. It may be called the deep layer of the superficial fascia ; it deserves attention from the fact that the femoral hernia, in its ascent on the abdomen, lies between it and the super- ficial layer. It is to this fascia that Scarpa must allude under the name of " aponeurotic web" of the muscle of the fascia lata," and hence some have called it Scarpa's fascia.* The whole of the superficial fascia has been called Camper's "fascia, because it was first fully described by that writer.f On the posterior wall of the abdomen, in the lumbar regions, the cellular tissue is more abundant and more lax; here we frequently find it infiltrated with serous fluid, in conse- quence of the usual supine posture of the body after death. It is continuous above with the subcutaneous tissue in the dorsal region, and below with that in the gluteal regions. It, too, is firmly adherent along the middle line to the lumbar spine anteriorly, and to the skin posteriorly. 3. Muscles and aponeuroses. — The abdo- minal parietes owe their thickness chiefly to the muscular lamellae and the aponeurotic ex- pansions, which enter into their composition. In the anterior and lateral walls we find on each side five pairs of muscles, of which four are constantly present. These are, 1, M. obli- quus externus ; 2, obliquus interims ; 3, trans- versalis; 4, rectus abdominis ; 5, pyramidalis, which last is frequently absent. 1. Obliquus externus. (Obliquus descen- dens ; costo-abdominal ; ilio-pubi-costo-abdo- minid.) 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 dovsi from the tenth to the twelfth. From these points of attachment, described by most English anatomists as the origin of the muscle, the fibres pass obliquely downwards and forwards, with different degrees of ob- liquity, the middle fibres being the most ob- * Vid. Scarpa on Hernia, by Wishart, p. 22 ; aho Todd on Hernia, Dub. Hosp. Reports, vol. i. p. 246 ; and Flood's plates of Inguinal and Femoral Hernia. \ Camper, Icones Hcrniarum, 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 Gimbernat'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 interculumnul bunds. 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 Fallopivs, are also used synonymously with Poupart's liga- ment. Velpcau calls it bandelctte 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 hernias they are particularly strong. I cannot, confirm this remark from my own observation, as in my dissections of old hernia?, I have not found them particularly developed; nor is itcon- sistent with the general result of pressure from within on tendinous fibres to believe that such pressure would produce an increase of deve- lopment in them. The size of the external abdominal ring is greatest in the male subject, but here it varies considerably, sometimes closely embracing the cord as it passes through it, and at others appearing much too large foV 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 sperntatica. This fascia consequently forms a covering of any hernia that may be protruded through the external ring; and, accordingly, in old hernia: 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: inferiprly the fascia lata of the thigh is related to the margin of the external oblique muscle, both as it covers the gluta;i,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." — 3/cr'nrl. 6 ABDOMEN. ternal oblique is removed from its osseous at- tachments, and raised inwards, it is found to cover the internal oblique, with part of the ten- don of which it is ultimately united as the two tendons approach the linea alba. 2. Obliquus internus (obliquus ascendens, ilio-abdominal, ilio-lumbo-costi-ubdominal) 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 ihi, between the external oblique and the transver- salis as far forwards as the anterior superior spine : 3. to the groove in the upper or abdo- minal surface of Poupart's ligament for about its external third. The superior fibres pass upwards and inwards, and are inserted by fleshy slips into the cartilages of the twelfth, ele- venth, and tenth ribs, in the intervals between which they are either separated from the inter- costal muscles by a fibrous intersection, or con- founded with them, and by a tendinous aponeu- rosis into the cartilages of the ninth, eighth, and seventh ribs as well as into the xiphoid cartilage. Lower down, the fibres which arise from the crista ilii, as well as those from Poupart's liga- ment, pass inwards, the superior obliquely upwards and inwards, the inferior more hori- zontally, and the lowest fibres inclining a little downwards, and are all inserted, like those of the vbliquus 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 lamina, 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 lamina? going to be inserted into the ensiform cartilage and linea alba, the one in front, the other behind, the rectus muscle. (See fig. 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 interims divides into two lamina:, 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 (xgepcia, 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 fhis 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 (Jig. 3 ). Inferiorly, this bundle, a ABDOMEN. 7 Fig. 3. c, the 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 along the inner side of the testicle and cord, keeping more pos- teriorly : this constitutes the second bundle ; it gradually increases in size as it ascends by re- ceiving the transverse fibres from the bundle of the opposite side, and it is inserted, sometimes by a distinct tendon, into the pubis near its spine. In some cases I have totally failed, even after the most careful dissection, in detecting a conti- nuity by muscular fibre between these two bun- dles, insomuch as to lead me to imagine that they may be connected by a very condensed cel- lular tissue or thin aponeurotic lamella after the" manner of the digastric muscles. In general the external bundle is larger than the internal, but Cloquethas 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 interims and the obliquus externus. At the infe- rior edge of the obliquus internus the spermatic cord is seen emerging from the abdomen and passing obliquely inwards and a little down- wards to the external abdominal ring. Here it lies in a groove or channel, called the inguinal canal, which extends from the point at which the spermatic cord emerges from the abdomen, (the opening in the fascia transversalis called in- ternal abdominal ring) to the external abdo- minal ring. This canal is bounded or covered anteriorly by the tendon of the obliquus externus ; posteriorly by the fascia trans- versalis and some fibres of the tendon of the transversalis muscle towards the inner side; superiorly by the margin of the obliquus in- ternus and transversalis muscles ; and inferiorly by the groove of Poupart's ligament.* (A full description of this canal will be found in the article Groin, Region of the.) 3. Transversalis ( lumbo-abduminal, lumbo- ili-abdominal ). This muscle is immediately under cover of the obliquus internus ; its name is derived from the transverse direction of its fibres. In its general character it resembles the obliqui, being like them a muscular lamella, inserted into a tendinous expansion, which again is inserted into the linea alba. Supe- riorly the fleshy fibres of this muscle are attach- ed by distinct bundles to the internal surface of the cartilages of the ribs forming the lower margin of the thorax, where these bundles in- digitate with those of the diaphragm : 2dly, in the interval between the last rib and the crista Fig. 4. a * " The obliquus internus corresponds to the in- ternal intercostals by the direction of its fibres, by its being situated under cover of the obliquus externus, and because its fleshy fibres extend much further forwards than those of the last-named mus- cle."— Meckel. ABDOMEN. ilii, the fibres arise from a tendinous lamella, which itself is trifoliate in its origin. This ten- don is found as an undivided lamella between the outer margin of thequadratuslamborum and the commencement of the fleshy fibres of the muscle, extending vertically from the last rib to the crista ilii. (Fig. 4, 1.) The three lamina? 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'ascia 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 (fig. 4, h) ; and the anterior arises from the pedicles which connect the transverse processes to the bodies of the vertebra, and covers the quadratus lumborum muscle in front (fig. 4, f). lnferiorly, the transversalis muscle at- taches itself to the inner lip of the crista ilii for its three anterior fourths, and to the ex- ternal third or half of Poupart's ligament, cor- responding to the attachments of the obliquus internus. The fleshy fibres of the muscle pass from these several points of attachment trans- versely inwards, the middle being the longest, and the superior the shortest, and are in- serted into the outer convex margin* of a tendinous aponeurosis, which extends to the linea alba. This aponeurosis is intimately connected with the posterior division of that of the obliquus internus for an extent corre- sponding to the three superior fourths of the rectus muscle, behind which both pass to be inserted into the ensiform cartilage and linea alba, (fig. 4, a,) forming the posterior wall of the sheath of the rectus. lnferiorly, 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 the folded fibres of the transversalis. They adhere to the subjacent fascia, (fascia transversalis,) and add to the strength of the inner portion of the pos- terior wall of the inguinal canal. They cor- respond, in a great measure, to the external abdominal ring, and may be counted as one of the obstacles provided against the direct descent of a hernia. Such is unquestionably the usual mode of * This margin forms the linea semilunaris of Spigelius. t Cooper on the Testicle, p. 35. insertion of the tendon of the transversalis muscle ; but Mr. Guthrie has lately called the attention of anatomists to a variety which it is important to know, although it cannot be of frequent occurrence. In this variety the spermatic cord appears to pass through a slit in the inferior margin of the transversalis muscle, so that a bundle of muscle passes behind as well as before the cord ; the posterior one end- ing in tendinous fibres, which, like the folded fibres above described, are inserted into Pou- part's ligament.* It is very generally believed that the inferior fibres of this muscle contribute, as well as those of the obliquus internus, to form the cremaster. The two muscles are so closely connected externally by their inferior margins, that it is natural to suppose that both do send fibres to the cremaster. Sir Astley Cooper expresses the relation of the cremaster to these two muscles in the clearest way, when he says that it arises from Poupart's ligament within the inguinal canal, and there blends with some of the fibres of both these muscles.f A thin layer of cellular tissue covers the transversalis muscle, and separates it from the obliquus internus. At its superior margin it is intimately related to the diaphragm, and some of its fibres seem to be continuous with it : posteriorly, by the triple partition of its tendon, it ensheaths the lumbar muscles, and it lies upon the fascia transversalis, which, with a layer of cellular tissue, separates it from the peritoneum. J 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. X " 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 Uneat transversa. ;* 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.— W insltne. They are, says Meckel, incontestably incomplete repetitions of the ribs in the walls of the abdomen. t Hence Meckel classes it among the polygastlic 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 vesicae 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 fcetus 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 of the umbilicus, which apparatus does not exist at the inguinal ring or femoral arch."* In the foetus the ring of the umbilicus is proportionally larger than at any period after birth when the cicatrix is fully formed : it is, however, at the full term, or even at the seventh or eighth month, and in the healthy state of the parts, equally filled up by the umbilical vessels and urachus, and we would say is equally capable of resisting intestinal protusion as at any subsequent period. Hence it may be in- ferred that congenital umbilical ruptures are always of very early date, being attributable to the persistence of the opening at the umbilicus, and the continuance in it of the intestinal pro- longation which exists there naturally at a very early period. It may likewise be inferred that the rupture in the adult can much more easily occur in the vicinity of, than through the umbi- lical ring; and experience confirms this deduc- tion from the anatomy of the parts. * Scarpa on Hernia, p. 373. 10 ABDOMEN. Above the umbilicus the linea alba is from two to four lines broad in the greater part of its extent; and below the umbilicus it gradually tapers down to the pubis, at the same time in- creasing in thickness.* 5. Pyramidalis (pubio-sub-umbilical ). At the inferior extremity of the recti, and separa- ting their origin, are two small muscles of a pyramidal form ; their bases are inferior, and attached to the symphysis and body of the pubis, and uniting ligaments, and their apices superior and inserted into the linea alba by small tendons, from two to three inches above the symphysis pubis. Each muscle is enve- loped in a distinct sheath, and lies a little more prominently than the origin of the rectus of the same side. These muscles are not unfrequently absent. Sometimes, on the contrary, there have been two on one side and one on the other, or even two on each side.f The muscles which enter into the composi- tion of the posterior wall of the abdomen are chiefly those which occupy the lumbar region of the back, filling up that empty space which in the skeleton is observed on each side of the spinal column between the crista ilii and the last rib. In dissecting from behind forwards in this region, having removed the skin and lax cellular tissue already described, we come upon the strong fibrous expansion, the fascia lumbo- rum. This has extensive osseous attachments, and thus firmly binds down the subjacent mus- cles. When it is removed, the lumbar portions of the sacrolumbal is 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 die 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 Quadratus lumborum ( ilio-costal, ilio-lumbi- costal ). The term quadratus is applied to this muscle, more from its quadrilateral form than from any nearer resemblance to a square, in- asmuch as all its sides are unequal. The most fixed attachment of this muscle is its inferior, where it is inserted by tendinous fibres into the iliolumbar ligament and into the inner lip of the crista ilii for about an inch to the outer side of the insertion of that ligament. From these points the fibres proceed vertically upwards, the ex- ternal ones going to be inserted into the inferior margin of the last rib for nearly its entire length, and the internal fibres, those in parti- cular which are attached to the ligament, ter- minating by four aponeurotic tongue-like bun- dles, which are inserted into the anterior surface of the transverse processes of the four superior lumbar 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, (^oa, lumbus) (prelombo, trochanterien, lur/ibaris.) 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 vertebra, 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 Jig. ^,f; see also Jig. 5, where on one side the muscle has been removed from between the laminas 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 vertebra1 ; 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 vertebra;, (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 Transvcrsi. Op. Minora, torn. 1. any influence upon the contents of the cavity. The iliac fossa affords a large surface for the attachment of one of the principal muscles connecting the thigh with the trunk. This muscle is named Iliacus internus, (iliaco-trochanterien.) This muscle fills up the iliac fossa, to the whole of whose concavity as well as to its margin, and the two anterior spinous processes of the ilium and the interval between them, its fibres are attached. From these several points of origin the fibres converge to form a thick and broad belly, which passes over the upper part of the acetabulum and horizontal ramus of the pubis, filling up the external portion of the 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 iliuca, the union be- ing indicated by a white opaque line formed by a thickening of the membrane, taking the course of Poupart's ligament and the crista ilii, except where it is interrupted for the passage of vessels or other parts. Superiorly, the fascia transversalis also degenerates into a cellular lamella, which passes on the transversalis muscle to the diaphragm. It is for a short distance above Poupart's ligament that this fascia demands most attention ; here it forms the posterior wall of the inguinal canal, and at a point a little external and superior to the middle of Poupart's ligament it presents an opening or separation of its fibres, through which the sper- matic vessels and vas deferens united by lax cellular tissue pass into the inguinal canal, carrying around them a funnel-shaped mem- brane which seems to be a prolongation from or continuation of the margins of this opening, but which is in texture merely a condensed cel- lular layer. This prolonged membrane is the first covering which the spermatic cord receives upon its formation, which takes place as its several constituent parts meet at the opening or slit in the fascia transversalis ; it immediately invests the cellular tissue connecting these parts, which is the tunica vaginalis of the cord ; as it proceeds, the cremaster muscle adheres to it from the external oblique and transversalis muscles, and this again receives at its exit through the external abdominal ring another cellular expansion, to which we have already alluded. The opening or slit in the fascia transversalis which we have just described is denominated by anatomists the internal abdominal ring, although, if we speak with reference to the mid- dle line, it is external to the opening in the tendon of the obliquus externus, which is called the external ring. It would certainly be more consistent with the ordinary use of these ad- jectives in anatomy to reverse their application, or if the term anterior were applied to the ex- ternal ring, and posterior to the internal, every purpose would be answered. The direction of the internal abdominal ring is vertical and inclined very slightly outwards. When the fibrous character of the fascia trans- versalis is obvious, we can generally observe two very distinct portions of it, one on each side of the ring. The fibres of the external portion pass upwards and inwards ; those of the internal portion, which are generally stronger and more developed than in the external, pass upwards and outwards so as to decussate with the external fibres at the upper extremity of the ring. The outer margin of this internal portion often presents towards the ring a lunated ap- pearance, over which the vas deferens turns at a sharp angle ; it can be best seen by examining the parts from behind after the peritoneum has been removed.* The fascia transversalis is continued upwards along the posterior and lateral surface of the abdominal muscles and over the diaphragm under the form of a fine lamina of very condensed cellular membrane, which adheres pretty closely to the muscles, but especially to the diaphragm, where it seems to be incorporated with the proper cel- lular covering of that muscle. We refer to the article Groin, Region of the, for further particulars respecting the fascia transversalis. In the iliac fossa we find a very distinct fibrous expansion covering the whole abdo- minal surface of the iliacus internus muscle. This is 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 circumflexa ilii artery. On the inner side of the iliac fossa this fascia unites with the pelvic fascia along the brim of the pelvis, this union being likewise indicated by an opaque line similar to that already noticed along the crista ilii. To arrive at this point the fascia, in proceeding from without inwards, passes over the iliacus internus, then over the psoas magnus and parvus, upon which it is thinner than elsewhere ; it then passes behind the iliac artery and vein, and arrives at the pelvic margin. Posteriorly this fascia is con- tinuous with a thin and less fibrous expansion which covers the psoas and quadratus lumborum. muscles, adheres to the ligamentum 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. Collesa comparison which is constantly referred to by anatomists. " It may be said to resem- ble," he says, " a funnel, the wide part or mouth of which occupies the hollow of the ilium and lower part of the abdominal muscles, and the narrow part or pipe of which passes downwards on the thigh. The mouth of this funnel may be supposed to rise as high as the upper edge of the iliac muscle, and to be turned toward the cavity of the abdomen : the pipe joins the wide part where the external iliac vessels are passing under Poupart's ligament, and it is continued down on the thigh, so low as to reach the insertion of the saphena into the femoral vein."f From the preceding sections it appears that a fibro-cellular expansion lines the whole in- ternal surface of the abdominal parietes. It is so likewise with the pelvis, and also with the thorax. The cavity of the cranium, too, is lined with a fibrous membrane, although of a different nature, and doubtless performing a dif- ferent office. 5. Between the internal fibrous expan- sion of the abdomen and the peritoneum is a cellular tissue, which presents different cha- racters in each region ; it is the subperitoneal cellular tissue. Along the anterior wall it is thin and fine, except inferiorly opposite the in- ternal abdominal ring, where it becomes more abundant, as well as in the hypogastric region, immediately above the pubis. In the iliac fossa and lumbar region it is lax and abundant, especially in the latter, where there is also a considerable quantity of fat surrounding the kidney. In the iliac fossa this cellular tissue is stretched across the crural ring, and forms what Cloquet describes under the name of septum crurale. On the superior wall it is ex- tremely fine, and in very small quantity. Im- mediately behind the sternum, and in the mid- dle line, this cellular tissue communicates with that of the mediastinum through a separation of the anterior fibres of the diaphragm. This subserous cellular tissue forms the pri- mary covering of all hernia3, 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 Colles' Surgical Anatomy, pp. 68, 69. Opposite the crural canal this cellular tissue is often so abundant, as, when condensed by the pressure of the hernial tumour, to form an ex- pansion over the sac of considerable thickness. Sometimes it contains fat, and not unfrequently we find a large lymphatic ganglion in it, filling up the crural ring. 6. Peritoneum. — A considerable part of the abdominal surface of the walls of the abdomen is lined by a very fine transparent serous mem- brane— the peritoneum, which is likewise con- nected, to a greater or less extent, with every viscus within the cavity. In consequence of this double connexion, it happens that in various situations the peritoneum is reflected from the wall of the abdomen upon an adjacent viscus, and thus are produced various folds of this mem- brane, which demand the attention of the ana- tomist. These folds are rendered distinct when such a section of the anterior abdominal wall is made as without dividing them to allow of it being held apart from the viscera. I shall enumerate these folds in describing the relation of the peritoneum to the several walls. The anterior wall of the abdomen is entirely lined by peritoneum, and has in connexion with it four folds, all of which, as it were, radiate from the umbilicus. In the adult these folds are reflected round four ligamentous cords (three of which are the remains of bloodvessels in the foetus), which meet at the umbilicus and diverge, one upwards, backwards, and to the right side (the obliterated umbilical vein), two downwards and outwards towards Pou- part's ligament on each side, so as to pass behind the inguinal canal, nearly midway between the two rings (the obliterated um- bilical arteries), and the fourth nearly ver- tically downwards along the middle line to be inserted into the apex of the bladder ( the ura- chus ). The four folds are similar in direction to that of the fibrous cords contained within them : the fold which passes upwards towards the liver is falciform, the concavity being di- rected downwards and backwards. From its connexion with the convex surface of the liver it is also called the falciform ligament of the liver, and the fibrous cord contained in its in- ferior margin, the ligamentum teres. The in- ferior and external folds pass each from the umbilicus, downwards and outwards to the iliac fossa, to a point a little on the inner side of the internal abdominal ring, where it dis- appears, being continued externally over the iliac fossa, and internally behind the rectus muscle. This fold, when stretched towards the umbilicus, evidently forms the partition between two pouches, the external and in- ternal inguinal pouches, which correspond re- spectively to the internal and external abdo- minal rings, and indicate the situations at which make their escape those two forms of inguinal hernia, which, from their connexion with these pouches, are called by Hesselbach external and internal inguinal hernise ; 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 fcetus in consequence of the greater size of the virachus 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 the right sacro-iliac symphysis ; the right lamina is situated quite on the right side of the spine. In the iliac fossa? the peritoneum is in con- nexion with tine fascia iliaca, except where it is separated by the ccecum 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 vesica? supra pubem, and the high operation for the stone may be per- formed with impunity to the serous membrane. At the posterior wall an instrument may be passed into any part of the posterior surface of the kidney without injury to the peritoneum ; the pelvis of the kidney, or any part of the abdominal course of the ureter, may be opened too, or the vena cava ; and by cutting into the bodies of the vertebrae, and the muscular por- tion of the posterior wall in the dead body, a view of all the parts which lie upon that wall may be obtained without at all injuring the peritoneum.* Further details respecting the anatomy of the peritoneum will be found in the article under that head. Vessels and nerves of the abdominal walls. — a. The arteries. — The most important arterial ramifications are found in the anterior wall. In the superficial fascia we find the superficial epigastric artery or tegumentary artery, which exists as a trunk in the iliac regions. This artery, arising from the femoral, pierces the fascia lata, and passes over Poupart's ligament upwards and inwards, crossing the anterior * The reader may examine with advantage, Lud- wig, Icones cavitatum thoracis et abdominis a tergo apertarum. Leipzig, 1789. ABDOMEN. 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 circumjiexa ilii. The epigastric artery arises in general from the external iliac a little way above Poupart's liga- ment ; it at first inclines downwards to that ligament, and then turns upwards, and directs itself forwards and inwards, crossing the iliac vein; it then runs along the posterior surface of the anterior wall of the abdomen, inclosed be- tween the peritoneum and fascia transversalis, at first situated between the external and inter- nal abdominal rings, and on arriving at the rectus muscle, the sheath of which it enters about two inches above the pubis, it gives off branches from either side to the abdominal muscles and peritoneum, and behind the linea alba, establishes a very free inosculation with its fellow of the opposite side. As it lies behind the inguinal canal, the epigastric artery is much nearer to the internal than to the external abdo- minal ring, being to the pubic side of the former ; here the vas deferens, as it passes up from the pelvis to the inguinal canal, hooks over it, and receives one or two small branches from it. In passing to the rectus muscle, this artery lies internal to the linea semilunaris. It enters the sheath of the rectus, and then termi- nates by anastomosing with the internal mam- mary. The course of this artery demands par- ticular attention from the surgical anatomist in reference to the operations for inguinal hernia?, 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 m any operation performed in that line, or in the internal half of the rectus muscle, and its security in such operations is increased under the altered state of parts con- * Diet, de Medecinc, art. Abdomen. sequent on pregnancy, ascites, or any abdomi- nal tumour pressing similarly on the abdominal wall. In these cases the distance of the artery from the linea alba is increased by the flattening of the rectus muscle, which results from its compression. — (See Groin, Region of; Hernia; Iliac Artery.) The circumjiexa 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, obstructionf or retardation of the circulation, in the deep-seated veins of the ab- domen, more especially the inferior vena cava. The veins which accompany the superficial epigastric artery empty themselves by one or more trunks into the vena saphena at the upper part of the thigh. Two veins generally accompany the deep epigastric artery, which empty themselves into the external iliac vein. These veins are equally subject to enlargement with the preceding, and from similar causes, and they are often found in a varicose condition in women who have borne many children. Some curious anomalies have been observed in the venous circulation of the anterior abdo- minal wall, which, as being calculated to in- terfere with the operator, the practitioner would * See the interesting case of obliterated aorta re- corded by Messrs. Crampton and Goodissen. Dub. Hosp. Reports, vol. ii. t As in the case of obliteration of the infeiior vena cava from the pressure of an aneurismal tumour observed by Reynaud. Journal Hcbdom. de Med. vol. ii. p. 110. 16 ABDOMEN. do well to note. M. Meniere* has described a case in which a very large vein, arising from the external iliac, passed up along the linea alba to the umbilicus, was continued along the obliterated umbilical vein, and opened into the vena portae. In another case, recorded by Manec, the vein originated in the same manner by two roots, reached the umbilicus, taking a course parallel to the umbilical artery, formed an arch outside the navel, and having re-entered the abdomen, opened into the vena portae. In another instance which occurred to Cruveilhier the superficial veins in the hypogastric region were enormously enlarged, at the umbilicus they ended in a trunk as large as a finger, which communicated with the vena cava as it passed under the liver.f Berard proposes to explain, by the supposition of the existence of such anomalies as those above described, the occurrence of fatal hemorrhages from wounds inflicted at the umbilicus, which have been attributed to the persistence of the um- bilical vein.J c. The lymphatics. — Those on the anterior wall communicate above with the axillary glands, and below with those of the groin : the deep-seated lymphatics of the posterior wall communicate with the glands which lie along the lateral and anterior surfaces of the lumbar spine. d. The nerves. — The nerves of the abdo- minal parietes are derived from the inferior intercostals and from branches of the lumbar plexus. The seventh, eighth, ninth, tenth, eleventh, and twelfth intercostal nerves termi- nate in supplying the transverse and oblique muscles and die 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 thegenito- 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. cd. 2. vol. ii. p. 32, and Manec, Dissertation inaugurate. Paris, 1826. t Diet, de Med. art. Abdomen. ' to the ribs, the vertebrae, and the pelvis, it becomes evident that they must likewise be destined to act upon the thoracic and pelvic cavities, as well as upon the vertebral column. In the constitution of the abdominal parietes we observe, as Berard* remarks, the most happy adaptation of structure to uses. A completely osseous covering would have greatly interfered with the functions of the abdominal organs, which are liable to experience changes both extensive and often very rapid, either by reason of the introduction of alimentary matter, whether solids or fluids, or by the disengage- ment of gases within the digestive tube, or by the progressive development of the impregnated uterus. We may moreover add that an exact repetition of the structure of the walls of the thorax would not have been well adapted to the abdomen for the same reason, namely, the too great resistance which it would afford to compression from within, thereby interfering with the distensibility of the enclosed viscera. The resistance, too, which a wall so constituted would afford to impulses from without could not have been so easily adapted to the impetus of the forces likely to act upon them as a purely muscular wall whose contractions and the intensity of them are obedient to the will. The consideration of the action and uses of the abdominal muscles naturally comes under two heads: — 1. their action upon the abdo- minal cavity and its contents ; 2. their influ- ence on the trunk generally, or parts of it. It is the muscles that enter into the compo- sition of the anterior and lateral walls of the abdomen which act chiefly on the cavity and its contained viscera. The solidity of a con- siderable portion of the posterior wall, and the great strength of die 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. I? 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 Ilaller had arrived at long ago, and clearly expresses it in the following passage : " Evidentissimum ergo videtur, vomitus qui- dem causam esse in ventriculo eumque in con- tractionem niti propriis vinbus atque aliquando vomitum perficere. Plerumque tamen irrita- tionem in ventriculo natam et sensum summae anxietatis, quae vomitum praecedunt, facere ut ad levandam aegrimoniam vires diaphragmatis et musculorum abdominis excitatae atque mo- lestiam de homine amoliturae, vomitum per- * Vide Haller, Elemenla Physiologic, t. vi. sect. iv. § xiv. VOL. I. ficiant. Unde neque a sola voluntate in pie- risque certe mortalibus vomitus cieri potest neque a sola absque voluntate natura — Quare recte conjunctas vires ventriculi et oraanorum respirationis CI. Viri fecerunt. Et videtur dia- phragma et abdomen 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 arid interesting review of M. Velpeau's Treatise on Midwifery. It so fully illustrates the part which the abdominal muscles take in promoting parturition, that I venture to tran- scribe it, " It is certain," says the reviewer, " that a woman who ' bears down ' as it is termed, with all her force, who makes the most of her pains, however feeble they may be, will thus accelerate her delivery ; and that another may more or less delay delivery by voluntarily opposing muscular action as much as she can. For example; — a woman was admitted for de- livery at M. Baudelocque's theatre ; labour went on regularly, and the pupils assembled. The dilatation of the cervix now slackened, and no progress was made during the whole night. The 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- ologic par lSerard, art. Digestion, § xxiv. t Medicul 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- terni,) says Dr. Barclay, " from occupying the whole of the lateral aspects extending be- tween the ilia and ribs, and from acting at the greatest lateral distance from the centre of motion, must always be muscles principally concerned in producing inflexions dextrad and sinistrad on the lumbar vertebrae, principal di- rectors in all the inflexions sternad and dorsad ; and, from the assistance which they give to the recti, principal librators also of the trunk, whe- ther we be sitting, standing, or walking." The reciprocal action of the recti and ob- liqui on each other is one of the most beauti- * Barclay on Muscular Motion, p. 522. ful parts of the mechanism of the abdominal muscles. This is mainly to be attributed to the close connection which subsists between these muscles in consequence of the formation of the sheaths of the recti by their aponeuroses, and the adhesion of the anterior wall of those sheaths to the tendinous intersections of the recti. When the recti contract, the antero-pos- terior diameter of the abdomen is diminished, and consequently the viscera are pushed to- wards the sides ; when, on the other hand, the obliqui contract, they diminish the transverse diameter of the abdomen, and push the viscera forward in the middle line. In the one case, then, it will be evident that the obliqui act as moderators to the recti, and in the other the resistance of the recti moderates the action of obliqui, — the former muscles being, as Cru- veilhier remarks, as it were, two active pillars compressing forcibly the viscera against the an- terior surface of the spine. It is probably to enable the recti to act more completely as moderators upon the several segments of the obliqui that they are intersected by tendinous lines, with which the aponeuroses of those muscles are connected. Another use has been assigned to these intersections by Benin, viz., — to multi- ply the points of attachment of the obliqui muscles, and to associate them, in many ac- tions, with the recti muscles. This is explained by a reference to the action of the recti in flex- ing the pelvis : were these muscles uncon- nected with the obliqui, they would act only on the pelvis, into which they are inserted ; but in consequence of the insertion of the internal oblique into the intersections of the recti, and the attachment of that muscle also to the crista ilii, the force of contraction of the recti is com- municated not only to the pubis, but also through the fibres of the obliquus internus to the rest of the pelvic margin.* The action of the pyramidales seems to be chiefly on the linea alba, which they render tense ; thus limiting the separation of the recti, and opposing the tendency to visceral protru- sion. Fallopius supposed that they acted on the bladder, especially when it was in a dis- tended state ; and Parsons conjectured that they might depress the suspensory ligament of the bladder (the urachus), and thus facilitate the contraction of that organ. The other muscles which are from situation abdominal muscles in consequence of their connexion with the posterior wall of the abdo- men, are chiefly agents in the extension of the vertebral column : in their contracted state, however, they form a tense and resisting sur- face, against which the viscera are compressed by the contraction of the anterior muscles. II. Of the Abdominal Cavity. — The annexed engraving (Jig. 5.) exhibits a view of the abdo- minal cavity, the anterior and part of the lateral walls having been cut away and the viscera removed. The subject is so bent backwards as to render the bodies of the vertebrae very * Berard, loc. cit. , et Bcrtin, sur l'usage des enervations des muscles dioits du basventre, in Mem. de l'Acad. des Sciences de Paris. ABDOMEN, 19 (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 fcetus ; and these differ- ences are dependent on the great or incomplete development of the pelvis. In the female the abdomen is generally more capacious than in the male ; and this greater size is more remark- able at the inferior part of it in the hypogastric region. In fact in the male it would seem that the great extremity of the oval is toward the thorax, and its smaller one towards the pelvis; but in the female it is just the reverse, the larger extremity being toward the pelvis. It should be observed, however, that the modern fashion of tightly compressing the lower part of the thorax has a material effect on the external characters of the female abdomen, otherwise there is no reason that the superior part of it should be proportionally less than in the male. In the fcetus the abdomen is proportionally larger than at any other period of life : this is to be attributed to the imperfect development of the pelvis, and likewise to the great size which some of the abdominal viscera possess ; and as some time must elapse before the pelvis reaches its full dimensions, or the viscera lose their superfluous parts, the abdomen continues of this large size for a long period after birth. The subdivision of the abdomen into regions is especially useful in reference to the contents of the abdominal cavity, which it is highly de- sirable the student should examine, so as to be able to assign to each compartment its appro- priate contents. The abdominal viscera may be subdivided into the membranous and the parenchymatous ; the former being such as the stomach and intestinal canal, the latter, such as the liver, spleen, pancreas, &c. The viscera have likewise been distinguished in reference to their position with respect to the peritoneum, by the names intra-peritoneal and extra-peri- toneal ; but it is sufficient to know that no serous membrane contains any organ within it (i. e. within its sac) to see the error of such a distinction. But we cannot adopt a better di- vision of the abdominal viscera than that which has reference to the functions of those organs, and which Beclard has adopted ; viz. 1. the organs of digestion — the stomach, the intes- tinal canal, the liver and its appendages, the spleen, and the pancreas : 2. the urinary organs — the kidneys and the ureters, to which may be added from their close relation to the kid- neys, the suprarenal capsules: 3. the organs of generation in the male — the vasa deferentia, and in the male foetus at the sixth or seventh month of intra-uterine life, the testicles : none of the organs of generation can strictly be said to be abdominal organs in the female. In both male and female the other internal generative organs are pelvic viscera. If we add to the above enumeration of parts the abdominal por- tion of the aorta, its primary subdivision into the common iliacs ; the anterior subdivision of these arteries under the name of external iliacs ; the branches of the aorta which are distributed to the viscera as well as to the walls of the abdomen ; the common and external iliac veins ; the vena cava ascendens; the system of the vena porta? ; 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, Boyer, Portal, Bichat, Meckel, Cloquet, Marjolin, Hildebrandt, &c. for the titles of whose respective works see the Bibliography of A NATOMY, ( Introduction. ) — Velpeau, Anat. Chirurgicale. Paris, 1833. t. ii. Blandin, Anat. Topographique. Cru- veilhier, Dictionnaire de Med. et Chirurg. ait. Abdo- men. Beclard et Berard, Diet, de Medecine. Ed. 2d. art. Abdomen, Pierer Anatomisch- Physiologisches Realworterbuch. herausgegeben von J. F. Pierer. Leipzig, 1816. art. Abdominal- muskeln. Gerdy, Anat. des formes exterieures. Paris, 1829. p. 122 and 199. Cloquet, Recherches Anat. sur les Hernies de 1' Abdomen, or the trans- lation by McWhinnie. Lond. 1835. Scarpu, on Hernia, by Wishart, Lawrence on ditto. Todd, on ditto. Dub. Hosp. Reports, vol. i. Flood's plates of Inguinal and Femoral Hernia. Lund. 1834. Cam- per, Icones Herniarum. Guthrie, on Inguinal and Femoral Hernia. A. Cooper, on ditto, and on the Testicle. Nance, Dissertation Inaugurale sur l'fier- nie. 1826. Colles's Surgical Anatomy. Dublin, 1811. Barclay on Muscular Motion, p. 337 et sqq. (R. B. Todd.) ABSORPTION in physiology (from ab- sorbeo : Lat. absorptio, Fr. absorption, Ger. die einsaugung, Ital. assorbimento.) The term absorption is employed in physiology to de- signate a vital organic function, the primary or immediate object of which is to furnish the system with a due supply of matter for its growth and subsistence. It is proposed, in the following article, first, to give an account of the organs by which the function is performed ; this will lead us, 2dly, to consider the question of venous absorption ; in the third place, we shall inquire into the mode in which the ab- sorbents act; and, lastly, we shall offer some remarks upon the specific uses of the different parts of the absorbent system, and upon the re- lation which it bears to the other vital functions. §. 1. Description of the Absorbent System. — VVe propose, in the first instance, to restrict the term absorbent system to those organs, which are supposed to be exclusively appropriated to the function of absorption ; these may be in- cluded under the two heads of vessels and glands, the vessels being again subdivided into the lacteals and the lymphatics. Although the absorbents are distributed to al- most every part of the body, and perform so im- portant an office in the animal economy, they were among the organs which were the latest in being discovered by anatomists. There are, indeed, some passages in the writings of Galen,* which would lead us to suppose that certain * De Anat. Admin, lib. 7, sub finem ; De usu partium, lib. 4. cap. 19; An sanguis in arteriis &c. cap. 5. parts of the absorbents had been seen by Erasistratus and Herophilus, as well as by himself; but it appears that they were, all of them, unacquainted with the relation which these vessels bore to the other organs, and were entirely ignorant of their office and destination. These scanty observations of the ancients seem to have been entirely neglected, or even for- gotten, until the study of anatomy was revived, together with that of the other medical sciences, in the sixteenth century. In the course of the researches which were then made into the structure of the animal body, various parts of the absorbent system appear to have been brought into view, and are noticed, among other writers, by Fallopio,* who discovered the lym- phatics, connected with some of the abdominal viscera, and by Eustachio,t who detected the thoracic duct. But although their descriptions, especially that of Eustachio, are sufficiently correct to enable us to identify them, as forming a part of the absorbent vessels, yet they were unacquainted with their specific nature and office, and with their relation to the sangui- ferous system. It is generally admitted that the merit of the discovery of the lacteals is due to Aselli ; this discovery he made in the year 1622. While he was examining the abdominal viscera of a dog, he observed a series of vessels attached to the mesentery, which appeared to have no direct connexion with the arteries or veins, and which, from the circumstance of their con- taining a white opake fluid, he denominated Lacteals.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 * " 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. i Dissertatio de Lactibus ; first published in 1627. See Bartholin, de Lact. Thor., c. 4; Sheldon on the Absorbent Syst., p. 20, 1. Aselli's work is ac- companied by plates of very rude execution, but sufficiently expressive of the object. § Exper. nova anat. ; first published in 1651 ; Bartholin, c. 5. In 1652, Van Home published the first plate of the thoracic duct. There is some reason to suppose that Vesling had an imperfect view of it previous to Pecquet ; he published his Syntagma Anat. in 1647. In describing the pancreas he speaks of the vena? lacteae, lately discovered by Aselli, which convey the chyle to the liver, and figures them in tab. 4. fig. 3. ABSORPTION. 21 of the fluid which they contain, the lymphatics, was posterior to that of the lacteals. The trans- parency of their contents rendered them less conspicuous and less easy of detection, so that, although certain parts of them appear to have been seen by Fallopio, and afterwards by Aselli and others, yet it was not until the year 1650, that they were distinctly recognized, and their connexions ascertained. The discovery of the lymphatic system was the subject of a warm controversy between Bartholin and Rud- bek, on the merits of which we are, after so long an interval, scarcely able to decide. It appears, however, to have been the opinion of Haller, and the most distinguished anatomists of the last century, that the lymphatics were detected, in the first instance, by Rudbek ; that Bartholin had some intimation of the dis- covery, that he then took up the subject, and pursued it much farther than it had been done by Rudbek* There is a third individual, on whose behalf a claim of priority has been made, which pos- sesses at least considerable plausibility. We are informed by Glisson, that an English ana- tomist of the name of 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.f 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 flewson, 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. J * El. Phys., ii. 3. 1 ; Bibl. Anat., t. i. §. 378 and 415; and Not. 4. ad 121. Boer. 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. t For the most original and correct desciiption of the lacteals, the reader is referred to Haller, El. Phys. xxv. 1. 4 . . 8 ; Mascagni, Vas. Lymph. Corp. With respect to the minute anatomy of the lacteals, we are informed that they originate from certain small projecting bodies, termed villi, which are attached to the interior surface of the intestines, styled from this circumstance the villous coat. These villi are described as consisting of a number o( capillary tubes, which terminate with open mouths, and that by the union of these tubes the branches of the lacteals are composed, which are suffi- ciently large to be visible to the eye. We must remark, however, that although these villi, as constituting the mouths of the lacteals, have been minutely described, and even figures given of the appearance which they exhibit in the microscope, yet that considerable doubt is still entertained of their existence, and that they are even entirely discredited by some anatomists of the first eminence.'* Upon the whole we may conclude that the opinion, which has been generally adopted, respecting the capillary termination of the lacteals, is somewhat theo- retical, rather derived from the supposed ne- cessity of such a formation to cany on the functions of the vessels, than from any actual observations that have been made upon them. When the lacteals have acquired sufficient magnitude to become visible to the eye, they are seen to proceed along the mesentery, the small vessels running together to form large brandies, 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; Samorini, Tabula;, No. 13. fig. 3 ; Magendie, Physiol, t. ii. p. 158 . . 0. The translation of Mascagni's work, with copious notes by Bellini, may be advantageously consulted ; it is not accompanied by plates. For the lymphatics we may refer to Haller, ii. 3. 2 ; Meckel, Diss. Epist. de Vasis Lymphaticis ; Hew- son, Enq., ch. 3. pi. 3, 6 ; Mascagni, ps. 1. sect. 7. tab. 4 et seq. ; Cruikshank, on the Absorb., p. 143 et seq. ; Soemmering, Corp. Hum. Fabr. t. v. p. 388 et seq. ; many of Mascagni's plates are transferred into Cloquet's valuable " Manuel." Art. " Inhalation," par Rullier, in Diet, des Sc. Med. t. xxv. 3. Art. " Lymphatique," par Chaussier et Adelon, ibid, t. xxix. p. 249, 260 ; Meckel, Manuel, sect. 6. ch. 2; Quain's Elem. of Anat. p. 560. .574. In Elliotson's Physiol, ch. 9. p. 140 .. 2, we have a "short account of the first discovery of the absorbent system." 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, Prad. 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 Chyliferous System; Lac- teal. * These were very minutely examined by Ruysch, Bilucid. 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. Ixxxvi. p. 231, et seq. ; this action was not, however, supposed to depend on contractility. Wrisberg informs us that he has frequently seeii 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, EI. Phys. ii. 3. 4, and the later account of M. Magendie, Physiol, t. ii. p. 174, and Jour, t. i. p. 3, who conceives that absorbent vessels have not been detected in the brain, the spine, and the organs of sense. Dr. Alison likewise conceives that they have not been detected in the cranium or ner- vous system, Outlines of Physiol, p. 76. Mas- cagni, however, appears to have detected a few small lymphatics in the brain, tab. 27. fig, 1. Monro secundus argues in favour of their existence, but it does not appear that he actually detected them in any part of the nervous system ; on the Nervous System, ch. v. sect 1. and Three Treatises, ch. 4, 5. ABSORPTION. 23 exists between them during their course, and we are not aware of any physiological cause of this arrangement. With respect to the mouths or origin of the lymphatics there is even more uncertainty than with respect to that of the lacteals ; no anato- mical investigation has hitherto been able to detect them, and although numerous facts of constant occurrence would seem to prove that their capillary extremities are distributed over all the surfaces of the body, it is from various pathological observations and from the analogy of the lacteals that we arrive at this conclu- sion.* The thoracic duct is a vessel of considerable size, which is situated near the spine, and which extends from about the middle of the dorsal vertebra 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 01 of different sizes, and we have not unfrequently partial appen- dages, which are added to the main trunk in different parts of its course. J 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 * Sec Magcndie, Physiol, t. ii. p. 175 Watson, however, conceived that he had detected their open mouths on the surface of the bladder, Phil. Trans, for 1769, pi. 16. Monro, in speaking of the lym- phatics of fishes, remarks that there is " no doubt that they begin by open mouths," p. 30. t For descriptions and plates of the thoracic duct the following works may be referred to; Haller, Prim. Lin. c. xxv. § 565; Op. Min. t. i. p. 586 et seq. tab. 11, 12 ; and El. Phys. xxv 1. 10 . . 3 : Albinus, Tab. Vas. Chylif. ; liolius and Saltzmann, in Haller, Disp. Anat. t. i. ; Cheseldcn, 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. 185, 187. upon some mechanical cause. It is, however, a circumstance of considerable importance in respect to the pathological conclusions that have been sometimes drawn from the obstruc- tions of this organ, as well as from the experi- ments that have been performed upon it.* The structure and properties of the thoracic duct appear to be similar to those of the large trunks of the lacteals and lymphatics ; its coats are comparatively thin and transparent, yet it is possessed of considerable strength, and is ca- pable of being distended much beyond its ordinary bulk ; it is furnished with numerous valves, and exhibits a great degree of con- tractility. The lymphatic or conglobate glandsf com- pose a very important part of the absorbent system, if we may judge from their number and their general diffusion over every part of the body. They are of various sizes, and are grouped together in various ways; occasionally they are single, but more frequently connected together in masses of considerable extent. They are found in almost every part of the body, always connected with the lacteals and lympha- tics, and it is asserted that each one of these ves- sels, in some part of its course, passes through or is connected with one or more of these glands. £ There are certain parts of the body in which they are more numerous, and are connected in larger masses ; the lacteals are furnished with numerous glands in their passage along the mesentery, while the glands that belong to the lymphatics are found in the greatest number and largest masses in the groin, the axilla, and the neck. It is necessary to remark that this account of the distribution of the lymphatic glands applies only to the animals which belong to the class of the mammalia; in birds they are much more rare, and still more so in fish, while among the lower animals, where we have suffi- cient evidence of the existence of an absorbent system, the glands have not yet been satisfac- torily demonstrated. § With respect to the structure of these glands, as well as that of glands of other descriptions, a controversy has long existed among anato- mists, whether they consist of a series of cells or follicles, as they have been termed, or whe- ther they are composed simply of a congeries of vessels. The question may be regarded as still at issue ; but it may be remarked that whereas the older anatomists generally leaned to the opinion of the follicular structure of the * See on this subject Sir A. Cooper, in Med. Rec. and Res. p. 86 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 h s 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 have more frequently adopted the hypothesis of their vascular texture, so that we may consider this doctrine as sup- ported by the most recent and elaborate re- searches.f See Lymphatic ; Gland. § 2. The 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 lacleals and the lymphatics. The ancient anatomists and physiologists being unacquainted with the existence of the lacteal s 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 tliey are not found connected wiih 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 Crmkshank, 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 ; Eeclard, 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 ; Kullier, 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. % Boerhaave, Pradeet. §103. and §247; Haller, in not. 1. ad § 106, Boerhaave, Pra?lect., and not. 1. ad § 245; also El. Phys. ii. 1.28; Monro secun- dus, De 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 duct, 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 * Some experiments of this kind are referred to by M. Majendie, as having been performed by M. Dupuyiren, Physiol, t. ii. p. 167. See also Ri- cherand, Elemens de Physiologie par Berard. t Medical Comment., passim ; Cruikshank, In- trod.; Walter, § 10 et seq. ^ Dissert, de Sem. et Test, in Smellie, 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, IIewson,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. ami. 1770, p. 19 et seq. The researches of some of the most accurate among the anatomists of the present day seem also to show tliat occasional communications exist be- tween some of the lymphatics and the contiguous veins; hut 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 " lllus- 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 arteriolar lym- phatics, 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 perhans a little doubtful ; Phil. Trans, for 1796, p. 27 ei 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. 1033, 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, which 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 other 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 hi"h au- thority of Meckel, De Fin. Ven. et Vas. Lymph. 1772 ; and of Walter, Sur la Resorption, ubi supra. See particularly his 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. 26 ABSORPTION. 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 Hunter; 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. ex. p. 73 ct 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. J 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. Tiedemann and Gmelin, and which bear di- rectly upon the question of venous absorption. Their object was to ascertain whether there * Magendie, Journ. t. i. p. 25 . . 7. t Journ. t. i. p. 23 et seq. ; Elem. t. ii. p. 183 . . 5. J See Rullier, ubi supra, p. 150 . . 2 : and Adelon, " Absorption," Diet, dc 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, assafcetida, &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 ease 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. Med. Journ. vol. xvii. p. 455 et seq. On the absorption of foreign bodies sec the early experiments of Lister and Musgiave, Ph. 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, £1. Phys. xxiv. 2. 3 ; see also J. Hunter, in Med. Com. 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. t 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 consistedrin 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 experimentsof MM.TiedemannandGmelin, and those of an analogous kind, in which extra- neous substances were found in thevenous blood, and in some of the secretions, when they could not be detected in the chyle, as more directly 28 ABSORPTION. 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' Assort), 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 as 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 the operation, 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^ 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 ca^e 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. f 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. 2i . . 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 lie 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. Phys. 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, Rechcrches 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 rrmarks of Tiedemann, Traitc 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 Intest. 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 et seq. % Med. Reports, ch. xix. § Ed. Med. Journ. v. ii. p. 10 et seq. 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 system 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. J 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 PInfluence des Agens, &c. ch. xii. p. 345 et seq. t De Flnfiuence, &c. ch. xiii. p. 556 et seq. See on this subject, Ma^endie/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. Uuisson 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. t 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, we 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. t 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 off 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 be any 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, Klein, 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," ibid. t. v. p. 239; Desgenettes, Journ. Med. t. xc. p. 322, et seq. ACALEPIIiE. 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- . traduction of oxygpne, 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. Adehn, in Diet. Scien. Med. 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Cruikshank, on the Absorbents ; Ditto, Letter to Clare. 4to. Lond. 1786. Currie's Med. Rep. Desgenettes, in Journ. Med. t. Ixxxiv. Douglas, Bibl. Anat. Dumas, Physiol. Duvernoi, in Mem. Petrop. t. i. Edwards, stir 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. lxxxv, lxxxvii, xc. Fleming's Zoology. Fodera, Recherch. sur l'Ab- sorption ; Ditto, in Magendie's Journ. t. iii. Foh- mann, Commun. Lymph, et Veines. 4to. Liege. 1832. Fourcroy, in Ann. Chim. t. xc. ; Ditto, Medecine Eclairee. Franchini, Consid. fisiol. sull' Assorb. Galeni Opera, a Charterio. Glisson, Anat. Hepat. 12mo. Lond. 1654. Gordon's Anat. Graves, Lect. on the Lymph. Sys. Hause, 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. Linear Hedioig, Disq. Ampull. Lieb. Hewson's Enquiries ; Ditto, in Phil. Trans. 1768, 9. Hudgkin, 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 Matte's Ab. of Phil. Trans. Lauth, Sur les Vaiss. Lymph. 4to. Strasb. 1824. Lieberhuehn, Fab. Vill. Intest. Lippi, Illust. Fisiol. Lowthorp's Ab. of Phil. Trans. Lyster, Ln Phil. Trans. 1683. Magendie, Physiol.; 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. Meckel, Diss, de Vas. Lymph. 4to. Berol. 1757; Ditto, Manuel d'Ana- tom. par Jourdan et Breschct ; 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 Vein's Lymph. 8vo. Berol. 1757.; Ditto, on Fishes ; Ditto, on the Nervous System ; Ditto, Three Treatises. Monro (3), Elem. of Anat. Musgrave, in Ph. Tr. 1701. Nuck, 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. Quain'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. Araes. 1653. Rullier, Diet, de Med. " Chyme ;" Ditto, Diet. Sc. Med. " Inhalation." Ruysch, Dilucid. Valv. Sabatier, Med. Acad. 1786. Sulzmann, in Haller, Disp. Anat. t. i. Santorini, Tabulae, fol. Parmae. 1775. Segalas, in Majendie's Journ. t. ii. Sheldon, on the Abs. Sys. fol. Lond. 1784. Soemmering, Corp. Hum. Fab.; Ditto, de Morbis Vasor. Abs. 8vo. Traj. s,d Mcen. 1795. Tiedemann, Physiol, par Jourdan. Valentin, in Journ. de Med. t. lxxxvi. Vauquelin, in Ann. Chim. t. lxxxi ; Ditto, in Ann. of Phil. vol. ii. Veslinq, 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, Obseiv. Anat. Vas. Abs., in Com. Gott. t. ix. Young's Medical Literature. (J. Bostock.) ACALEPHiE (from a>caA*j(p>?, a nettle) ; syn. urtice 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 otx.oihi)(pri to de- signate some of these animals ; but it was by Cuvier that the class was formed, and the term acalephas 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 hi/drostatiques of Cuvier. On many accounts the acalephs 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 d 2 36 ACALEPHiE. 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 a large size, so as to measure several feet indiameter; andyetwe cannot always 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,f whose arrangement is nearly the same as that adopted by Eschscholtz. J 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. Stephanomia. Agalma. Protomedea. Rho- dophysa. II. D iphyda. 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. " Zoophytes." 1830. % 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- rainis. 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- lymene. 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. Diancea. Fa- vonia. Cyteeis. 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 Actinoxoaires, 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 acaleplvae, 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 acalephee 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 Beroidee. 2. Non-symmetrical, the upper pole disciform or umbelliform, imper- forate 2 Medusas. B. Body multiple or aggre- gated. a. Homogeneous. 3. Composed of two pieces adhering together, and capable of separation . 3 Diphydes. 4. Composed of numerous pieces aggregated toge- ther 4 Poli/toma. 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- pullae, and terminal suckers 5 Physaophorce. '** Vesicle large, irregular, without stalk or am- pullae, but having ter- minal suckers and cir- riferotis processes . . 6 Physaliee. II. With a central cartilaginous axis. 6. Body simple, with suckers and lateral ten- taenia. a. Body irregularly oblong, with a veitical lamina on its upper surface . 7 Velellce. b. Body discoid, flat 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 rtot 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 ACALEPH7E. animal's sinking into the deep when danger threatens. In the other physograda, the air-ve- jp;„_ 7> side 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- Rhizophysa Melon. ?ained ™ thfe vesicles 1 J nas 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 to them, in the same animal, there is a two-lobed organ, the use of which is doubt- ful. In ugalma, (fig. 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- 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 Gaedii, 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. 9. Fig. 8. Agnlma okenii. Diphyes Campanulifera. been examined by Dr. Grant,* with his usual care, in the Beroe pikus;\ 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. Cydippe p. Esch. ACALEPHvE. 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. Eschscholtz 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 waterwithout 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 campauulate, 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 aurita 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 very 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. + Spallanzani, Travels in the Two Sicilies, iv 218. 40 ACALEPHvE. Fig. 10. Rhizostoma carulea. 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 pulmogrjrda 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. Velella septentrionalis. * In the tentacula of some of the physograda, also, a similar extensibility exists. The lower sur- face of physulvs, for instance, which itself seldom exceeds six inches in length, is provided with ten- tacula sixteen and even eighteen feet long. Fig. 12. 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 acalephee. It somewhat re- sembles m 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 tlie 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. Porpita 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 Acalephse. 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 Lond. i. 10. Rataria cordata. ACALEPHjE. 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 acalephae 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 acalephse, 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 acalephse 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. He 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 of the organs concerned in the function of digestion in the acalepha; 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, lie 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 ACALEPIIiE. Tlie mouth is large, tlie 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, salpoe, &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 coeca; 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 circum- * Journ. de Phys. xlix. 438 t Ann. dcs Sc. Nat. xxviii. 24't. ACALEPIIvE. 43 stance of fishe.; 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 capillata) have the four gastric sacs in free communication with one another ; and, frequently, (e. g. in pelugiu, chtysaora, and cegina,) 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 timet ; 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 mur- supiaiis, (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. J In Aurelia phosphurea, (Lam.) (Pelagia, Esch.) which formed the principal subject of Spallanzani's observations on the acalepha?, 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, Beytrage zur Anat. und Phys. der Medusen. t Ann. des Sciences Nat. xxviii. 251. } 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 own 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 acalepha?. 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, winch 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 Berue 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 ACALEPHiE. 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 Ber'ue ovatus, 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 cestum naiadis, Eschscholtz thought that he saw the system of vessels more dis- tinctly than in any other of the acalephoe. 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. Worn. 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 branches 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/)- 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. 430. t Gaede, Anat. der Medusen. % Cams, Comp, Anat. (by Gore,) ii. 266. ACALEPHiE. 4.3 gastric cavities in medusa aurita as subser- vient to the same function. These sacs com- municate directly with the gastric cavities by mearis 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 acalepha? 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 acalepha?. 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 physalns, (" 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 had 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 acalepha? 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 single drop of the same fluid to the conjunctiva.f In most of the acalepha?, 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. 46 ACALEPH/E. 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 Gaimard 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.* Fis. 13. A portion of the ovigerous filament of Dipkyes muck magnified. 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 Miiller in medusa capillata, and M. aurita, and by Eschscholtz in some species of cyunea, sthe- nonia, pelagia, 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 Miiller considered them as ovaries. Miiller 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 pvrifera and polypifera.f The colours of the acalepha? often depend on the tints of their ova: these are generally red, but sometimes brown, yellow, or purple. VIII. Geographical 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 acalephse. 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 cyaneee 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 acalephae swim on the surface. In winter, they probably sink to the bottom. Bibliography. — Madeer, Tentamen systematis Medusarum stabiliendi, in Nova Acta Acad. Natur. curios, vol. viii. Append, p. 19 ; and Papers in the Sveaska 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 marina; difierentiis : Miscel. Societat. Taiirinens. v. iii. p. 206. Miiller, Beschreibung zweier Medusen : Beschaeft. der Ber- liner Gesellsch. Naturfor. Freunde Bd. 2. S.290. Cuvier, Sur l'organization 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 Saml. Deel.3, S. 250. Sivartx, Medusa pelagica beskrifven ; Svenska Vetens. Acad. Hand. A. 1791, S. 188 in the German transl. T. 1791, S. 172. Gaede, Bey- traegn 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. ACIDS, ANIMAL. ACRITA. 47 AC:iDS, 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. kwo, discerno,) a pri- mary division of the animal kingdom founded by Virey, and so called by Macleay,|| composed of the lowest classes of the radiate animals of Cuvier, and characterised by an indistinct, dif- fused, or molecular condition of the nervous system. The necessity for a dismemberment of the Radiataof Cuvier, which RudolphiK justly calls a chaotic group, has been felt, and directly or indirectly expressed, by most naturalists and comparative anatomists.** It is impossible, in- deed, to predicate a community of structure in either the locomotive, excretive, digestive, sensitive, or generative systems, with respect to this division, as it now stands in the " Regne Animal." As in the animal organization the nervous * First obtained by Dr. Prout from the pure lithic acid, of which the excrements of the boa constrictor consist. t Procured from the expressed liquor of ants. t Supposed by Vauquelin to exist in the liquor amnii of the cow. § Extracted by Chaussier from the silk-worm, but its existence is very problematical. || Horas Entomologies, vol. i.pt. ii. p. 202. it Synopsis Entoaoorum, p. 572. ** Lamarck observes, " Lies animaux apathiquet (as he terms the Acrita) furent tres-improprement appeles zoophytes: ils ne tiennent lien de la nature vegetale, tt tons generalemeut sont completement des animaux. La denomination a" animaux ra- yonnes ne leur convient pas plus que la prece- dente ; car ellc ne peut s'appliquer ; qu'a une partie d'entr'eux ; et il s'en trouve beaucoup parmi eux qui n'ont absoluimnt rien de la forme rayonnante." Anim. sans Vertebras 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 Poh/astric In- fusoria of Ehrenberg, the Polypi of Cuvier, the Entozoa parenchymatosa, Cuv. or Sterel- mint-ha, and the Acalepha?, differs in the absence or obscure traces of nervous filaments from the second division, including the Echinoderma, the Entozoa cuvitaria or Calelmintha, the epi- zoa, and the Rotifera, Ehr., in which nervous filaments are always distinctly traceable, either radiating from an oral ring, or distributed, in a parallel longitudinal direction, according to the form of the body. These different conditions of the nervous system are accompanied with corresponding- modifications of the muscular, digestive, and vascular systems, and a negative character, ap- plicable to the higher division of Cuvier's Radiata, may be derived from the generative system. With respect to the muscular system, we find that although all the Acriia 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 planaria?, and parasitic trematoda, and also in the echinorhynchi, in some species of which genus the cutaneous canals form a rich net- work.* In the acalephae the condition of the vascular system is equally simple with that of the lowest Acrita, as is exemplified in the mar- ginal reticulate canals in the disk of the rhizos- toma. In the Nematoneura, on the contrary, those classes which manifest a circulating sys- tem distinct from the digestive tube, as the echinoderma and rotifera, possess vessels with proper parietes, distinguishable into arteries and veins. No Nematoneurous class presents an example of generation by spontaneous fision or gem- mation, but these modes of reproduction are common in the Acrite division. The planariffi among the sterelmintha are capable of indefinite multiplication by simple division; and the medusa? 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 acalepha ; and thus constituted it may be characterized as follows. Sub-kingdom Acrita. — G elatinous polymor- phous animals, without distinct nervous fibre, or visceral cavities. Alimentary canal excavated 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 * Rudolphi terras one species echinsrhynchus vasculosis, 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. That, again, in tracing the successive complica- tion of the sterelmintha from the hydatid to the echinorhynchus we also come to perceive traces of longitudinal nervous filaments in the latter highly organized genus of parenchymatous worms. In the acalephse 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- sidffi 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 planariee, 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 absoip- tione externa vel interna semper sistit. Anus nullus. " Reproductio fissipara vel gemmipara, gemmis modo exteris, modo internis, interdum acervatis. " Pleraque ex individuis pluribus semper cohae- rentibus animalia composita sistunt." — Horae Ento- 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 tamia? 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 themollusca ; in the fleshy living mass which suirounds 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, ffrom ad-ha'rere, Lat. adhesio, Ti.adherence,GeTm.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-ce! hilar. 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- * Macleuy, 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." Erom 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, imperforations 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. 50 ADHESION. a certain epoch of embryo life, imperforate. These organic states, which nosologists have so often considered as diseases, are, therefore, simply primitive conditions preserved by ano- maly, and become permanent instead of tran- sient.* It may, therefore, be inferred that the greater number of cases adduced as evidence of adhesion in intra-uterine life are not in point, and if they were it may still be asserted, and the assertion be borne out by analogy, that they had not occurred in the absence of inflammation. John Hunter seems to have had the idea that adhesion may occur in the absence of inflam- mation in certain cases, namely, in those where blood has been effused, that this blood may become organized and form a bond of union. He says, " It does not seem necessary that both surfaces, which are to be united, should be in a state of inflammation for the purpose of effecting an union ; it appears only necessary that one should be in such a state, which is to furnish the materials, viz. to throw out the coagulating lymph, and the opposite unin- flamed surface accepts simply of the union ; nor is it even necessary that either surface should be in a state of inflammation to admit of union : we often find adhesions of parts which can hardly be called inflamed. "f I believe that no solution of continuity can be obliterated in the absence of inflammation, the injury which has occasioned the solution of continuity, and the effusion of blood, being sufficient to excite inflammation. The only circumstance under which it seems to me to be possible that union could be produced in the absence of inflammation, is one which can only rarely occur ; and even then, although the possibility of the occurrence can hardly be denied, its reality may be reasonably ques- tioned. If a portion of blood, for instance, be effused into a serous cavity, its colouring matter is, after a time, removed, and a fibrino- albummous coagulum remains. This coagulum coming in contact with a previously uninflamed serous membrane, may become united to this membrane : and it is believed by some pa- thologists that this union occurs without the supervention of inflammation. Another si- tuation where it is believed by certain patho- logists that union is produced by similar means, is in a portion of artery included be- tween two ligatures, the blood which has been included between the two points undergoing a similar change to that which I have already described, and adhesion of the clot to the in- ternal tunic of the artery being effected in the absence of inflammation. Such cases may carry conviction to the mind of a superficial observer, but a more careful in- vestigation will lead to an opposite conclusion. My own observations induce me to think, that of all the causes by which adhesive inflam- mation of serous membranes maybe produced, the most remarkable perhaps is an extravasation * Isid. Geoff. St. Hilaire, Hist, des Anomalies de l'Oreanization, t. i. p. 532. t On the Blood and [nflam. Ed. 1828, p. 319. of blood into their cavities, which appears to excite just the precise quantity of inflammation necessary for the production of adhesion. If we examine the point at which such coagula are maintained in contact with serous mem- branes, before perfect union is established, we shall find between the coagulum and the mem- branes a stratum of exhaled matter, the exist- ence of which would lead to the conclusion that the clot has excited in the membrane as much inflammation as is necessary for the pro- duction of such exhalation. In solutions of continuity where blood has been effused between the edges, it was main- tained by John Hunter* that this blood was the provisional bond of union ; this, I appre- hend, is not the case. Whether protected from the atmospheric air, which appears to exercise a very decided influence in decomposing it, as in some fractures, or directly exposed to it, as in ordinary solutions of continuity, this coagu- lum never, during the early periods, adheres with sufficient firmness to attach to each other the borders of a wound If, however, any por- tion of the coagulum remain after a fibrino- albuminous exhalation has been formed upon the divided surfaces, it may become in this way organised, and permanently adherent. After the preceding remarks, it will therefore be held in this article that whenever an adhe- sion has been effected between two surfaces, naturally or artificially separated, that that adhesion must have taken place through the in- tervention of inflammation ; that inflammation arrived at a certain height will be accompanied by afibrino-albuminous exhalation ;— that if the inflammation be carried beyond that point, a purulent secretion may be established, and when this is developed, union, by what is termed the first intention, cannot occur ; granu- lations are then developed, and union by what is termed the second intention, may follow. The process by which each kind of union is effected I shall now proceed to describe in de- tail. In all cases, whether two naturally separate tissues are to be united, or whether a solution of continuity is to be repaired, there appears to be a certain uniformity in the means by which the union is accomplished. Inflammation is developed, and a material susceptible of or- ganization is exhaled, which becomes the con- necting medium. This matter in its greatest state of simplicity is exuded under the form of lymph, upon the surface of the parts to be united ; it is coagulated, and transformed into a soft pulp ; it gradually increases in density, acquires a reticular or porous aspect, a first rudiment of organization, and as a second de- gree exhibits in its substance red spots, then striae, which have the appearance of vascular ramifications, and at last bloodvessels. It is hardly possible to collect this lymph in a state of purity except in the canal of an artery where it has been exhaled between two ligatures. It is then presented under the form of a whitish matter, of a soft and fibrinous consistence, which * Loc. cit. p. 253. ADHESION. 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 hours after we have irritated a serous membrane, the pleura of a dog, or of a rabbit for instance, that this membrane is much injected, and that there has been formed upon its surface an extremely thin, pulpy stratum, which may very easily be removed : the second period commences when this exudation has assumed a membraniform appearance, and is characterized by an aug- mentation of thickness and of density : the third period is characterised by still greater density and the presence of vessels. Stoll believed that these membranes might become organised in twelve, nine, or even eight days after the inva- sion of the disease. Home believed that vessels might appear in twenty-four hours. In the fourth period, the membrane loses some of its thickness, and every day assumes more and more of the appearance of cellular tissue; and when perfected, there is not only identity of appearance between cellular tissue and these membranes, but also, according to Laennec,* identity of use, and even of disease, except that this tissue very rarely contains adi- pose mattei'.f Nothing in our subject is more curious or more important than the organisation of these membranes ; their vessels are thin, delicate, and similar to those of the pia mater ; their form and their direction are extremely simple ; they are not tortuous, and they proceed, usually, in fasciculi, almost like the lymphatics of the extremities. We may easily convince ourselves that their formation is sometimes very prompt, by the perusal of the following case. A por- tion of strangulated intestine, which, after the incision of the herniary sac, did not present many bloodvessels, was examined after the death of the individual, which occurred in twenty-nine hours after the operation, by Sir Everard Home : he found the portion of in- * De 1' Auscultation Mediate, torn. ii. p. 293. t Laennec states that he has " quelquefois " seen fat developed in these cellular laminae. Loc. cit. — Ed. testine which had been strangulated profoundly inflamed, and covered in many points by a " layer of coagulable lymph : " this intestine was injected with very fine size, and two small bloodvessels were found passing along through the new membrane into which the injection had penetrated. According to Laennec* we may observe the following phases in the organisation of these membranes. The rudiments of bloodvessels are at first presented under the form of striae of blood, which are more voluminous than the vessels by which they are to be succeeded. The blood appears to have penetrated into the tissue of the membrane, as if pushed by a strong injection; yet in examining the points of the membrane,on which the layer of" coagulable lymph" is depo- sited, we find no destruction, nor any orifice of a vessel, but only spots of blood. Soon, ac- cording to Laennec, " these lines of blood take a cylindrical form, and ramify in the manner of bloodvessels, still preserving a considerable diameter. If, at this epoch, we carefully ex- amine them, we find that these vessels have an external coat which is soft, and formed of blood scarcely concrete, to which they owe their colour. After having incised this coat, we withdraw a sort of mould, or rounded fasci- cular body, whitish and fibrous, evidently formed of concrete fibrine, and of which the centre appears perforated and permeable to the blood. 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, Monro, Soemmering, do not speak of this mode of development. Hunter and Home explain it differently; they say there is at first a formation of small ampullae, containing only a colourless fluid: second, a union of these ampullae, and production of a vascular net- work, not yet supplied with blood : third, an inosculation between the newly developed vessels, and those of the inflamed membrane and next the ingress of blood. Beclard was of the same opinion.^ 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, beino- 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. Generate, p. 195. t Hist. Anat. des Inflam. torn. ii. 6 1303. and 1571. £ 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 prolonged : ulterior observations, however, have shewn that these media are really or- ganised. We have no general rules as to the time when such organisation shall commence. It seems to be dependent upon inexplicable individual dispositions. It may, however, be remarked, that the greatest analogy exists be- tween the mode of development of vessels in these media of adhesion and their mode of production in the membrane of the yolk in the chick, saving always this remarkable circum- stance, namely, the inconstancy, the irregu- larity of the work of organisation in the former, and, on the contrary, the constancy and the regularity of the occurrence in the latter case. These media are in fact secreted by a tissue, the vitality of which is exalted to a certain extent, and it appears to impress upon the pro- duct of its secretion a commencement of vitality, as in generation. All these circumstances ap- pear to me to demonstrate that these vessels are the product of a spontaneous generation — a true epigenesis ; so indeed, to a certain extent, thought Hunter. He says, " In a vast number of instances I have observed, that in the sub- stance of the extravasation there were a great number of spots of red blood, so that it looked mottled. The same appearance was very ob- servable on the surface of separation between the old substance and the new, a good deal like petechial spots. Was this blood extra- vasated along with the coagulating lymph ? In this case I should rather have supposed it would have been more diffused. I have there- fore suspected parts have the power of making vessels, and red blood, independent of the circulation."* If the inflammation be not strictly confined to that state in which the albumino-fibrinous exhalation is accomplished, but proceeds to the next stage, the exhalation entirely changes character ; pus is produced, a granulating sur- face is developed, and union is accomplished by the intervention of another tissue, and by a slower process than that which we have already described. This is the process which is always observed in mucous membranes, scarcely ever in serous; for in the former, the albumino-fibri- nous matter never becomes organised, and can therefore never be the medium of a permanent union. In these membranes, if adhesion occur, the inflammation must proceed to the succeed- ing stage. Adhesion of mucous membranes, however, does not often occur — it is not com- patible with the performance of their functions. Soon after the secretion of pus is established granulations are developed, and a state favour- able to adhesion is produced. The develop- ment of granulations occurs in the following manner : — upon the surface, about to suppurate, is exuded a layer of" coagulable lymph ;" this lymph becomes penetrated by bloodvessels, nerves, and absorbents, which give birth to granulations. These granulations are developed much earlier in some tissues than in others — in a stump, for instance, we see them first upon the cellular tissue, then upon the mus- cular, then the fibrous, and lastly upon the osseous tissue : they appear to form as much * Phil. Trans. 1818. pp. 172 and 185. * Loc. cit. pp. 388-9. ADHESION. 53 more readily as the tissue may be 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.* lie carefully observed the changes which occurred in an ulcer of the leg. By using a lens which enlarged objects eight times, he saw that granulations were formed in the fol- lowing manner : first, is seen a mass of capil- lary vessels differently arranged ; secondly, small sinuosities containing pus. The ulcer ob- served during ten minutes, offered, in the first place, an extremely thin and transparent pel- licle, under which were disengaged globules of gas, then canals having a horizontal direction, and containing blood. The tunics of these vessels were so delicate that they were ruptured by the simple motion of the leg. These canals anastomose with each other, taking different directions ; those which are developed the first were the next day changed into true vessels. Soon these new vessels have enough of solidity to admit of our passing a needle under them and raising without rupturing them. The forma- tion of all these parts is due, according to Home, to the coagulation of pus, and the de- velopment of carbonic acid gas ; " for if the puriform matter be wiped off, these phenomena are not produced." 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 more rapidly developed there, but because it much more frequently occurs there than in other tissues. If we examine the surfaces of two such mem- branes which have been recently united, com- mencing at a certain distance from the point of adhesion, we see the layer of coagulable matter effused between the two surfaces become thinner as we approach the point of contact. If the adhesion be sufficiently recent to admit of our separating the surfaces, we see the intermediate layer tearing, but remaining adherent to the inflamed surfaces. If the inflammation be more advanced, and the pseudo-membrane be more dense and organised, we find that the very thin layer of new deposition by which the union has place is more resistent than the thicker layer of org misable 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. hernise 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 hernias thus circumstanced have been described as having no hernial sac. This sac has, however, originally existed, but has disappeared by the adhesions which have been formed between it and the displaced organs, adhesions by which the cellular tissue which replaces the serous membrane has been deve- loped. If we consider these adhesions in relation to their frequency in the serous cavities, we see that they exist most frequently in the pleura, existing in nearly half the adult bodies ex- amined. After the pleura comes the perito- neum, then the pericardium ; those of the tunica vaginalis are less common, but the arachnoid is, of all serous membranes, especially relative to its extent, that where these adhesions are most unfrequent. The absence of mobility appears singularly to favour this phenomenon : thus in the pleura they most frequently occupy the superior parts, and in the peritoneum most frequently occur between the viscera forming a hernia, and be- tween the convex surface of the liver and the diaphragm. The membranes between which such adhe- sions occur, must usually, of course, be in intimate relation, the one with the other during the time when the process is in progress of accomplishment, though now and then the distance is considerable; but they may after- wards become separated to great distances : those cellular bands which are so commonly seen in the thorax are evidences of this fact. Some circumstances tend to demonstrate that these bands in serous structure may at a certain period of their existence be absorbed and disappear, and the secreting surface be reproduced. M. Ribes states that occasi- onally we do not find any trace of such bands, nor any adhesion in the peritoneum of persons who have had penetrating wounds of the ab- domen. Beclard examined an insane person who had several times stabbed himself in the abdomen. At the points where the more recent of these wounds had been inflicted considerable adhesions were found; beneath the older cicatrices no vestige of adhesion was found. A case of artificial anus occurred in the practice of M. Dupuytren, by which faecal matter passed during twelve days. The pa- tient died at the end of seven months. At the examination after death, it was found that the portion of intestine in which the accidental opening had existed, was distant from the ab- dominal cicatrix between four and five inches. A very attenuated cellular band extended from the cicatrix to the portion of intestine. Doubt- less a short time would have sufficed for the absorption of this band, when the intestine would have been set at liberty and the serous surface restored. In the course of lectures which Bichat de- livered only a few months before his death, he maintained that adhesion was never pro- duced between mucous surfaces, and that con- sequently the cavities lined by this tissue were never obliterated. Few statements have given rise to more extensive discussion than this ; few discussions have up to the present moment been attended by less satisfactory results. In his first dictum I believe he was clearly right, in the second as clearly wrong. Mr. Hunter's opinion was in accordance with that of Bichat : he says, " that in all the outlets of the body called mucous membranes, the order of inflammation differs from that which occurs in cellular membrane, or in cir- cumscribed cavities. In these latter adhesive inflammation is immediately admitted to ex- clude, if possible, suppuration." In internal canals, where adhesions would in most cases prove hurtful, the parts run immediately into the suppurative inflammation, the adhesive in- flammation being in common excluded.* Mucous membranes, when unchanged by disease, are not capable of becoming adherent the one to the other, and the reason of this is simple. 1 have already stated that no per- manent adhesion can occur in the living body without the intervention of a new tissue, which at a certain indefinite or undetermined period of its existence becomes organized. A pseudo-membrane of considerable extent may be thrown out upon an inflamed mucous surface; but this membrane, 1 apprehend, never becomes organised, and union between mucous surfaces cannot therefore be permanent unless some other agency be called into action. But, as soon as inflammation has destroyed the characters from which these membranes derive their name ; when the mucus, which like an inorganic layer appears to oppose itself so successfully against immediate contact, thereby preventing the organization of the effused mat- ter, no longer exists ; when the cellular element which forms the basis of this membrane is developed, then adhesion by means of the union of granular surfaces is effected with the greatest facility ; of this we have evidence in most of the mucous canals. It is not rare, for instance, to meet with complete obliteration of the vagina, of the cystic duct, and so on. It is stated very generally that the opinion of Bichat is entirely unfounded ; that inflam- mation of the vagina is followed by complete occlusion, without destruction or transforma- tion of the mucous membrane, and that similar effects may occur in the Fallopian tubes, the uterus, and other mucous canals. That these are produced is perfectly true, but never until the disorganization to which I have alluded has occurred. It is maintained triumphantly as a con- firmation of the opinion that no transformation occurs, that when these adhesions are sepa- rated, we have the healthy mucous membrane performing its functions as before. This, how- ever, is not the case ; the membrane is essen- tially different, and it is not without difficulty that we can overcome its tendency to enter into adhesion again. That a membrane is pro- duced, which performs functions analogous to * Loc. cit. p. 305. ADIPOCERE. 55 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- lermef and Guersent.J I have never seen this membrane present the slightest vestige of organization, nor have I ever found any one, with the exceptions I have named, who has, although, to my knowledge, they have been sought for during many years, by a number of the most competent observers of the present day. And as I believe the investigations of morbid phenomena are more accurately made at present than at any former period, I adhere to the opinion that organization of these mem- branes upon mucous surfaces never occurs ; and that union by " the first intention " can never occur in those canals which are invested by mucous membrane. But when the com- position of the mucous membrane becomes destroyed or disorganized by inflammation, and a granular surface is presented, adhesion may be and is frequently produced. The epidermis with which the skin is fur- nished forms an inorganic stratum which is opposed to all adhesion ; but remove this epidermis, render the surface bleeding, or sup- purating, and adhesion may be produced with the greatest facility. It is against this ten- dency we have constantly to struggle for the purpose of preventing the adhesion of fingers to each other, to the palm of the hand, and so on, — so common a consequence of burns. Adhesion may in this tissue occur, therefore, by the development of the fibrino-albuminous medium, or by that of granulations. The synovial membrane of joints may become adherent, constituting a species of ankylosis, which is termed " false." In these cases the secretion of synovia diminishes and ultimately ceases, the contiguous surfaces lose their polish, become rugous, and contract adhesions. (See Joints.) In osseous tissues, adhesion may be effected either through the agency of the albumino - fibrinous exhalation already de- scribed, or that of granulations. (See Bone.) In cartilaginous tissues the mechanism of ad- * Rapport du Concours sur le Croup. t Diet, rles Sc. Med. torn, xxxii. p. 260. t Diet, de Med art. Croup. hesion is different; and in speaking of the process in these tissues, it is necessary to di- vide the tissue into those which are invested by a more or less dense fibrous perichondrium, and those which are without it. To the first appertain the cartilages of the ribs, of the larynx, and all those which Bichat termed fibro- cartilages. The second class comprehend the diarthrodial. It is in fact, I believe, upon the presence or absence of the perichondrium, that are dependent the principal differences which are presented in the pathological condition of these organs. The non-diarthrodial as well as the fibro-cartilages, when they are ruptured or divided, are not united by a cartilaginous substance. In the wounds of cartilages, with loss of substance, there is formed a kind of cellulous matter, which is a secretion from the perichon- drium ; in fact no phenomena of reproduction are observed where this membrane does not exist ; thus it is never observed in diarthrodial cartilages. We may cut and mutilate these latter, and after many days we shall find the wound almost as it was on the first day. When the cartilages of the ribs are ruptured, their union is often effected by an osseous ring which surrounds the two fragments. See the articles Artery, Encephalon, Nerve, Fi- brous tissue, Muscle, Vein, for the pheno- mena of adhesion in these structures. BIBLIOGRAPHY. — Freeke, on the art of healing, cicatrising, incarning, &c. 8vo. Lond. 1748. Bezoet, De modo quo natura soliitum redintegrat. 4to. Lugd. Batav. 1763. (Rec. in Sandifort Thes. Diss, vol. iii. p. 147.) Spallanzuni, Prodromo, &c. sopra la reproduzione animali, 4to. Modena, 1768. Ejus, Opuscoli de fisica, &c. 2 vol. 8vo. Modeua. 1776. Eyting, De consolidatione vulnerum. 4to. Argent. 1770. Moore, On the process of nature in the'rilling 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. Gotting. 1782. Murray, De redintegratione partium, &c. 8vo. Cassel, 1786. Bell, Discourses on wounds. 8vo. Edin. 1795—1812. Balfour, Obs. on Adhe- sion. 8vo. Lond. 1815. Stall, Ratio Medendi, pars v. & vii.8vo. Vienna, 1768. Hunter on the Blood, Inflammation, &c. Biclmt, Anatomie Gen. Beclard, ditto. Breschet, Diet, de Med. art. Adherence. Cruveilhier, Diet, de Med. et Chir. Prat. art. Adhesions. Laennec, De l'Auscultation Mediate, torn. ii. pp. Ill, et seq. Brande, in Phil. Trans. 1818. Gendrin, Hist. Anat. des In6. passim. 2 torn. Paris, 1826. Andral's Pathological Ana- tomy. Home on Ulcers. 8vo. Lond. 1801. C 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 Fourcroy's presence, had been full, and closed for fifteen years. When the coffins were opened, the bodies appeared shrunk and flattened, and the soft solids were converted intoabrittle 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, Clievreul, and some other emi- nent chemists, conceive that muscular fibre, skin, &c. is not convertible into adipocere, but that this compound results entirely from the fat originally present in the substance, and that the fibrin is completely destroyed by putrefaction. There are cases, however, in which the conversion of muscle and of fibrin into fat can scarcely be doubted, (Annals of Philosophy, xii. 41,) though the propriety of applying the term adipo- cere to such fatty matter may be questionable. The action of very dilute nitric acid upon some of the modifications of albumen is also attended by their conversion into an adipose substance. The chemical properties usually ascribed to adipocere are the following: it fuses at a tem- perature below 100°; it dissolves in boiling alcohol, and the greater portion is deposited as the solution cools; the action of ether resembles that of alcohol ; it is saponified by the fixed alkalies, but not by ammonia. It would ap- pear, however, from Chevreul's experiments, that adipocere is not a mere modification of fat, or a simple product, but that it is a soap composed of margaric acid and ammonia. These combinations of adipose substances and their further chemical history will be given under the article Fat. Bibliography. — Fourcroy ,Acad. Rle. des Sciences de Paris, 1787. Gibbes, Conversion of animal muscle into a substance resembling spermaceti. Phil. Trans. 1794. Conversion of animal sub- stances into fatty matter. Phil. Trail*;. 1795. Vide also'Annales de Chimie, t. v. 154 ; t. viii. 17 — 72 ; Crell's chemische Annalen for 1792 and 1794 ; and John's Tabcllen. 1. B. p. 35. ( W. T. Brunde.) * If a portion of the fatty degeneration of the liver he 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 subst ince. — R. B. T. ADIPOSE TISSUE. — fLat. Telaadiposa Fr. tissu adipeux, tissu graisseux, Germ, das Fttt, Ital. adipe. Many of the old anatomists, as Mondini, Berenger, Vesalius, and Spigelius, represent the fat (adeps vel pinguedo) of the animal body as entirely distinct from the membrana carnosa, or cellular membrane. The separate existence of a proper adipose membrane, however, si- tuate between the skin and the filamentous tissue, or membrana carnosa, was first taught by Malpighi, then distinctly maintained by De Bergen and Morgagni, and finally demon- strated by William Hunter. Collins, James Keill, and other anatomists adopted the views of Malpighi, and Haller was disposed latterly to imitate De Bergen and Morgagni, in assigning to the fat of the animal body a situation dis- tinct from that of the cellular membrane. And in this country the independent existence of the adipose membrane was recognized by Bromfield, John Hunter, and others. It was still, however, confounded with that of the filamentous tissue under the general name of cellular membrane, adipose mem- brane, and cellular fat, by Winslow, Dionis, Portal, Sabatier, Bichat, and Meckel, and described as a variety or modification of the cellular membrane; and Blumenbach considers it as a secretion into that membrane. Its dis- tinct existence from the cellular membrane was finally admitted by M. Beclard, and its anato- mical and physiological relations as well as its chemical properties have been since minutely investigated by M. Raspail. According to the dissections of De Bergen and Morgagni, the demonstrations of Hunter, and the observations of M. Beclard, the struc- ture of the adipose membrane consists of rounded packets or parcels ( 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 sacadi, 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- * Ostcologia Nova, Lond. 1691, and Obs. Nov. de Ossibus, Amst. 1731. ADIPOSE TISSUE. 57 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 slated in the following manner. First, the vesicles of the adipose membrane are closed all round, and, unlike the cellular tissue, they cannot be generally penetrated by fluids which are made to enter them. If the temperature of a portion of adipose membrane be raised by means of warm water to the liquefying point of the contents, they will remain un- moved so long as the structure of the vesicles is not injured by the heat. If again an adi- pose packet be exposed to a solar heat of 104° Fahrenheit, though the fat be completely lique- fied, not a drop will escape until the vesicles are divided or otherwise opened, when it ap- pears in abundance. The adipose matter, therefore, though fluid or semifluid in the living body, does not, like dropsical infiltra- tion, obey the impulse of gravity. Secondly, the adipose vesicles do not form, like cellular tissue, a continuous whole, but are simply in mutual contiguity. This arrangement is de- monstrated by actual inspection, but becomes more conspicuous in the case of dropsical effu- sions, when the filamentous tissue interposed between the adipose molecules is completely infiltrated while the latter are entirely unaf- fected. Thirdly, the anatomical situation of the adipose tissue is different from that of the filamentous tissue. The former is found, 1st, in a considerable layer extended immediately beneath the skin ; 2dly, in the trunk and ex- tremities round the large vessels and nerves ; 3dly, between the serous and muscular tissues of the heart ; 4thly, between the peritoneal folds which form the omentum and mesentery ; 5thly, round each kidney; and, Gthly, in cer- tain folds of the synovial membranes without the articular capsules. In each of these situations it varies in quan- tity and physical properties. In the least cor- pulent persons a portion of fat is deposited in the adipose membrane of the cheeks, orbits, palms of the hands, soles of the feet, pulp of the fingers and toes, flexures of the joints, round the kidney, beneath the cardiac serous membrane, and between the layers of the me- sentery and omentum. In the more corpulent, and chiefly in females, it is found not merely in these situations, but extended in a layer of some thickness, almost uniformly over the whole person; but is very abundant in the neck, breasts, belly, 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- guedo, 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 od 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 epiploic^) 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 58 ADIPOSE TISSUE. same distinct arrangement of an appropriate organ, but simply masses of adipose, or rather sebaceous matter, interposed between the at- tached surface of the serous membranes and the adjoining or the contained organs. Fat occurs in a third modification in the marrow of bones. The adipose granules, which are soft, whitish-yellow, and oleaginous, are here contained in a peculiar membrano-cellular web, forming numerous vesicles, which may be regarded as an ultra-osseous adipose tissue. It is a remarkable proof of the influence of the vital principle that during life the substance of the bones is never tinged with this animal oil, but the moment life is extinct, the marrow begins to transude and impart to the bones a yellow tint and a greasy aspect. Fat, though chiefly observed to occur in the bodies of animals, is nevertheless not confined solely to these bodies. Thus not only do va- rious kinds of oil and consistent oleaginous matter occur in certain vegetables, but sub- stances similar even to tallow are found in some vegetable productions. A sort of tallow is obtained from the vateria Indka, a forest-tree of the camphor family, indigenous in the Indian Archipelago. In a species of croton indigenous in China, namely, the croton sebiferum of Linnaeus, the stitlingia 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- * De Omento, Pingucdinc, ct Adiposis Ductibus, p. 41. rangement is that each individual grain or adipose particle is supported by its artery and vein as by a footstalk or peduncle, and those of the same packet are kept together not only by contact, but by the community of ramifications from the same vessel. These grains are so closely attached that Mascagni, who examined them with a good lens, compares them to a cluster of fish-spawn. Grutzmacher found much the same arrangement in the grains and vesicles of the marrow of bones.* It has been supposed that the adipose tissue receives nervous filaments; and Mascagni con- ceives he has demonstrated its lymphatics. Both points, however, are so problematical, that of neither of these tissues is the distribution known. The substance contained in these vesicles is entirely inorganic. Always solid in the dead body, it has been represented as being fluid during life, byWinslow, Haller, Portal, Bichat, and most authors on anatomy. The last writer, indeed, states that under the skin it is more consistent, and that in various living animals he never found it so fluid as is represented. The truth is that in the human body, and in most mammiferous animals during life, the fat is neither fluid nor semifluid. It is simply soft, yielding, and compressible, with a slight degree of transparency, or rather translucence. This is easily established by observing it during incisions through the adipose membrane, either in the human body or in the lower animals. The internal or sebaceous fat, however, espe- cially that interposed between the fat of the serous membranes, is much more consistent and solid. The reason of these differences will be understood from what is now to be stated re- garding the proximate principles of animal fat. The microscopical and atomical structure of fat has recently formed the subject of investi- gation by M. Raspail.f By placing a portion of lacerated fat upon a sieve, with an earthen vessel below it, and directing upon it a stream of water, numerous amylaceous granules are de- tached and pass through the sieve, and after 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. Baspail, when examined microscopically, these granules present forms and dimensions varying in different animals, in the same animal and even in animals of dif- ferent ages, but in all clearly resembling grains of fecula. In the human body these particles are polyhedral and not susceptible of isolation. As they are more fluid also than in other animals, it is necessary to immerse the portion subjected to examination in nitric acid or liquor potusscE, either of which has the effect of consolidating the inclosed or central portion * De 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 (area.^, sebum, sapo,j and elaine, (tXcuov, oleum.) The former is a solid substance, colourless, tasteless, and almost inodorous, soluble in alcohol, and pre- serving its solidity at a temperature of 176° Fahrenheit. Elaine, on the contrary, though colourless, or at most of a yellow tint, and lighter than water, is fluid at a temperature of from 63° to 65° Fahrenheit, and is greatly more soluble in alcohol. To the presence of stearine in a large proportion, the intra-serous sebaceous fat owes its solidity and firmness ; whereas the elasticity and softness of the sub- cutaneous adipose tissue, and the marrow, depend upon the predominance of elaine. It is farther important to attend to the ele- mentary composition of fat. Each variety of fat consists of carbon, hydrogen, and oxygen ; and a few, as hog's lard, blubber, nut oil, and almond oil, contain a small trace of azote. The proportion of the carbon is greatest and varies in general from 7-10ths to 4-5ths of the whole. The proportion of hydrogen varies from l-10th to l-5th. That of oxygen varies from four or five parts in the hundred to 12 and 13. It appears, therefore, that fat and each of its constituent principles are a highly carbonaceous animal substance. Little doubt can be entertained that animal fat is the result of a process of secretion. But it is no easy matter to determine the mode in which this is effected. Previous to the time of Malpighi it was a very general opinion that the blood exuding from the vessels was con- verted into adipose matter. This fancy was refuted by Malpighi, who, departing, however, from strict observation, imagined a set of ducts, (ductus adiposi) issuing from glands, in which he conceived the fat to be elaborated and pre- pared. To this fancy he appears to have been led by his study of the lymphatic glands, and inability to comprehend how the process of secretion could be accomplished by arteries only. The doctrine, though embraced by Perrault, Collins, and Hartsoecher, was over- thrown by the strong arguments which Ruysch deduced from his injections; and Malpighi afterwards acknowledged its weakness and re- nounced it. In short, neither the glands nor the ducts of the adipose membrane have ever been seen, unless we admit the testimony of the Members of the Parisian Academy, who state that they saw them in the civet cat, and to this we must oppose the fact that Morgagni, by anatomical evidence, disproved their ex- istence. Winslow, though willing to adopt the notion of Malpighi, admits, nevertheless, that the particular organ, by which the fat is sepa- rated from the blood, is unknown. Haller, on the contrary, aware of the permeability of the arteries, and inferring from the phenomena of injections either of watery liquors or melted tallow, their direct communication with the cells of the adipose tissue, and trusting to the testimony of Malpighi, Ruysch, Glisson, and Morgagni, that fat exists in the arterial blood, saw no difficulty in the doctrine of secretion, or rather of a process of separation ; and upon much the same grounds is this opinion adopted by Portal. Bichat, again, contends that no fat can be recognized in the arterial blood, and justly adduces the fact, that none can be dis- tinguished in blood drawn from the temporal artery. To the accuracy of this fact I can bear direct testimony, having repeatedly ex- amined with the view of recognizing the buffy coat, and detecting oily particles, blood, which I had drawn from this vessel, — the latter sub- stance invariably without success. In wounds in the human body during life, and living animals, oily particles may be seen floating on the surface of the blood ; but these, it may be said, proceed from the division of the adipose vesicles ; and hence it has been inferred that the arterial blood contains no adipose or olea- ginous matter. It may be doubted, however, whether facts of this kind are adequate to prove whether adipose or oily matter does not naturally exist in the blood, and both from the experiments of Chevreul, and those of Lecanu and Boudet it appears that small quantities of adipose or punloid matter may be obtained from this fluid. M. Chevreul, for example, shows that fatty matter may be obtained from the fibrine of arterial blood ; and from a series of elabo- rate and accurate experiments, estimates the quantity of fatty matter in fibrine at from four to five per cent.* Lecanu and Boudet have also recently shown that crystals of pearly- coloured matter having the characters of an adipose substance exist in, and may be ob- tained in small proportion from the serum of the blood. f These inferences apply, according to the authors, to blood in its healthy state. In certain states of the system the blood drawn from the veins has presented serum of an opaque or milky appearance, and which has been proved to depend on the presence of adipose or oleaginous matter. Thus, indepen- dent of opaque or milky serum noticed by * Journal de Physiol, torn. iv. p. 119. t Journal de Pharmacie, 1830-33. 60 ADIPOSE TISSUE. Schenke, Tulpius, Morgagni, and others, Hewson and several cotemporary observers remarked instances of opacity and milkiness of the serum of the blood, and from ocular inspection as well as experiment and obser- vation, inferred that these appearances arose from the presence of oil in the blood or its serum. Soon after Dr. Gregory, in his Con- spectus, or View of the Institutions of Medicine, was led to infer apparently from the fact stated by Hewson, that in persons in whom the serum was opaque or milky, this depends on the presence of fat which is undergoing ab- sorption, or resumption into the system. This representation, however, w;as entirely conjec- tural ; and no direct proof of the fact that oil does exist in certain states in the venous blood was given till Dr. Traill, in 1821 and 1823, furnished accurate chemical evidence on the point. The inferences of Dr. Traill have been since confirmed by the experiments of Dr. Christison, who found that milky serum con- tains oleaginous or adipose matter, consisting of the two adipose principles elaine and stearine.* The general conclusions, therefore, that may be deduced from the facts now stated are that in the healthy state adipose matter in small proportion exists in the fibrine of the blood, and in a still smaller portion in the serum ; and that in certain morbid conditions of the system, in which there is any process of mis- nutntion or parutrophia, oily matter in con- siderable quantity may be found in the blood, either in consequence of absorption or non- deposition. To account, however, for the secretion of adipose matter, it is not absolutely requisite to prove that oleaginous or adipose matter exists in the circulating fluid. Even were it ascer- tained that oil or adipose matter does not exist, or cannot be detected in any of the elements of healthy blood, the fact would not form a stronger argument against its formation from that fluid, than in the case of several other principles which enter into the composition of the animal tissues, and which nevertheless do not exist in the blood. Thus neither gela- tine, which exists abundantly in skin, tendon, cartilage, ligament, and bone, — nor osmazome, which is found in muscle, are contained in healthy blood. But we know that the chemical element of these substances exist in the blood, and we farther know that gelatine consists very nearly of the same chemical elements as albu- men ; and we must infer, therefore, that it is the faculty of the living tissues or vessels to arrange these elements in that manner and proportion in which they may constitute re- spectively gelatine and osmazome. The same reasoning may be applied to explain the for- mation of fat in the adipose tissue. Its ele- ments already exist in the blood, and the living- agency of the tissue seems all that is requisite to effect its deposition. Its composition and history would also show that it is a secreted product which consists of superfluous chemical * Edin. Med. and Surg. Journal, vol. xxxiii. p. 274. elements not required in the formation of the albuminous and gelatinous tissues. On this subject the interesting experiments of Berard* and Dobereinerf may, perhaps, fur- nish some intelligible means of illustration. The former chemist found that by mixing one measure of carbonic acid, ten measures of carburetted hydrogen, and twenty of hydrogen, and transmitting the mixture through a red-hot tube, he procured artificially several white crystals which were insoluble in water, soluble in alcohol, and fusible by heat into an oily fluid. The latter chemist prepared a similar substance from a mixture of coal-gas and aque- ous vapour. It may therefore be inferred that while ani- mal fat is chiefly a combination of bicarbonated hydrogen with oxygen, or, in other words, a highly carburetted hydrate of oxygen, and con- tains either little or no azote, it is the animal substance which makes the nearest approach in chemical constitution to the vegetable prin- ciples. So close, indeed, is this approxima- tion that Raspail thinks it may be in this re- pect compared with starch ; and as the different forms of fecula are prepared by the vegetable tissues for the nutritious stores of the vegetable during the process of development, he ob- serves that, in like manner, fat is deposited whenever the nutritious function is in excess in the animal organs. It was a singular fancy of Fourcroy that the deposition of fat in animal bodies was in- tended as a sort of vent for the superfluous and unnecessary proportion of hydrogen, since the idea is at variance with chemical facts ; and it is not less singular that such a hypothesis should receive any countenance from Blumen- baeh. Carbon is the principle which predo- minates most largely in fat ; and if any atten- tion is to be given to such views, the adipose tissue ought to be regarded as the outlet for superfluous carbonaceous matter, or at least carbonaceous matter in a much larger pro- portion than hydrogen and oxygen. The pro- per physiological view, however, of this ques- tion appears to be, — that as the tissues of tlie animal body consist chiefly of carbon, hy- drogen, oxygen, and azote united in variable proportions, and as most of these tissues either contain or seem to require azote, the adipose appears to be destined to receive whatever carbon, hydrogen, and oxygen, are not re- quired to be united with the azote, in the forma- tion of the albuminous, the gelatinous, or the albumino-gelatinous tissues. On the mechanism of the deposition of fat we possess no exact information. But various facts may tend to throw some light on the cir- cumstances under which it takes place, and the history of the state of the adipose tissue at different periods of life is instructive. In the foetus the adipose tissue contains a sort of whitish, solid, granular matter, which resembles adipocere rather than genuine fat. * Ann. de Chimie, 1817, t. v. p. 290. t Zur Pneumadschen Phytocliemie, 8vo. Jena. 1822. ADIPOSE TISSUE. 61 Thus it is less oleaginous, and more brittle and friable than true fat. In the infant this layer continues the same in quantity, but a little more oleaginous, till the period at which the individual begins to exert the muscles of loco- motion. The fat then rapidly diminishes in quantity, and after the child has begun to walk and run, the fat has almost entirely dis- appeared from most parts of the adipose tissue, except the orbits, cheeks, neck, buttocks and the flexures of the joints ; but even in these regions it is much less abundant and much more consistent. The marrow presents similar changes. The bones of the foetus are void of a distinct me- dullary canal, and present merely a reddish, homogeneous, vascular pulp, somewhat con- sistent, but presenting soft compressible por- tions. This state continues some time after birth. As the individual passes from infancy to childhood, the interior of the bone is formed into cuncelli, adipose or oleaginous matter is deposited in the intra-osseous tissue within the cancelli, and as the vessels of the medullary membrane gradually mould the medullary canal, this oleaginous matter is most abun- dantly deposited in the interior of the cylin- drical bones. The marrow, however, is much less oleaginous, and more like a pulpy paste than it is in the adult. During the periods of boyhood and youth fat continues very sparing in the adipose tissue, and especially in the male sex. After puberty, however, it becomes more abundant, especially in females. After this period the deposition of fat depends more or less on the habits of the individual, as to eating and drinking and corporeal exertion. In general the deposition of fat becomes more copious and general after the age of forty or forty-two than previously. From these several facts it appears to result that fat. is to be regarded as a secretion by the capillary vessels of the adipose tissue from the blood, and that the tissue and its vessels are to be distinguished from the fat or the matter secreted in the relation of vital agents and organic products. Upon the whole the idea of Ilaller as modified by Mascagni regarding the origin of the fat appears to be the most probable, viz. that, while the arteries secrete an imperfectly formed oily fluid, the thinner parts are absorbed either by lymphatics or by veins, and the residue is left in a more con- sistent and solid form. I think, in conclusion, that, taking all the circumstances already stated into consideration, it may be inferred that adipose matter, or its constituent elements exist in the blood, chiefly as complementary elements of the albuminous, gelatinous, osmazomatous, or gelatino-albu- minous principles employed in the nutrition of the several tissues ; and that, as the carbon, hydrogen, oxygen, and azote are employed in the formation of the latter tissues, the great excess of carbon, and the smaller excess of hy- drogen and oxygen, not employed in the for- mation of these tissues are arranged by the capillaries in such proportions as to form adi- pose matter ; and that this adipose matter, though fluid, when first formed, becomes more consistent and fixed after deposition in its appropriate tissues. The pathological conditions of the adipose tissue. 1. Inflammation.- — From various facts, and especially, observing the phenomena of certain cases of what have beeu denominated diffuse inflammation of the cellular membrane, 1 for- merly inferred that the peculiar phenomena of certain intense and malignant forms of this disorder, depend on inflammation not of the cellular membrane, but of the adipose tissue. This conjecture I have since had opportunities of completely verifying as to certain, if not the majority of cases of diffuse inflammation. a. In cases of diffuse inflammation affecting the arm, the inflammation has spread along the adipose membrane, producing sero-puru- lent suppuration and sloughs of the adipose tissue. In cases of inflammation at the verge of the anus, the disease spreads along in the same manner, and affects, almost exclusively, the adipose tissue around the anus and rectum, and along the glutai muscles. It is in the same manner that the adipose cushion, with which the bloodvessels are surrounded, is oc- casionally the seat of a species of bad inflam- matory action terminating in fetid and sloughy suppuration. That these forms of diffuse inflammation truly depend on inflammation of the adipose membrane, I must further maintain, from the fact that the disease occurs not only in the ex- ternal adipose cushion, but in the internal or sebaceous fat. I have seen an example of in- flammation in the adipose cushion surrounding the left kidney, in which the whole of this substance was converted into an ash-coloured, fetid, semifluid pulp, mixed with shreddy fila- ments, and in which this suppurative slough- ing process had opened a passage from the fat of the left kidney into the interior of the trans- verse arch of the colon. The instance of in- flammation and subsequent mortification of the adipose membrane surrounding both kidneys, detailed by Dr. Thomas Turner, in the fourth volume of the Transactions of the College of Physicians in London, is an example of the same species of disease. In the case witnessed by my- self, the disease gave rise to the usual symptoms said to attend diffuse inflammation. Though no great degree of pain was felt, the pulse was quick and small, the tongue brown and dry, the countenance dingy and lurid, and the eyes heavy, the bowels difficult to be affected by medicine, the urine scanty and high-coloured, and at length suppressed ; and the patient, after muttering delirium and ti/phomunia on the second day of the attack, with subsultus tendi- nurn, passed into a comatose state, which ter- minated on the fourth day in death. b> This doctrine further does not rest upon evidence deduced from the mere symptomatic characters of the disorder. In fatal instances of diffuse inflammation, we find the adipose membrane not only partially mortified and suppurated, but that part of it adjoining to the skin and to the bloodvessels very much loaded, 62 ADIPOSE TISSUE. with injected vessels containing dark-coloured blood. c. It is chiefly in the corpulent, either by habit or by age, that this disease assumes its most exquisite, intense, and unmanageable forms. In persons of this description, who it is matter of common observation are generally not only plethoric but bloated, and liable to imperfect circulation, and disorders of the cir- culation and secretions generally, and in whom very slight causes often induce serious disor- ders, the adipose tissue appears to lose a great proportion of the small degree of vital energy which it possesses, and the more abundant its secreted product is, the less active are its vessels and the inherent properties of the membrane. In consequence of this greatly impaired energy, slight causes, as cold, injury, punctures, &c. produce suddenly a complete loss of circula- tion and action in the tissue ; for it is not in- creased but diminished action ; and this im- paired energy continues, until the natural func- tions of the tissue become extinct. It is thus that the secreted or inorganic matter of the adipose tissue becomes, as it were, a cause of strangulation of the tissue itself, or at least leads so directly to suppress the energies of its organic part, that it is incapable of resisting morbific agents of ordinary power, and hence the organic part either may be smitten with immediate death or is very easily made to assume a very low and imperfect form of mor- bid action, which speedily terminates in death. On this subject it is further proper to ob- serve that Mr. Bromfield, surgeon to St. George's Hospital, who sixty years ago main- tained the distinct characters and situation of the adipose membrane from the cellular, taught also that the former was liable to inflammation, but erroneously imagined that this inflamma- tion was of the circumscribed kind only.* 2. Hemorrhage. — Effusion of blood into the adipose tissue is not very common. It is ob- served in the same circumstances nearly in which it occurs in the filamentous tissue. Thus it has been seen in land and sea-scurvy. Hux- ham observed it in fevers with petechial erup- tions. And Cleghorn states that one of the appearances after death in the continuous and malignant tertians of Minorca was extravasa- tion of blood in the form of black patches in the adipose layer of the mesentery, omentum, and colon. 3. Excessive deposition. — In certain subjects, and in peculiar circumstances, the quantity de- posited is enormous. The average weight of the human subject at a medium size is about 160 pounds, or between eleven and twelve stones. Yet instances are on record of its attaining, by deposition of fat in the adipose membrane, the extraordinary weight of 510 and 600 pounds, or from thirty-five to forty stones. Cheyne mentions a case in which the weight was 448 pounds, equal to thirty-two stones. In the Philosophical Transactions are recorded two cases of persons so corpulent, that one weighed 480 pounds and another 500 pounds. * Chirurgical Observations, vol. i. p. 94. And the Breslau Collections contain cases in which the human body weighed 580 and 600 pounds. In females and in eunuchs it is more abun- dant than in males ; in females deprived of the ovaries it is more abundant than in those pos- sessed of these organs ; and it is well known that sterility is frequent among the corpulent of both sexes. In some circumstances this accu- mulation may be so great as to constitute dis- ease, ( polysarcia udiposa of several nosolo- gists); and in other circumstances the deposi- tion of fat is a means which the secreting system seems to employ to relieve fulness and tension of the vessels, and if not to cure, at least to obviate morbid states of the circula- tion. (Parry.) Accumulations of fat are said to take place in some animals in a few hours in certain states of the atmosphere. During a fog of twenty-four hours continuance, thrushes, wheat-ears, ortolans, and red-breasts are report- ed to become so fat that they are unable to fly from the sportsman. (Bichat.) 4. Extreme diminution. — The diminution or disappearance of fat is much more frequent than its extraordinary abundance. This dimi- nution is said to depend on one or other of the following causes. 1st. Long abstinence, as in fasting, and the periodical sleep of dormant animals ; 2d, organic diseases, as consumption, cancer, disease of the liver, of the heart, ulce- ration of the intestines, &c. ; 3d, purulent col- lections or secretions ; 4th, leucophlegmatic and dropsical states ; 5th, gloomy and melan- choly thoughts or passions ; 6th, long and un- interrupted effort of the intellectual powers ; 7th, preternatural increase of the natural evacu- ations, as in cholera, diarrhoea, diabetes, fkc. mucous discharges, especially from the pulmo- nary and intestinal membranes, as in chronic catarrh, inflammation of the intestines, and dysentery ; 8th, long and intense heat, whether natural, as during hot summers, or artificial, as in furnaces, hot-houses, &c. ; 9th, running, riding, and every species of fatiguing exercise long-continued, as is exemplied in the case of grooms at Newmarket, Doncaster, &c. ; 10th, states of long disease, not organic; 11th, night- watching and want of sleep in general; 12th, immoderate use of spirituous liquors; 13th, habit of eating bitter and spiced or acid aliments. Yet even in these states the fat of the animal body is seldom entirely wasted. In several organic diseases, in which great emaciation takes place, a considerable quantity of fat is always found in the orbits behind the eyeball, round the substance of the heart, around the kidneys, in the colon, and in the mesentery and omentum. Thus one or both lungs may be extensively occupied by tubercles and indu- rated portions giving rise to the usual symptoms of pulmonary consumption terminating fatally, yet without removing the fat from the subcuta- neous layer of the chest and belly ; and in various organic affections of the brain espe- cially, a considerable quantity of fat is found, not only in the subcutaneous layer, but at the outer surface of the serous membranes. ADIPOSE TISSUE. 63 According to the observations of William Hunter, anasarcous dropsy is the only disease in which the fat of the adipose membrane is entirely consumed. " This disorder, when in- veterate, has that effect in such a degree, that we find the heart or mesentery in such subjects as free from fat as in the youngest children." This, however, is in some degree denied by Bichat, who contends that it is not uncommon to find much subcutaneous fat in subjects greatly infiltrated* It is obvious that much will depend on the stage of the disease. It cannot be expected that the moment serous infiltration appears in the filamentous tissue, all the fat should be at once removed from the adipose. The process of absorption is gradual as is that of deposition ; and the infe- rence of Hunter may be regarded as nearly exact in reference to long-continued, or what he terms inveterate dropsy. It is certain, that while it is very difficult to deprive the bones of ordinary subjects of oil, those of dropsical sub- jects are the only ones which it is possible to obtain free from this substance. In certain diseases, especially those the ter- mination of which is attended with serous effusion into the cavities of the serous mem- brane, the fat is partly absorbed or may be converted into a sort of sero-gelatinous fluid. In chronic dysentery, for example, the subcu- taneous fat and that of the heart and omentum, in a great measure disappear, while in their place we find effused an orange-yellow coloured sero-albuminous fluid, of a jelly-like aspect, which coagulates on the application of heat or the addition of re-agents. In the bodies of those, also, cut off by scirrhous disorganization or cancerous ulceration, the greater part of the fat is in like manner absorbed, and in its place appears a dirty orange-yellow coloured sero- albuminous fluid. The removal of the fat from its containing membrane is effected by the process of absorp- tion, the agents of which are supposed by William Hunter, Portal, Bichat, and Mascagni, to be the lympathics. According to the results of the experiments of Magendie, Mayer, Tiede- mann and Gmelin, Segalas and others, it must, in some measure at least, be ascribed to the in- fluence of minute veins. It is a point of some interest to know in what form it is absorbed, whether as oily matter, or after undergoing a process of decomposition The observation of Dr. Traill, above quoted, would lead to the former view; but it is not easy to conceive that this should be uniform. We want, in short, correct facts on the point at issue. 5. Adipose sarcoma. — This consists in an un- usual deposition of firm fatty matter in cells, the component fibres of which are sufficiently firm to give it consistence. The tumour, which is generally globular, is always surrounded by a thin capsule, formed by the condensation of the contiguous filamentous tissue. The tumour is supplied by a few bloodvessels, which pro- ceed from the capsule, but which form so slender an attachment that they are readily * Anat. Gen. vol. i, p. 57. broken, and the tumour is easily scooped from its seat. This sort of tumour occurs almost invariably in the adipose membrane, and seems to consist in a local hypertrophy of the part in which it is found. It may have a broad basis, but is often pendulous, or attached by a narrow neck or stalk. It is the most common form of sarcomatous tumour, and may occur in any part of the body in which there is adipose mem- brane, but is chiefly found on the front and back of the trunk, and not unfrequently on two places at the same time. 6. Steatoma. — In adipose sarcoma the adi- pose matter is deposited in cells, and the tumour derives a degree of firmness from the fibres with which it is thus traversed in every direction. In other instances, however, the adipose matter is deposited in a mass in the cavity of a spherical or spheroidal cyst, formed in the filamentous or adipose tissue ; and the tumour is soft and compressible, and seems to contain fluid or semifluid matter. When cut open it is found to contain a soft semifluid matter of the consistence of honey, but of oily or adipose properties. In such circumstances the inner surface of the cyst, or at least the vessels of this surface, are the agents which secrete the fatty matter. This tumour may occur either in the filamentous or the adipose tissue, but is to be regarded as an example of local deposition of adipose matter. It may appear in any region of the filamentous tissue, but is most frequent about that of the head and face. Small steatoms are not unfrequent in the eyelids and in the scalp. Larger ones are more frequent about the neck. 7. Lipoma. — This name was first applied by Littre to a wen or cyst, filled with soft matter, possessing the usual properties of ani- mal fat. The matter of steatom, according to this surgeon, is either not or imperfectly in- flammable, by reason of its degeneration or commixture with some other animal secretion. The propriety of this distinction has been de- nied by Louis and others, who maintain that these tumours differ in nothing, unless per- haps in degree. It has been favoured, never- theless, by Morgagni, and adopted by Plenck, Desault, Bichat, and various foreign surgeons, and is defended by Boyer, who represents the steatom as differing from lipoma in the matter being white, firm, and changed from its origi- nal character, and in possessing the tendency to degenerate into cancer. Plenck had previ- ously distinguished the lipoma by its being destitute of a cyst, a circumstance not required by Littre. Though thus admitted to differ, the anato- mical character, as given by Morgagni, and confirmed by Boyer, is in both nearly the same : a cyst, containing unchanged fat, or granular adipose matter, in cells formed by the original fibres of the adipose membrane, ac- cording to Morgagni, or those of the filamen- tous tissue, according to Boyer. At the base or stalk, in the case of pendulous steatom, the cells are compressed, but loose in the body of the tumour. This description, with the alleged cancerous 64 AGE. tendency, accords more with the characters of the adipose sarcoma than those of the genuine wen. Personal examination enables me to say, that, in the case of small steatoms of the scalp, eyelids, face, &c. no fibres of this kind are re- cognized ; and to such, if any distinction be adopted, the name of lipoma should be con- fined. In the case of such larger steatoms as 1 have seen in other regions of the body, though the contents are firmly connected together, and some filamentous threads may be seen here and there, or the tumour may even be separa- ble into masses, I have not been able to trace the distinct arrangement of cells, mentioned by Morgagni and fioyer. Weidmann mentions, that in one case the matter of steatom was a sort of liquefied fat, and in another firm and dense, and not divided into lobes or cells. The other forms of encysted tumours, distin- guished by the names of atheroma, (o.Sjjgwju.a, pulticula, ab aGa^a, pultis genus,) and meliceris (piXtxrig i;, met and cera, honey wax,) are to be viewed rather as varieties of the steatom than as generically different. The substance con- tained may differ in consistence, but is nearly the same in essential qualities. 8. Melanosis. — The adipose membrane is a frequent seat of this singular deposition. The black or melanose matter is found in the sub- cutaneous adipose membrane, and the subja- cent cellular tissue of the chest and belly ; it is not uncommon in the fat of the orbit ; it is very commonly seen in the adipose cushion on the forepart of the vertebral column, on that sur- rounding the kidneys, and in the fat of the anus and rectum ; it, is found in the anterior and posterior mediastinum ; and it is found be- tween the folds of the mesentery, of the meso- colon, and of the omentum. It is also found in the substance of the marrow of bones ; and, perhaps, in most cases in which the osseous system appears to be stained with the melanose deposite, the dark matter may be traced to the medullary particles, the situation of which it is found accurately to occupy. In all these situations it appears in various degrees of perfection, and in different forms. It may be disseminated in black or inky spots, through the adipose membrane ; it may be ac- cumulated in spherical or spheroidal masses of various size and shape ; or it may be found in the form of brown or ebon-coloured fluid or semifluid, enclosed in a cyst formed of the contiguous tissue, more or less condensed. The melanose matter is entirely destitute of organization, and is to be regarded as the result of a peculiar secretion. No vessels have been traced into it; and when bodies affected with this deposite are minutely injected, the vessels can be traced no farther than the enveloping cyst. (Bresehet.) It is also to be noticed that it is never deposited exactly in the site of orga- nic fibres, but always between them, and very generally in the precise situation of the adipose particles. These several circumstances show that the melanose disease consists not in a de- generation or conversion into another substance, but in the deposition of a new form of matter in the manner of a secretion. In what form the melanose substance is first deposited we have few accurate facts to enable us to form a judgment. Laennec is of opinion that it is first deposited in a solid form, and afterwards becomes fluid. The former he con- siders the stage of crudity, the latter that of softening (ramollisement.) Several facts, how- ever, would lead to the conclusion, that when first deposited it was fluid, and afterwards ac- quired consistence. Thus in several dissec- tions performed by Drs. Cullen and Carswell,* the matter of the small tumours, which are supposed to be of short duration, were found to be softest, and sometimes as fluid as cream. In like manner, in a case recorded by M. Chomel, in which the disease was found in the liver in the shape of large cysts, the melanose matter was more fluid in the centre than in the circumference of the cysts. Upon the whole, if the melanose deposite be, as is supposed, an inorganic secretion, the idea of its being poured forth from the vessels at first in a fluid or semi- fluid state is most probable, and most consis- tent with the usual phenomena and laws of animal processes. Bibliography. — Malpighi, de omento, pingue- dine, et adiposis ductibus. Op. Omn. fol. Lond. 1686. C. A. lie Bergen, Programma de Mem- brana Cellulosa in Haller Disp. Anat. Select, torn. iii. Haller, Eleme::ta Physiologiae, lib. i. sect. 4. W. Hunter, On Cellular Memb. in Med. Obs. and Inquiries, v.ii. p. 26. Bachiene, Diss, de Adipe humano, 4to. Ultraj. 1774. Janssen, Pin- guedinis Animalis consideratio. 8vo. L. B. 1784. Redhead, Diss, de Adipe. 8vo. Edinb. 1789. Vogel, Diss, sur la graisse. 8vo. Paris, 1806. Alhner, Diss. In. De pinguedine animali, 4to. Jena; 1823. Heusinger, System der Histologie. 8vo. Gruetz- macher, De Medulla Ossium. (Rec. in Haller. Disp, Anat. vol. vi.) Lorry, Sur la graisse (Mem. Soc. R. de Med. 1779. K'uhn, De pinguedine. 4to. Lips. 1825. Beclurd, Anatomie Generale, p. 156. Chevreul, Recherches Chimiques sur les corps gras d'origin animale, 8vo. Paris 1823; and Ma- gendie's Journ. de Phys. torn. iv. Baspail, in Repertoire Gen. d'Anat. torn. iii. et iv. et Nouveau Systeme de Chimie Organique, or Henderson's Translation. (David Cruigie.J AGE.' — (Lat. atas. Gr. nXtzia,. Germ. Alter. Fr. age. Ital. eta.) This word, in its most extended sense, may express any period of duration. In reference to the human body it is used to denote either the whole time occu- pied by this system in passing through its several stages from birth to decay, or, in a more limited signification, that particular por- tion of existence commonly designated old age. It is in the former of these meanings that we employ the prefix to the following arti- cle ; in other words, we propose to give an account of the organic and functional changes which the human system undergoes, from the commencement of extra-uterine life to the period of its dissolution by natural decay. The term of human existence has been va- riously divided, and in many instances with a view to adapt its divisions to certain fanciful notions respecting the power of num- * Trans. Med. Chir. Soc. Ediob. vol. i. p. 264. AGE. 65 bers; but the only rational principle on which we can distinguish certain definite periods, must be that of observing alterations in the condition of the whole body or of its several organs, and the correspondence which they bear to particular epochs. The old Aristo- telian division of human life into three stages, growth, maturity, and decline, is founded on this principle ; for, viewing man as a whole, the conditions in which he is an imperfect, a complete, or a declining member of his species, are well marked. But these conditions are capable of subdivision according to the changes which particular organs have undergone ; in other words, man, in the progress of his per- J'ectionnement, makes certain acquisitions in his structures and functions, and in his decline suffers certain losses and impairments ; the more striking of these additions to, or sub- tractions from his resources, suggest the well- known division of existence into infancy, boy- hood, puberty or adolescence, manhood, old age, and decrepitude. It is not our intention to discuss the subject of age by describing the characteristics of the stages last enumerated ; we think it better to take a view of the general revolutions which transpire in the human economy during growth, maturity, and decline, and under each of these heads to mention the changes which particular organs undergo in the course of time, without limiting ourselves to distinct stages, the determination of which must be, to a certain extent, arbitrary. The consideration of the alterations which take place in the body during its progress from infancy to manhood might very properly be preceded by some remarks on those ultimate processes which are essential to growth, viz. — nutrition, secretion and absorption ; but, for information upon this interesting subject, the limits prescribed to this article compel us to re- fer the reader to that upon nutrition, in which the processes alluded to will be viewed in rela- tion not only to the development, but also to the maintenance, and to the decay of the tissues. On comparing a young with an adult animal we are at first struck by the difference in bulk ; but immediately afterwards our attention is attracted by the difference in their respective capabilities of action, — a difference not merely proportionate to that of size. A closer ex- amination informs us, that in the infant many of the parts of the body are absolutely incomplete, as organs or instruments, and we proceed to in- vestigate whether this imperfection holds with all the organs or only with some of them ; and if the latter be the case, whether the parts thus existing only in a rudimentary state belong to a particular class. Now, the organs and func- tions of man, in common with those of other animals, are divided into those which he shares with organic beings in general, and those which distinguish him as an animal; the former subserving his own independent existence, the latter his existence in relation to external ob- jects of his consciousness ; these more or less subjected to the control of volition, those re- moved, under ordinary circumstances, from the VOL. I. government of this principle. Hence these two classes have been variously named organic and animal, nutritive and relative, automatic and voluntary ; and, as life is a term employed to designate the collective functions according to some physiologists, or the cause of them ac- cording to others, we have organic life and animal life, &c, &c. But the animal functions are truly supplemental ; they could not subsist but by virtue of the organic ; while, on the other hand, the latter are perfectly capable of a separate existence, as in the vegetable world, or in those conditions of animal life in which its characteristics are all but suspended, such as profound sleep and apoplexy. Yet, al- though the functions of relation are thus de- pendent on those of nutrition, it is evident, at a moment's glance, that the latter viewed col- lectively in an animal structure, would present an aspect altogether incomplete, and different from that which we notice in the system of a vegetable. In the one case they were obviously intended to act only for themselves and for one another ; in the other they have an ulterior object to fulfil, but for which they would not have been called into existence and opera- tion; this object is the production and support of the functions that constitute the animal. If we now look at the new-born infant in con- trast with the full-grown man, we at once per- ceive that the essential difference between them has reference to the life of relations ; in other words, the immaturity of the former is not de- termined by the state of the vegetative organs, which, as organs, are perfect, but by the unde- veloped conditions of the parts which are to receive impressions from, and to re-act upon surrounding objects. Thus, on the one hand, we observe that the food adapted to the little being is rapidly converted into chyle, that the blood, after undergoing its requisite changes, performs its circuit freely and effectively, and that the activity of the nutritive, secernent, and absorbent processes is evidenced by the quick increase of growth, and by the abundant fluids contained in the various tissues. But, on turning to the relative functions, we find the case altogether reversed ; sensation is dull, faint, and flitting ; voluntary motion scarcely ex- ceeds the amount necessary for obtaining nutri- ment from the parent ; while the demonstra- tions of intelligence are the very lowest com- patible with our belief in the possession of such a principle by the being in question. An examination of the organs devoted to these several actions leads to results in accordance with what we observe in the functions them- selves ; in the one class the organization is complete, in the other much remains to be accomplished. If the apparatus of digestion be inspected, the parts employed in deglutition, viz., the tongue, pharynx, and oesophagus, will be found fully formed ; in the stomach the parts required for accommodating the aliment during its stay and for mixing certain fluids with it, are properly developed ; no deficiency is observable in the structure of the liver and pancreas; and the chyliferous vessels are pervious, extensile, and perhaps contractile. If 66 AGE. we proceed to the organs of circulation, similar conditions are observable. In the heart the seve- ral cavities, valves, and fibrous arrangements are duly proportionate to each other, and possess such qualities of firmness, pliancy, distensibility and contractility as are required for receiving, expel- ling, agitating, and keeping in separate compart- ments the two different kinds of blood ; the arteries are found resistent enough to hold the blood within their calibres, and at the same time elastic enough to adapt themselves to the varying quantity of their contents, while the veins are found so organized both as to the muscularity of their coats, and to the perfection of their valves, as to be quite capable of con- veying the fluid back to the heart. Not less complete is the apparatus of respiration, whether we regard the development of the diaphragm, or the elasticity of the thorax, or the cellular and tubular arrangements in the lungs and their appendages. For affording the necessary conditions for the occurrence of those molecular motions which constitute deposition and absorption, and upon which secretion also depends, we find an infinite number of capillary tubes well formed for supplying the fluids from which new particles may be taken, and to which old ones may return, and so disposed as not to interfere with the action of any supposable chemical affinities. If we next direct our at- tention to the organs of the animal functions, an opposite set of facts will directly meet us. In the locomotive system, the bones are dis- covered imperfectly ossified, the muscles de- ficient in fibrin, and the tendons and ligaments in firmness and density. Of the organs of sensation it may be said, in general terms, that the mechanism employed in the application of the appropriate stimulus is, for the most part, incomplete, while a difference is also observa- ble in certain properties of the nervous sub- stance. From this view it might at first be con- cluded that, in order to trace the changes that ensue between the commencement of extra- uterine life and the attainment of maturity, we have only to look for them in the organs of the relative life. But the survey that we are about to take of the changes in question will show that the other class of organs are by no means exempt from alteration, although the changes are not those of development. They will be found to have reference to degree or amount of function rather than to capacity. The external characters of the infant just eliminated from the uterus at the full period of gestation are as follows: — the integuments are thin, tender, and covered with a white unctuous matter ; the nails just reach the ends of the fingers ; the trunk and limbs are round and plump ; and the articulations are in a state of flexion. The average weight of the body is about six or seven pounds ; the length varies from seventeen to twenty-one inches, sometimes falling short of or exceeding these limits. The point which lies midway between the two extremities is at the umbilicus. The dimensions of the head and of the abdomen are very large in proportion to the other cavities, and as compared with their own measurements in after periods of life. The pelvis looks con- tracted, the thorax flattened at its sides and prominent in front, and the lower extremities are less developed than the upper. A line drawn from the occiput to the chin measures five inches and three lines ; from the occiput to the forehead four inches and three lines ; and from the vertex to the base of the skull three inches and six lines. The circumference of the head, taken along the course of the median line, is from thirteen to fourteen inches ; but taken horizontally, and passing over the parietal protuberances, it seldom measures more than ten or eleven inches. The contrast between this general aspect and that of a full- grown man is too obvious to require any repre- sentation of it here. The characters of the interior will be best described and understood by examining ana- lytically the several apparatuses of the func- tions. Of the latter the most simple and primitive is assimilation, consisting of certain molecular motions which maintain, repair, and mould the organic tissues. We have already observed that the requisites for this function are perfect in the new-born infant ; a copious supply of the fluid from which the textural particles are to be elaborated, a ready ingress for this fluid, and a no less ready egress for that which receives the particles no longer required in the process. All that we know of the mechanism employed is a porous ex- tensile substance, varying in its chemical con- stitution according to the nature of the tissue. Porosity is resolvable into a collection of infinitely minute tubes, and the degree of porosity is, therefore, determined by the number of the tubes ; the extensibility depends on the composition of the tubes. The tissues of the infant are soft, they abound in fluids, and are more capable of imbibition or artificial injection than at later periods of life ; this being consequently possesses a complete me- chanism of nutrition. But this mechanism can be of little utility unless the nutrient fluid be supplied liberally, and after furnish- ing the atoms for the formation of the several textures give place to fresh supplies. These conditions are afforded by the arteries and veins. There is no period of human existence in which the processes of interstitial growth are so active as in infancy, whether they be instanced in the accretion of matter, in the change of composition, or in the modification of form. This fact is in harmony with the state of the capillary system just described, and it will be found to correspond no less with the relative construction of the arteries and veins. The function of the former of these is to convey the blood into the tissue, of the latter to take it away ; consequently in a part where the growth is most energetic, we might, a priori, expect that the former would be more numerous, capacious, and distensible. This is well known to be the case from actual observation, partly of the effects of artificial injection, and partly of AGE. 67 the phenomena of disease. An examination of the textural properties of the two sets of vessels leads to the same conclusion. Sir Clifton Wintringham, in his Experimental Enquiry, fully demonstrated that the venous coats in the young animal far exceed the arterial in density, and that, consequently, they are less subject to distension. When maturity is attained, the disproportion between the resistances of these vessels no longer exists. However well provided the infant may be with the mechanical apparatus of pores and vessels, these can be of no avail unless the fluid they contain possesses certain chemical properties. Now the blood in early extra- uterine life presents the same general characters as in more advanced periods ; but there is yet wanting a comparative analysis of this fluid at different ages.* Inferentially we can enter- tain no doubt that it is fully adapted to the purposes of nutrition, when we consider the conditions of the chylifactive and respiratory functions, and that, although the differences of its composition in early and in more mature periods have not been defined by experiment, they must bear a relation to the different de- grees of nutrition and secretion. The differ- ence, however, between the blood of the infant and that of the aged is perceptible to the senses, and will be noticed hereafter. Pursuing the channels of the blood to the heart, we find this organ, as stated above, complete in its functions. Its volume, how- ever, is large in proportion to the size of the body. Its parietes are less firm in texture, and of a paler colour than they afterwards become ; but their contractility is more active. The pulsations are from 120 to 140 in a minute. The large volume is in harmony with the quantity of the fluid, the comparative weakness of its parietes with the small extent to which their impulse requires to be propagated, and with the trifling resistance ; and the quick successions of its contractions furnish the fresh supplies of the nutriment required by the energy of growth. In the progressive develop- ment of this organ we notice that the bulk, although increasing so long as general growth continues, is proportionately smaller, a cir- cumstance that corresponds with the diminution of the circulating fluid ; the fibres become stronger and of a deeper hue, so that the contractions are more capable of propelling the blood through the greater extent which it has now to traverse, or, more strictly speaking, of communicating a shock to a greater column; but the pulsations are slower, agreeably to the- diminished requirements on the part of the capillary actions. We must not omit to ob- serve that at birth the parietes of the left ventricle scarcely exceed those of the right in thickness; but from this period an alteration * De Blainville states, on the authority of Fourcroy, that in infancy the albumen of the blood is more abundant, that the fibrin is softer and more gelatinous, and that the phosphates are in smaller proportion than in succeeding periods. Cours de Physiologie, t- P- 262. commences, and rapidly proceeds until the thickness of the latter is to that of the former as 1:4. This change corresponds with the closure of the foramen ovale, the obliteration of the ductus arteriosus, and the consequent execution of the systemic circulation by the left ventricle only. The relative capacities of the right and left cavities begin to alter soon after birth. From tables given by Meckel it appears that, while at birth the capacity of the former compared with that of the latter is as 1 : \\, at the age of 50 it is nearly 3:1.* The lungs at the moment of birth undergo a more remarkable alteration in their form, their texture, and their contents, than any other organ in the system ; but during infancy and childhood they present no appreciable change in their organization, although a change must be inferred from the increase of their function. In infancy there is a smaller con- sumption of oxygen ; and the power of gene- rating heat, a function so intimately connected with respiration, is inferior to that possessed in later periods. Much light has been thrown on this subject by the researches of Dr. Ed- wards ; and practical observations of the highest importance in the management of infants,, founded upon the facts which he has ascer- tained, are to be met with in his valuable work.f The inspirations and expirations are more frequent at this early period, although the chemical actions between the air and the blood are less considerable. This greater fre- quency is a necessary accommodation to the rapidity of the circulation. At puberty there- is a marked development of the organs of respiration; the volume of the lungs increases in conformity with the expansion of the thorax; while the greater determination of the blood to their vessels is indicated by the deeper hue of the parenchyma, by the liability to pulmo- nary hemorrhage, so characteristic of this period, and perhaps also by certain diseases which affect the nutrition of these organs. The corresponding activity of function is indi- cated by the increased power of calorification, the energy of muscular motion, and the exalta- tion of the cerebral actions ; functions well known to have a direct relation witli that of respiration ; while the establishment of the generative faculty appears to own a connexion, though somewhat more remote, with the pul- monary development. We pass from the system which imparts new properties to the blood to that which supplies it with nutriment. No imperfection is discoverable in the apparatus of digestion in the new-born infant ; every organ is com- plete as an organ, but passes through va- rious changes in adaptation on the one hand to the food that is supplied, and to the mode of receiving it, and on the other hand to the demands of the other parts of the body. The organs employed in conveying and modifying the chyle, viz. the lacteals and the mesenteric * Manuel d'Anat. t. ii. p. 284. + On the Influence of Physical Agents, &c. translated by 0rs. Hodgkin and Fisher. 68 AGE. glands, are in a state of high development, as indicated both by their size and by their tendency to disease. The stomach and duo- denum are fully formed, but the sensibility of their mucous membrane is adapted only to the milk, of the mother; any other kind of food has a greater or less tendency to produce irritation. This membrane is thick, extremely villous and vascular, and consequently of a rose-colour.* In young persons it assumes a milky or satin-like appearance; in the adult it becomes slightly ash-coloured, especially in the duodenum and in the commencement of the ileum ; in the old subject it is more de- cidedly ashy. Its whitish appearance, according to Aiidral,f is found either in very old persons or in younger subjects who have died of ma- rasmus. In the adult the small intestines, according to QrftlaJ; bear a proportion of eight to one as compared with the distance from the mouth to the anus ; in the infant the propor- tion is no less than twelve to one.§ The large intestines are longer with respect to the small intestines in the infant than in the adult; but their calibre is proportionally smaller. Ascending to the mouth we might be tempted to say that there is evidence of incompleteness in the ab- sence of teeth; but a moment's consideration assures us that the organs collected in this part are all eminently adapted to their function. The food is already prepared by the mother, and only needs to be extracted and conveyed into the pharynx ; actions which are perfectly achieved by the lips, cheeks, and tongue. When the period has arrived at which this food can no longer be furnished with safety to the mother, and when all the purposes are accomplished which were intended in this close connexion between the two beings — purposes in all probability of a moral as well as a physical character' — the infant is prepared for a more independent existence by the emer- gence of teeth. This event generally begins about the sixth or seventh month by the appear- ance of the two middle incisors in the lower jaw ; these are followed by the corresponding teeth in the upper jaw ; next are seen the lateral incisors below and above : the rest appear in the following order; — the first molars, the canines, and the second molars ; those of the lower jaw having generally the priority of emergence. The milk-teeth, as they are called, by the end of the seventh year have given way to the second and permanent series. For the different characters of the two sets, the order of their appearance, and other par- ticulars, we beg to refer the reader to the article Teeth. That the first series should be only temporary is a necessary provision, in conformity with the change in the conforma- tion of the maxillary bones which ensues at the same time. We must not leave the alimentary tract with- * Billard, Traite des Maladies des Enfans, &c. t Precis d'Anat. Pathol. ', | Lecons de Med. Leg. t. i. p. 62. § This statement is at variance with that of Meckel, who says that the small intestine is much shorter in the early period.-. Op. cit. t. iii. p. 424. out observing that the fibres of the stomach and intestines in infancy and childhood are, like those of the heart and other involuntary muscles, more irritable than in after life ; hence the contents of these viscera are propelled more rapidly, and the evacuations are more frequent; their tissue is also softer, and their colour more approaching to white. The liver undergoes a great change after birth both in form and in function. The pecu- liar circulation of which it formed so important an organ during fcetal life being abolished, the left lobe which nearly equalled the right in volume, is diminished to a third of its original size. But while the umbilical vein and the canalis venosus are obliterated, the vena porta? is developed, and the bilious secretion becomes the predominant function. Of the further changes which this organ experiences, we have very little knowledge, except that the whole bulk is greatly lessened, and that the colour of its parenchyma becomes darker, and that it is more subject to disease in after periods. Oc- casionally we meet with instances in which the fcetal proportions of the liver continue through life (Andral). The bile has not been carefully examined with reference to particular ages, but it is known to be less viscid and to contain a smaller quantity of its peculiar principles in infancy ; while its greater liability to con- cretions at more advanced periods indicates an alteration in its composition. The gall-blad- der, though small at birth, contains bile, green in colour and bitter in taste, and soon becomes enlarged. The spleen also increases in volume, but what alteration takes place in the progress to maturity, in its function, must, of course, be doubtful until the function itself be better understood. Probably its enlargement is con- nected with the distended condition of the venous system. Of the changes in the pan- creas and salivary glands, we know little more than that their texture increases in firmness. The lacteals, lymphatics, and their respective ganglions have a very marked development. It is to be regretted that no observations have as yet been made upon the composition of the chyle at different ages. There are doubtless many alterations corresponding to the varying activity of the digestive function, and to the kinds of aliment used at those periods. So much for the organs and functions which are concerned in augmenting or modifying the nutrient matter. Before proceeding to those of the relative life, we must allude to the organs of excretion. The kidneys at birth have not lost the traces of their lobular forma- tion, but these are soon effaced. The weight of these organs at birth is to that of the whole body as 1-80; in the adult 1-240. The me- dullary portion is more abundant than the corti- cal in early life. The supra-renal capsules soon be- gin to shrink from their fcetal size. The ureters are large, and the bladder has a more elongated form than in after periods ; it also occupies a higher situation above the pelvis. The func- tional qualities of these forms are not so well ascertained as the analogy of their organization to AGE. 69 that of inferior animals. The urine is retained a shorter time in the bladder ; it is more aqueous and less impregnated with saline and animal ingredients than in after life; there is also a particular deficiency of urea. Of the intes- tines we have already spoken ; their contents are copious but less feculent than they after- wards become. The perspiration affords a si- milar character to that of the other excrernenti- tious secretions, being more aqueous, less sa- line, and less odorous. On the whole it may be said that less activity is indicated in the egestivc than in the ingestive system. Of the defensive organs, or those which are exposed to surrounding agents, we may remark, in general terms, that although fully adequate to the demands of the infant under the circumstances of his existence, they acquire a development proportionate to his growing in- dependence of the care of others. The skin increases in firmness, and the epidermis in thick- ness ; the sebaceous follicles become larger and more numerous, and the hair is more abundant. There is a portion of the nervous system which we have every reason to consider more related with the functions which have been just reviewed, than with those of the animal life, and which might a pr-iori be expected to bear a corresponding ratio of developement. We allude to the ganglions; they appear to be fully formed at birth, but what changes they undergo between that period and maturity we do not profess to know. In old age their tissue is found hardened, shrunken, and of a greyish colour. (Bichat.) The changes that we have next to take notice of are of a totally different character from the foregoing. They consist not merely in augmentations of size, correspondent^ with the general increment of the body, or in modi- fications of organs according to the altered circumstances under which they have to act, but in processes essential to the completeness of certain organs. These are the parts em- ployed in locomotion, voice, sensation, and thought. We shall begin with the osseous system. Bones are not subservient to locomotion only ; they have, in some parts of the body, the important office of enclosing and defending from external injury the more delicate organs of the system. We shall find, therefore, that in the young animal, according as they fulfil the one office or the other, their development will differ. But whatever be the functions of the bones, they require, for the perfection of that function, three mechanical properties, — firm- ness, lightness, and tenacity. They must not admit of flexion, and, at the same time, the density of their substance must not render them cumbrous by weight, or brittle in texture. To present these three conditions, the organs in question consist of two principal ingredients, an animal matter and an earthy matter, most intimately interwoven ; the one preventing such vibrations as would occasion risks of fracture, the other affording the necessary strength in supporting weights, and in resisting the divellent tendencies of antagonist muscles. The pro- portion which these parts bear to each other varies with the ages of the human subject. Viewed as a part of the system devoted to the life of relations, bones are used as pillars of support, as levers in various attitudes and mo- tions, and as points d'appui to the muscles and tendons. On examining the constitution of these portions of the osseous system in the new-born infant, we find the quantity of cal- careous salts comparatively small, and even the animal substance softer than in later pe- riods, in consequence of the greater ratio of gelatine. In growth these proportions undergo a gradual alteration ; the gelatine is diminished, the cartilage becomes firmer, and both give way to the deposition of earthy particles : in the increase of density produced by this de- position consists the process of ossification. To particularize the incompleteness of the osseous system would require us to enter upon the anatomy of almost every bone in the body, an investigation incompatible with the limits of this article. Some idea of it may be obtained from the fact that all the epiphyses of the long bones, and the greater number of the apophyses are as yet but cartilaginous ; they derive their ossification, not from an extension of the pro- cess in the bones to which they are attached, but from ossific centres within their own spheres. In the tarsus the only bones in which ossification has commenced are the as- tragalus and os calcis. The carpus is entirely cartilaginous. The os innominatum of the pel- vis consists of three separate bones ; ossifica- tion has but just commenced in the descending ramus of the pubis, and the ascending part of the ischium ; and the consolidation of the pel- vis is not complete till after the thirteenth year. The long bones have no central medullary cavity in the early periods of intra-uterine life ; but in the foetus at its full term, the animal matter which occupied that space has begun to be absorbed, and the deposition of osseous matter takes place in the form of a cylindrical sheath, so that the canal exists at this period, though in an incomplete state. The medullary canal is analogous to the cells of the short and flat bones, and of the extremities of the long bones, which are also incomplete in infancy. The shape of the cylindrical bones is mani- festly different from that which they afterwards assume ; thus there is a much smaller dispro- portion between the diameters of the extremi- ties and that of the shaft ; the surface is less furrowed by sinuses or roughened by ridges; differences exactly corresponding to the imper- fect development of the muscles, which, when more bulky in their middle portions, require a larger space for their accommodation about the body of the bone, and when stronger in contraction, require attachments that will match them in firmness. The_osseous system is not complete till after the age of twenty. There is no part of the skeleton in which we have a more striking illustration of its gradual development than in the bones of the face and in the cranium. It is not till the seventh year that a separation begins to take place between the tables of the skull, that the frontal sinus begins 70 AGE. to open, that the nasal bones lengthen, that the cells of the malar and upper maxillary bones are enlarged, that in consequence of this ex- pansion of their cavities the outer lamina pro- jects, and that the lower jaw is elongated. The stationary condition of the tabula vitrea is conformable to the arrest in the increment of the brain ; the extension of the outer table to the increasing power and action of the muscles attached to it ; the development of the sinuses and cells to that of the voice and certain of the senses; and the projection of the jaws to the increased number of the teeth. But although these changes commence as early as the seventh year, they are not complete till the twenty-first, or even later. At this time the countenance becomes settled, not merely by the full deve- lopment of the muscles, which express the predominant emotions of the individual, but also by the complete adjustment of the bony arrangements just enumerated. Those portions of the osseous system which are employed in protecting the organs enclosed by them from external compression or injury, have attained a degree of growth far surpass- ing that of the bones devoted to locomotion and to the mechanism of sensation. The ribs, for instance, defending the lungs and the heart, and playing so important a part in respiration, are farther advanced in the ossific process than the bones of the extremities. But the most striking fact of this kind is presented in the spinal column. The annular portions of the vertebra which form the canal of the medulla spinalis, are found strongly ossified at birth, but the bodies of these bones, which are to be used hereafter in supporting the weight of the head and trunk, are very slightly expanded, and all but devoid of earthy particles, while the processes to which the muscles employed in the flexion and extension of the column after- wards contract attachments, are either only shaped in cartilage, or may be said to have no existence. Passing from the bones to the muscles, we observe the latter no less incomplete in infancy as it regards their physical characters ; they are pale, flabby, and easily torn ; they contain less fibrine than in after years; their contractility is weak though easily excited ; and the fasciculi and fibres are but loosely connected from the want of the fascia; and aponeuroses which brace them in later periods. As life advances, the fibres become redder, more distinct, and stronger. A readiness to contract is manifested very early, but it is not till maturity that these organs are able to maintain contraction for any length of time. They suffice well for the quick and buoyant motions of the lively child, but fail in those violent and prolonged exertions required by the labours of manhood. The form of the muscles changes materially in the progress of years ; thus, they swell out in the middle, and occasion a great difference in the proportions of the limbs. Those portions of the locomotive apparatus attached to the muscles and articulations, viz. the tendons and liga- ments, undergo corresponding changes. In infancy they are soft and gelatinous; gradually they become firmer, their gelatine acquires a more glutinous character, and the membrane which envelopes them ismore condensed. Every one knows the different products obtained by boiling the tendinous parts of young and adult animals ; in the one they have the qualities of jelly, in the other of glue. The readiness with which the joints of a child are strained or dis- located is likewise well known. The imma- ture condition of the infant is strongly marked in the ankles, which are turned inwards, and would never suggest the use to which the feet are to be applied, but for our familiarity with the change that afterwards occurs. The car- tilages and fibro-cartilages are subjected to a development corresponding to that of the fibrous tissue. Into the composition of the vocal appa- ratus we know that muscular, fibrous, and cartilaginous tissues enter; and, as these are altered by age, the mechanism which they constitute might a priori be expected to suffer similar modifications. The larynx of the infant is small and almost circular ; consequently the lips of the glottis and the superior ligaments are very short. This configuration, viewed in connection with the immaturity of the muscular tissue, accounts for the shrill wailing cry, which is the only vocal sound produced at this early period of human existence, and the only one required, since the quick instinct of maternal affection can interpret these simple notes into an eloquent language. No very appreciable alteration takes place in these parts at the time when speech is acquired, for this attainment has more con- nection with the development and command of the muscles of the pharynx and mouth, as well as with the organ of intelligence, which enables the human being to discriminate sounds and to imitate them. Fortunately the oral and pha- ryngeal muscles are some of the foremost in development, being required in suction and deglutition. A progressive change goes on in the larynx, though it is not very evident till the period of puberty in the male, when the thyroid cartilage is elongated, and with it the thyro- arytenoid muscle. At this epoch occurs the moulting of the voice, or an accession of gravity in the tones, occasioned by the elongation of the parts just mentioned. The projection of the pomum Adami takes place at the same time. In the female larynx scarcely any change occurs, and the voice in consequence remains acute. We have already spoken of the facial bones and their cavities, parts which exercise a very decided influence on the sonorousness of the voice. We must now hasten to the consideration of the parts employed in that other distin- guishing function of animals, viz., sensation. There are two grand divisions of the organs of sensation, those which we understand, and those which we do not. The former consist of the various kinds of animal mechanism whereby the external causes of sensation are modified, the latter of the nervous substance intermed iate to the external excitant, and that state of consciousness which we denominate sensation. We know AGE. 71 that the eye collects rays of light and con- centrates them on its internal surface, but are utterly ignorant of the changes which the re- tina, the optic nerve, and the brain undergo in producing that condition of our sentient exis- tence which we call vision. It is true that we are aware that certain states of these parts are incompatible with sight ; but why they are so is quite beyond our knowledge. We are, as it regards our acquaintance with the adaptation of nervous tissue to the production of sensation, in the same predicament as a man who watches the working of a steam-engine, and knows that a certain quantity of fuel, of water, of valvular compression, &c. is necessary to its motion, but has no idea of the laws of caloric, vapori- zation, constitution of elastic fluids, &c. Our science demonstrates the fitness of the external and internal ear for receiving, propagating, multiplying, and diffusing vibrations, but why the contact with the auditory nerve produces sound, is an all but impossible inquiry ; as well as the reason why the sensation may be absent when the organ is in perfect order, and the nerve to all appearance unchanged ; or why the sensation may occur without vibrations, as in dreaming, and many nervous disorders. The same may be said of the skin ; it is well adapted for coming in contact with the points or superficies of bodies, but who can say why the nerves spread over it occasion certain feel- ings ? These remarks are premised merely to shew that it must not excite surprise, if we are unable to point out completely the changes which age produces in the human body, corres- pondently with the changes of its sentient fa- culties. It has already, in all probability, struck the mind of the reader, that the great develop- ment of the cerebral system in the infant is inconsistent with the principle which we have been endeavouring to demonstrate, viz., that the growth of the human body consists essentially in the elevation of the organs, subservient to the animal functions, from a rudimentary state. The more we grow, the smaller is the proportion of the brain to the rest of the fabric. But it is no less true that the Junctions of the brain grow with our growth. How then are we to reconcile these opposite facts ? We must cer- tainly discard the opinion, that the bulk of the organ is proportionate to its power, and exa- mine the composition and the relations of its various parts to each other. Limited as our knowledge is of the requisite conditions of nervous substance for its func- tion, we are notwithstanding aware of two ex- tremes of softness and hardness, which comprise those states of the tissue which are compatible with the exercise of its peculiar faculty. Patholo- gists well know that ramollissement and indu- ration of the brain may produce the same lesion of function, viz., abolition of sensation ; while it is equally well known that approximations to the same conditions will produce impairment of this faculty. Now in infancy the brain is ex- tremely soft, almost pultaceous, while in old age it is extremely hard in comparison, and the similarity of the two ages in many respects, but particularly as it regards the functions of the nervous system, is matter of universal ob- servation. It might then a priori be suspected that one of the changes in cerebral growth would be a tendency to a certain intermediate degree of consistence, and this is found actually to be the case. From a careful comparison of the size and weight of the brain at different ages, it was ascer- tained by the Wenzels, and is demonstrated in tables contained in their work, De Penitiori Cere- bri Structura,* that although the organ increases very sligthly in bulk after the third year, its weight does not attain its maximum till after the seventh, so that up to this time there is a progressive increase of density. After the seventh year there is no great difference either in size or density. (The size of the brain must not be confounded with that of the head, which after the period that we speak of, is determined by the growth of the external table of the skull, correspondently with the projection of the bones of the face.) There must, therefore, be some other change than that of density, to account for the augmentation of intellectual power in the suc- ceeding periods, and herein our information is most at fault. Nevertheless we are not altogether without intimations of organic changes. The majority of physiologists are agreed that the function of the cortical substance is of a higher character than that of the medullary. The lower we descend in the animal series, the less we find of the cineritious matter, which is not apparent at all in the invertebrata, nor indeed in fishes. It is, therefore, not without proba- bility conceived that this matter is more imme- diately concerned in thought ; and, conformably with this view, we find its colour more strongly marked, as boyhood stretches on to manhood. f We may mention as corroborative of this cir- cumstance, that M. Foville, an eminent in- vestigator of the pathology of mental diseases, asserts that the principal lesions in the brains of maniacs occur in the grey tissue.^ The convolutions again afford us some hints upon the subject before us. Intelligence is in direct proportion to their extent, and we accordingly find that these parts are deeper as age advances. As the existence of the posterior cerebral lobes, and of the corpus rhomboideum in the cere- * See the notes to Milligan's Translation of Magendie's Physiology. f This observation refers to the cineritious matter of the convolutions. In certain other parts this sub- stance diminishes after birth. Thus, in the full- grown foetus, the medulla oblongata is grey through- out, but soon begins to whiten, first in the corpora pyramidalia, and afterwards in the olivaria. The outer surface of the tuber annulare, and of the crura cerebri, is also grey at the commencement of extra-uterine life ; but they lose this colour after a few weeks. In the thalami optici and corpora striata there is no distinction of white and grey matter, the latter alone being visible. See Meckel, Manuel d'Anatomie, t. ii. p. 717. Till the functions of these parts in mature age are better understood than at present, it would be useless to speculate upon the physiological relations of the changes which they undergo in earlier periods. % Diet, dc Med. ct Chir. Pratique, art. Agna- tion Mentalc. 72 AGE. bellum, is observed only at the top of the animal scale, we might expect that in the pro- gress of age there would be a change in the relations of these parts to the whole mass, but we cannot find that any researches have been prosecuted in elucidation of these points. Most of what we have predicated of the pro- gressive actions in the brain, is likewise eppli- cable to the cerebellum and spinal marrow, and nerves. The latter parts, however, are more forward in their organization, being de- voted to the more primitive functions of sensa- tion and voluntary motion, while the former is the instrument of the faculties more eminently intellectual. The proportion of the cerebellum to the brain at birth, is, according to Meckel, as 1-23 ; the former weighing nearly 3£ drachms, the latter 9 or 10 oz. A month after birth the ratio is 1-17 ; after six months, 1-8. The proportion between the spinal marrow and the brain at birth, and for five months after, is 1-107 or even 1112 ; the brain at the former period weighing 9oz. 4dr., and the spinal marrow 45gr., while at the latter period the cerebral organ weighs 21 oz., and the spinal l^dr. In the foetus of five months the propor- tion is 163, of three months 1-18. In the adult it is 1-40. The diminishing ratio of the brain to the spinal marrow is in obvious har- mony with the elongation of the vertebral column, and with the general growth of the members. The medulla oblongata is propor- tionally larger in early than in advanced life; the corpora pyramidalia and olivaria being dis- tinct and prominent; a fact which corresponds with the development of the brain. The longitudinal dimensions of the corpora quadrigemina at birth exceed those of the adult period ; after the former period they increase only in their transverse diameter. The concretions of the Pineal glands have not begun to be formed till the seventh year. They are sometimes wanting in very advanced age, according to the observations of Meckel and the Wenzels, which we have had oppor- tunities of verifying by our own dissections. The number of these bodies increases with the progress of life, and their colour is paler in youth and old age than in intermediate periods.* So much then for the nervous organs of sensation. Our attention must next be directed to the mechanism intermediate to the nerves, and the excitants of sensation. The simplest kind of sensation is that which informs or re- minds us that we are possessed of bodily parts, such as members and internal organs. The me- chanism employed, if there be any, is unknown. Nerves are distributed through the tissues, we feel those tissues, and conclude that these feel- ings result from relations between the nerves and the other textural molecules with which they are in contact. These feelings must of course vary with age because the tissues alter, but whether the susceptibility is increased we cannot say, and only venture to remark that the proba- * For further details see the works of Meckel and Tiedemann. bility of this being the case is suggested by the fact, that adults are more subject to perver- sions of sensibility than children; witness the various nervous, hypochondriacal, and hys- terical disorders with which adults are almost exclusively visited. The next order of sensations in respect of simplicity are those of tact, or those by which we are made acquainted that foreign bodies are in contact with our skin. It is perhaps m some respects only a modification of the first- mentioned sensation, but it requires the pre- sence of something not belonging to us. It is true that other parts than the skin may convey the notion of an external body being applied to them, but they do not afford any perception of the qualities of the body ; it is merely the affection of themselves which is produced by that body. We are aware that all sensation may be analysed in the same manner with similar results, but it is enough for our present purpose that the sensation excited on the skin is less selfish, if we may use the term in this sense, and ought to be so, in order that it may serve its office of supplying some knowledge of the external world. Doubtless the organization of the epidermis and of the skin itself, as well as the greater distribution of nervous matter, occa- sion the difference. The dermoidal tissue in modifying the external cause stands in the same relation to the nerves of tact, as the eye to the optic nerve, or the nose to the olfactory. The organ of tact is affected by age ; the skin in very early life appears less susceptible of im- pressions, and differs in its tissue, the papillae being less developed. A change, however, is soon effected in this respect, and as we advance towards manhood, it becomes less gelatinous and more fibrous. It must be confessed, how- ever, that the modifications which it undergoes in reference to its function of sensation, aie not well defined. This circumstance is owing to the variety of sensations to which it ministers, such as (in addition to what we have men- tioned) feelings of heat and cold, dryness and moisture, &c. and, secondly, to its being also an organ for other and very different func- tions, such as transpiration, secretion, and ab- sorption. Touch has a far more complicated mechanism than tact. It is one of the senses properly so called, or the special senses, and like the others of its class is distinguished by its requiring the assistance of muscles. Its sensations are com- pounded of tact and muscular resistance, and the organ is that wonderful instrument the hand. The imperfect state of this organ in infants must have been noticed by every one ; it is generally closed and capable of grasping but very feebly ; at all events a long time occurs before the little being learns to arrange the sensitive tips of the ringers, and to adjust the thumb in such a manner as to ascertain with nicety the form, consistence, and other properties of bodies. Whether the skin is less sensitive in these subjects we cannot say, but it is quite certain that the muscles, which effect the digital motions alluded to, are not developed any more than those in other parts of the body. Fine- AGE. 73 ness of touch, tactus eruditus, is one of the most difficult attainments of manhood. Concerning the alterations in the olfactory apparatus we have already spoken, when the development of the facial bones was under consideration. The sense of smell is mani- fested pretty early, but there can be no great precision and nicety in its exercise, both from defect of surface, and from the want of mus- cular power and command, in adjusting the quantity and impetus of the air that conveys the odorous particles. Thus, some agents are only appreciated by a sudden inhalation through the nostrils, as if to bring the particles with a certain degree of force upon the Schneiderian membrane. This art the child does not under- stand. Taste being a sense so essential to the main- tenance of the system, whether by inducing the animal to take the trouble of eating, or by warning him of improper aliment, is mani- fested very early. The usual description of the mechanism of taste would give just cause for questioning what was said respecting the ne- cessity of a co-operation of muscular action with the five senses. Taste is described as the result simply of the application of sapid bodies to the tongue, palate, velum palati, &c. But these bodies excite no sensation without the aid ot muscles. A certain degree of com- pression is necessary, which is accomplished by pressing the tongue against the roof of the mouth. Any one may assure himself of this fact by placing a strongly flavoured substance on the tongue when projected from the mouth ; no taste will ensue till the member is with- drawn and then pressed against the palate. This observation applies not only to the tongue but also to the palate itself, and that sensitive surface the velum. In each instance, however, the effect may be imitated, by compressing with the finger the part where the substance is applied. Taste must undergo a progressive develop- ment correspondently with the muscular or- gans. It is, to say the least, very doubtful if a child could perform those delicate manoeuvres of the tongue and palate, which are practised by gourmands or professed wine-tasters. There is something more than this muscular action, however, to be taken into consideration. The more refined flavours are probably felt and estimated by the lining membrane of the nasal passages. It is common to remark that the scent of a substance is similar to its taste, but in all probability the two sensations are iden- tical ; for the taste in question is not perceived if the nostrils be closed ; witness the abolition of taste during a catarrh. If therefore so close a connection exists between the two senses, it is clear that the development of the organi- zation belonging to the one must influence the other function ; and it has been already pointed out that the olfactory surface increases with growth. The new-born infant is probably all but deaf; even the loudest sounds produce no sensible impression. The nurse's lullaby, therefore, is for some time superfluous ; by degrees, how- ever, the shrill tones, of which such strains for the most part consist, begin to be appreciated ; the precise period however we do not know. In correspondence with this obtusity we find the organ incomplete, but the incompleteness has reference rather to the external than to the internal ear. Thus the pinna is very inelastic, and therefore unfitted for collecting vibrations ; the same may be said of the meatus auditorius. In like manner, the membrana tympani is very oblique, and scarcely more than a continuation of the superior surface of the meatus, and thus little calculated to receive the vibrations. These parts are also covered with a soft matter very unfavourable to vibrations ; the tympanum is very small, and the mastoid cells do not exist. In the progress of age all these parts gradually increase in hardness, and consequently are bet- ter adapted to their function. There are mus- cles attached to this sense also, but we are deficient in observations on their degree of de- velopment, though we may infer their condition from analogies in the rest of the muscular system. Lastly, we come to the organ of vision, of which, however, there is not much to be said. The differences between the visual organ in the in- fant and in the adult consist more in degree than in kind ; thus the sclerotic membrane is less elastic, and the cornea is less conical, in conse- quence of the smaller quantity of aqueous hu- mour; (the greater thickness of this coat is pro- duced by the serosity contained between its la- mina?;) thecrystallinelens is lessdense, but more convex in form. The pigmentum is in smaller quantityat birth than afterwards; while the retina is thicker and more pulpy than in more ad- vanced periods. The yellow tint of the foramen of Soemmering does not become visible till some time after birth, but deepens with the progress of life, till the stage of decline, when it grows paler. It has been ascertained that perfect images are formed on the retina ; and yet for the first few days the child gives no indication of visual sensation, and when objects appear to attract its attention, they are only those which are vividly illuminated. The de- ficiency therefore must exist in the optic nerve, though we are ignorant, of the organic condition on which this insensibility is dependent. We observe, moreover, that the eye is much more passive than in the adult, that it follows the motion of luminous bodies, or is fixed upon them with little or no apparent interference of the will. This muscular incompleteness, then, tallies with what we have noticed with respect to the other senses. The eye is known in its advance towards manhood to increase in the capability of adapting itself to different distances; but as we are ignorant of the mechanism made use of for this purpose, it is useless to look for cor- responding organic alterations. We must not omit to notice those appendages to the appara- tus of vision, called eyebrows, which become much more prominent as life advances, by the development of the frontal sinuses, and are therefore better adapted for shading the eyes. The generative apparatus is situated inter- mediately to the animal and the organic system. 74 AGE. The evolution of the organs connected with this function marks the age of puberty; and the changes in which this evolution consists, both in the male and in the female, are too well known to require their specification here. The influence of this development on the mental and moral characters of either sex, is likewise sufficiently familiar even to the most superficial observer. The human being is related with the external world passively and actively, independently of those organic actions and reactions that are constantly occurring in his system with regard to outward agents. He derives perceptions from objects about him, and he reacts on them by his power of muscular motion. But in his growth we mark that the perfection of those organs, which are scarcely more than passive in his relative life, advances much more ra- pidly than those which enable him to take a more active part. Thus the eye and the ear attain a certain maturity of organization and function, long before the bones and muscles, which officiate in locomotion. The bones and muscles connected with the organs of sensation, and therefore partaking of the passive character, are also equally forward in their development. What is the probable final cause of this arrangement? If all our voluntary motions were the immediate consequences of our sen- sations, as some of them undoubtedly are, such as those which close the dazzled eyes, or refuse the bitter food, or withdraw from pain- ful contact;— if all these followed directly on sensations, it would indeed be a strange ano- maly, if the systems that belong to each were not precisely on the same level of development. But this is not the case; all the more impor- tant motions, important as it regards that world in which man exists, as an intelligent and social creature, though less so as it respects his individual being, are the results of a mental condition, no less distinct from sensation than from muscular motion. This state is desire, or as it is commonly called when the antecedent of action, will or volition. Probably no men- tal state is more simple than this, and it may follow any other. It is therefore the more necessary that it should be preceded by such intellectual changes as will give it a right direction; in other words, that it should come under the dominion of certain faculties. But in early life the faculties to which we allude are very imperfectly developed ; those only have attained any thing like maturity which are in immediate relation with the senses; such are perception, memory, association, and imagination ; while the reflective faculties, such as comparison, reasoning, abstraction, all in fact that constitute man a judicious expe- rienced agent, are rudimentary. The conse- quence is that the desires or volitions are pro- verbially vain and dangerous. Let us observe a child of seven years old ; his senses are suffi- ciently acute for all ordinary purposes, although they are deficient in precision and delicacy; he has seen many attractive objects, he has heard many wouderl'ul stories, and tasted many exquisite delights; he remembers them vividly, he associates them rapidly, and often in shapes very different from those in which they were formerly combined. Desires follow which would prompt him to execute the most ridicu- lous and mischievous schemes. But happily the muscular system, by which alone he could accomplish them, is too immature and feeble for his puerile purposes. Here then is the final cause that we were in search of ; the active corporeal functions of relation must not ad- vance beyond the governing faculty of the mind. But why, it might hastily be asked, should not the senses, the mental faculties, and the motive powers, all have been equally deve- loped? The question is absurd, if we consider but a moment the manner by which the mind accomplishes its growth ; that its higher powers result from the accumulation of innumerable sensations, by which in fact the former are nourished and exercised. We shall now introduce a brief account of some researches upon the height, weight, and strength of the human body, at different ages, prosecuted by M. Quetelet, of Brussels. Not having room for the numerical tables, or the particular observations, from which his general conclusions are derived, we must content our- selves with a statement of the latter, and refer those of our readers who may be desirous of seeing the former, to the author himself. His deductions as to the growth of human stature are as follows: (1) the growth is most rapid immediately after birth ; it amounts in the first year of infancy to about two decimetres (nearly eight inches.) (2) The growth dimi- nishes as the child advances towards the fourth or fifth year; thus, during the second year his increase of height is only half what it was the first year, and during the third year it is not more than one-third. (3) After the fourth or fifth year, the stature increases pretty regularly until the age of sixteen, and the an- nual growth is about fifty-six millim, (two inch.) (4) After puberty the stature still increases, though slightly ; thus, from the sixteenth to the seventeenth year, the increase is about four centim. (lfinch); and in the two following years, only two centim, and a half (one inch.) (5) The stature does not appear to be quite completed even at the age of twenty-five. — These observations refer only to absolute growth, but if the annual increase of stature be com- pared with the height which has been attained, it will be found that the infant, after birth, increases in the first year by two fifths of his height; in the second by one-seventh; in the third by one-eleventh ; in the fourth by one-fourteenth; in the fifth by one-fif- teenth ; in the sixth by one-eighteenth ; &c. so that the relative growth continually dimi- nishes after birth. In addition to these statements M. Quetelet has ascertained that the rules of growth are not the same in both sexes ; 1st, because the female at birth is less than the male ; 2dly, because her development is completed earlier; 3dly, because her annual growth falls short of that of the male. It appears likewise that the stature AGE. 75 of persons living in towns, taken at the age of nineteen, exceeds that of residents in the coun- try by two or three centim (1 or \\ inch) ; and that the children of persons in easy circum- stances, and those of studious habits, are gene- rally above the middle height* A memoir by the same author devoted to an examination of the weight of the human subject at different ages, contains a series of interesting conclusions,from which we select the following. (1.) At'the period of birth there is an inequality both as to weight and to stature, in the two sexes ; the medium weight of males being 3 kil. 20, (rather more than 7 lbs.), that of females 2 kil. 91, (about 6^ lbs.); the height of the former Om. 496, (about 19 inch.); that of the latter Om. 483, (about 18 inch.) (2.) The weight of the infant diminishes the first three days after birth, and does not begin to increase till the second week. (3.) At the same age the male is generally heavier than the female ; it is only about the twelfth year that their weights are equal. Between the first and eleventh year the difference of weight is from 1 kil. to 1 kil. and a half ; between sixteen and twenty, about 6 kil. and after this period from 8 to 9 kil. (4.) At full growth the weight is almost exactly twenty times what it was at birth, while the stature is only about three and a quarter more than it was at that period. This holds good with both sexes. (5.) In old age both sexes lose about 6 or 7 kil. of their weight, and 7 centim. of their height. (6.) During the growth of both sexes, we may reckon the squares of the weights, at the different ages, as proportional to the fifth powers of the heights. (7.) After full growth in each sex, the weights are very nearly as the squares of the heights. (From the two prece- ding statements it may be deduced that the increase in the longitudinal direction exceeds that in the transverse, including in the latter both width and thickness.) (8.) The male at- tains his maximum weight towards the fortieth year, and begins to lose it sensibly towards the sixtieth. The female does not attain her maxi- mum weight till about the fiftieth year. (9.) The weights of full-grown and well-formed persons vary in a range of about 1 to 2, while the heights vary only from 1 to 1 J. This state- ment is deduced from the following table :f Maximum. Minimum. Medium. KIL. KIL. KIL. Male weight . . . . 98.5 49.1 63.7 63.7 55.2 MET. MET. MET. Male stature . , .. 1.990 1.740 1.684 1.408 1.579 * Recherches sur la loi de la Croissance de l'Homme, par M. Quetelct. Annales d'Hygiene Publique, &c. t. vi. p. 89. t Ann. d'Hygiene, t. x. p. 27. To the above memoir M. Villerme has appended some extracts from manuscript notes found among the papers of M. Tenon, and written about the year 1783. They contain observations which correspond, in many re- spects, with those of Quetelet. The last researches of this industrious ob- server have been devoted to the muscular power of man at different ages, and have been but very recently published. In the course of his memoir he refers to two tables ; one stating the relative power of draught (la force renale), at the several periods ; the other, the relative ma- nual strength (la force manuelle) ; in each case estimated by the dynamometer. The results are very much what might be expected a priori. It appears that the maximum of the " force renale " is at the age of twenty-five ; and that the difference in the extent of this kind of mus- cular power between males and females, is less during childhood than at the adult age. Thus, in the former period the male surpasses the female by one-third, towards puberty by one- half ; and at full growth, his strength is double that of the other sex. The manual force is greatest at the age of thirty, and at all ages is greater in the male than in the female ; before puberty, in the ratio of 3 : 2, after this period, in the ratio of 9:5. The average manual strength of a man is equivalent to 89 kil. and exceeds his weight by 19 kil., so that he might support himself by his hands only, even with a considerable weight attached to his feet.* This and the preceding memoirs, we are told by M. Quetelet, are extracted from a work which he is about to publish, entitled " Sur l'Homme et le developpement de ses facultes; ou, Essai de Physique Sociale." We need scarcely add that we are justified in expecting from the specimens already presented to us, a series of valuable and highly interesting facts, together with deductions of no ordinary im- portance and originality. Having thus briefly traced the changes that precede maturity, we may ask what is it that prevents the processes of growth from advancing at the same rate as they have hitherto done ? Why, so long as they are undisturbed by dis- ease or unnatural circumstances, should they not advance ad infinitum, or at least why should they not raise man to the strength and dimensions which poets have fabled in their Titans ? The same food, the same atmosphere, the same light and heat, the same electric agencies, by which the organs have been main- tained or excited, are still around them and exerting their influence. Why, then, should they never transcend a certain point? Why should the stature, however much it may vary between a Boruwlaski and an O'Brien, yet never rise above a certain measure ? Why does the strength never exceed the powers of a Milo or a Desaguliers, or the intellect surpass the limits of Aristotle, Shakspeare, or Newton? These are interesting but impossible problems. If we say that a certain quantum of vital power is allotted to the growth of man, and that while a portion is expended in raising him to matu- rity, the residue must be husbanded for con- ducting him through the remaining portion of his duration, else he might suddenly stop short * Ann. d'Hygiene, &c. Oct. 1834, t. Mi. p. 294. 76 AGE. in his career without passing jthose stages that prepare him for the cessation of his existence ; — what do we gain by such an explanation ? Nothing ; for the term vital power which we employ is but a hypothetical cause, or if more closely examined, is scarcely even this ; it is but an abstract term applicable to a number of actions that do not occur in the inorganic world. The vital power of a body is but the collective manifestation of its vital actions, and to say therefore that only a certain quantum of vital power is inherent in it, is but to express in other words the simple fact that those actions are circumscribed. Discarding this explana- tion, shall we say that the fact must be referred to some deficiency in the media of the being's existence; that, although the aliment, the air, the light and caloric are competent to the pro- duction of a certain degree of growth, they cannot extend it, and that, were their conditions different, the animal development would be more perfect. It is easy perhaps to suppose this, but we do not see how it can be proved, nor indeed that existing analogies favour it. On the surface of our globe there is every variety in the temperature, in the humidity, and in the electric conditions of the atmosphere, and every diversity in the articles of food em- ployed; in more limited spheres there are the greatest diversities in these several respects produced artificially by the various occupations of mankind ; and although we find, both among races and individuals, great varieties of deve- lopment, which may occasionally be traced to some relation with the media in which they live, these varieties are by no means in propor- tion to the differences of the media, and in the majority of cases the former are independent of the latter. In the temperate zone, with a due proportion of animal and vegetable diet, man appears to attain his most perfect deve- lopment, and with however great skill he adapts these circumstances, he never surpasses a certain point, and from what we know of his physiology no great alteration in any one of the external stimuli of his existence could be tole- rated. A different proportion of the oxygen, nitrogen, and carbon in the atmosphere, we know full well to be noxious ; a larger or smaller quantity of aqueous vapour suspended in it will occasion many well-known maladies ; the same may be said of alterations in the ba- lance of the electricity that surrounds us. Great extremes of heat and cold may be borne for awhile, but it is obvious that they are not so well adapted to a healthy state of the system, and therefore to its growth, as intermediate de- grees ; and consequently it is not easy to con- ceive any degree either above or below these limits consistent even with existence. Fami- liar enough also are we with the effects of full and sparing, of simple and mixed dietetics, and with the fact that between certain well- known bounds lie the salutary quantities and qualities. From all which it appears suffici- ently evident, that we cannot conceive any difference in the amount or properties of the known stimuli of life, that would be more favourable to the growth of man, than those which are to be found in the range of the known variations, whether natural or artificial. From the beginning there must have been established a direct relation between the organization of the body and the outward elements; the latter are nothing but stimulants adapted to co-exist- ing susceptibilities, or to put it more closely, man is not made by, but for or with, the sur- rounding agents ; his lungs are fashioned in cor- respondence to the atmosphere which he breathes, his digestive organs to the food that is spread so plenteously before him, and his nervous system to the subtle imponderable agents that play about him ; consequently as his organs only act in concert with, and do not result from the media of his existence, a development be- yond that which he is known to acquire must proceed quite as much from the former as from the latter; and the supposition, the value of which we have been endeavouring to estimate, thus falls to the ground. If man could become a larger, more powerful, or more sagacious animal than he now is, he must not only live in different media, but must possess a different constitution ; in other words, the characters that distinguish him as a species must be altered. The question, then, that offered itself remains to our apprehension unsolved by either of the hypotheses. The limitation of man's development is like the definite period of his duration, and a hundred other circumstances connected with his existence, an ultimate fact ; no event that we are able to discover intervenes between its production and the will of the Deity. Maturity, though varying with every indi- vidual, may be said to take place somewhere between the ages of twenty-five and thirty. It is a general opinion that it is a stationary con- dition ; that when such changes have taken place in the frame, as render the human being capable of undertaking the various duties and occupations to which adults alone are adequate, there are no further alterations till the period of declining age ; that, in short, growth has entirely ceased. But this idea is not strictly correct, for there is in all probability no period when the system is absolutely stationary; it must either be advancing to or receding from the state of perfection. This is of course more obvious when we know that augmentation of bulk is only a part of that process which per- fects the organization. (See Nutrition.) It is true that at the adult age the determinate height and figure, the settled features, the marked mental and moral character, naturally give rise to the idea that a fixed point has been attained ; but a little inquiry soon teaches us that the individual is still the su'bject of some progressive changes. It is the stature only that is stationary, for this depends on the skeleton, which ceases to lengthen before the period we speak of. But the capability of powerful and prolonged muscular exertions increases for some years ; there must consequently be a change in the muscular tissue. The intellectual faculties have not attained their maximum, although we do not hesitate to consider them mature ; we must therefore infer that there is a correspond- ing organic development of some kind in the cerebral substance. Maturity then would, ac- cording to this view, require to be dated at a period much later than that which is usually assigned to it. It is enough, however, without referring further, to know that although at the adult period the organs of animal life are so developed, that we cannot consider them im- perfect instruments, they are even afterwards the subjects of a perfectionnement. What is commonly meant then by maturity, is in strict- ness that period of human existence, during which the processes of growth and decline are passing into each other by such slow degrees as to be imperceptible. In this important era of the life of man, more important even than the season of adole- scence, we must leave him in the full posses- sion of all the faculties and energies which his Maker has allotted him, fulfilling his destiny of good and evil, encountering and triumphing over peril, toil, and pain, scaling the rough steep of ambition, threading the dark intricate paths of gain, labouring for the happiness or misery of his fellow-creatures, supported all the while by the consciousness of a strength that seems never to fail him, of resources never to be exhausted ; we must allow a few years to roll by, and then return to him, when weary, wayworn, and broken with the storms of life, he has discovered that there are limits to his powers of action and endurance ; that of the objects which he proposed as the ends of his labours, while a few have been accomplished, the majority are either vain or unattainable; and that a race fresh in vigour, and high in hope, the images of his former self, are over- taking and thrusting him away from the scenes of his exertions. What are the revolutions that have transpired in his system ? The formative organs of all the tissues of the body are in reality the tissues themselves ; whether it be a muscle, or a gland, or the coat of a vessel, the parts which essentially produce its growth are nothing more or less than its own constituent molecules, the mutual attrac- tions of which in deposition and absorption constitute assimilation ; for there is no proof that vessels are used for any other purpose than that of conveying the nutrient fluids to and from the places, where the ultimate mole- cules arrange themselves in the form of tissue. The altered qualities, then, which are presented by the tissues, in whatever organs, in the de- cline of life, must depend immediately upon alterations in their own molecular motions and affinities. The nature of these alterations will of course correspond to the nature of each tissue ; and unless we mistake, they will all be found to agree in one character, viz. a sim- pler composition, a lower kind of organization than they formerly possessed. But the discussion of this point will be more conveniently deferred till we shall have briefly recited the principal changes in the more important parts of the body. As the nutritive secretions of the various structures are supplied with materials by the fluids in those structures, it is evident that they must at any time be increased, diminished, or otherwise modified by changes in the quantity and properties of these fluids. It is therefore a natural commencement of the subject to begin with the circulating system. Nothing is more obvious in the condition of the aged as contrasted with the young than the different ratio between the fluids and the solids, the former being remarkably deficient. There is not only a notable diminution in the quantity of oleaginous or serous secretions, which are generally contained in the cellular parts of the body, but it is manifest that the tissues are per- meated by a much smaller proportion of blood. This fluid moreover is very different in quality from what it was in earlier life ; it is less arte- rial, its colour has not the same bright red it once presented, it has a large proportion of serum, and its coagulum is less firm in con- sistence.* Correspondently with the defi- ciency of fluids, many parts which once contained them are shrunk or obliterated. The capillary system becomes infinitely less ex- tended than it once was ; many of the extreme branches of the arteries themselves are no longer to be penetrated, and those which remain per- vious, are far less distensible than formerly. There is indeed a remarkable change in the coats of these vessels ; they are not only con- tracted in diameter, but are become denser and more rigid in texture. In this respect they dif- fer from the veins, which in old age are more dilatable than in youth, and consequently con- tain a larger quantity of blood. The final cause of this is evident ; in youth the arteries must convey a relatively larger quantity to sup- ply the increasing structures ; in the decline of life, when the latter are decreasing, there can no longer be any need for the same supply; the permission, however, of an accumulation in the veins, where it is less likely to be productive of injury, appears to be an accommodation to the diminution of the circulating powers. If we trace the arteries from their extremities back to the heart, we shall find their calibres every where diminished, their coats less elastic, less capable of adapting themselves to the varying quantity of their contents, in some places resembling the texture of ligament, in some that of cartilage, and in others studded with deposits of osseous matter. The heart itself presents marks of degeneration no less decided ; its cavities are shrunk, its fibres pale, and but feebly contractile, and fat will some- times seem to take the place of the muscular substance. Frequently, also, the coronary arte- ries are found ossified, and the same alteration is not uncommon in the valves. All these facts account for the slow, languid, staggering circulation characteristic of advanced life ; there is less blood to be transmitted to the various organs, and that which is sent is pro- pelled with a degree of feebleness that shows how little energy is required in its motion, when * De Blainville is of opinion that these changes are exaggerated. Cours lie Physiologie, i. 262. 78 AGE. so few nutritive actions are transpiring. We have spoken of the altered character of the blood, of its being less arterial and of a darker tint : this change is explained by the alteration in the respiratory system. The lungs are be- come lighter, the cells being relatively much larger,* and the parenchyma, which consists principally of bloodvessels, being greatly di- minished. This alone would not explain why the blood is imperfectly arterialized, because, although the respiratory surface is diminished, less of that fluid enters the organ. But the bronchial membrane is always in a more or less unhealthy condition, being covered with a thick and copious secretion, that constitutes the " old man's catarrh," and prevents a due intercourse between the air and the blood. Besides this circumstance, the expansion of the chest is less perfect in consequence of the diminished elas- ticity of the parietes of the chest produced by the ossification of the cartilages and other causes : the muscles also participate with less energy in the respiratory movements. Every thing in the history of advanced life indicates the diminution in the vigour of the circulation and respiration. The apathy and languor of mind, the deficiency of many secretions, and the general decrease of animal heat, but par- ticularly in the parts most distant from the heart, are all more or less intimately connected with the failure of these vital actions. On turning to the digestive apparatus we have abundant marks of deterioration. The teeth fall out, the alveolar processes are ab- sorbed, and the gums become hardened. In addition to these there is a change in the mus- cularity of the stomach; it has become weak, attenuated, and less contractile. The same is true of the intestines. The lacteal vessels are much fewer in number, and scarcely any lym- phatic glands are to be met with. Every thing intimates that the food is less perfectly acted upon, and that consequently less chyle is ex- tracted, and transmitted to the circulation. Since, then, in these several systems, we find marks of diminution, impairment, depravation, it is not wonderful that nutrition, which is per- formed by means of the materials supplied by those systems, partakes of the same characters. But as nutritive changes must have occurred in the various deteriorated parts just spoken of, it would be incorrect to say that alterations of tissue depend solely on the alterations of these * M. Andral, in his description of the atrophy of the lung which occurs in aged persons, says, " In some cases the walls of the cells disappear alto- gether, and we only find in their stead some delicate laminae or filaments, traversing in different directions cavities of various sizes. In the parts of the lung where these alterations exist, there are no longer to be found either bronchial ramifications, or vesicles properly so called, but merely cells of greater or less diameter, divided into several compartments by im- perfect septa or irregular laminae. Many of these cells bear a perfect resemblance to the lung of the tortoise tribe, and they all approach to it more or less as to a type of organisation, towards which the human being in this case seems to descend. Pathol. Anat. v. ii. p. 528, translated by Drs, Townsend and West. systems, though they are promoted by them ; they must, in fact, have assisted each other. The altered tissues could not have been easily thus changed, without a defect in the quantity or quality of the matters out of which they are formed ; nor could the latter defects have easily occurred without some alteration in the texture of the parts employed in conveying and ela- borating the nutrient fluid. It is an old saying, that the functions of the body form a circle : if this be true of their healthy condition, it is not less so of their diseases and decline. The organs and tissues subservient to the organic life having undergone vitiation and diminution, we may expect to find equal or even greater decay in the parts which are alto- gether dependent upon them, or the organs of the supplemental life. These indeed, as they are the last to be developed, are some of the first to present marks of decline, and evi- dently for the same reason, viz. because they are appended to and generated by the other parts of the system, and also are more open to our observation. The body is indeed, in this respect as in many others, not unlike a poli- tical community ; no great change can occur in its internal arrangements, such as a failure or derangement of its energies and resources, without a manifestation of this weakness or disorder in its foreign relations. Let us proceed, then, to examine the ravages which are wrought by the hand of time on the organs of locomotion and sensation, in the same order in which we have traced the deve- lopments and amplifications, once lavished by the self-same agent. And first of the bones. The process of development in these parts consisted of a certain adjustment of the animal to the earthy matter, in order to give the requisite firmness, toughness, and solidity. As life advances, the phosphate and carbonate of lime are found to exceed the proportion of the cartilage and gelatine. The general conformation of the bones is less regular ; they look shrunken and worn. When handled they feel lighter, not- withstanding the osseous substance is in excess; a fact, which results from the diminished quantity of the fluids, and one or two other circumstances to be mentioned presently. The processes and ridges, once so eminent and dis- tinct, are comparatively effaced; this alteration accords with the wasting and diminished exer- cise of the muscles that were attached to these eminences. On looking for the lines and spaces, which are occupied in early life by cartilages or membranes, and which are visible even in manhood, we now find every trace of them vanished. Thus, the divisions between the epiphyses and shafts of the long bones, the line of union between the bones of the pelvis, and, in a still more marked degree, the sutural outlines of the bones of the head, are no longer perceptible. They are all filled up with bony deposit, and the pelvis and cranium form single bones ; even the foramina by which the nutrient arteries entered the tissue are con- tracted or obliterated. The cellular structure between the tables of the cranium is removed ; AGE. 79 and the outer plate has approximated and indeed become identified with the inner; hence we see more depressions on the surface of an aged skull. On inspecting the internal structure of these organs, we find the cavities that contain the marrow much more extensive than formerly, and the medullary tissue reduced to a con- sistence scarcely exceeding that of oil. The cells also of the short bones and of the ex- tremities are more expanded, and the lamina? which form them are very much attenuated. The deficiency of animal matter renders the bones of the aged fragile ; they are broken by the most trivial accidents. It is also the cause of their slowness to unite; for the activity of assimilative, and consequently of reparative processes, is dependent on the vascularity and fluidity of a tissue. The lightness, however, of these organs produced by the same cause is beneficial, or at all events in harmony with the state of the muscular system. If we next turn our attention to the ar- ticulations, we shall find that similar pro- cesses of disqualification for former functions have ensued. The spinal column, which once adapted itself with such ease and flexi- bility to the motions and curves of the body, has become almost as rigid as a single bone by the drying up of the intervertebral cartilages, and sometimes by the encroach- ments of ossification.* Scarcely any traces of cartilages between the ribs and the sternum can now be found; one of the causes to which we alluded above, in connection with dimi- nished respiration. The same deficiency of cartilage is observable in the bones of the wrist and of the tarsus. A change, the opposite of mobility, may also be detected in the liga- ments which embrace the joints ; they are dense, dry, and inelastic. The gelatine which enters so largely into their composition has become altered in its chemical properties ; it is less easily soluble in water, and has all the characters of glue rather than of jelly. Ill-adapted as this state of the articulations is to the purposes of motion, it is, we think, not altogether difficult to discern its appropriateness to the human being at this advanced period. Were the joints supple and flexible, while the muscles have so little power, how much greater would be the risks of accidents to the aged man in the slight motions which he achieves. In order to preserve their frames from falling, those whose joints move easily upon each other are compelled to exercise those * '' Cependant il est rare que les fibio-cartilages s'ossifient chez les sujets avarices en age. A la verite on voit souvent les vertebres se reunir avec les autres au moyen d'une substance osseuse, mais cotte soutiue depend bien plus rarement de l'ossi- fication des fibio-cartilages que de la formation de lames osseuses a la ciiconterence des deux faces par lesquelles se regardent les coups des vertebres. Cependant j'ai observe quelquefois aussi l'ossifica- tion des fibro-cartilages intervertebraux, et j'ai trouve alors, en sciant longitudinalement la colonne epiniere, que plusieurs vertebres etaient soudees ensemble, ct confondues en une seule masse." — Meckel, Manuel d'Anat. t. i. p. 364. muscles which keep the limbs in the requisite degrees of extension and stability, during cer- tain attitudes and motions; but this end is accomplished in the feeble old subject by the very stiffness of his articulations. The muscles are subject to changes no less decided than those in the organs just men- tioned. They are pale, flabby, atrophied, and indisposed to contract on the application of stimuli ; but the fibre itself is tough and not easily torn, and the true muscular substance seems to have given way in some places to a sort of dense cellular membrane, or a yellow- ish degeneration of tissue particularly de- scribed by Bichat. Their tendons are often studded with calcareous matter, and the sheaths in which they play are rigid and unmoistened with synovia. They obey the stimulus of the will tardily and irregularly ; the uncertain tremulous movements, the tottering gait, the stooping posture, the unsteady grasp of the aged, are familiar to every one. The organ of voice comes next to be con- sidered. The larynx, once composed of seve- ral cartilages that moved freely on each other, is now a cavity capable of much less variation in its dimensions, owing to the rigidity of its parietes; the extent of the cavity gives in eariy old age that depth of tone, which by its gravity and solemnity excites our homage. In more advanced age, however, the tone becomes hoarse, shrill, and piping ; this in all pro- bability is produced by the contraction and stiffness of the rima glottidis, but still more by the want of vigour in the muscles of the mouth and throat. The incapability of ma- naging the tone, and the tremulous articu- lation, are also results of changes in the muscles of the larynx, pharynx, and tongue, similar to those which transpire in other parts of the muscular system. Many senile impediments of speech are also produced by the loss of teeth, by the falling in of the cheeks, and by the disproportion of the lips to the space which they occupy. In our investigation of the signs of decay in the parts that are subservient to sensation and thought, we shall be met by the same difficulties which formerly opposed our way, when inquiring into the phenomena of their development. We traced the progress of the nervous substance both in the nerves and in the cerebro- spinal centre from the almost pulpy state recognized in the infant, to its firm consistence in the adult. If we now inves- tigate the anatomical quality presented by the tissue in advanced life, we shall find that it has shared the alteration of nearly all the other tissues, — that in short it has increased in density. This fact viewed in connection with another, namely, that ramollissement and induration produce very nearly the same lesion of func- tion, will account for the failure in the sensific powers of old age. Besides this alteration in the substance of the nerves, they are found to be diminished in diameter ; their neurilemmes are become, like other membranous parts, much harder and stronger. Moreover, Bichat has remarked that the nervous tissue of old ani- 00 AGE. mals is much less easily affected by reagents than that of younger ones ; so that there would appear to be an alteration in the chemical composition as well as in the mechanical con- sistence. That which has been said of the matter of the nerves is also true of the brain. The whole bulk is diminished and the density greater than in earlier years. Some, however, assert that it is even softer than in manhood. M. Blandin makes a remark of this kind, in commenting upon Bichat's statement of a greater hardness in the tissue, and says that it might be expected a priori, since there is so strong a correspondence between the two ex- tremes of life. There is reason, however, to think that this remark, if true at all, applies only to the cerebral organ of persons very far advanced ; and it is not improbable that dis- eased softening has in other cases been mis- taken for the natural effect of age. The mem- branes investing the brain like the neunlemmes (for they belong to the same system) are also thicker and more resistent. The vascularity of the organ is greatly diminished ; on a di- vided surface no red dots are visible as at periods less advanced. The alterations in the mechanism of the senses must next be considered. The skin, which is the medium between the nerves of tact, and external agents, undergoes great changes in the progress of life. It becomes drier, harder, less flexible, and at the same time looser, in consequence of the absorp- tion of the adipose substance. By the latter qualities the function of the skin is more evidently impaired, in that modification of it more expressly denominated touch, or the sense of tact united with certain muscular feelings in the fingers and hands. By the looseness of the integuments, the slowness and weakness of the muscles, the stiffness of the digital joints, and that dulness of sensation which exists in this as in every other part of the system more or less, the hand is notably deteriorated in old age. In the olfactory apparatus we find that, although the cavities and sinuses, through which the Schneiderian membrane is ex- tended, are rather increased than diminished in size, the membrane itself is attenuated and less pulpy. The nerve also is mentioned by Rnllier* to be evidently contracted and wasted. The sense of taste so closely connected with that just spoken of survives to the extremest limit of existence; the final cause of which is evi- dent. It is too intimately connected with one of the processes of organic life to be easily dispensed with, although one of the functions of the superadded life. It is, however, feebler than at periods less advanced, and requires the excitement of more piquant aliment ; this is partly owing to the diminished sensibility of the gustatory nerve itself, and partly to the diminution of the sense of smell, on the per- fection of which depends our appreciation of the more delicate species of sapidity. The * Diet, de Med. art. Aye. Surface of the tongue is more rugose than in younger subjects, and there is generally a de- ficiency of moisture, which is an additional cause of diminished sensation. The ear, both in its external appendages and in its internal structure, presents certain conditions which very well account for the frequency of deafness among the aged. It is true the cartilages become harder, more elastic, and therefore more vibratory, but the internal surface of the meatus is often thickened, and obstructed by a dense cerumen. The mem- brana tympani is more rigid and therefore less capable of varying with the degree of the vibra- tions. In the internal cavity, although the mastoid cells are enlarged as life advances, the deficiency of the liquor cotunnii in the vestibule, the cochlea, and the semicircular canals, must greatly interfere with the produc- tion of hearing. In addition to all these cir- cumstances there is probably an idiopathic insensibility of the nerve. The modifications of the organ of vision are familiar to all who have paid even the most superficial attention to the science of optics. The cornea is less transparent and less convex, partly from the diminution of the aqueous humour, and partly from the condensation of its texture. The latter change is more marked at the circumference, where a nebulosity is often formed, which has gotten the name of gerontotoxon, or arcus senilis. The pigmentum diminishes, and the iris grows paler in con- formity with the altered colour of the hair. The crystalline lens is denser, less transparent, and often acquires a yellow tint ; the vitreous humour likewise suffers a decrease. The retina is considerably attenuated, but has increased in firmness. The punctum luteum is paler, and not unfrequently altogether effaced ; a change which, in the opinion of Meckel,* bears a direct ratio to the diminution of the transparency of the cornea. These several alterations are ne- cessarily followed by two results — diminished refraction of the rays of light, and torpor of the nervous function, both of which produce pres- byopia. That long sight bears a relation with nervous as well as more mechanical causes is, we think, attested by the fact that this kind of vision is modified by temporary excitement of the brain, as in phrenitis.f If we now take a retrospect of the revolu- tions which have occurred in the several struc- tures enumerated, and endeavour to arrange them under specific heads, it will be found that diminution of bulk, deficiency of fluid, and condensation of substance, comprehend them all or nearly all. The attenuation has been generally ascribed to a preponderance of absorption over deposition, or a reverse of that condition in which incremental growth consists. But we cannot enter upon the question here, and must refer to the article Nutrition, con- tenting ourselves with the remark that it seems a superfluous multiplication of causes to sup- * Op. cit. t. iii. p. 261. f See Abci-crombie on Diseases of the Brain. AGE. 81 pose that absorption increases, when the cessa- tion or diminution of deposition fully explains the fact, provided the absorption is only main- tained in its usual ratio. Concerning the lessened quantity of fluid we have already made some remarks, and hinted at its relation with impaired digestion and slackened circulation. Here it is sufficient to observe that the fact is a sign of diminished vitality, by which we mean merely a diminu- tion of vital actions, especially of those of nu- trition. The abundance of fluid in the young succulent body is adapted to the constant accu- mulation of new particles, and to the increasing complexity of the organization of the tissues, as well as to the reparation of waste, or to the counteraction of decomposition ;— by the still abundant though diminished quantity in the adult the composition is maintained and ren- dered more exquisite ; — in the old man there is only enough required to keep up that degree of renovation, which is necessary to the integrity of the structure, and even this action is less than in former periods, because the organiza- tion, from its chemical nature, is less prone to decomposition. This brings us to the con- sideration of the third general fact, or the condensation of tissue, which will require more particular notice, because great impor- tance has been assigned to it by some writers. The condensation is a result of the deficient humidity just spoken of; but this is not all, otherwise the condensation would be merely that of dryness ; the tissue itself is of firmer materials. Thus membrane becomes ligament, ligament cartilage, cartilage bone, and bone increases in its earthy proportions. This har- dening of the whole body is spoken of by many writers as the cause of decay, and ulti- mately of death, by the gradual closure of all the small vessels, and the obstruction to vital motions; while the methods of averting old age, proposed by the same authors, turned chiefly upon an artificial supply of moisture to the body. Galen constantly alludes to this condition when treating of old age, and the means of resisting its tendencies* Lord Bacon, in his curious and highly interesting treatise, entitled Historia Vita? et Mortis, has much to say upon desiccation and the methods of pre- venting it, such as bathing and inunction. The fable of the restitution of old TEsop by the cauldron of Medea, he considers typical of the utility of the warm bath in softening the substance of the body. So much stress does Haller lay on the effect of the universal tendency to induration, that he tells us that one of the reasons why fishes are so long-lived is because their bones are never hardened to the same degree as in the higher animals — " Inter animalia aves longaeviores sunt, longavissimi pisces, quibus cor minimum, et lentissimum incrementum, et ossa nunquam indurantur." Primse Linea;, § 972. There is, however, we think, but little foundation for the supposition that induration stands in the relation of cause * See his treatises De Sanitate Tuenda, and De Marasmo. VOL. I. to the general failure of the functions of the body. It is rather a symptom of decline, ot one of the phenomena in which decline con- sists, and is therefore itself the effect of the failure or alteration of some of the functions, more especially of the assimilative. It is a deterioration of interstitial secretion, partly promoted by the changes in circulation, in di- gestion, and probably in innervation, and partly itself contributing to these changes, but pri- marily owing its origin, like the latter, to the ultimate law, which determines that at a certain period decay shall transpire. It is in one re- spect a descent in the scale of organization. This indeed is indicated by the paucity of fluids and by the slow nutritive motions, which conditions are always sufficient to warrant our application of the terms, diminished vitality or less vitalized structure; but the substance itself, indepen- dently of these deficiencies of action, belongs to a more simple organization. We examine a bloodvessel, and instead of finding its coats of that complex texture which enables it to ac- commodate itself by a property, known only in living bodies, similar but superior to elasti- city, we mean tonicity, we observe a plate of osseous matter, unyielding, insensible, immo- bile, possessing no other vital character than bare assimilation or molecular growth. We search for those admirably constructed sub- stances which are interposed between the ribs and the sternum, and by their elasticity give extent and facility to the respiratory move- ments, and we discover them converted into the same matter as the contiguous bones, with the coarse property of cohesion, and, as in the former instance, with nothing but its growth to redeem it from the character of mere inorganic matter. We untangle the muscle, and instead of the irritable fibre, soft in texture but firm in contraction, we find a torpid substance, scarcely fibrous in form, firm in mere physical cohesion, weak in vital contraction, and consequently of a degraded organization. The processes of induration about the joints, the glands, and the integuments, will all, when examined, be found to approximate more than the former conditions of these parts to the qualities of the inanimate world. Homogeneousness of sub- stance is alone an indication of a low organi- zation, and a body which possesses both this property and hardness, may be considered on the very outskirts of the region of vitality. Such are the properties of osseous deposits. May we not here perceive an analogy with the animals of the inferior classes ? In many of the mollusca how trifling a degree of vitality seems adequate to the formation, growth, and reparation of their calcareous coverings and appendages; or to go down to the coralines, madrepores, and porifera, we observe that the very lowest structure that can be considered animal is sufficient to secrete or assimilate those vast collections of earthy matter which pave the ocean, and rise into islands, moun- tains, and mighty continents. In this har- dened constitution, this simplified but dege- nerate structure, we see that the frame of man, in its natural decay, loses the characters that 82 AGE. once distinguislied it from the dust, and that not less literally than truly it has become more and more " of the earth earthy." We have now traversed as far and as mi- nutely as our space would allow, the organs and tissues, with their various alterations. It remains for us to inquire whether any one of them may be considered to stand in the rela- tion of cause to the others. We have already dismissed the supposition, that rigidity and con- cretion are productive of the other alterations, and we also partly entertained the question, when treating of the relations between assimi- lation, the fluids, and the organs subservient to circulation and digestion. But there are one or two additional points which must be alluded to in this place. The decay of all the organs, concerned in the life of relations, has been shewn to depend on a failure in the actions which are necessary to their generation and maintenance ; these organs may, therefore, be dismissed at once from our inquiry into the causation or priority of the processes of degeneration. Yet the observation of the marked declension of the function of the nervous system throughout the body, has led to the hypothesis, that the failure in this power is the ultimate fact in the history of our decline, the fact to which all the others may be traced. This view is suggested by Dr. Roget in his justly-admired article on Age, in the Cyclopaedia of Practical Medicine. He considers the general condensation of tissue throughout the system, to be occasioned by a diminished force of circulation, which allows the capillaries to collapse and become obli- terated; the weakened circulation this distin- guished author is inclined to attribute to a diminution of nervous power in the muscular fibres of the heart ; whence he infers that the declension of nervous power bears the priority in the chain of events. We do not feel pre- pared to adopt the inference ; for if we admit this failure in the innervation of the heart, (and whether its fibres are dependent on nerves for their contractility, is still an unsettled ques- tion,) are we to pass over the condition of the blood ? Might we not say that the enfeebled contractions of the heart are referable to an alteration in the properties of its appropriate stimulus 1 It is known that this vital fluid has been less affected by respiration than in former periods of our existence ; we might therefore, when searching for the earliest antecedent in decay, stop at the imperfect arterialization of the blood. But this would be, in our humble opinion, to pause too soon. The deficient oxygenation of the circulating fluid is sufficiently well known to be the effect of certain changes in the apparatus of respiration. And to what do these changes belong ? To a variety of structural, functional, and nervous phenomena, which, if pursued, would lead us into a maze of events, from which it would be impossible to select that which was earliest in its occur- rence. Or if we leave the respiratory system, and follow the blood backward to the process of chylification, and ultimately to digestion, we shall, as was shewn above, be equally unsuc- cessful in obtaining satisfaction. Or finally, if we return to the heart, and investigate the dimi- nished nervous power, admitting this diminu- tion to be alone sufficient for the debility of circulation, is it possible to stop at this pheno- menon ? Nervous power is nothing but the function of nervous substance, and whether the latter belongs to the ganglionic system, or to the cerebro-spinal, it may have undergone some change, or have been stimulated differently from usual. We know that the sensibility of the nervous system is most intimately connected with the quality of the blood, and with the force of its impulse ; so that if it be true that diminished circulation is the effect of diminished innerva- tion, it is no less true that the latter is also the result of the former. Thus it appears that in this inquiry we are constantly arguing in a circle, and it can scarcely be otherwise ; the principal structures and functions of the organic life commenced simultaneously ; they must^de- cline simultaneously : they assisted one another to grow ; they accelerate each other in the way to dissolution. If, however, we are disposed in some measure to qualify this remark, and still hold that there must be some organic changes primary in the work of decay, all ana- logies must, we think, conduct us to the simple processes of assimilation and secretion, into which all the more complicated functions must be ultimately resolved ; but we can go no farther, for we know not what determines or modifies the play of those subtle affinities, motions, and contractions, in which such changes consist. Some fancy that the enigma is solved by the hypothesis of a diminished vital power ; but we have already attempted to show that the interpretation is without value, when applied to the cessation of development; the same reasons render it equally useless as a key to the hiero- glyphics of decay. Not less vain were the endeavours of those who could satisfy their philosophy with such a subterfuge of ignorance as was afforded in the theory of a sum of exci- tability, originally allotted to the system, and gradually exhausted, &c. ; as if excitability could possibly mean any thing more than an expression of the collective phenomena of ex- citement, or vital movement. It is exactly on a par with the doctrine of decreasing vitality.* Some talk prettily and poetically of the vital flame burning out, of oil gradually wasting, of fuel expended,— phrases applicable enough as metaphors, but absurd when propounded, as they too often are, as statements of matters of fact. When philosophy has failed to discover an- tecedences, she may still find a prolific source of employment in the study of harmonies. There is no event to be found in the relation of cause to those organic changes which, without the intervention of accidental agents, ultimately affix a bound to the duration of man's existence. As no cause can be elicited for the termination of development, neither can we better explain * "La gene de l'influence vitale s'accroit sans cesse." — Cabanis. ALBINO. 83 why growth does not continue stationary, and maintain the bodily structures for a series of ages, so long as external circumstances remain the same. We live in the midst of agents that both supply us with life and infest us with poison : for a time we resist the baneful tendencies, and then gradually succumb, but in what manner we are at present ignorant. The prevalence of certain functions has been supposed to fortify certain animals against the outward agents or inward processes that would otherwise urge them to dissolution. \The in- fluence of respiration upon nutrition is well known, and consequently a large sum of respi- ration has been alleged to account for the longevity of birds ; but there are equal or much greater instances to be found among fishes and reptiles, the amount of whose respiration is extremely small. In the one case the vitality is said to be less rapidly consumed, in the other to be more abundantly supplied ; expla- nations which amount to little more than statements of the same facts in different lan- guage. Lord Bacon was of opinion that birds owe their lengthened existence partly to the smallness of their bodies, and partly to their being so well defended by their teguments from the atmosphere ; while he accounted for the long life of fishes by the non-occurrence of desiccation in their aqueous element. There is nothing satisfactory to be obtained from speculations of this sort. The most that we can learn is the variation in the term of exist- ence by the influence of various outward agents and modes of life. But whatever variation may be discovered, it will still appear that climate, and time, and custom, and science have never prolonged the date beyond certain limits. The study of these circum- stances, and the appliances of art, undoubtedly tend to enable a greater number to attain the extreme goal, but can never give the power of transgressing it. Vain, then, as Boerhaave observes, are the hopes of men who look for an agerasia! Although at present, then, we cannot trace the causes of the bounded nature of our existence, yet it is not difficult to discern its fitness to our constitution, and to the universal frame of things. The brevity of life is an ancient com- plaint ; lamentations have been chaunted over it time out of mind : but its antiquity does not redeem this, any more than many other opinions equally hoary, from the character of a prejudice. Every consideration of the fact in question with reference to the universe must "justify the ways of God to man" in the dis- position of this as of every other event. We have only to conceive the circumstance altered, in cor- respondence to the idle wish of some aspirant to longevity, and we see that every thing else also would require to be changed ; that, in short, the beautiful arrangements of the world and of our social relations would be broken. To notice one or two of these : if the life of man were longer than it now is, his progeny would need to be greatly abridged from their present numbers, or they would soon exceed the ratio of subsistence. The time occupied in attaining maturity bears a direct proportion to the period of existence in the mammalia ; consequently, if life were prolonged beyond its present limits, that time during which the offspring of man is either helpless or very dependent on the parents, would be also length- ened, and the accidents of disease or other casualties remaining the same, it is clear that confusion, distress, and manifold calamities would accrue to a rising generation. After the attainment of maturity and of its accompa- nying faculties, it is not clear that any thing would be gained by the possession of these for a longer period than is now allowed ; since we know but too well that men, after a time, lose the spirit of enterprise once engendered by the con- sciousness of increasing or lately-acquired powers, and fall into habits of action which they are unwilling to abandon, but which do not advance the resources of the species beyond a certain limit. Hence the advan- tage of their giving way to others, to whom they can commit their knowledge, and who, by their unworn energy, will advance it fur- ther. " Life is sufficient for all its purposes if well employed," was well observed by Dr. Johnson ; and what follower of medicine can forget that the immortal sage of Cos, by the example which he afforded in his well-spent life, disarmed his own antithesis of its woful point: h |3'o; j3g«%&?, « te%v*i ^ap^jj. Bibliography. — Lord Bacon, Historia vitas ct mortis. Pollich, Diss, de nutrimento, incrcmento, statu, et decremento corp. hum. 4to. Strasb. 1763. Ploucquet, Diss, sistens aitates humanas corumque jura, 4to. Tubing. 1778 ; (Recus in Frank Delect. Opuscul. vol. vii.) Daignam, Tableau des varictcs de la vie bum. 2 vol. 8vo. Par. 1786. Rvsh, Med. inquiries, vol. iv. Esparron, Ess. sur les ages de l'homme, Thes. dc Paris, an. xi. Ranque, Des predominances organiques des differens ages, Thes. de Par. 1803. Wesener, Spec. hist, hominis varias ejus periodos, &c. sistens, 8vo. Krabcrg. 1804. Lucas, Grundriss der Entwickelungsgeschichte des menschlichen Kdrpers.8vo. Marburg, 1819. Burdach, Die Physiologie als Erfahrungswissenschaft, 8vo. Leipz. 1803. Renanldin, Diet, des Sc. Med. art. ' Age.' Rullicr, Diet, de Med. art. ' Ages.' Betjin, Diet, de Med. et Chir. Prat. art. 'Age' Roget, Cyc. of Pract. Med. art. ' Age.' Copland's Diet, art. ' Age.' Also the anatomical and physiological systems of Addon, Beclard, Bichat, Bostock, &c. &c. &c. (J. A. Si/monds.) ALBINO. (Syn. Albinismus,leucopathia, leu- ctethiopia). — This term, as employed in phy- siology, appears to have been first used by the Portuguese* to designate a peculiar condition of the human body, which was occasionally observed among the negroes in the western parts of Africa. It consists in the skin and the hair being perfectly white, while in the * Vossius, dc Nili origine, cap. 19. p. 69; see also Ludolf, Hist. jEthiop. Com. lib. i. cap. 14. No. 100. p. 197. The name by which the African Albinoes are known among their countrymen is Dondos : by the French they are frequently termed Blafards. G 2 84 ALBINO. form of the features and in all other respects the individuals in question exactly resemble the negro race. Another striking peculiarity of the Albino is the state of the eye, which is of a delicate pink or rose colour ; it is likewise so sensible to light as to be unable to bear the ordinary light of the day, while in the evening, or in a dark shade, its functions appear to be sufficiently perfect. We learn from Wafer, who accompanied Dampier in one of his voy- ages, and who relates his adventures in crossing the Isthmus of Darien, that Albinoes are not unfrequently found among the inhabitants of this district.* We are also informed by various travellers and naturalists that they are often met with in some of the oriental isles, more especially in Java and Ceylon ;f in all these cases exhibiting the peculiar appearance of the skin, hair, and eyes, while, in other respects, they conformed to the external and physical characters of the people among whom they are found. The same circumstance occurs in this country and in the other parts of Europe, al- though, if we are to place any confidence in the accounts of travellers, the Albino is much more frequently met with in tropical climates, especially in the western parts of Africa, and in Darien, than in the more northern regions.}: * Wafer's New Voyage, p. 134 . . 8 ; Buffon, Hist. Nat. t. iii. p. 500; Wood's Trans, v. iii. p. 419, 10 ; Pauw, Recherches sur les Americains, par. 4, sect. 1. t. ii. p. 1 et seq. ; Kaynal, Hist, des Indes, t. iii. p. 288. The earliest account which we have of the South American Alhinoes is by Cortez, in the narrative of his conquest of Mexico, which he transmitted to Charles V. In describing the palace of Montezuma, among other objects of rarity or curiosity which were found in it, he says, " In hujus palatii particula tenebat homines, pueros, fcemi- nasque a nativitate candidos in facie, corpore, ca- pillis, superciliis, et palpebris." De Insulis nuper inventis narrat., p. 30 of " Nar. Sec.;" sec also Clayton, in Manch. Mem. v. iii. p. 261 et seq. t Buffon, t. iii. p. 399 and 415 : Wood's Trans, v. iii. p. 328, 9 and 344. We have not been able to procure the " Voyages de Legat," which is re- ferred to by Buffon and others, as containing the original account of the Albinoes, or, as they have been termed, Chacrelos, of Java. With respect to the Bedas of Ceylon, as originally described by Ribeyro, Hist, de Ceylon, ch. xxiv., and more lately by Percival, Account of Ceylon, ch. 13, and by Cordiner, Desc. of Ceylon, v. i. c. 4, it seems evident that they are not to be considered as Albi- noes. The only remark which Ribeyro makes on their physical character is, " lis sont blancs comme des Europeens, et il y a meme des roux parmi cux," p. 178. Percival, who saw some of them, states that their complexions are fairer and more inclined to a copper colour, than those of the other inhabitants ; while all that is said by these writers respecting their habits and modes of life indicates that they are a distinct race or tribe. The term Beda, or Badah, appears to be a corruption of Vaddah, or Veddah, which Knox informs us is the name of the aborigines of the island ; Account of Ceylon, p. 61 ; see also Brown, in Brewster's Encyc. art. " Ceylon," p. 704 ; Cordiner and Per- cival, ut supra. $ Vossius and Ludolph, ubi supra ; Argensola, Conquist. de las Islas Malucas, lib. ii. p. 71, speaks of Albinoes as not uncommon in these islands; De la Croix, Relation de l'Afrique, par. iii. liv. ii. sect. ii. 4. 13, " Albinos, hommes blancs, ou We meet with a few scattered remarks in the writings of the ancients, which render it evident that this peculiar state of the human body had fallen under their notice. We have the follow- ing passage in Pliny : " Idem " (Isigonus Nicasensis) " in Albania gigni quosdam glauca oculorum acie, e pueritia statim canos, qui noctu plus quam interdiu cernant."* The same circumstance is referred to by Aulus Gellius : " . . . . in ultima quadam terra, qua Albania dicitur, gigni homines, qui in pueritia canescunt, et plus cermint oculis per noctem, quam inter diem;"f and by Solinus : he says that the Albanians " albo crine nascuntur ;" " glauco oculis inest pupula, ideo nocte plus quam die cernunt."I Pliny, in speaking of the inhabi- tants of a certain district in the interior of Africa, names them Leuceethiopes ;§ and, as it has been supposed that in this passage he referred to the Albinoes, the term has been applied to them by some eminent modern naturalists ; || but it appears more probable that the Leucaethiopes were a tribe of negroes whose complexion was rather less dark than that Mores blancs," informs us that they compose a considerable body of attendants at the court of the king of Loango ; the same statement is made by Ludolf, ubi supra, and by the author of the Hist. Gen. des Voyages, t. vi. p. 250 et seq. : Bowdich, Mission to Ashantee, p. 292, observes, that the king had at his court " nearly one hundred negroes of different colours, through the shades of red and copper to white ;" he adds that they were " generally diseased and emaciated ;" some of these were probably Albinoes. Cook, in his first voyage, saw six Albinoes in the small population of Otaheite, v. ii. p. 188 ; in his second voyage he saw one in New Caledonia, v. ii. p. 113, 4; and in his third voyage, he met with three in the Friendly Isles, v. i. p. 381, 2. These, it may be remarked, must have belonged to the Malayan variety. See also Winterbottom, Account of Sierre Leone, v. ii. p. 166 et seq. ; Stevenson, in Brewster's Encyclopaedia, art. *' Complexion," p. 41, 2; Bory St. Vincent, L'Homme, t. ii. §. " Hommes Monstreux," p. 143-7 ; also in Diet. Class. d'Hist. Nat. art. " Homme,"' p. 166 et seq.; Renauldin, in Diet, des Scien. Med. art. " Albino ;" Lawrence's Lect. p. 287 ; Is. St. Hi- laire, Anom. de l'Organization, t. i. par. ii. liv. iii. ch. i. p. 296, 314, 5, and art. " Mammiferes," in Diet. Class. d'Hist. Nat. p. 113. Some of the earlier writers did not hesitate to affirm, that they were confined to the offspring of negroes, Monge, Journ. Phys. 1782, p. 401 et seq. Suppl. We have no very distinct account of Albinoes among the Chinese and Mongols, but they appear to be as frequent among the Malays and native Americans as among the /Ethiopians. * Hist. Nat. lib. 7. cap. 2. See the note of Cuvier, in his edition of 7th . . 11th books of Pliny, t. i. p. 18. t Noct. Attic, lib. 9. cap. 4. i Polyhistor, cap. 15. p. 25. See the remarks of Saumaise, Exerc. Plin. p. 134, and of Pauw, t. ii. note in p. 13. § Lib. 5. cap. 8. We also find the same term in Pomponius Mela, lib. 1. cap 4, and in Ptolemy, Geog. lib. 4. cap. 6; but it is not accompanied by any description of the people so designated. f| Among others by Blumenbach, Gen. hum. var. $ 78. See Is. St. Hilaire, p. 297, note. We may remark that the term is objectionable, as indi- cating that the Albino is confined to the .lEthiopic variety. ALBINO. 85 of the Africans generally* It has been like- wise supposed that Celsus alluded to the Al- bino, when he speaks of a peculiar condition of the skin under the name of Leuce ;f but this appears to be a morbid cutaneous affection, and to have no reference to the subject now under consideration. From the number of Albinoes which were supposed to exist in certain countries, as well as from the marked peculiarity in their ap- pearance, an opinion was long entertained that they formed a distinct race or variety of the human species,J originating in some unknown cause, and bearing the same relation to the other inhabitants of the countries in which they are found that the acknowledged varieties of the human species bear to each other. But this opinion, although sanctioned by high authority, may be considered as decisively disproved by the well-ascertained fact, that Albinoes are born of parents who do not possess this characteristic peculiarity of the skin, hair, and eyes.§ Although Albinoes are of comparatively rave occurrence in Europe, yet we have had a suffi- cient number of examples to render us per- fectly familiar with the appearance which they present, and with the precise nature of the * See the note of Hardouin in loco, Valpy's ed. p. 1285, Le Maire's, t. ii. p. 438 ; also the remark of M. Marcus in M. Ajasson's Trans, of Pliny, t. iv. p. 185. It is, perhaps, to this lighter coloured negro, rather than to the proper Albino, that we must refer, in part at least, the accounts which are given by travellers of the great number of white Africans that have been collected in certain situa- tions. We may remark that all accounts of Albi- noes that are given in general terms only, should be received with a certain degree of caution, unless the peculiar state of the eye is distinctly noticed. Humboldt ^remarks that the missionaries, when they amet with any Indians that were less black than ordinary, were accustomed to call them white; Pers. Nar. by Williams, v. iii. p. 287 et seq. See Prichard, in Medical Cyclop. Art. " Tem- perament," p. 163. f De Medicina, lib. 5. cap. 28. § 19. X This appears to have been the case even with Haller, El. Phys. xvi. 4. 13. p. 492. Voltaire main- tains this hypothesis, Essai sur les mceurs, CEuvr. t. xiii. Introd. and p. 7, 8. Bnffon inclines to it; but his opinion on this point is not decided or uniform, t. iii. p. 501. See Is. St. Hilaire, p. 295. § In addition to the authors already referred to, we have a case of this kind by Helvetius, Hist. Acad. Sc. 1734, p. 15 . . 7. The Albiness described by Buffon was born of black parents : see also Castillon, in Berlin Mem. 1762, p. 99 . . 105 ; Dic- quemarc, Journ. Phys. 1777, p. 357 . . 0, and 1788, p. 301 et seq. ; Hist. Acad. Scien. 1744, p. 12, 3; and Maupertuis, Ven. Phys. p. 135 etseq. : Jeffer- son, Notes on Virginia, p. 103 . .5, mentions an in- stance of three Albino sisters born of black parents ; two of these had black children ; Firmin, Descrip. de Surinam, t. i. p. 153, 5 ; Goldsmith's Anim. Nature, t. i. p. 452 , 3 ; Brue, Hist, des Voyages, t. iii. p. 370, 0. See on this point Is. St. Hilaire, p. 303. We have a decisive proof that the peculiarity of the 'Albino is merely accidental and individual, and does not constitute a distinct variety, in the state of the offspring of an Albino and a black negro, which is not intermediate between the two, as in the case of the Mulatto ; Hunter, on the Anim. (Econ. p. 248 ; Is. St. Hilaire, p. 305.. .7. circumstances which characterize them.* The skin is of a milky whiteness, without the slightest admixture of the brown or olive tint which is found in the complexion of even the fairest European female ; the hair is also per- fectly white,f and is generally of a soft or silky texture, while all the coloured parts of the eye are of a delicate rose colour. We are informed that the skin of the African and American Albino is not only completely free from any shade of brown or olive, but that it is also devoid of the pink tinge which is found more or less in the complexion of the European. It would appear, likewise, that the skin of the tropical Albino is frequently in a diseased state, being covered with scales of a leprous nature, and with a serous exudation, which proceeds from the fissures or clefts that take place in various parts of the surface. J It has been a very general opinion, that be- sides the peculiar state of the integuments, the Albino possesses a general delicacy of habit and constitution, and that he exhibits a defici- ency even of mental power.§ For this latter opinion there appears to be no sufficient foun- dation, and with respect to the former we may remark, that any general weakness of the phy- sical frame, if it be actually found to exist, may be probably referred, at least in some degree, to the peculiar condition of the eyes and the skin, which are not well adapted either to a * We have a copious list of references in Blu- menbach, p. 278 . . 0, in Lawrence, p. 281 . . 9, and in Is. St. Hilaire, ut supra and §. 5. One of the earliest of what may be considered as the correct descriptions is that of Buffon, Supp. t. iv. p. 559 et seq. The descriptions of Blumenbach, S. 78, and of Saussurc, Voy. §. 1037 . . . 1043, are par- ticularly correct and characteristic : to this we may add the more recent account of Is. St. Hilaire, t. i. par. 2, liv. 3. ch. 1, §. 2 and 5. We are informed by Ludolf, ubi supra, that the first modern writer who distinctly mentions the Albino is Tellez. t Blumenbach particularly characterizes the whiteness of the hair of the Albino as being " gilva , colori cremoris lactis quodammodo comparanda," p. 275. X See Vossius, Ludolf, De la Croix, Cook's First Voyage, and Winterbottom, ut supra ; Blumen- bach, p. 274; Buffon, in Hist. Acad. Scien. 1760, p. 17 ; St. Hilaire, p. 304, 5 : Wafer, in his de- scription of the white inhabitants of Darien, p. 134, et seq., says that there is a white down on their skin. § Wafer, p. 134-8 ; Buffon, t. iii. p. 503; Wood's Trans, vol. iii. p. 420 ; Voltaire, t. xv. p. 269,70; Pauw, t. ii. p. 9, 10 ; Raynal, t. iii. p. 288 ; Du- bois on the People of India, ch. xv. p. 199 et seq. ; Finnin.t. i.p. 153 . . 5; Dalin, in Amcen. Acad. t. vi. p. 74, note ; Isert, Voy. en Guinee, ch. xv. p. 199 et seq. ; Labillardiere, Voyage, t. ii. p. 141 ; Win- terbottom, ut supra; Rayer, sur le Pean, t. ii. p. 193 . . 203 ; Blandin, Diet. Med. Chir. Prac. "Al- binie ;" Breschel, Diet, de Med. " Albino;" Sonini, in his edition of Buffon, t. xx. p. 355-6, note. So far as regards the state of the intellect, the charge is repelled by M. Sachs, who gives a minute account of the peculiarity in his own person and that of his sister ; Hist. Nat. duor. Leucaethio- pum. Jefferson informs us, that the Albinesses, of whioh he gives an account, were " uncommonly shrewd, quick in their appehension and reply," p. 103-5. 86 ALBINO. bright light or to a high temperature, and there- fore render the individuals less able to bear exposure to the weather, or to perform the ordinary occupations of life. To the same cause may be ascribed the morbid condition of the skin, which, as was remarked above, occurs not unfrequently in hot climates, and which is not observed in the European Albino. Partly from the circumstances stated above, and partly from the idea of imperfection or defect, which is connected with their appearance, the tropical Albino is generally regarded by his country- men with a degree of compassion or even of contempt ;* and hence is derived one of their popular denominations, chacrelas, which is a corruption of kakkerlakken, the Dutch name for the cock-roach, as being, like those animals, able to leave their haunts only in the evening.! Besides the complete Albino, which we have now described, there are occasional examples of individuals, where the whiteness of the skin exists in certain parts of the surface only, while the remainder of the body is of its ordinary colour. I In the majority of cases the peculi- arities whidreonstitute the Albino are connate, and continue during life without any change. There are, however, some instances, where the whiteness of the skin does not exist at birth, but makes its appearance at a subsequent pe- riod, generally by slow degrees, until the com- plete Albino character is induced.§ When * Vossias, p. 68, informs us that they are avoided by the other negroes, as supposed to be diseased. De ]a Croix says the negroes regard them as mon- sters, and do not permit them to multiply, ut supra. Dubois, p. 199 et seq. observes that they are named lepers by birth, and that when they die their bodies arc not buried or burnt, but cast on dunghills. See also Firmin, ubi supra. t Blumcnbach, p. 277 : Lawrence, p. 287 ; St. Hilaire, p. 296. t Phil. Trans, vol. xix. p. 781, and Lowthorpe's Abridg. vol. iii. p. 8 ; Buffon, t. iv. p. 565. tab. 2, et p. 571, tab. 3; Arthaud,in Journ. Phys. 1789-!pt. 2. p. 277,8 •, Rush, in Amer. Trans, vol. ii. p. 392 et seq. ; Gumilla, El Oron. Ilus. t. i. p. 109 et seq. ; Ditto, Hist, de l'Oronoque, trad. t. i. p. 150 et seq. ; Jefferson, p. 105; Blumenbach, §48; Rayer, ut supra ; Is. St. Hilaire, p. 309 et seq. ; Isert, p. 156. Bell, in Travels in Asiatic Russia, p. 217,8, saw a number of persons with white spots on the skin, but it seems probable that this was the effect of some cutaneous disease. The partial Albino appears to have been noticed by the ancients ; Lucian, Prometh, t. i. p. 15. § Blumenbach, p. 276, says it is " semper con- natus ;" see, also, Lawrence, p. 285. There are, however, certain well authenticated cases, where the skin of the negro has gradually changed its co- lour from black to white ; sometimes the change has been general, sometimes only partial ; Bates, in Phil. Trans, vol, li. p. 175 et seq. ; Gualtier, in Journ. Phys. t. lxx. p. 248 et seq. ; Le Cat, sur le Peau, p. 112 et seq. ; Rayer, ut supra ; Fisher, in Manch. Mem. vol. v. p. 314 et seq. ; Rush's Re- marks on the same, Amer. Trans, vol. iv. p. 289 et seq. In one of the four cases which are men- tioned by Le Cat, the change of colour appears to have been the consequence of a severe burn or scald. Besides the partial Albino, we have what has been termed the imperfect Albino, where the peculiarity exists in a certain degree only ; Is. St. Hilaire, §. 4. p. 312 et seq. once formed it does not seem that it ever dis- appears, or is even in any degree diminished, nor have we any authentic accounts of its being removed by any constitutional change, either natural or morbid, or by external applications. Although, as has been stated above, this peculiarity occurs in individuals, who did not derive it from their parents, yet, like all those deviations from the ordinary structure of the body, which have been styled accidental varie- ties, when once produced, it is disposed to propagate itself by hereditary descent. There are also certain individuals, who have a ten- dency to produce it; so that even among the few European Albinos, of which we have a minute account, we have cases of its occurrence in two or more members of the same family, either as connected by parental descent, or by collateral relationship.* ■ We have no instance on record of the offspring of a male and female Albino. The whiteness of the skin and hair, both general and partial, is not confined to the hu- man race ; it is found in most, if not in all the species of the mammalia, and in some of these, as in the dog, the horse, and the rabbit, is the subject of daily observation ;f in most of them, however, the peculiar state of the eye does not exist. These white varieties, like other analogous cases among the lower animals, when once produced, are strictly hereditary, in which re- spect they differ somewhat from the human Albino. Various opinions have been entertained by physiologists respecting the nature of this pecu- liarity, whether it should be considered as a morbid affection,j depending upon a diseased state of the constitution, and also respecting its immediate or efficient cause. The first of these points may be regarded as a verbal con- troversy, depending altogether upon our defi- nition of morbid action ; but we conceive, that according to the ordinary definition of the term, we should not consider it as a disease, but as a connate deviation from the perfect structure of the animal frame, not produced by an external cause, and not removable by a remedial agent. For a correct knowledge of its physical cause, we are indebted, in the first instance, to an in- genious conjecture of Blumenbach's, who ac- counted for the red colour of the eye, and its extreme sensibility to light, by the absence of the pigmentum nigrum.§ * See particularly Saussure's account of the two boys of Chamouni and Sachs's Narrative ; also Blu- menbach, p. 276 and 279, note ; Firmin and Jeffer- son ut supra ; Pauw, t. ii. p. 25 ; Bory St. Vincent, L'Homme, 'p. 144, mentions an Albino of the third generation ; Is. St. Hilaire, passim. ' + Blumenbach, p. 281, 2; Is. St, Hilaire, p. 297 . . 9. t " Ad cachexias referenda videtur affectio," Blumenbach, p. 274 ; Is. St. Hilaire, §. 6, supposes that there are two species of Albinism, one the effect of disease, the other a true anomaly ; but we con- ceive that the term is not correctly applied to the former state. § Comment, de Oculis Leucanhiopum, et De Gen. Hum. var. §. 78. ALBINO. 07 This conjecture was shortly after verified by Buzzi of Milan, who took advantage of an opportunity which presented itself, of dissecting the eye of an Albino, in which the pigmentum nigrum could not be detected.* He also ex- amined the structure of the skin, which appeared to be deprived of the rete mucosum, that part of it in which its specific colour is supposed to reside ; the hair was also found to be deficient in its central coloured part.f Whether, in these cases, the pigmentum nigrum of the eye and the rete mucosum of the skin are absolutely deficient, or are only deprived of their colouring matter, so as not to be detected by the eye, is a point on which different opinions have been formed by anatomists; X perhaps, upon the whole, we may be induced to consider the lat- ter opinion as the most probable. What are the circumstances in the consti- tution of the parents which should lead to this peculiarity in their offspring is entirely un- known, nor have any conjectures been formed on the subject which can be considered as even plausible.§ The hypothesis of Buffon, which at one time obtained a considerable degree of credit, that white is, as it were, the primitive colour of nature, which, by various external causes, is changed to brown or black, but which the body lias always a tendency to resume under favorable circumstances,|| is completely without foundation : nor does it appear that we can explain it upon the principle, that do- mestication and the habits of civilized life have a tendency to produce a lighter shade of the complexion, because we trace no connexion between the supposed cause and the effect, * For some remarks " on the colour of the pigment of the eye," and its effect on vision, as applicable to the eye of the Albino, see Hunter, p. 243 . . 253 ; also Blumenbach, 51. " Capillorum cum cute consensus," and §. 53, " Irides oculorum cum capil- lorum colore consentientes." f Sachs gives us a minute account of the analysis of the hair of the Albino, compared with Vauquelin's analysis of hair in its ordinary state, from which it appears that no iron could be detected in it. | Blandin, Diet. Med. Chir. Prat. " Albinee :" Rayer, §. 630. § Mansfeldt is disposed to ascribe the production of the Albino state to some shock given to the fcetus, by an impression made upon the mother ; it is characterized as a " cessation totale, momentanee d'action cerebrate ; " Journ. Compl. t. xv. p. 250 et seq. Is. St. Hilaire essentially adopts this hypo- thesis, ascribing the peculiar state of the skin to an " arret de developpement," in consequence of which the colouring matter is not formed at the requisite period, p. 319,0. The idea, that it depends upon something peculiar in the seminal matter of the parent, which was maintained hy Herodotus, Thalia, §. 101, and was controverted by Aristotle, Hist. Animal, lib. 3. cap. 22, has been revived by Mau- pertuis, Diss. 2, and by Pauw, t. i. p. 179, and t. ii. p. 21. Lc Cat refers the colour of the negro to a pecu- liar substance, which he names " /Ethiope animal," which he supposes is contained in their fluids, ana- logous to the black inky matter of the cuttle fish ; par. 2. art. 1 ; the absence of this substance con- verts the negro into an Albino. || T. iii. p. 502,3. ; Wood's trans, t. iii. p. 422. We may remark that this speculation of Button's is precisely the reverse of that of Hunter, p. 243 ct seq. and because the production of the Albino is complete in the first instance, and not brought about by any gradual or progressive alteration. It appears that we must come to the con- clusion, that although the anatomical or phy- sical cause of the peculiarity is ascertained, yet that we are entirely ignorant of its remote cause, or of that train of circumstances which leads to its production.* * " The following cases have not been referred to in the body of the article; DelaNux, Hist. Acad. Scien. 1744, p. 13 ; Camelli, Phil. Trans, v. xxv, p. 2268; Duddell on the Eye, Suppl. to, sect. iii. §. 30 et seq.; Percival, Irish Trans, v. iv. p. 97, 8 ; Hunter, Anim. (Econ. p. 250, 1 ; Traill, in Nich. Journ. v. xix, with an Add. by the editor ; Mansfeldt, Journ. Compl. t. xv ; Ansieux, in Journ. Med. de Corvisart, t. xiv, p. 263, 4. For the following epitaph, which appears to have been written on an Albino child, we arc indebted to a literary friend, the Rev. Jos. Hunter. " Upon Thomas, son of Ric. Elmhurst by Mar- garet his wife, daughter to Ric. Micklcthwaite : whose promising parts, were interrupted by an early death. "... This boy no Albian was, yet gray hair'd borne Who saw old age and night as soon as morne. His grave's a cradle ; there his God him lay'd Betimes to sleep lest he the wanton play'd. Bid him good night ! i'th bed of dust sleep on Until the morne of Resurrection. " Anagram. " Lo Earth misseth me, 1632." From the Church of Worsborough, Com. York. BIBLIOGRAPHY. — Ansieux, in Journ. Med. de Corvisart, t. xiv. Argensola, Conquist. de las Islas Malucas. Lond. 1609. Aristoteles, Opera uDuVal. Par. 1619. Arthaud, in Journ. Phys. pour 1789. Bates, in Phil. Trans, v. li. Bell's Travels. Glas. 1763. Blandin, in Diet. Med. Chir. Prac. " Albinie." Blumenbach, Gen. Hum. var. (ed. 3.) Gott. 1795; Ditto, Comment, de Oculis Leuca>th. Gott. 1786. Bory St. Vincent, in Diet. Class. d'Hist. Nat., " Homme ;" Ditto, l'Homme. Par. 1827. Bostock, in Brewster's Encyc. " Albino." Bowdich, Mis- sion to Ashantee. Lond. 1819. Breschet, in Diet, de Med., " Albino." Brown, in Brewster's Encyc, " Ceylon." Brue, in Hist. Gen. des Voyages, t. iii. Buffon, Hist. Nat. (ed. 2). Par. 1750. ; Ditto, by Sonnini. Par. An. 8; Ditto, (trans.) by Wood. Lond. 1812. ; Ditto, in Hist. Acad. Scien. pour 1766. Camelli, in Phil. Trans, v. xxv. Castillon, in Ber- lin Mem. 1762. Celsus, De Medicina, ab Alme- loveen. L. B. 1730. Clayton inManch. Mem. v. ii. Cook's first voyage, ]by Hawkesworth. Lond. 1773. Ditto, second ditto. Lond. 1777. Ditto, third ditto. Lond. 1784. Cordiner's Description of Ceylon. Lond. 1807. Cortesius, De Insulis nuper invent. Narrat. Colon. 1532. Dalin, Amcen. Acad. t. vi. De la Croix, Relation de l'Afrique. Lyon. 1688. De la Nux, in Hist. Acad. Scion, pour 1744. Diane-- marc, in Journ. Phys. pour 1777 and 1788. Dubois, on the people of India, (trans.) Lond. 1817. Dud- dell, on the eye, and Suppl. Lond. 1729. Firmin, Descrip. de Surinam. Amst. 1767. Fisher, in Manch. Mem. v. v. Gellius, Noctes Atticse. Basil, 1565. Goldsmith's Animated Nature. Lond. 1822. Gaultier, in Journ. Phys. t. lxx. Gumilla, El. Oro- noco ilust. Madrid. 1745. Ditto, Hist, de l'Oro- noque (trad.) Avignon. 1758. Haller, Elem. Physiol. Laus. 1757. Helvetms, in Hist. Acad. Scien. pour 1734. Herodotus, by Beloe (3d. ed.) Lond. 1812. Humboldt's Pers. Nar. by Williams. Lond. 1814. Hunter, on the Animal (Economy. Lond. 1792. Isert, Voyage en Guinee. Par. 1793. Jefferson's Notes on Virginia. Phil. 1794. Knox's ALBUMEN. Account of Ceylon. Lond. 1681. Labillardiere, Voyage. Pai. 8. Lawrence's Lectures. Lond. 1819. Le Cat, Traite de la Peau. Arnst. 1765. Lowthorpe's Abridg. of Phil. Trans. (2d. ed.) Lond. 1716. Lu- cianus a Grarvio. Amst. 1687. Ludolf, Hist. jEthiop. comment. Franc. 1691. Mansfeldt, in Journ. Compl., t. xv. Maupertuis, Venus Physique. Haye. 1746. Monge, in Journ. Phys. pour 1782. Pauw, Recherches sur les Americains, Lond. 1760. Per- cival's Account of Ceylon. Lond. 1803. Ditto, in Irish Trans., v. iv. Plinius, Hist. Nat. a Valpy. Lond. 1826. Ditto, a Lemaire. Par. 1827. Ditto, lib. vii. . . xi„ a Cuvier. Par. 1827. Pline, Hist. Nat. par Ajasson (trad.) Par. 1829. Pomponius Mela, a Gronovio. L. B. 1782. Prichard, in Cy- clop, of Pract. Med., " Temperament." Ptolemaeus, Geographia, a Bertio. Amst. 1618. Rayer, Traite des maladies de la Peau. Par. 1826. Raynal, Hist, des Indes. Neuch. 1785. Renauldin, in Diet, des Sc. Med., " Albino." Ribeyro, Hist. Jde Ceylon. Trev. 1701. Rush, in Amer. Trans., v. ii. and iv. Sac?is, Hist. Nat. duor. Leucaethiopum. 1812. St. Hilaire, ( Isid,), Anomalies de l'Organization. Par. 1832. ; Ditto, in Diet. Class. d'Hist. Nat., " Mam- miferes." Saussure, Voyages dans les Alpes. Ge- nev. 1787. Solinus, Polyhistor, cum Salmatii, Exerc. Plinian. Traj. ad Rhen. 1689. Stevenson, in Brewster's Encyc. " Complexion" Traill, in Nicholson's Journ. v. xix. Voltaire, CEuvres. Par. 1819. Vossius, de Nili Origine. Hag. Com. 1666. Voyages, Hist. Gen. des, Haye, 1747. Wafer's New Voyage. Lond. 1699. Winterbottom's A ccount of Sierra Leone. Lond. 1803. (J. Bostock.) ALBUMEN, {Yx.Albumine, Germ. Eyweis- sstoff,) is one of the most important proximate principles of animal bodies ; it is the leading ingredient of the blood, of many of the secretions, and of muscular fibre, cartilage, and membrane : the white of egg (whence the generic term albu- men) presents it in considerable purity, and it is from this source, and from the serum of the blood, that we chiefly obtain it for the purposes of experiment. In this article we shall describe the leading properties of albumen ; and in others, refer to its principal modifications. The white of egg may be regarded as a combination of albumen with water; it con- tains small quantities of saline substances, which are inseparable in its liquid state. When it is evaporated at a temperature below 120°, it dries into a brittle, shining, transparent sub- stance of a pale yellow colour, inodorous and tasteless. Its ultimate constituents, exclusive of saline matters and a trace of sulphur, are carbon, hydrogen, nitrogen, and oxygen ; of these the relative proportions have been deter- mined by Gay Lussac and Thenard, who analysed the white of egg dried at 212°; and by Dr. Prout, who employed the dried serum of slightly inflammatory blood ; the following table shows its theoretical composition as con- trasted with these experimental results : — Atoms. Equivs. Theory. G. Lussac. Prout. Carbon. . 8 48 51.61 52.883 50.00 Hydrogen 7 7 7.53 7.540 7.78 Nitrogen 1 14 15.05 15.705 15.55 Oxygen 3 24 25.81 23.872 26.67 1 93 100.00 100.000 100.00 White of egg, when heated to about 150°, coagulates, that is, it becomes a white, translu- cent, and somewhat elastic substance, which, when cautiously dried, shrinks up and assumes the appearance of horn, becoming tough, yel- lowish, and insoluble in water. Two parts of white of egg and one of water entirely co- agulate when duly heated ; equal parts remain, under the same circumstances, semi-fluid ; a mixture of one part of white of egg and ten of water becomes opaque, but is not coagulated ; and a milkiness is perceptible when the al- bumen only forms a thousandth part of the solution * Fresh-laid eggs, and those which have been oiled upon the surface do not per- fectly coagulate when put into boiling water, in consequence, probably, of the dilute state of the albumen. One hundred parts of the fresh albumen of the egg, when carefully evaporated in vacuo, leave a residue = fifteen parts. One hundred parts of the coagulated white of a duck's egg (dried in vacuo with sulphuric acid) leave 13.65 parts, which, steeped in water, acquires its original appearance, but in four days only took up 68 of water, though it had lost 86.35.t When albumen is made part of the voltaic circuit, it presents appearances dependent upon the power used, which, when considerable, excites so much heat as to coagulate it; but with a feeble power and the poles sufficiently distant, coagulation ensues most plentifully at the negative platinum wire ; a coagulum also forms at the positive wire, where acid is also sparingly evolved. These phenomena are much interfered with by the evolution of gaseous matters at the respective poles, which occasion a froth, and the appearance of more extensive coagulation than actually occurs. When coagulated white of egg is boiled for several hours, it shrinks up and becomes har- dened, communicating traces of animal matter to the water. Heated by high pressure steam in a copper digester to 400°, it blackens the interior of the vessel, and dissolves, leaving a small residue of unaltered albumen. The solution is brown, and has the odour of boiled meat (from osmazome ?). This action deserves further investigation. J White of egg soon runs into putrefaction, and evolves sulphuretted hydrogen. The se- rum of blood kept for two years in a well- stopped phial, blackened its interior, and be- came a stinking, pale, yellow liquid, still co- agulable by heat, and containing hydro-sul- phate, carbonate, and acetate of ammonia, and a fetid volatile matter : a portion of yellowish white purulent-looking matter, containing un- decomposed albumen, remained at the bottom of the phial. Coagulated white of egg, even under water, long resists putrefaction. * Bostock, Nicholson's Journal, vol. xiv. and Medico-Chirurgical Transactions, vol. i. and ii. t Chevreul, Mem. du Museum vii. 180. Ann. de Ch. et Ph. xix. 46. | Gmelin, Handbuch der Theoretischen Chemie, ii. 1053. 3rd ed. Frankfort, 1827. ALBUMEN. 89 One hundred parts of dried white of egg, subjected to destructive distillation, yielded carbonic acid, carburetted and sulphuretted hydrogen, prussic acid, carbonate of ammonia partly in solution and partly sublimed, stinking volatile oil, and 14.9 of spongy difficultly com- bustible carbon, which, by incineration, left 2 21 of ash composed of carbonate of soda, phosphate of soda, and phosphate of lime, (Hatchett.) Nitric acid, dropped into a solution of albu- men, forms a white, flaky precipitate, which is more or less abundant according to the state of dilution of the solution, and which is soluble in ammonia and potash. When coagulated white of egg is kept for some weeks in very dilute nitric acid, it acquires a yellow colour, and if digested in boiling water it dissolves, and has acquired the properties of gelatine, and is precipitated by tan and muriate of tin. Hatchett.)* Cold nitric acid sp. gr. 1.25, gradually tinges coagulable white of egg of a yellow colour, dissolving a little of it, and forming malic acid, with the evolution of nitro- gen ; its surface becomes tallowy, and in twenty-four hours it falls into a pale yellow powder, which is acid and composed of nitric, nitrous, and malic acids with albumen ; when thoroughly washed with water, it becomes more neutral and of an orange colour, still reddening litmus, and remaining insoluble in water, but soluble in caustic potash .f When coagulated white of egg is digested in hot nitric acid, nitrogen, nitrous gas, carbonic acid, and prussic acid are formed, and a dark yellow solution obtained, which is precipitated by the addition of water and ammonia, and which contains malic and oxalic acids, bitter matter, and fat. (Hatchett.)! Sulphuric acid is a less powerful precipitant of albumen than nitric acid. Dilute sulphuric acid dropped into an aqueous solution of albumen occasions a precipitate which is so- luble in excess of acid ; ferrocyanate of po- tassa throws it down. When coagulated albu- men is digested in sulphuric acid, very slightly diluted, it yields a deep crimson solution.§ Coa- gulated serum digested in sulphuric acid diluted with six parts of water, converts it into acid sulphate of albumen, which, when edulcorated with cold water, becomes more neutral, and is soluble in warm water, forming a gelatinous solution, which is precipitated by sulphuric, muriatic, and nitric acids, and by the alkalies. (Berzelius.)|| Coagulated white of egg digested in hot sulphuric acid becomes carbonized without forming artificial tan. (Hatchett.) When a solution of recently fused phosphoric acid (pyro-phosphoric acid) is added to solution * Phil. Trans. 1799. t Berzelius Lehrbuch der Thier. Cheinie, p. 38. WShler's Translation. Dresden, 1831. X Phil. Trans. 1799. § According to Raspail, when sugar is previously dissolved in the sulphuric acid, the albumen is co- loured purple, which is deeper in proportion as the acid and sugar are in greater quantity. |] Lehrbuch der Thicr. Chemie. of albumen, it occasions an abundant pre- cipitate : the acid gradually loses this property, and again acquires it by fusion and ignition. (Berzelius.) Muriatic acid occasions a precipitate in al- buminous solutions, and entirely throws down the albumen when aided by heat ; but the precipitate is soluble in excess of acid, and in ammonia and potassa. A muriated albu- men may be formed in the same way as the sulphate. (Berzelius.) Coagulated egg-albu- men digested in muriatic acid gradually ac- quires a purple colour. (Hatchett.) Albumen which has been precipitated by muriatic acid, often becomes reddish when collected and ex- posed upon a filter. When coagulated seralbumen is digested in acetic acid, it becomes soft and transparent, and, aided by a gentle heat, dissolves with the evolution of a little nitrogen. This solution is precipitated by the alkalies, but a slight excess again renders it clear : it is also precipitated by sulphuric, nitric, and muriatic acids, and by ferrocyanate of potassa. When this acetic so- lution of albumen is evaporated, it leaves a transparent sour residue, soluble in warm water acidulated by acetic acid. (Berzelius.) Albumen is slowly soluble in liquid ammo- nia. In solution of potassa it becomes gelati- nous, and yields a pale yellow green solution, precipitable by acids and alcohol, and by acetic acid. Heated in liquid potassa, albumen evolves ammonia. Alcohol and ether coagulate ovalbumen, but pure ether (free from alcohol) does not co- agulate seralbumen. (Gmelin.) When serum is shaken with ether, it soon separates upon the surface, holding fatty matter in solution. (Gmelin.) Coagulated serum digested in al- cohol or ether yields a solution of fatty matter. Coagulated ovalbumen, when long boiled in water, becomes bulky and falls into pieces, and a small portion is dissolved : the filtered so- lution, evaporated at 212°, leaves a pale brown film, and is alkaline ; it is rendered turbid by mineral acids, acetic acid, and tincture of galls, and by many metallic salts. When albumen which has been cautiously dried at a low temperature (without coagula- tion) is triturated with four parts of water, it yields a solution resembling fresh al- bumen. A solution of the white of an egg in a pint of water occasions no precipitate in lime, bary- tic or strontia water, nor in solution of sulphate of lime. Some of the neutral salts render it more or less turbid, and it is copiously precipitated by solution of alum. Nitrate, acetate, and subacetate of lead are precipitated by albuminous solutions. One part of fresh ovalbumen in 2000 of water, or one of dried albumen in 10,000 of water is rendered turbid by subacetate of lead. A four-hundredth part of liquid, or a two thousandth of solid albumen is precipitable by corrosive sublimate. (Bos- tock.) The precipitate is blackened by potassa, and is probably a compound of muriate ofalbu- 90 AMPHIBIA. men and calomel. Nitrate of silver, muriate of gold, and of platinum, also precipitate albumi- nous solutions. These precipitates are mostly triple compounds of acid, albumen, and oxide, and several of them are redissoluble in excess of liquid albumen. Albumen is precipitated by tannin in the form of a yellow viscid combination. Water, holding a thousandth part of solid or a two- hundredth of liquid ovalbumen, becomes tur- bid after some hours by the addition of a solution of galls containing 2.5 per cent, of solid matter. (Bostock.) The above are the principal chemical pro- perties of liquid and solid albumen as obtained from the egg and from serum of blood ; several of their modifications will be noticed under other heads, such as Fibrin e, Milk, Bile, &c. The cause of the coagulation of albumen is, in many cases, obscure and even inexplicable. It ap- pears possible that the acids by which it is co- agulated enter into combination with it so as to form insoluble compounds ; the same change pro- bably happens with certain metallic salts, and with tan ; its coagulation by alcohol has been ascribed to the abstraction of water. Having remarked the copious coagulation of albumen at the electro-negative pole in the voltaic cir- cuit, I was induced to ascribe the fluidity of albumen to combined soda, the evolution of which seemed to cause its solidification, and it appeared possible that the acids and even alcohol might also occasion coagulation by the abstraction of soda ; and that its more enigma- tical coagulation by heat only, might be as- scribed to the transfer of soda from the albu- men to the water. It has been objected to this statement that the addition of alcali to coagulated albumen does not reproduce liquid albumen, and that acetic acid causes no co- agulation ; but when albumen is once coagu- lated, its properties are essentially modified, and acetic acid, or even acetate of soda appear to form soluble compounds with it. (Gmelin.) Dr. Turner* supposes that albumen combines directly with water at the moment of being secreted, at a time when its particles are in a state of minute division ; but as its affinity for that liquid is very feeble, the compound is decomposed by slight causes, and the albumen thereby rendered quite insoluble. The or- ganization of albumen may certainly be con- cerned in its singular properties with respect to many coagulants : there are several albuminous fluids, which we shall hereafter refer to, which contain globules resembling those of the blood. In the voltaic coagulation of albumen, that which separates at the positive pole contains globules, which, under the microscope, resem- ble the blood-globules deprived of their co- louring matter.f The readiest tests of the presence of albumen in fluids are its coagulation by heat, alcohol, * Elements of Chemistry, 4th ed. 868. + Provost et Dumas, Ann. de Chiinie et Physique xxiii. 52. and acids; when it is too dilute for such detection, it may be subjected to voltaic elec- tricity, or tested by corrosive sublimate, or by ferrocyanate of potassa; the alcali should, in the latter case, be previously neutralized by acetic acid. It would appear, from Orfila's experiments, that white of egg is an antidote to the effects of corrosive sublimate when taken into the stomach, and that, if administered in sufficient quantity immediately after the recep- tion of the poison, it prevents the progress of the symptoms. The white of one egg appeared sufficient to render four grains of the poison ineffective. The readiness with which some metallic oxides are received into the system may per- haps be ascribed to their affinity for albumen, with which some of them form compounds not easily decomposable, and in which the metallic oxide cannot be detected by the usual tests, till they have been subjected to heat sufficient to decompose the organic matter. Mercury and silver are thus, in certain cases, detected in the secretions and excretions. (W. T. Brande.) AMPHIBIA. — (AfipK, utrinque, /3io;, vita. Fr. Amphibies. Germ. Amphibien. Ital. Amphibie.) A class of vertebrated animals, hitherto almost universally considered as an order of Reptilia, constituting the Butrachia 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 branchiee 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 palpebrae. Genera, Proteus, Siredon, Menobranchus, Siren, Pseudobranchus. Order 2. — Anoura. Body short and broad. Feet during the tad- pole state wanting ; afterwards four, the hinder ones long and formed for leaping. Tail before the metamorphosis, long, compressed ; after- wards totally wanting. Ribs wanting. Ver- tebrae few and anchylosed. Tympanum open. Respiration at first aquatic by branchiae ; after- wards atmospheric by lungs. Branchiae at first external, but withdrawn within the chest before the metamorphosis. Impregnation effected ex- ternally during the passage of the ova. Genera, Rana, Hi/la, Cerutop/irys, Buf'o, Rhinella, Otilopha, Ductylethru, Bombinutor, 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, Salamaudra, Molge. Order 4. — Abranchia. Body long, formed for swimming. Feet four. Cranium solid. Tail compressed. Respi- ration by means of lungs only : branchiae none. No metamorphosis known. Genera, Menopoma, Amphiuma. Order 5. — Apod a. Body elongate, slender, anguiform. Feet none. Tail very short, almost wanting. Lungs one larger than the other. (The existence of branchiae at any period of life unknown.) Ribs very short. Sternum wanting. Ears concealed. Impregnation unknown, probably internal. Genus, 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- 02 AMPHIBIA. less, the body contracted longitudinally into as short a space as possible, the vertebrae very few, and anchylosed or soldered together into a single immoveable piece, and wholly devoid of ribs. On comparing with this formation, on the other hand, the extensive developement of the tail, the long flexible body, and gracile form of the newts or aquatic salamanders, and reflecting upon the obvious object of this structure in facilitating their motions in the water, we should hardly be prepared to find that the extraordinary extension of the hinder extremities in the frogs, the primary object of which is to afford the great powers of leaping just alluded to, is made subservient also to their aquatic life, by enabling them to swim with great facility, aided by a web of skin extending between the toes of the hinder feet. Now as we shall hereafter see, when treating on the respiration of these animals, that the occasional presence of water, and its applica- tion to the surface of the skin, is equally essential to the well-being of both these forms, it is very interesting to observe how admirably this peculiarity in the general re- quirements is provided for by the very different, and even opposite, construction of their form and limbs, which their individual habits of life demand. But to return to the detailed anatomy of the skeleton. On examining the general texture of the bones in this class, there is an obvious advance towards the firm calcareous substance of those of the higher forms of vertebrated animals when compared with the bones of fishes, they being more compact, and less tran- sparent and flexible than in the latter animals. The cranial bones, though they retain to a certain extent the character of those of fishes, in the permanent disunion of the different centres of ossification, at least in many in- stances, yet they do not overlap each other, as in that class, but, on the contrary, remain with their margins at least in contact, and in many cases actually united, though not by true sutures. The elements of which the cranium is essentially composed, and which in a higher grade of organization are found consolidated, are here still exhibited as distinct pieces ; a state of things which is strikingly imitated in the progress of the development of these parts in the highest classes during their growth. It is also to be observed that the bones of the face are more closely united to those of the cranium and to each other in the higher than in the lower forms of the class, exhibiting distinct and obvious links in the development of these parts, which we see so beautifully and gradually perfected in the as- cending series from fishes up to man. The following enumeration of the separate cranial bones of the amphibia, as existing in the menopoma alleganiensis, the gigantic sala- mander of America, will illustrate the general relations of the distinct centres of ossification, here remaining permanently detached. Fig. 14. In figs. 14 and 15 the different elements are thus designated: — a. the frontal; b. the exterior frontal ; c. the parietal ; d. the nasal ; e. the occipital ; f. the pterygoid ; g. the tympanic ; h. the jugal ; i. the superior maxillary; k. the intermaxillary; I. the vomer; m. the sphenoid ; n. corresponding to the or- bitary processes or alae of the sphenoid. In the frog and most others the palatine bones are distinct. We here find that the separate portions or elements which in this class are permanently detached, correspond almost ex- actly with the number found in the cranium of fishes. It will be observed by a reference to the figures, that the intermaxillary bones— and this is more or less the case in all the amphibia — are much developed transversely, as in the fishes, an affinity which has been already so much insisted on, and which is borne out by the condition of all the other parts of the cra- nium. The lateral extension of the upper and lower maxillary bones, for instance, as well as of the tympanic and jugal, expands the general form of the skull, without involving any ex- pansion of the cavity of the cranium, which is restricted to a small, central, elongated space. The latter bones also terminate in a condyle, which is received into a shallow glenoid cavity of the lower jaw, a peculiarity which offers a AMPHIBIA. 93 still further illustration of the proximity of this class to the fishes. The lower jaw consists of three distinct pieces on each side, an anterior, a lateral, and a posterior or articular portion. The anterior bone supports the teeth in those genera which have teeth in the lower jaw, and unites with its fellow at the symphysis. In frogs the lower jaw is devoid of teeth, but they are found in the upper jaw, bordering the in- termaxillary and the maxillary bones ; and the vomers are also furnished, each with a trans- verse row of teeth ; but in the salamander, the menopoma, the proteus, and others, they are found occupying the margin of the lower jaw. In the toads there are no teeth in the lower jaw, but the edge of the jaw-bone is serrated. The second bone of the inferior maxilla occupies the side, and is larger even than the former. It has at the posterior part a coronoid process, behind and within which is placed the third bone, which forms the medium of articulation with the cranium. It is to the os hyo'ides 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 hyo'ides, 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 vertebra are fewer than are found in any other animals. In the common frog Fig. 16. there are but nine, and in the pipa only eight. Of the nine vertebra in the frog, the first, the atlas, a, has no transverse processes ; there are two articular surfaces situated anteriorly, by which it is articulated to the two occipital condyles. In the seven following vertebra the anterior articular surfaces of the bodies are concave, and the posterior convex. This con- vex tubercle, which enters the concavity of the next vertebra, consists of the intervertebral car- tilage converted into bone. In the tadpole condition of the animal (and this remains per- manently the case in the perenni-branchial forms, as the menobranchus, the proteus, &c.) this intervertebral substance retains the soft con- sistence which characterises it in fishes ; and, as in that class, it is contained in the circum- scribed cavity formed by the cup-like hollows of the two articular surfaces of contiguous vertebra. The elongated fish-like form of those amphibia which retain their branchia 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 vertebra of the adult frog have long- transverse processes (Jig. 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 (Jig. 16, c J directed a little back- wards, to which the ilia (Jig. 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 (Jig. 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 vertebra 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 vertebra, commencing with the second, bear ribs, which are extremely small, and in fact merely rudimentary. In the tail the trans- 04 AMPHIBIA. verse processes are only found on a few of the most anterior vertebras. 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 c«dZi'a,'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 rounded head, received into the glenoid ca- vity of the shoulder-joint. The opposite extre- mity forms an almost globular surface for its articulation with the bone of the fore-aim, 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, I,) 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 calcis 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, (],) 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. The hinder legs are first seen, and are early employed as a feeble assistance to the more effective tail, as instruments of progression. The tail is developed, however, to a great degree, occupying the same relative size and situation as it is found to do in fishes. The coccygeal 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 the extraordinary magnitude of the flexors and extensors of the thigh, leg, and foot, which are in perfect ac- cordance with the great length of the bones of this extremity, which has been described. The muscles which form this important apparatus of motion are exactly analogous to those which are so peculiarly developed in the human leg. Thus the large glutei extend the femur, the rectus and triceps extend the leg, and by their united and sudden action forcibly throw the whole limb into a straight position, whilst the 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. — The foregoing consideration of the various structures of the organs appertaining to locomotion would pre- pare us for corresponding differences in those belonging to this important office. These variations, however, are not found exactly to follow those which have been described in the former class of organs. The tadpole condition of the higher amphibia does not correspond in the nature of its food, nor consequently in the structure of the alimentary canal, with the class of fishes, nor indeed with that per- manent tadpole, as it may be called, the larviform axoloth. The teeth, as has been already stated, vary in the different genera not so much in their size and form as in their situation. Thus the whole of the amphibia have teeth in the palate; the sala- manders have them also' in both the upper and lower jaws, the frogs in the upper only, and the toads in neither. In the two latter genera the palatine teeth are placed in a trans- verse line, interrupted in the middle. In the salamanders they form two parallel lines, con- taining not less than thirty on each. In the menopoma they occupy the anterior palatine margin of the vomer, forming a line on each side parallel with the maxillary and inter- maxillary teeth. In the axoloth they are arranged in the quincuncial order, and are nu- merous. But the most remarkable form and arrangement of the palatine teeth is found in the siren, in which they have the quincuncial arrangement; they are placed on two small 96 AMPHIBIA. bony plates on each side, probably rudiments of the vomer and palatine bones. Each of the larger has six or seven lines of teeth, about twelve on each line ; and each smaller bone bears four ranges of five or six teeth ; making in all nearly two hundred teeth in the palate. Those of the lower jaw in this animal are placed in similar order. In the proteus the teeth nearly resemble those of the salamander. The maxillary teeth are always slender, sharp-pointed, and closely set. The frog has about forty on each side of the upper jaw, of which eight belong to the intermaxillary bone. The salamander has about 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 oesophagus is wide and comparatively short. The stomach single, consisting of a simple sac, elongated in the lengthened forms of the sala- mander, the proteus, and other aquatic species. The intestine is but slightly convoluted, even in the short tailless family ; and there is com- paratively little difference in the diameter of its two distinct portions. It terminates, as in the reptilia, in a cloaca, or pouch, which also receives the openings of the urinary and genital organs. The anus in the toads and frogs opens on the hinder part of the back ; in the other forms it is situated beneath at the commence- ment of the tail, as in the reptilia. The liver, the pancreas, and the spleen are found in the whole of the amphibia ; and these organs are observed, in the elongated aquatic forms, to assume a corresponding lengthened shape. The liver is of considerable size, particularly in the salamanders. The gall-bladder exists in all cases, varying, how- ever, in size and form in the different genera. IV. Lymphatic and lacteal system. — This system is highly interesting in the amphibia, on account of its extreme development, and of its presenting several important and remark- able peculiarities in its structure. The investigations of Professor Muller of Berlin have lately brought to light the existence of pulsating cavities in the course of the lympha- tics, constituting a sort of ventricles for the pro- pulsion of their fluids towards the veins into which they are received. In the frog two pairs of these little pulsating sacs are found ; at the pos- terior part one is situated on each side of the extremity of the coccygeal bone, behind the hip- joint, and the anterior ones under the posterior edge of the scapula by the transverse process of the third vertebra. These cavities are of considerable size, and pulsate with some degree of regularity : the pulsations, however, do not coincide with those of the heart, nor are those on the one side always synchronous with those on the other. The posterior ones convey the lymph received from the legs and hinder parts of the body into the ischiatic veins, and the anterior pair, into which the absorbents of the arms and the anterior parts of the viscera, &c. open, convey this fluid into the jugular veins. The internal structure of these sacs is cellular; they communicate freely with each other on each side by anastomosing vessels. On inflating the organ, not only the lymphatic vessels are inflated, but the whole of the veins also. Dr. Marshall -Hall had previously observed a somewhat similar pul- sating cavity in the eel. These lymphatic ventricles in the amphibia have still more recently received further exami- nation and illustration by Professor Panizza of Pavia, who published the result of his researches in the year 1833.* Professor Muller's discovery was published in the previous year in the Berlin Annals. The lymphatic system is developed to an extraordinary degree in the frogs, as well as in several other genera of this class, its vessels being found in numbers and of considerable size immediately under the skin. The lacteals ramify upon the surface of the intestine in two layers, anastomosing and forming intricate plexuses on the mesentery, and terminating in two trunks, or thoracic ducts, which pass forwards one on each side of the spinal column. V. Of the sanguiferous system. — If the changes, so frequently alluded to, which the animals of this class undergo in passing from the condition of a fish to that of a reptile, have received repeated illustrations in the considera- tion of the structure of the skeleton, of the organs of motion, and of those of digestion, far more interesting and important are those which occur in the character of the circulation ; in which the view which has been taken of the true situation of the amphibia in the chain of animal development receives the most satis- factory proof. Beginning life with all the essential characters of the fishes, even in the functions of circulation and respiration, pos- sessing the single branchial heart of that class, how wonderful and beautiful are the changes which these systems of organs undergo, as the branchiae become obliterated to give place to pulmonic cavities, and the heart at the same time assumes the compound character and form of a systemic and pulmonic heart, in accordance with the change in the respiratory organs. The newts, or water-salamanders, afford the most satisfactory opportunity of observing these * Sopra il sistema linfatico dei rettili. fol. Pav. 1833. AMPHIBIA. 97 changes, as the branchiae are large in propor- tion, and remain external during the whole period of their existence ; the animal also acquires considerable size before these organs of aquatic respiration are lost. The heart in the early stage of these animals consists of a systemic auricle, which receives the whole of the blood from the system after circulation, and of a ventricle which propels it through a third cavity, the bulbus arteriosus, to the branchial arteries, of which there is one given to each branchial leaf. From the capillary branches of these arteries the aerated blood is received by the branchial veins, which, as in fishes, concur to form an aorta without an intervening ventricle. From the last, or posterior branchial artery, on each side is given off a branch which goes to the rudimentary pulmonic sac, and which ultimately forms the trunk of the pulmonary artery. But the most interesting and important change is that by which the continuous branches of what were originally the branchial arteries combine to form the two trunks of the aorta. This is effected by means of small communicating branches between the branchial arteries and the branchial veins, which, as the branchiae become absorbed, and their minute branches are obliterated and lost, gradually enlarge until they become continuous trunks; and the artery, which was originally branchial, then becomes the single root of the two descending aortas, 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- chiae, has decreased in the same proportion. The anastomotic branch (14) has acquired the size of the arch of the aorta, whilst the continuation of 2 is diminished, and the branchial leaflet is contracted in a corresponding degree. The branch 3 has become exceedingly small; and 4, which was before the smallest, is now the largest of all. By these changes in the relative di- mensions of the different vessels, especially in the enlargement of the anastomotic branches, the whole system of the circulation is gradu- ally being altered, until, in the third period, (fig. 20,) it has assumed the character of that in the reptile, by the total obliteration of the branchiae and their vessels, and the enlarge- ment of those branches, which, at first only anastomotic, have now become principal. In the adult condition of the animal, there- H 98 AMPHIBIA. Fig. 20. fore, the heart consists of a single ventricle, and of two auricles. The existence of a se- cond auricle was first demonstrated in the higher forms, the frogs and toads, by Dr. Davy,* and, although in the latest works of Cuvier and Meckel the auricle in these forms is de- scribed as single, yet the more complicated structure has since been amply confirmed by many other anatomists. Weberf especially has described the biauricular structure in a large American frog ; but he failed to demon- strate it in the perennibranchiate amphibia. From a very interesting paper by Mr. Owen, in the first volume of the Zoological Society's Transactions,^ it appears that the biauricular structure of the heart was ascribed by Hunter to all the amphibia except the perennibranchiate forms ; in which, however, the existence of the left auricle has been satisfactorily deter- mined by Mr. Owen, who has also given some very interesting illustrations of the mode in which the coexistence of branchiae and rudi- mentary lungs is associated with certain pecu- liarities of the circulation. The circulation in the adult amphibia, then, assumes exactly the character which we find in the reptilia, but in the most simple form. The little pulmonic auricle receives the blood perfectly aerated from the lungs by means of the pulmonary veins. The systemic auricle at the same time receives the impure blood from the system by the venae cavae. The blood from the two auricles is sent together into the single ventricle where it becomes mixed, and this mingled arterial and venous blood, thus but half purified, is propelled by the same impulse, partly into the pulmonary arteries to be more perfectly purified, and the remainder through the aorta and the whole circulating system to the different organs of the body. The aeration of the blood, therefore, is but imperfect ; a condition which is met with equally in the whole of the reptilia. VI. Resph'ation. — 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 Heizen der Batrachier, 8vo. 1832. \ Part iii. p. 213. to which its organs are subjected in the transit of the amphibia from the pisciform to the reptile state. Breathing water, in the first instance, exclusively, these animals are fur- nished in the tadpole condition with branchiae or gills, of a leaf-like form, considerably sub- divided, though far less so than in the fishes. These branchiae are, in the first instance, in all cases external ; but in the higher forms of the class they remain so situated only for a brief space, becoming, as in the frogs and toads, internal at a very early period of their ex- istence. They are supported by cartilaginous or osseous arches, connected with the os hy- oides, and the changes which they undergo are accompanied by alterations in the form of that bone, to which allusion has already been made, and an account of which will now be given. At that period of the tadpole's existence, at which its branchiae are in full action, and the lungs still restricted to the state of a black- ish, rudimentary tissue, we find the tympanic bones, (figs. 21, 22, e,) developed to a great -F%. 21. Fig. 22. d 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 branchise 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. 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, «,) the single piece (b,) and the two rhomboidal pieces (r, c ,) in the meantime become united and extended, (figs. 25, 26,) and gradually lose by absorption Fig. 25. Fig. 26. d ). The pteropods are commonly found floating in immense numbers at the sur- 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- lopoda 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 chylopoietic organs is seen in those of the loligopsis guttata, (Jig. 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 (fg). The crop (d) ends in the strong muscular giz- zard (e), and from the third stomach (,f g) the short intestine (/>) 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- Fig. 44. 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 spiki-cebebeata, 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 (Jig. 45, A) and the cod (Jig. 45, B). The oesophagus (a) of the frog-fish (Jig 45, A) leads to a large globular stomach (c) with a strong muscular cardiac sphincter (b). The pyloric extremity is also surrounded with strong muscular bands (d), and beyond its pyloric valve two pancreatic simple glandular follicles (ce) 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- ANIMAL KINGDOM. Fig. 45. ties (c e) along with the ductus communis choledochus ( /'). 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 vertebrate.'. This is shown in the annexed figure of the chylopoietic viscera as I found them in the xiphias gladius (Jig. 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 (_/") in a very short but distinct colon, which presents no ccecum in its course to the anus (g). The bilocular heart of fishes is entirely branchial ; it is often pre- ceded by a sinus venoms, and is always succeeded by a bid bus 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 branchise m the young. The lungs are always rudimentary, when present, sometimes in form of a shut single air-bag, sometimes divided or ramifie'd, and most generally communicating by a ductus pncumuticus 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 branchire, 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. Rcptilia, 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 116 ANIMAL KINGDOM. greater than in the amphibia. Their bones are more consolidated than in the lower vertebrata, theirpelvic arch, 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 coinpetely 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 diaphragm, 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 Reptilia.) 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 coeca-coli, as seen in the annexed diagram {fig. 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 musculai 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 coecum often indi- cates the original entrance of the yolk-bag. The two long coeca-coli (g) commence by nar- row entrances (A), and the short colon ends in a common cloaca (/) for the genital and urinary secretions. Inthepredaceous birds, as the eagles (Jig. 48), the oesophagus (a), the crop (i>), the infundibu- lum (c), and the gizzard (r/e), are capacious, thin, ■Fig. 48. 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 («) and genital organs (kk) enter the cloaca (I) 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 pleura to the back part of the trunk, the last rings of the trachea form an inferior larynx, the bronchi pass in a mem- 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 unsymmetrical 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 (Jig- 49), receives the end of the rectum (a), which forms a wide Fig. 49. rectal vestibule (b) : 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 ( /'), 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 (Jig. 50), where the rectum (a) opens into a wide and distinct rectal vestibule (b), 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. (k h A* 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 vertebras 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 ccecum, 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 unsymmetrical 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-regnum, Cyclo-neura vel Radiata. (JIassisl. Polygastrica. 2. Ponfera. 3. Polypifera. 4. Acalephas. 5. Echinoderma. II. Sub-regnum, Diplo-neura vel Articulata, Classis 6. Entozoa. 7. Rotifera. 8. Cirrhopoda. 9. Annelida. 10. Myriapoda. 11. Insecta. 12. Arachnida. 13. Crustacea. 118 ANIMAL. III. Sub-regnumCyclo-gangliatavel Mollusca. Classis 14. Tunicata. 15. Conchifera. 16. Gasteropoda. 17. Pteropoda. 18. Cephalopoda. IV. Sub-regnum Spini-cerebrata velVertebrata. 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. Grunt.) ANIMAL (from anima, breath, the living- principle. Lat. animal. Gr. ^ov. Fr. animal. Germ. Tliier. 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 Cyclopaedia, 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. Modem 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 liurmony 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, silrnium, 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, fluor, silicium, aluminium, magnesium, potassium, sodium, 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 fiuids 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 and urea, for ex- ample, have been formed synthetically, and a substance bearing a remote affinity to fat has also been produced. No one, however, lias ever suc- ceeded in forming fibrinc, 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 will 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, tremellae, &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 eases 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 in 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. The 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 with 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'm 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, &;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 generul, 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 espec ially set at nought both by plants and animals, 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 arc 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 pre-ervation. 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 witli 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 Ace ) 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. \\ hatever 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 a,fogether 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, months, 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 series 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 compounds of carbon, hydrogen, and oxy- gen, such as starch, gum, sugar, the resins, woody fibre, fixed oils, volatile oils, camphor, extractive mat ter,$c. 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, &c, &c, which appear to be com- pounds of carbon, united in large proportion with a little oxygen, hydrogen, and nitrogen. Comparison of the organic composition or texture of animals and vegetables. — We 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 which 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, &c. 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 we 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 betvveeu every part of individual organized beings. The cellu- lar tissue consists of filaments and lamina?, 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, Phvsioloeie, lstcr Band, S. 182. 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 the 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 snorter, 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 ! 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 fibrous. 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. Thefibro-carti/aginous is a mere modification, although an interesting one, of the cartilaginous or rather of the fibrous tissue. The fibro-car- tilages 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 128 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 oft' 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 has 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 them acquainted 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 brairPand 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. 129 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 thein, 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 conferva? and tremella? 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 engenderroent 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 ofgamzed beings, — namely, origin or repro- duction, nutrition or self-preservation, changes VOL. I. 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 jemule, 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. Conferva; 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 Jen/ale, — is also exhibited by vegetables and animaV; 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. tlie 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 mo'.lusca, 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 vegetables 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 diacious plants the males of which are distinguishable from the females ; there are very few tribes 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-fold 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 which 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 plants 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. Die 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 they 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 by vegetables is, therefore, some- thing different from what 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, acalephae, 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 2 132 ANIMAL. 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 amont; 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 prorer 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 bodies 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 mav ap- 1 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, branchiae or gills, and tracheae 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 ; oxygen 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 involuntanness 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 now to be distributed ; this is done by means of a peculiar motion impressed upon the fluids in 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 mot. on 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 purnp 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 holothunae, 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 acalephae 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 actineae, 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, &c. 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 in 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 ANIMAL. 135 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 cavities 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, &c. 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, medusa?, 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 m 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, &c. 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. Heat. — 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 wa'er 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 France (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 agents 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 among physiologists, and many titles have been ima- gined by which the agent or primary cause of the act has been sought to be 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, &c. 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 ; in 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, medusa?, and other similar tribes appears to be peculiar. The motions exhibited by the conferva?, tremella?, 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 genera! 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 oi.e 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 eiti.er 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. Fliysical 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 flattened membrane (the cyclides). Various animals, again, from exhibiting no uniform or regular shape, have been entitled amorphous or heteramorplious. 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. V\ iih 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 oft' 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 ; bv-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 brum, with its prolongation in the verlebrata 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 witli reference to their struc- ture naturally leads to the inference of di- versity of function in harmony with the pecu- liar organization possessed by each. In the lowest grades of animal existence we have seen to how simple a process the act of nutrition — this act so complicated among the more elevated tribes, — is reduced. It consists merely of imbibition or absorption by and of exha- lation from the general surface of the body. The matters absorbed appear to be assimilated incontinently, or to be made a part of, and to receive the form proper to, the animal in the instant of their assumption : applied imme- diately to the homogeneous organism, the nutriment is forthwith made a portion of its substance. The vital decomposition of the bodies of these lower animals is accomplished with the same simplicity and directness : the surface that absorbs is also that which exhales the worn-out particles of the system. The first step by which nutrition becomes more complex, as we rise in the scale of cre- ation, is the institution of a process of solution (digestion), by which the matters appropriated as aliment are prepared for reception into the body. This process of solution is accom- plished by powers inherent in the animal itself, within a cavity destined for the purpose. In 142 ANIMAL. our survey of the structure we have already seen to how great an extent the organization became complicated as a consequence of this centralization of the office of digestion, and with what variety of superadded function this complication was attended, namely, external absorption, sanguification or the formation of a fluid, the pabulum of nutrition, confined within vessels, respiration, circulation, and, finally, assimilation, in regard to the compo- sition ; whilst with reference to the vital de- compositions we have discovered another spe- cies of interstitial or internal absorption, and depuration of the system by one principal apparatus, the kidney, to which the cutaneous and pulmonary exhalations may be added as supplementary. But every one of these functions, and its organic apparatus, are themselves modified, according to internal aptitude, and in con- formity with the circumstances surrounded by which animals commence and continue their existence. Digestion is a very simple process in those cases in which it takes place within a single cavity, having but one opening, and no complementary apparatus of any kind, compared with what it is when connected with an apparatus for bruising the food, for mixing it with saliva, for macerating it in a crop or a series of reticulated and foliaceous pouches, mixing it with bile, pancreatic juice, &c. &c, and transmitting it along a muscular canal, of six, eight, or ten times the length of the body to which it belongs. Absorption, in like manner, among the most inferior classes is essentially one and undi- vided either in kind or destination. It is in itself adequate to the entire office of nutrition, seizing and transmitting the matters which are fitted for this end, elaborating the food and atmospheric air at the same instant of time, and effecting immediately the composition of the whole animal organism. In animals higher in the scale, we perceive, in the first place, that there are several species of absorption : there is, in the first place, the absorption from the surface of the digestive passages and that from the surface of the lungs, gills, skin, &c. or of the respiratory apparatus. Again, absorption is not limited to furnishing materials for the com- position of the organism ; it is also entrusted with the office of abstracting from its interior the particles which are worn out and no longer fit to continue the ends of their existence in the places they occupy. Nor is this all ; for it is by absorption that the amount of those exhaled fluids which moisten internal cavities, having no external communications, is regu- lated, and by which, as it would appear, many of the secreted fluids, the bile, and the sper- matic fluid in particular, are inspissated and rendered more fit to accomplish the important ends they subserve in the economy. Absorp- tion in the highest classes of all is even per- formed by two, and perhaps three different orders of vessels, the lacleals, namely, the lymphatics, and the veins. Further, absorption is not in the higher as it is in the lower classes of animals a function effecting immediately the composition and de- composition of the parts and particles of the organization. It is intermediate to the pre- paration of the nutritious juices and their ap- propriation or assimilation by the organism. The lacteals or absorbent vessels of the in- testines collect the fluid called chyle, from the pultaceous alimentary mass in its progress through the intestines. But this fluid is not yet fitted to subserve nutrition; as a pre- liminary it has to be subjected to the action of the atmospheric air in the gills, lungs, &.C., where, being converted into arterial blood, it first becomes apt to minister to the growth and reparation of the body and its parts. So also in regard to decomposition : the fluids collected from all parts by the lymphatics and veins, are not immediately rejected from the economy, as useless and having already accom- plished all of which they are susceptible, but being first exposed to the contact of the at- mosphere, and then made to undergo the scrutiny of the depurative organs, they are either retained, being restored to their pristine capacity to subserve nutrition, or are abstracted from and thrown out of the body as no longer fit to aid in its growth and maintenance. Intercourse with the air of the atmosphere is essential to every living thing, and we should a priori have anticipated very considerable variety in the means by which, as well as the mode in which this intercourse is established. Among the inferior tribes which are nourished by ab- sorption immediately from the surface of their body, and which find the materials of their nutrition ready prepared for their use in the circumambient media, we may presume that the matters absorbed have either undergone the needful changes by exposure to the air previously to their assumption, or that these changes take place at the time they are ap- propriated. Where digestion is a preliminary to absorption and assimilation, it is evident that this could not have been the case ; and hence the necessity for that modification of the function of aeration entitled respiration. Look- ing generally, we observe two principal varieties in the mode by which aeration is accomplished: in some classes there are a number of holes arranged symmetrically along the sides, and communicating with air-vessels entitled tra- cheae, which are subsequently distributed to every part of the body. The air in this case is evidently brought into communication with the nutrient juices already arrived at their destinations ; and the necessary changes are wrought in them at the instant of their assimi- lation. Here the respiration is very properly said to be diffuse or disseminated. In other classes, again, in which the respiration is local or concentrated, in harmony with the existence of a special apparatus, which we have spoken of under the title of lung or gill, aeration is accomplished by the access of the air on the one hand, and the exposure to its action of the nutritive fluid on the other, the effect of which is to convert the latter into arterial blood, and to make it fit, upon its distribution by appro- priate channels, to accomplish the ultimate and ANIMAL. 143 immediate nourishment of every part of the organization. The different media in which animals live involves the supposition of another modifica- tion as to the mode in which the blood or nutritive fluid is aerated. Those that live in air respire this elastic fluid immediately; those that live in water, again, respire it mingled with or dissolved in the surrounding medium. The tracheae of those animals whose respira- tion is diffuse, and that exist on the surface of the earth, consequently are filled with air; those of the creatures that exist in water are conduits for the constant transmission of this fluid. When the respiration is concentrated, corresponding modifications in the function are encountered according to the medium in which animals live : the air is either received immediately into the body, when the apparatus is known as a lung, or, suspended among water, it is passed over the surface of the respiratory organ, which is then denominated gill. Quadrupeds and birds respire univer- sally by means of lungs, fishes and the mol- lusca by means of gills. In certain reptiles the function is carried on by means both of lungs and gills, and as it would appear even by the general surface of the body either vica- riously, or at one and the same time. These are the only true amphibious animals. A circulation, properly so called, is the ap- panage of an organization already somewhat complicated, consequently of an animal con- siderably raised in the scale of creation. This function, it is evident, as implying in its sim- plest sense a progressive motion of the general nutritive fluid or blood, can only exist where such a fluid is encountered. It is altogether wanting, therefore, among those animals in which nutrition is accomplished immediatelv. We ascend but a little way in the scale before we find the function consisting not only of an outward or progressive motion of the nutritive fluids, but of a retrograde motion also of these same fluids modified in their nature, and re- quiring exposure to a greater or less degree in some form of respiratory apparatus to fit them anew for distribution to the organization at large. The fluid in this instance parts from a centre, and returns thither after having made the round of the system. Circulation in this acceptation only occurs among those animals that have a separate respiratory apparatus, and in which we meet with absorption of nutri- ment from without, and of lymph, &c. from within. The pabulum of nutrition is taken up by lacteals and veins from the digestive apparatus, and by veins and lymphatics from the rest of the organism for transmission, under the name of venous blood, to the apparatus of respiration, whatever its form. In this the fluid, still immature and unapt for assimilation, is exposed in vessels of infinite minuteness and extreme tenuity to the action of the at- mospheric air, and having undergone in these a certain change, it begins to be collected by another set of vessels, which form branches suc- cessively of larger and larger size, until finally it is projected from the respiratory apparatus in one or more trunks, under the name of arterial blood, fitted for assimilation by the organization at large, and proving the principal stimulus under the influence of which its various par- ticular organs accomplish their offices. Circulation, however, as a function, is com- plicated in the same degree as the apparatus by which it is effected. In some classes we find the circulation taking placing through vessels only, one set distributing the blood from the respiratory apparatus to the body generally, another collect. ng this fluid again, and the newly-absorbed matters from the body at large, and transmitting these for elaboration anew in the organ of respiration. In other tribes, and this invariably after the very lowest grades of the scale are passed, we find the hollow muscle, or forcing apparatus, which, in glancing at the differences of structure, we have spoken of as the heart superadded to the circle of vessels, which even in its simplest state consists of at least two cavities communicating with one another, one for the reception of the blood from, the other for the projection of this fluid to the general system. But the blood does not follow the direct and simple course here supposed in almost any case. There is the aeration of the fluid in the way, and means to accomplish this important end must of course be provided. Among many animals it would appear by no means necessary that the whole of the blood should undergo exposure in the respira- tory apparatus, in order to fit it for the wants of the organization ; a part only is sent thither, and this on admixture with the remainder suffices to revivify the mass. In this case it is not imperative that the two kinds of blood — the unaerated or venous, and the aerated or arterial — should be kept distinct; there is con- sequently no occasion for more than one re- cipient cavity or auricle, into which the aerated blood from the organ of respiration, and the unaerated blood of the system are poured in common and mingled, and one projecting cavity or ventricle from which the mixed cur- rent is distributed partly to the respiratory ap- paratus and partly to the system at large. Here the blood in its course describes no more than a single circle, beginning and ending in the heart, which is then characterized as simple, consisting, as has been said, of a single auricle and a single ventricle. Among other tribes of animals, however, the whole mass of blood requires to undergo aeration in the respiratory apparatus each time it completes its round before it can again subserve the wants of the organization. In this instance it is evident that the aerated and unaerated blood require to be most particularly prevented from commingling, and that a single or simple heart will no longer suffice as the implement of circulation. This complex circulation is met with among ani- mals so low in the scale as to be unprovided with a heart, 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 secret ion, 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. Hi 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 perforin those partial motions which their preservation as individuals require — taking their food, respiring, voiding their excretions, &c. Those that can move from one place to another have organs in relation to the mode in which this motion is accomplished, whether it be by creeping, by swimming, by running, leaping, flying, &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 ,thatanimalsdiffer 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 part, it is evident, suffices for its own existence. In the higher classes of animal existence, how- ever, nutrition requires the concurrence of a mul- titude of peculiar acts ; and in order that life may be continued in any fragment of one of the mem- bers of these, it is plain that this fragment must voi.. r. contain the organs of every one of the functions essential to nutrition. Further, it is certain that the nervous system, when once it has fairly made its appearance, strictly dominates the nutritive function, and that every part of the nervous system itself becomes progressively more and more dependent on one of its portions, the encephalon or brain, as animals stand higher in the scale of creation, and as the functions over which the nervous parts preside respectively are themselves of a higher order. These are new and additional reasons for the centraliza- tion of life, or for the complete dependence of the organs and their functions one upon another among the more perfect animals — man, the quadrumans and quadrupeds, birds, &c. So much for the acts that minister to the preservation of the individual. Let us now turn to the interesting series by which species are continued. In the very lowest grades this end is accomplished without the concurrence of sexes : at a determinate period of its life the animal either separates into several fragments, which become so many new and independent individuals, or it throws out a number of buds or germs from its external surface or from a particular internal cavity. The first of these modes of reproduction is entitled fissiparous, the second external gemmiparous, and the third internal gemmiparous. When we examine animals in the next grade, we find reproduction taking place by the con- currence of sexes, or rather of two kinds of organs which we afterwards discover divided between different individuals, who are then said to be of opposite sexes. When the male and female organs are united in the same indi- vidual it is denominated an hermaphrodite ani- mal, and in some cases seems to suffice for its own impregnation ; more generally, however, hermaphrodite animals are not capable of per- forming this act upon themselves, but require the concurrence of another individual of similar constitution: the two hermaphrodites meet and severally impregnate one another. Among the more perfect classes of the ani- mal kingdom the organs of reproduction are universally allotted to two different individuals, males and females, which consequently become in their dualism representatives of their species . Agreeing in this single feature, the modifica- tions in the process of reproduction are never- theless extremely numerous. In some cases the fecundating fluid of the male is only ap- plied to the egg or germ of the female after its extrusion from her body, as happens among fishes, several reptiles, &c; in others the male fluid is injected into the body of the female, and made to fecundate the germ still attached to its parent. This act is generally, though not invariably, accomplished by means of a penis, or male external organ, with which many birds and all the animals above them in the scale of animal creation are then provided. With this contact or intermixture of bodies we have the following varieties in the after-parts of the process : the egg or germ now fecun- dated is either forthwith expelled from the body, and it is only subsequently, under the in- 146 ANIMAL. fluence of a certain temperature, and after the lapse of a certain time, that the young being bursts the shell and commences its independent existence ; this is the case among oviparous animals. Or oth erwise i 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 intra-uterine existence ; the young being- still depends upon its mother for the whole of its nourishment, and very generally for the supply of warmth it requires and the protection needful to it till able to provide for itself. Many of the particulars now merely glanced at, and numerous others, the mention of which has been omitted entirely, will be found de- tailed, and their bearing and importance illus- trated in the article on Generation, to which the reader is therefore referred. BIBLIOGRAPHY. — Stahl, De diversitate corporis mixti et vivi, 4to. Halae, 1707. Berzelius, in Af handlingen i Fisik, Kemi, &c. (on the means of ascertaining the definite and simple proportions in which the component elements of organic bodies are combined), t. iii. Stockh. 1810, and in Thorn- ton's Annals of Philosophy, vols. iv. and v. ; Ejus, Lchrbuch der Chemie, B. 3. Drcsd. 1827 ; Traite de Chemie Trad, par Jourdan, t. v. Gay-Litssac et Thenard, Proportion des principes des sub- stances vegetales el animates, in Rech, physico- chymiques, t. ii. 8vo. Paris, 1811. Ure, Ultimate analysis of vegetable and animal substances, in Phil. Trans. 1822. Emmet, Chemistry of animated nature, 8vo. New York, 1822. 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Brera, Program, de vitas vegetabilis et animalis analogia, 4to. Ticin. 1796. Rufn, Ent- wurf einer Pflanzen-physiologie a. d. Dan. uebers. Kopenhagen, 1798. Senebicr, 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. Goetting. 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, Urber die Temperatur der Vegetabi lien .Tubing. 1826. Hunter, Obs. on certain parts of the animal economy, 4to. Lond. 1786, 1792. Edwards, Influence des agens physiques sur la vie, 8vo. Paris, 1824; Anglice, 8vo. Lond. 1832. * * * * Vianelli, Luci nolturne dell'acqua marina, Venez. 1749. Viviani, Phos- phoiescentia maris illustrate, 4to. Genoa?, 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. still' elettricita animale, Bologn. 1797. Volta, Sail' elettricita ani- mate, 1782. Valli, Still' elett. animale, Pavia, 1792. Aldini, Diss, de animali electi icitate, Bo- logn. 1794. Pfuff, Ueber thieresche Electricitaet and Reizbarkeit. Leipz. 1795. Hitter, Beweisdass Galvanismus den Lebensproccss in dem Thierreiche begleite, Weimar, 1790. Ejus, Beitrage zur kennt- niss des Galvanismus, Jena, 1800. * * * * Glisson, De initabilitate fibrarum (in Ej. 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 Gorier, Exercitat. medica?, 4to. Amst. 1737-48. Lups, De irritabilitate, 4to. Leid. 1748. Haller, P rim as lirieae Physiologiae, 8vo. Gotting. 1747 ; Ej. Ele- menta Physiologiae ; Ej. Mem. sur la nature irrita ble et sensible des parties, &c. 4io. Lausan. 1756 ; Ej. Op. minora, 4to. Humboldt, Ueber die gereitzte Muskel-und Nervenfaser, t. ii. 8vo. Berl. 1797. Bichat, Rech. stir la Vie et la moit, 8vo. Paris. Anatomie generate. 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 ANKLE. 147 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 gastroenemii 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 digitoruni 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 i. 2 118 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 ruga;, and hence, in making an incision, to give exit to matter, it may be proper to prefer a transverse to a vertical direction. 2. The subcutaneous cellular tissue. — The structure and properties of the subcutaneous cellular tissue are not the same throughout the whole region, but like the skin, which we have just considered, its characters vary in dif- ferent situations. Thus, upon the instep, it is at the upper part loose and distensible, full of adipose cells, and similar in every respect to the subcutaneous tissue of the leg, of which it is a prolongation : as it descends, however, it becomes more dense and unyielding, and ad- heres more closely to the skin which covers, and to the annular ligament which is placed beneath it. This anatomical fact at once ex- plains why it is that when subcutaneous ab- scess or infiltration occurs on the anterior part of the leg or foot, the passage of the fluid either upwards or downwards is, for a time at least, impeded at the ankle-joint. It is like- wise owing to the density of the subcutaneous tissue across the ankle, that its cells do not permit the accumulation of adipose substance here ; hence in very fat persons and also in children whose subcutaneous fat is usually abundant upon the leg and foot, the instep is as it were strangulated by a deep transverse furrow. Upon the malleoli the characters of the subcutaneous tissue present great differ- ences : upon the inner one it is scanty and delicate, but of a compact structure, and con- tains few if any adipose cells. Upon the outer one it is, on the contrary, much more copious, of a loose and yielding texture, and usually contains a greater quantity of fat. These dif- ferences of texture will explain why, after severe contusion, extravasations so frequently occur upon the outer part of the joint and so seldom upon the inner; why abscess is so much oftener met with in the one situation than in the other ; and why the transmission of pus and serum from any of the neighbour- ing regions takes place so much more easily about the outer than about the inner ankle. At the posterior part of the region, the sub- cutaneous tissue assumes again new characters : losing here its soft lamellated texture it be- comes suddenly dense and filamentous, ad- hering with great firmness to the integuments above, and to the fascia beneath : as we trace it down it becomes more dense and elastic ; the cells formed by the decussation of its filaments become loaded with a firm granular fat ; in a word, it already begins to put on the characters of the dense fibro-adipose cushion, which is found in the sole of the foot. Hence it is that wounds and abscesses of the part we are now considering, approach in character those of the plantar region : hence the slight swelling, the severe pain ; hence in both cases the necessity of a prompt and free evacuation of the matter. Before leaving this subject we should ob- serve that the subcutaneous tissue of the region we are now considering transmits certain ves- sels and nerves. In front of the inner ankle we meet with the incipient branches of the great saphena vein and the ultimate filaments of the saphenus nerve : the venous branches are here of such a size that they have fre- quently been selected by the phlebotomist as the seat of operation. Anteriorly we find the filaments of the musculo-cutaneous nerve, and externally the roots of the lesser saphena vein, and its accompanying nervous filaments. 3. The fascia or aponeurosis forms the next stratum we have to examine: it is placed be- tween the subcutaneous tissue and the tendons. The fascia, like the two preceding layers, forms a general investment for the whole region. Its structure and properties, like those of the preceding layers, vary considerably, according to the situation in which we view it. Upon the instep it becomes continuous, above with the aponeurosis of the leg, and inferiorly with the dorsal aponeurosis of the foot, but, for very obvious reasons, surpassing both of these in strength. This additional strength is owing to the accessory band of fibres which passes transversely across the instep, interlaced with the proper oblique fibres of the fascia, and to which is given the name of anterior annular ligament. Arising from the anterior edge of the inner ankle this annular ligament passes outwards and soon meets with the ten- don of the tibialis anticus : at this point it splits into two layers ; the one passes before, the other behind the tendon, and they unite again at its outer edge. The same mechanism is repeated in the case of the extensor pollicis tendon which lies immediately external to the last-named tendon ; and lastly in those of the extensor digitorum longus and peroneus tertius. In contemplating the mechanism and uses of this ligament, the surgical anatomist cannot but perceive that certain inconveniences must result from its division: its use being obviously to bind down the tendons in this situation, and to form canals for their free and separate trans- mission, it is clear that after its division in the REGION OF THE ANKLE. U9 living subject, when the individual attempts to flex the foot or extend the toes, these tendons will riot 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 botli 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 subcutaneous tissue, and which being super- ficial to the fascia can hardly penetrate deeply toward the joint ; another, occurring between the two layers of that membrane, in those situations where it splits to include the ten- dons ; such an abscess will have little tendency to point in front, being bound down by the superficial layer of the fascia, or to penetrate deeply for a similar reason ; but to its free passage upwards or downwards in the course of the tendons, little or no obstacle is presented. Lastly, matter may accumulate under both layers of the fascia, where its deep position and close confinement render it alike dangerous, and of difficult detection. 4. The next stratum is perhaps less entitled to that name than those we have hitherto described. Instead of forming, like them, a general investment for the whole region, it consists of several distinct and independent or- gans scattered irregularly about the joint : we shall enumerate them in the order in which we propose to treat of them, viz., tendons, mus- cles, arteries, veins, lymphatics, and nerves. a. Tendons. Upon the instep we find no fewer than seven tendons passing towards the foot: the internal is the largest of all, it is that of the tibialis anticus running obliquely for- wards and inwards to the inner cuneiform bone. Close upon its outer side is the tendon of the extensor pollicis; still more outwards we meet with the four tendons of the extensor digitorum longus, and most externally of all, or nearest to the outer ankle, that of the peroneus tertius. We need not revert to the subject of the fibrous sheaths furnished to these tendons by the fascia or annular ligament ; but we should here care- fully observe, that both sheaths and tendons are completely lined by a synovial apparatus. He who is at all acquainted with the general patho- logy of synovial membrane will understand why it is that effusions so frequently form about the instep ; why adhesion of the opposite walls of these synovial sheaths will almost destroy the power of extending the toes and of flexing the foot ; and, lastly, he cannot but draw the im- portant practical deduction, that in operations about the instep we should avoid, if possible, cutting into these synovial sacs. Behind the inner malleolus we meet with three tendons, — that of the tibialis posticus most anterior, and in close connexion with the posterior surface of the malleolus interims; 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, ceteris paribus, be more likely to prove dangerous than that of the tibialis posticus : for, as the synovial sheaths of the former extend along the whole sole of the foot, little or no obstacle is presented to the disease extending itself into that region : whereas the tendon of the tibialis being inserted, not upon the sole, but rather upon the inner edge of the foot, its 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 calcis; and here, though previously in close apposition, and in- deed contained within the same synovial sheath, they become separated by a ridge projecting from the bone. The peroneus longus tendon plays behind it as upon a pulley, and instances have occurred, where, owing to the fracture of this little osseous septum, the peroneus longus has been dislocated forwards upon that of the brevis. It has also happened that both peronei tendons have been dislocated forwards from their groove behind the malleolus, and thrown in front of that eminence. Were such an acci- dent left without surgical interference, it is inte- resting to reflect how completely altered would be the action of these two muscles, if that action were not completely suspended by the inflam- mation and obliteration of the synovial sheath consequent on the accident ; instead of extend- ing the foot and pointing the toe, as they do in their natural state, they would become con- verted into flexors and abductors of the foot. At the posterior part of the region, the tendo Achillis forms a remarkable projection. In our account of the fascia, we have described the sheath within which this tendon is contained. We may further observe that this tendon is separated from the joint, and also from the deep vessels and nerves of the leg, by a consi- derable interval, so that it has frequently been cut across without injury to the articulation or wound of any other important part. Its mode of insertion into the os calcis is also worthy attention ; 'instead of being fixed into the whole posterior surface of tPiat bone, it occupies by its insertion merely the lower half of it ; supe- riorly the bone and tendon are not even in con- tact, for here a distinct synovial bursa is inter- posed between them. The liability of this large bursa to inflammation and effusion should be carefully borne in mind by the surgeon : and he who is aware of its office, placed as a friction roller between the tendon and bone, will duly estimate how much disease of this bursa will impede the motions of progression. Owing to the interposition of the bursa, rupture of the tendo Achillis has occurred even below the upper edge of the os calcis ; and if, having cut across the tendon, we forcibly extend the foot so as to elevate the heel, we shall at once com- prehend how indispensably necessary it is to maintain the extended position in our treatment of this important accident. b. Muscles. — There arebut few muscular fibres met with in the region of the ankle: the flexor digitorum brevis arises upon the instep ; and posteriorly we find some of the fibres of the flexor pollicis longus, which are here continued down a considerable way upon the tendon. c. Arteries. — The arteries about the ankle, from their liability to injury and disease, become of great interest. Upon the instep the course and relations of the anterior tibial artery de- mand particular attention; the vessel here does not run exactly in the median line of the foot, but is somewhat nearer to the inner than to the outer malleolus : we may always reach it with perfect certainty, by cutting between the tendon of the extensor digitorum longus, and that of the extensor pollicis ; these overlap it upon either side, and afford considerable protec- tion against wounds or other injuries. Not- withstanding the facility of reaching the vessel in this situation, it is by no means advisable to do so when it is at all possible to avoid it, inas- much as to expose the artery here it is necessary to wound the synovial sheaths, and inflammation and adhesionwould be the probable consequence of such an injury. The branches of the in- ternal malleolar artery are found upon the inner part of the region, running upon and in front of the inner ankle, and anastomosing with others passing forwards from the posterior tibial, thus insuring a sufficient supply of blood to the joint, even when the trunk of the anterior tibial itself has been tied. But these vessels are of much inferior importance compared with the posterior tibial, whose main trunk lies in the fossa between the heel and the malleolus internus. It is here occasionally the subject of operation, and hence its course and relations should be very carefully noted. We have al- ready enumerated the tendons passing beneath the annular ligament in this situation ; the most anterior is that of the tibialis posticus, imme- diately behind it lies that of the flexor digi- torum, and still more posteriorly, at the interval of about an inch, is found the tendon of the flexor pollicis ; in this interval between the two latter tendons runs the posterior tibial artery, not however equidistant from both, but nearer to that of the flexor digitorum ; it rests upon the tibia and internal tibio-tarsal ligament, and is covered by the integuments and annular ligament ; its vena? comites run one upon either side ; and the posterior tibial nerve lies close behind it, but as the vessel descends get- ting gradually to its inner side. Notwith- standing the few coverings of the artery in this situation, yet owing to the heel, the ankle, and the tendo Achillis projecting around, and bearing off as it were those coverings from it, the vessel is here at a considerable depth from the surface; and any one who supposes it can be easily found in the living subject, will form a very erroneous idea of its true position: — hence it i« that all good writers on surgical anatomy recommend us to take up the artery in the lower third of the leg, rather than in the calceo-malleolar groove. Several small vessels ramify about the outer ankle, the external malleolar coming from before meets here with the terminating branches of the peroneal artery from behind, but these small vessels are interesting to the sur- gical pathologist rather than to the regional anatomist or operative surgeon. d. Veins. — Two veins, the " venae comites," accompany each of the larger arteries : in all operations upon the artery, the close apposition JOINT OF THE ANKLE. 151 of the veins, and the possibility of mistaking one for the other, should be remembered by the surgeon. In front of the inner malleolus we observe one or two openings in the fascia, through which small branches of communication pass between the superficial and deep veins ; these, no doubt, are the principal channels through which the venous blood of the integu- ments about the foot and instep is returned, after the operation of tying the great saphena vein. e. 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 lymphatic gland lying upon the instep, and receiving several of these deep absorbents ; in the majo- rity of cases there is no such gland, and its existence in any appears to us extremely doubtful. f. Nerves. — The nerves in this region have the same general distribution as the arteries. In our account of the larger arteries, we have already minutely assigned the relation which their accompanying nerves bear to them. We may thus briefly enumerate them : — in front, the musculocutaneous 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.) f John E. Brenan.) ANKLE, JOINT OF THE. — (Normal ana- tomy.) (Fr. articulation du coude-pied. Germ. Fussgelenk. Ital. caviglia.) The ankle-joint, or tibio-tarsal articulation, results from the junc- tion of the leg and foot. For reasons which will appear when we come to explain its mo- tions, it is ranked in the excellent and com- prehensive classifications of Bichat andCloquet as a perfect angular ginglymus. The security of the ankle-joint, more perhaps than of any other in the body, is owing to the peculiar form of its bones, and to their exact adap- tation to each other; in this respect it has aptly been compared to the tenon and mortise joint, so frequently used by mechanics, the strength of which, as is well known, is chiefly owing to the peculiar form and close fitting of its component parts. Upon the ripper 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 bones. 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 towards the mesial line ; this in the living subject is covered only by the intejjuments ; 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. The 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 is named the malleolus externus ; it is much larger than the internal, and placed behind and somewhat below it. The external surface of this fibular 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 its antero-posterior, and about an inch and a quarter in its transverse measure- ment ; (this transverse measurement is, however, a little greater in front than behind ;) the emi- nence is remarkably convex from before back- wards, and concave from side to side ; the outer edge somewhat more elevated than the inner ; it is completely covered with cartilage, and cor- responds to the articulating cavity upon the in- ferior exremity of the tibia. Upon the inner side of the astragalus, we find a small articu- lating surface of a triangular form, with the base above and apex below; it is convex in the vertical direction, and is tipped with car- tilage prolonged ftom the superior surface : upon thetriangular surface the internal malleolus plays ; the remaining portion of the inner side of the astragalus is rough, and occupied chiefly by the insertion of the internal tibio-tarsal ligament. The external side of the astragalus is also marked by an articulating surface of a much greater size for the reception of the ex- ternal malleolus: it too is of a triangular form with the base above; concave in the vertical, and slightly convex in the antero-posterior direction. b. Ligaments.— We have already compared the mechanism of this joint to that of the tenon and mortise ; the mortise cavity, however, is not, as we have seen, cut out of a solid bone, but 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 tibio-fibulur articulation. We shall not now describe the ligaments which here unite the tibia and fibula, referring to the article on the Ti bio-fibulae 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 Weitbrecht the deltoid ligament. There is, however, no reason why we should not apply to it likewise that principle of nomenclature which is so gene- rally and with such advantage applied to other ligaments. It arises by a truncated apex from the point of the inner malleolus, and from the little fossa at its outer surface ; its fibres change as they proceed downwards and are fixed into the inner surface of the astragalus and os calcis, some proceeding as far forwards even as the scaphoid bone. The posterior fibres are strong but short ; the anterior are much larger and not so thick. Its internal surface is lined by the synovial membrane of the joint; and on its internal surface it is covered by the tendon of the tibialis posticus, and it sends some of its fibres to the sheath of the flexor longus digitorum tendon. In flexion of the leg the anterior fibres are relaxed, and the posterior are rendered tense: in extension the reverse of course takes place. 2. The anterior tibio- tarsal ligament (Vg. 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 subdivided into two distinct parts. In extension of the foot it is rendered tense ; in flexion it is relaxed. 4. The middle fibulo- tarsal ligament (lig. fibulce medium perpen- diculare, Weitb., external lateral ligament, Cloq.) is a round fasciculus of fibres having almost the appearance of a tendon which arises from the apex of the external malleolus, de- scends obliquely backwards, and is attached to the outside of the os calcis. It does not appear to us that in any position of the joint this ligament takes a perpendicular course, although that epithet has been applied to it by Weitbrecht. It is related superficially to the peroneus longus tendon, and by its deep sur- face to the synovial membrane, to the astra- galus, and os calcis. In flexion of the foot this JOINT OF THE 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-tarsalliga.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 of the tibio-fibular mortise the synovial mem- brane passes downwards upon the astragalus, covers its superior articulating eminence, and sends prolongations upon its lateral articulating surfaces. It is remarkably loose upon the anterior and posterior parts of the joint, and is said to contain a greater quantity of synovia than any other synovial membrane in the body. Certainly its strength is much increased by those scattered fibres to which we have given the name of anterior tibio-tarsal ligament : posteriorly it is weakest, for here few if any ligamentous fibres can be detected, though Boyer and Weitbrecht speak confidently of such. c. Mechanism and function of the ankle-joint . — To understand properly the mechanism and function of the ankle-joint, we must carefully contemplate it in the opposite conditions of rest and motion. 1. Viewing it, then, in the first place, as the individual stands at rest, we observe that the leg and foot meet each other in the ankle-joint at a right angle, and we are particulaily 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 motionof 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. 1.54 ABNORMAL CONDITION OF THE ANKLE-JOINT. the same. It is no less interesting than instruc- tive to contrast these two articulations with each other, for in doing so we find that the modifications of structure here, as well as in all other instances, are referable to the peculiar function which each part is destined to perform. The hand in the human subject is exclusively an organ of prehension ; the foot is one merely of support : — now this simple fact at once fur- nishes us with a clue to all difficulties. The great strength and sudden expansion of the tibia and fibula at the ankle, are evidently a provision to sustain the weight of the body and to increase the basis of its support; in the radius and ulna such size and strength would have been to no purpose, and hence these bones at the wrist are comparatively thin and delicate. At the ankle we should naturally have expected frequent dislocations, owing to the great weight from above, and to the great mobility which for the purposes of progression must at the same time necessarily exist here ; these are two most formidable causes of displacement ; but, as if in compensation, we find two strong buttresses (the malleoli) projecting one upon either side of the joint, and rendering such displacement, under ordinary circumstances, almost impossible. At the wrist, where there is no weight to be sup- ported, such lateral splints would have been superfluous : hence the imperfect and almost rudimental malleoli of the radius and ulna; hence the shallow and imperfect cavity ; hence, in a word, the anatomical confor- mation which constitutes the ankle-joint a ginglymus, and the wrist an arthrodia. In the motions of the ankle and wrist-joints we observe likewise a striking difference: in the former, lateral motion would have been super- flous in reference to the function of the foot ; at the wrist, on the contrary, a free lateral mo- tion is indispensable to increase the sphere of action of the hand. For the BIBLIOGRAPHY of this article, see that Of ARTICULATION. (John E. Brenan.) ANKLE-JOINT, ABNORMAL CONDI- TION OF THE.— The deviations from the na- tural or normal condition of the ankle-joint may be classed under those which are referable to accident and to disease : any defects which may be considered to result from congenital malformation shall be elsewere treated of. (See Foot.) Accidents. — The different structures which immediately compose the ankle-joint, as well as those which surround this articulation, and are merely accessary to its functions, are, each and all, liable to numerous accidents, the most important of which we shall here advert to. These accidents may affect the tendo?is, the ligaments, or the bones. Tendons. — Those tendons which pass behind the inner and outer malleoli are occasionally displaced ; and, although the accident must be considered a rare one, it ought not here be overlooked. " The two peronasi 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 experiments, is of opinion that a slight accidental torsion of the foot inwards or outwards, amounting to a sprain, only produces an injury, in which * Wilson's Lectures on the Bones, &c. ABNORMAL CONDITION OF THE ANKLE-JOINT. 155 the ligaments are merely stretched ; but that a greater effort produces a separation of the lateral ligament from one or other of the mal- leoli by laceration of its compact tissue, or of the periosteum which covers it, while the liga- ments themselves remain unbroken. Oppor- tunities do not often occur of discovering the effects of sprains on the joints by anato- mical examination made at various periods after the accident; but although Dupuytren's opinion may be correct as to the majority of cases, still others have found the lateral liga- ments ruptured across, instead of having been torn from the bone. Mr. Wilson found, in a case where the patient died five days after a severe sprain of the ankle-joint, that the del- toid ligament binding the tibia to the foot was lacerated, and that the synovial membrane of the ankle-joint was also much torn. In older cases he found evidences of chronic inflamma- tion in the ligamentous structures around the joint ; that these structures were thickened and vascular, and had lost much of their plia- bility. The pain and inability to walk, the sudden effusion around the injured ankle, the ecchy- mosis, tenderness of the skin and tension, the signs of this injury expressed by the living structures, are all accounted for by the lesions which an anatomical examination of these in- juries of the ankle-joint discovers. This also explains what practical writers have noted of sprains, viz. that sometimes the ankle-joint which has been affected by this accident, rapidly and perfectly recovers, — that, on the other hand, it is not unfrequently so weakened by the injury, as to become peculiarly suscep- tible of a renewal of the sprain from slight causes ; sometimes the articulation contracts a rigidity, by which for a time, or even for life itself, its proper functions are interfered with, and a permanent oedema of the soft parts around the joint is too often in these cases established. Bones. — The bones which contribute to form the ankle-joint are liable to fracture and to luxation. These bones, we know, are the tibia, fibula, and astragalus; for an account of the accidents which affect the latter particularly, we refer to the article Foot, and shall here, as succinctly as we can, notice the various dis- placements of the bones of the leg at the ankle-joint, which have been observed to be the result of a fracture through one or both of the malleoli, or of an accidental rupture of the ligaments which tie these eminences to the foot. When we reflect on the great strength of the ligaments which connect the astragalus to the tibia and fibula, and the support which the ar- ticulation derives from the prolongation down- wards of the malleoli, we can easily perceive that a luxation of the foot must be the effect only of some very violent cause, and that this accident can very rarely (in a true sense) be a simple one. Effusions of blood, rupture of all the surrounding ligaments, fracture of the external or even of both the malleoli, wounds of the soft parts, and even protrusion of the bones, are contingences which frequently render the dislocation of the tibia at the ankle-joint a very complex accident. The most superficial view of the structure of the ankle-joint will convince any one that no lateral displacement of the bones of the leg can occur, without its having been im- mediately preceded by a fracture of either the tibial or peroneal 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 * Tott's Works by Earlc, 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 intern us 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. J%. 51. Fig. 52. Partial luxation of the Tibia inirards, 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 peronasi 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 interims to the point of fracture of the fibula: this line is well expressed in Jig. 51, representing the frac- ture of the fibula, and taken from the engrav- ing which accompanies the work of Pott. The retiring angle seen (Jig. 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, (Jig. 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 perona?i muscles, when the patient has at- tempted to walk after the fracture has occurred. It is on these combined movements when not corrected by a proper mode of treatment, that the deformity of the foot, and all the consequent difficulties in walking, depend. Complete luxation of the tibia inwards from the astragalus, complicated with a simple frac- ture of the fibula. — This is a very severe, and, fortunately, a very rare accident. In alluding to it, Dupuytren says,* that " the foot is not only susceptible of being carried outwards, but also upwards at the same time ;" a double displacement, which he had observed to occur only once in 200 cases of fractures of the fibula treated in the Hotel Dieu for fifteen years, " but the case was so marked," he says, " that in future it cannot be mistaken or passed over in silence." It cannot occur unless the fibula is fractured ; for this condition is indis- pensable to any displacement of the foot in- wards or outwards ; it requires besides a com- plete laceration of the short thick ligaments placed between the tibia and fibula, the strength of which is such that, in most experiments on * Sui' la Fract. de l'Extremite inferieurc dii Pe- rone, in Annuaire Med. Chir. des Hopitaux de Paris, 1809, 4lo. and folio. ABNORMAL CONDITION OF THE ANKLE-JOINT. 1.57 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 at;d 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 fascia? 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. ( Dujjuytren.) 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 well as those 158 ABNORMAL CONDITION OF THE ANKLK-.TOINT. 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 {fig- 54,o, b), 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 " Annuaire" contains the first accurate account of the external signs by which it may be recog- nized in the living subject. Luxation of the tibia outwards, complicated with simple fracture of one or both of the mal- leoli.— This, it is said, is one of the most dan- gerous of the dislocations to which the ankle is liable, for its production has been noticed to be attended with greater violence, and to be accompanied by more contusion of the integu- ments, more laceration of ligaments, and greater injury to bone, than we have occasion to ob- serve in the production of the other luxations of this joint. The astragalus in this accident is carried towards and below the external malleolusC^g. 55), whilst the outer edge of the foot is turned downwards, its inner edge upwards, and the sole inwards, the tibial malleolus disappears, and is hidden at the bottom of a retiring angle formed by the inner side of the leg and foot, and the peroneal malleolus forms, with the astragalus, a salient angle rounded off on the outside. Looking only to the change of form, situation, and rela- tive position of the leg and foot, we might sup- pose the case one of congenital club-foot.* The luxation of the tibia outwards, with inversion of the sole of the foot, is one of the most rare and most difficult cases to explain. Its pro- duction must be the result, we suppose, of co- incidences rare and unusual. There may be a certain obliquity in the line of direction of the * Dupuytren, Annuaire. Fig. 55. Fig. 56. Luxation outwards o f the Dissection of the luxa- tibia and fibula with ob- tion outwards ( Museum linue fracture of the tibia, of St. Thomas's Hospi- tal ). [Fig. 55.] fracture coinciding with a considerab'e 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 andoutwards,andthelowerfragment 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 (fig. 56 ), the interval be- tween the internal and external malleolus is much increased, the latter presses heavily against the integuments, which, when the limb is much exercised, have a strong tendency to inflame and suppurate, the outer edge of the foot throughout its whole line presses the ground, whether the patient be standing or walking, while the inner edge is somewhat elevated and curved inwards. In the dissec- tion of this accident, it will be found that the ABNORMAL CONDITION OF THE ANKLE-JOINT. 159 malleolus interims is fractured, and in general, we suppose, with the obliquity from above downwards, and within outwards, above de- scribed. The deltoid ligament remains un- broken, the capsular membrane is torn in front, the fibula has been found obliquely fractured, as well as the tibia, or the three ligaments which connect it to the tarsus have given way ; none of the tendons suffer, and haemorrhage to any extent in these cases seldom or never occurs, as the large arteries generally escape injury. Luxation of the tibia and fibula forwards, and also luxation of these bones backwards from the articular pulley of the astragalus, without fracture. — In the simple and complete luxa- tion of the bones of the leg forwards at the ankle-joint, (without fracture,) the articular pulley of the astragalus is placed behind the inferior extremity of the tibia, which last rests partly on the superior surface of the neck of the astragalus, and partly on the os naviculare. In the simple and complete luxation of the tibia backwards, (without fracture,) the inferior extremity of the tibia is placed behind the arti- cular pulley of the astragalus, and corresponds to the posterior part of the superior surface of the os calcis. In both these luxations, the na- tural connexion with each other of the bones of the leg remains undisturbed, and the two mal- leoli advance or recede together, according to the direction in which the displacement has occurred. In both, the capsular membrane and the posterior and lateral ligaments must be ex- tensively lacerated, and most of the flexor and extensor tendons, in some degree, put upon the stretch. The luxation of the bones of the leg forwards cannot take place, but in a forced and sudden extension of the leg on the foot, when the latter being retained by some obstacle, and solidly supported, we fall backwards. The luxation of the tibia backwards, on the contrary, cannot happen unless when the foot is strongly flexed, the toes being elevated and retained in this position, we fall forwards. Authors have seldom failed to notice these simple luxations forwards and backwards of the bones of the leg, yet for our part, no mat- ter to what source we apply for information, we cannot satisfy our minds that we can adduce a single well-marked example of luxation of the bones of the leg at the ankle-joint, unac- companied by a fracture of one or both of the malleoli ; we would not, however, be under- stood to deny the possibility of such an occur- rence, but merely to state our conviction that such an accident must be exceedingly rare. We have now to consider luxations of the tibia from the astragalus, forwards and back- wards, when complicated with a simple frac- ture of the fibula or tibia close to the articula- tion : these may be complete or partial. Complete luxation of the tibia forwards from the articular part of the astragalus compli- cated with a simple fracture of the fibula. — This accident may arise from the same causes nearly as those which may be supposed to influence the more simple luxation in the same direction; and as we know that when the fibula is fractured near its malleolus, the pe- ronaei muscles may under certain circumstances effect a luxation of the tibia inwards, so that displacement which we are now considering may be the result of the action of the gastro- cnemius and solaeus. These acting on the foot, which in consequence of the fracture is no longer fixed by the malleolus externus, cause the astragalus to slip from before backwards, and the lower end of the tibia forwards, and move the lower fragment of the fibula in such a manner that its malleolar extremity is carried backwards, and the upper part forwards. This action of these muscles, however, only pro- duces a very incomplete dislocation whenever the internal malleolus is uninjured, or the foot in this case being carried outwards and back- wards at the same time; but when, as often happens, either the internal malleolus or del- toid ligament is broken, this displacement may be as complete and direct as the simple dis- location forwards of the tibia. We then find the foot lengthened behind and shortened in front ; a semicircular excavation occurs in the former direction, and an osseous tumour raises the tendons and ligaments on the front of the ankle, but it is to be particularly remarked that, whilst in the simplest form of luxation of the tibia, i. e. where there is no fracture, the external malleolus follows the tibia and fibula, and forms a projection corresponding to that of the internal, it is in this case dragged backwards with the foot to which it is attached by the lateral ligaments, and no longer has the same direction as the bones of the leg. In the dislocation forwards of the tibia (whether simple or complicated with a frac- ture of the fibula) from the astragalus, the articular pulley of this bone is placed behind the inferior articular cavity formed for it in the tibia ; but this latter bone at the same time, it will be recollected, must now rest on the dor- sum of the tarsus, where it is formed by the upper part of the neck of the astragalus and os navi- culare. When the tibia has thus once advanced before the articular pulley of the astragalus, the luxation forwards is as complete as it well can be ; in our opinion, to imagine any more com- plete luxation of the tibia forwards, we should be obliged to presume that this bone in its advance on the dorsum of the foot had com- pletely cleared the astragalus, and then rested " on the os naviculare and os cuneiforme in- ternum,"* which last form part of the anterior * The weight that so justly attaches to any ob- servations from Sir A. Cooper, induced us to con- sider well the account he gives of the dissection of this complete luxation of the tibia forwards, in his work on Dislocations and Fractures ; and we find that we cannot reconcile it with our ideas of the anatomy of the injury. We are sorry in this in- stance to be obliged to differ from an authority, to which we feel indebted for many 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 cnnei- 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 67 and 58 are copied. As I ABNORMAL CONDITION OF THE ANKLE-JOINT. 161 Partial luxation forwards of the tibia at the external ankle, with fracture of the fibula near the malleolus. Fig. 57. Viewed on the external side. Fig. 58. Viewed on the internal side. a, b, semicircular excavation posteriorly, and projection of the heel backwards ; c prominence formed by the tibia projected on the dorsum of the foot ; d displacement of the external malleolus backwards along with the foot. was anxious, before these pages went to press, again to examine this case, I requested Mr. S. to make inquiry about her; he learned that the woman died dropsical a few days before, and with much difficulty procured for me an opportunity to examine the limb, which on careful dissection presented the following ap- pearances:— the whole extremity was somewhat wasted, the skin on the sole of the foot was smooth and fine, shewing that she had been able to walk but little since the accident ; the foot was in a position of almost rigid extension, the toes were directed downwards, the range of motion of flexion and extension did not exceed one inch, in short, all the usual characters assigned to the partial dislocation forwards of the tibia and displacement of the foot back- wards were seen ; when the skin was re- moved from the fascia of the leg and foot, the intervening cellular membrane was found infiltrated with serum, the skin was adherent to the inner malleolus, the vena saphena and the nerve of the same name were thick- ened and firmly connected together, the ex- VOL. I, tensor tendons were stretched over the tibia, and were somewhat flattened, and the grooves which transmit the tendons that play behind the inner and outer malleolus were deepened. We now directed our attention to the state of the bones; we found that the tibia was dis- placed forwards, that its anterior edge was ad- vanced more than one inch beyond its natural situation, and that it much overhung the os naviculare, but such was the direction and state of obliquity of the tibia with respect to the foot, that it could not be said to rest upon that bone ; between the os naviculare and the infe- rior articular extremity of the tibia there inter- vened much fat of a yellow hue and fibrous texture, like intervertebral substance ; the inter- nal malleolus itself had not escaped injury, the deltoid ligamenthad 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 frag- Fig. 59. Viewed on the external side. Fig. 60. Viewed on the internal side. Skeleton preparations of fig. 57 and 58. M 1(32 ABNORMAL CONDITION OF THE ANKLE-JOINT. ment of the fibula was directed from below upwards, a little inwards, and very much for- wards, so as to make with its shaft a remark- able angle salient anteriorly; this bone had been traversed by the fracture obliquely, from above downwards and from before backwards. The external malleolus was placed about one inch and a quarter behind its usual situa- tion, and was consequently dislocated at its tibio-fibular articulation, having burst those strong ligaments which connect these bones together, and which are so seldom found to yield. Luxation of the bones of the leg backwards at the ankle-joint . — A luxation of one or both bones of the leg at the ankle-joint backwards, whether the accident be what has been called complete or incomplete, whether accompanied with a fracture of the fibula, or merely with a rupture of the ligaments, is a displacement which must be considered exceedingly rare. Boyer, in his valuable work, gives no case of it from his own observation ; and in alluding to such an accident, states that no author, to his knowledge, has given a single example of it. Sir A. Cooper evidently has not seen it; for he says, " 1 have seen the tibia dislocated in three different directions, inwards, forwards, and outwards ; and a fourth species of disloca- tion is said sometimes to occur, viz. back- wards." Baron Dupuytren states that he has never seen this accident.* Mr. Colles has given me the notes of one ease, 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 iu their new and faulty position. Besides the partial dislocation backwards of the tibia, this bone with the outer malleolus of the fibula was inclined somewhat outwards; and the man walked lame and most awkwardly on * Je n'ai jamais vu de luxation du pied en avant, dans les fractures du perone et de l'extremite du tibia.-— Annuaire Medico-Chirurgical, 1819, Paris p. 159. the outer edge of the heel and foot, the inner side of which was somewhat curved inwards. I have had occasion to notice a displace- ment of the tibia backwards on the os calcis, in a case where the astragalus sloughed in con- sequence of a compound injury to the external malleolus and ankle-joint ; but such a case is different from that now under our considera- tion, although the possibility of such an occur- rence should not be lost sight of. 2. Morbid anatomy, a. Acute inflammation of the synovial membrane of the ankle-joint produces changes in the synovial fluid of the articulation both in quantity and quality, and alterations very generally in the appearance and structure of the membrane ; I say very generally, for I have known an exception to the rulej in a case* of acute synovitis of the ankle-joint which caused the death of the patient in fifty hours from its first onset ; during the whole of the time the patient never slept nor ceased to com- plain of the agonizing pain of the ankle-joint. At the post-mortem examination, before the skin was removed, the extensors of the toes were observed to be displaced by the fluid which distended the synovial sac of the articulation, and fluctuation was now, as during life, to be felt in two tumours which existed in front of the two malleoli ; the interior of the joint was occupied by a turbid oily synovial fluid ; no false membrane existed, and if there had been increased vascularity during life, no trace of it was discoverable at the time of examination : increased quantity with altered quality of the synovial fluid were the only deviations from the normal condition which could be noticed. Portions of the synovial membrane are, how- ever, occasionally found covered with false membrane. Pus has also been found in the joint, sometimes laudable, sometimes foetid, and of a brownish red colour; the membrane has been found thickened, and has afforded evidence of increased vascularity, and even in some points has presented a villous ap- pearance. In very young subjects I have known acute inflammation of the ankle-joint in a few days extend itself to the epiphysis, and produce separation of it from the shaft of the tibia ; and in such cases a displacement of the shaft inwards, and of the epiphysis and foot outwards, occurs from the action of the muscles, as in Pott's luxa- tion. Acute inflammation commencing in the synovial membrane of the ankle-joint sometimes extends farther than this : there have been cases in the Richmond Hospital, and the specimens have been preserved in the museum, of acute synovitis of the ankle in which the inflammation extended through the vascular junction of the epiphysis and shaft of the tibia, and having occupied the cellular junction of the periosteum with the anterior and inner surface of the tibia, soon ended in the formation of pus and lymph, which detached from the bone its immediate covering, and produced effects which termi- nated in the death of the patient. I have seen this detachment of the lower epiphysis of the tibia in an infant six days old, the result of acute * See Dublin Journal, vol. iv. p. 1. ABNORMAL CONDITION OF THE ANKLE-JOINT. synovitis, with purulent deposition in the joint, and in a young man aged twenty, but have not observed it ever to occur in older subjects ; and conclude that it is one of the consequences of synovitis of the ankle-joint, which is only to be noticed at an age when the epiphyses are not yet consolidated with the shaft of the tibia. In these very acute attacks of inflamma- tion, its ravages are seldom confined to the structure which seemed to be the 'point du depart' of the disease ; the cartilages are in some cases removed from the tibia, fibula, and upper surface of the astragalus with astonishing rapidity ; the porous surface of the bones has also been found exposed, and their substance to afford evidence of its having been in a state of inflammation. Surgeons should ever bear in mind, that the synovial membrane of the ankle-joint passes very far forwards on the upper surface of the astragalus, even as far as within a few lines of the junction of this bone with the os naviculare, so that an accidental wound high upon the instep might very readily give rise to a fatal synovitis of the ankle-joint. Moreover, by an experiment on the dead sub- ject, it may be shown that a very slight direc- tion too much upwards of the edge of the knife when the operation of partial amputation, ac- cording to Chopart, is performed, may wound the most anterior part of the synovial sac of the ankle-joint, and the consequences of such a mishap might prove fatal, or at all events greatly aggravate the ills which even without such cause too frequently follow Chopart's operation. Again, the synovial membrane extends very low down, even to the lowest point of the inner side of the peroneal malleolus, along the outer or fibular surface of the astragalus (Jig. 61, a). It has very frequently happened to the wri- ter's knowledge, that inflammation commencing in the body of the os calcis, or in the fibrous or synovial tissue of the articulation between the os calcis and under surface of the astragalus, has crept up to the ankle-joint by this route between the fibula and astragalus ; when, therefore, opera- tionsandcauterizations are performed by surgeons to cure the carious state of the os calcis, the close contiguity of such an important articulation as that of the ankle should be recollected. The great proximity of the ankle-joint to that be- tween the under surface of the astragalus and os calcis can only be estimated by making a vertical section of the tibia, fibula, astragalus, and os calcis, passing transversely across these bones and through the malleoli, as may be seen in fig. 61 ; and if a subject be selected in which the epiphysis has not been consolidated with the rest of the bone, a useful view may be had illustrating many of the preceding practical observations, and explaining clearly how in- flammation, traumatic or idiopathic, once esta- blished in the ankle-joint, can pass through the epiphysis to the periosteum of the tibia; and ori- ginating either in the body of the os calcis, or in some of the structures composing the articulation between this bone and the under surface of the astragalus, can be propagated to the ankle-joint : such a viewas this will shew thenecessity of con- Fig. 61. sidering, in connexion, the normal and abnor- mal state of these important articulations. b. Chronic disease.— The effects of chronic diseases on the tissues composing the ankle- joint are next to be considered ; these are vari- ous, and may be referred to the influence of specific diseases, such as gout, syphilis, struma, rheumatism, &c; but the effects of most of these on this particular articulation need not here be discussed, as they will be sufficiently dwelt on elsewhere in this work (see Joint) : we deem it, however, right to enter somewhat into detail in the description of those morbid appearances of the ankle-joint which are supposed to be of a scrophulous origin, and which are denominated white swelling of the ankle-joint. The external characters of the affection are pretty much those in common with the same melancholy disease, in whatever articulation of the extremity it is situated ; the swelling, at first soft, and appear- ing in front of each malleolus, seems divided into two by the extensor tendons ; after a time it becomes more solid, and assumes somewhat of a globular form ; here as elsewhere, however, it does not completely surround the joint. The limb above is wasted and the heel is retracted ; the foot is cedematous, and the toes are pointed downwards, no motion of flexion or extension can be communicated to the foot ; but when the bones are moved laterally, an unnatural motion is communicated to the foot, and a grating of rough and carious surfaces in advanced cases can be felt : the sides of the swelling are studded over with numerous fistulous orifices, from which even now a thin sanious matter can be pressed ; a probe introduced passes either directly through one or other of the malleoli, or by a circuitous route into the interior of the joint through the sinuses, which are, as M 2 164 ANNELIDA. it were, the excretory ducts leading from the interior^ and conducting out the sanious and sabulous matter which proceed from the dege- nerated cartilages, synovial membranes, and bones of the diseased joint. The skin is thin, soft, and shining, and moveable on the sur- face, except where the fistulous orifices exist. The anatomical characters of this disease in its advanced stage affecting this articulation we have many opportunities of observing. When the superficial coverings of the swelling are removed, the fat is remarked to be consistent and yellow, the cellular tissue interposed be- tween the ligaments, tendons, and muscles is infiltrated with a viscid, semi-fluid, spongy, homogeneous mass ; sometimes this tissue be- comes so thick, and is so connected with the lateral ligaments of the ankle-joint, and so in- terposed among their softened fibres, as to render a clean dissection of these last impracticable ; so that the ligamentous and cellular structures around the joint appear to have undergone a species of fibro-cartilaginous degeneration ; the viscid glairy matter infiltrated around the joint with the tumefied ligaments are the parts which cause the principal swelling, and give to the fingers examining it that deceptive feeling of fluctuation which characterises the white swelling wherever situated. The few muscular fibres to be found near this joint are pale and of a gelatinous appearance, being infiltrated with the same matter as that which pervades the more superficial structures. The tendons, nevertheless, preserve their natural colour and consistence. The periosteum will be found much thickened and easily detached from the bone. The bones of the joint, and those in its vici- nity, are very usually more or less atrophied, and have undergone a process of degeneration ; notwithstanding, however, what has been said on high authority to the contrary, these bones are occasionally enlarged and expanded ; they have lost much of their specific gravity, their spongy tissue is softened, yellowish, and easily penetrated by a knife, and filled with a matter resembling adipocere, or a yellow semi-fluid fat. The heel it has been noticed is elongated, and the foot measured from the tibia to the toes on the dorsum is shortened very generally, and pointed downwards. Dissection discovers the cause of this frequent phenomenon in a par- tial dislocation of the tibia forwards on the astragalus, the softened ligaments allowing the action of the gastrocnemii and solaei to drag the whole foot backwards. In the interior of the articulation, a more or less considerable quantity of a sanious matter is found ; while the cartilages covering the end of the tibia and fibula, and surfaces of the astragalus, are softened, adhere but slightly to the bones, and have been partially removed, leaving exposed the porous structure of the latter. The arteries, veins, and capillaries present no peculiarity, except that the naturally white ligamentous tissue is more freely supplied than usual with red vessels. The neurilema of the posterior tibial nerve is evidently much thick- ened, so as to give it an appearance of enlarge- ment ; the small nerves around the joint seem also hypertrophied. ( R. Adams.) ANNELIDA, (a generally adopted, but barbarous latinization of the French term ' Annelides,' from ' Annellus,' a little ring ; ought rather to be written ' Annulata'or ' An- nellata.') — The natural group of Annelida comprehends all the invertebrated animals which have a soft body divided into transverse segments or rings ; a distinct central nervous system disposed in the form of a longitudinal gangliated chord, blood coloured (generally red), and contained in a system of appropriate and very distinct vessels ; and, lastly, organs of locomotion, consisting either of fleshy appen- dages provided with bristles, or of bristles only ; or of a prehensile cavity situated at each ex- tremity of the body ; but never of articulated members, as in the Arachnida, Crustacea, and Insecta. The establishment of this class is due to Cuvier. Prior to him, Pallas, Muller, and Otho Fabricius, had made observations of great interest on the animals of which it is com- posed ; and we find in the writings of the author of the Miscellanea Zoologica the most happy ideas respecting the natural relations which these animals bear to one another. Nevertheless, these works had at first but little influence on the classification of the Inverte- brata, and for a long time naturalists persisted in following the method of Linnaeus, who united under the term Vermes, the Mollusca, Zoophyta, and Annelida, and dispersed the latter in three different sections of that great class ; confound- ing some with the Entozoa (intestinal worms), others with the Acephalous Mollusca, and others again with the Testacea. It was in the work entitled " Tableau Ele- mentaire de l'Histoire Naturelle des Animaux," published in the years 1797-8, that M. Cuvier laid the first foundation of a natural distribution of invertebrated animals. He collected together in the class Vermes the species which more lately have constituted the groups of Annelida and Entozoa, and established in it the two divisions corresponding to those which are generally adopted at the present day. Having subse- quently determined the presence of red blood in the leech, and having investigated the circu- lating apparatus in these animals, Cuvier sepa- rated the " red-blooded'' from the " intestinal" worms, and constituted for the former a distinct class, to which Lamarck afterwards gave the name of " Annelides," which has been gene- rally adopted, and is used at the present day by most naturalists.* This classification being based essentially on anatomical structure, has been adopted by Lamarck, Dumeril, Savigny, Leach, Latreille, * See Cuvier, Bulletin des Sciences par la Societe Philomathique, an vii. et x. Lamarck, Discours d'ouverture du cours des Animaux sans Veriebres prononce en Mai 1806, et Histoire des Animaux sans Vertebres. ANNELIDA. 165 &c., but is not received by all zoologists of the present day. M. De Blainville, in his metho- dical distribution of the animal kingdom, has adopted another plan. Taking the exterior organs for the base of his system, this naturalist divides the articulate animals, which he terms " Entomozoaires," into seven classes, of which the penultimate, viz., the " chetopodes," com- prehends the Annelidans provided with loco- motive bristles, and of which the last, viz, the " apodes," is composed of the Annelidans des- titute of those organs, together with the planariae and intestinal worms.* The general plan of organization exhibited in the animals which are grouped together by Cuvier under the name of " vers intestinaux," and the numerous affinities which connect the planariee and several helmintha to the Annelida, appear to us fully to justify a partial adoption of the innovations introduced by M. De Blain- ville, and to indicate that the natural position of the white-blooded worms is by the side of those with red blood, at the bottom of the sub- kingdom of articulate animals ; whilst in the system of Cuvier the Annelida are placed at the head of that great division of the animal kingdom, and the entozoa are left among the zoophytes. But, on the other hand, similar reasons appear to us to oppose the adoption of the divisions which M. De Blainville has proposed for the articulate animals. That zoologist, in fact, establishes a distinction between his che- topoda and apodaas wide as between the former and the insecta, arachnida and Crustacea, and thus separates from the setiferous annelidans to place among the intestinal worms the hirudines, which approximate to the former and deviate from the latter in many of the most important points of their organization ; for example, in the existence of a gangliated nervous system. This arrangement does not appear to us to accord with the spirit of a natural classification, in which the several divisions ought to be in- dicative of the different degrees of importance which the modifications of the animal organiza- tion present. In the present state of science the class An- nelida ought in our opinion to be preserved nearly as it was established by Cuvier, but should be joined with the entozoa and rotifera, to form a great division of the sub-kingdom articulata, distinct from the natural group, con- sisting of insecta, myriapoda, arachnida, and Crustacea. The affinities, indeed, between the setiferous annelidans and the hirudines are too close to admit of their being arranged in sepa- rate classes ; and, on the other hand, every day discloses new facts of a nature which demon- strate that the vermiform animals pass from one to another by almost insensible gradations. Thus the researches of M. Duges on the planariae show how closely their structure ap- proaches that of certain red-blooded worms, and the distinction founded on the colour of the nutritious fluid no longer suffices to separate * See the Bulletin de la Soc. Philomathique, 1818 ; De l'Organization des Animanx par M. de Blainville, torn. i. table 7 ; and the article ' Vers' of the Dictionnaire des Sciences Naturellcs, torn. lvii. them ; for on the one hand it is proved that the colour of the blood is yellow and not red in some of the annelidans properly so called ; while on the other hand I have recently ob- served on the shores of the Mediterranean an animal which differs from the genus prostoma only in the possession of red blood. We now know intestinal worms which have a circulation and a vascular system as well formed as that of the annelida, which they already resemble so much by their outward form. The absence o{ a rudimentary nervous system in the entozoa is called m question by skilful anatomists. Lastly, the excellent works of Ehrenberg on the in- fusoria of the class rotifera prove the analogy that exists between these minute beings and the articulate animals generally, but more espe- cially to the annelida. The differences which the annelida present among themselves have necessitated their di- vision into many secondary groups or orders. In the latest work* that has been published on the classification of these animals, they have been divided into four orders, under the names of Annelida errantia, Annelida tubicola, Anne- lida terricola, and Annelida snctoria (suceuses). This classification is based on the combination of the modifications which exist in the struc- ture of these beings, and does not materially differ from that proposed by M. Cuvier in the Regne Animal, and by M. Savigny in the great work on Egypt. The following; is a table of the principal characters which distinguish these groups. First Order. — Annelida errantia. Body, with soft appendages (cirri, branchiae, or antennae), generally disposed over the whole length of the animal, and not collected towards the cephalic extremity. Feet generally very distinct, armed with setie or bristles, which have very rarely the form of hooks. Head generally distinct, and provided with eyes, antenna?, and a retractile proboscis, often with jaws. (This order, which nearly corresponds to that of the Annelida dorsibranchiata of Cuvier, com- prehends the genera Aphrodita, Polyno'e, Polyo- dvntes, Acoetcs, Sigaliun, Palmyra, Amphinome, Chloeia, Euphrosyrie, Hippono'e, Eunice, Onu- phis, Diopatra, Lysidice, Lumbrincreis,Aglaura, OEnone, Nereis, Syllis, Hesione, Alciope, Myri- ana, Pliyllodoce, Nephtys, Ooninada, Glyce/a, Aricia, Aunis, Ophelia, Cirrhatulis, Periputus, Chetopterus, Arenicola.) Second Order. — Annelida tubicola. Body, with soft appendages, for the most part collected together at the cephalic extremity. Feet, almost always of two kinds, generally de- prived of cirri, and armed with hooked bristles, Head not distinct, without eyes, antennae, pro tractile proboscis, or jaws. (This order corresponds to that established by Cuvier under the same name, and includes the * See Classification des Annelides et description des especes qui habitent les cotes de la France, par MM. Audouin et Milne Edwards, torn. ii. des Recherches pour servir al'Hist. Nat. du littoral de la France. 166 ANNELIDA. genera Serpula, Sabellu, Tertbellu, Awphitrite, Hermella, and Siphosto?na.) Third Order. — Annelida terricola. Body, completely destitute of soft appendages. Feet, scarcely or not at all distinguishable, and represented only by some bristles. Head not distinct, without eyes, antennae, or jaws. This order comprehends the genera Clymena, Lumbricus, Nais, £?c. In the classification of M. Cuvier it is united to the Hirudinida to form the order Anne- lides ubranc/tes. Fourth Order. — Annelida suctoria. Body destitute of bristles for locomotion, com- pletely apodous, and without soft appen- dages. A prehensile cavity in the form of a sucker at each extremity of the body. Head, not distinct, but generally provided with eyes and jaws. This order is composed of the family of Hiru- dinida, and of the genus Branchellion. External conformation. — The Annelida have always an elongated, generally cylindrical, and vermicular form ; sometimes, however, they are flat or more or less oval. The body is com- posed, as we have already observed, of a series of rings, not of a horny or calcareous texture as in the majority of insects and Crustacea, but membranous and separated from each other only by a transverse fold of the integument; as is seen in certain larvae. The number of these rings is occasionally very considerable (some nereida have more than 500), and in many annelida it varies considerably in different individuals of the same species, and seems to increase with age. In some instances these segments are sub- divided into two or more transverse bands by furrows. In general each ring supports a pair of mem- bers, and when an apparently single segment gives origin to a greater number of these or- gans, it is easy to perceive that it results from the union of many rings blended together. The two extremities of the body are sometimes dilated in the form of suckers (in the suctorious annelidans), but in general nothing of the kind exists, and the anterior extremity either resem- bles the rest of the body, or it terminates in a head more or less distinct (as in the nereida, see Jig. 62), often supporting eyes («), and fili- Fig. 62. . I .V \J 1 form appendages called antennae, (6,c), the num- ber of which is generally three, four, or five. The mouth is situated at the extremity of the body, and in the acephalous annelida is di- rected forwards, but in the cephalous species this opening is situated below the base of the head. The anus is placed at the opposite ex- tremity, and is almost always found on the dorsal aspect of the body. A certain number of Annelida are completely apodous, and do not present the least trace of an appendage on any of the segments of the body (the hirudinidae). Others exhibit on either side many rows of bristles, which fulfil the office of feet (the terri- colae). In others, again, the bristles of which we have spoken are supported on a fleshy tubercle more or less prominent, and more or less complicated in structure, and to these organs the name of feet is applied. The feet of the Annelida, when they present the maximum of development of which they are susceptible in that class of animals, are com- posed each of two very distinct portions, placed one above the other, and appertaining the one to the dorsal, the other to the ventral arch of the ring. (See Jig. 63,which represents one of the feet Fig. 63. of an amphinome.) M. Savigny, who was the first to study with due care the zoological cha- racters furnished by these appendages of the annelida, gave to these portions of the feet the names of dorsal oar (a) and ventral oar (b) (rame dorsal et rame ventral). Sometimes these oars are pretty distant from one another, (Jig. 63.) sometimes they are separated only by a shallow fissure (fig- 64. which represents the foot of a nereid), and occasionally they are so intimately blended together that they can hardly be dis- ANNELIDA. 167 tinguished, and form, as it were, but a single organ ; lastly, there are cases in which only one of the oars would seem to be developed. If one were disposed to compare the loco- motive system of the annelida with that of the other articulate classes, the ventral oar should be regarded as analogous to the members which in the Crustacea, Insects, &c. are variously modified to constitute the legs, the jaws, or the antennae : and the dorsal oar ought to be considered as representing the appendages, which, though wanting in the greater number of articulate animals, yet acquire a considerable develop- ment on the last two rings of the thoracic segment of most insects and constitute the wings. In this particular the annelida afford an example of the greatest uniformity in the development of the appendicular system in the articulate division of the animal kingdom. Each oar is essentially composed of a fleshy tubercle more or less prominent, which sup- ports different productions of the integument, incloses the bristles (c), and which is more especially designated by the name of foot. Towards the base of the setiferous tubercle there is generally a membranous appendage, sometimes filiform, sometimes lamelliform, called the ci?rus (d, e) ; lastly, it is also above the margin and near the base of these organs that the branchiae (/) take their origin, but in general it is only the dorsal oar that supports them. All the above parts may exist simul- taneously, but it often happens that one or more are atrophied to a greater or less degree, or are altogether deficient; and this either along the entire body or on certain segments only. Thus in the terricolous annelida there are no cirri ; in the hermellae they are pre- sent on the ventral, but not on the dorsal oar; while in the cirrhatulae the reverse obtains. In most of the annelida errantia the setiferous tubercle of both oars is wanting on the first rings which follow the head, whilst the cirri assume a very great development, and form the appendages termed by systematic authors ten- tacular cirri. (Fig. 62, d.) A similar modification may be frequently remarked in the composition of the appen- dicular system of the last ring of the body, and thence results a certain number of filiform pro- ductions called styles. Lastly, the antenna? of the annelida, which must not be confounded with the antennae of insects and Crustacea, may also be considered as representing the cirri of the dorsal oar of those rings, the union of which constitutes the head.* The annelida pass in general a somewhat stationary life, and a great number among them remain constantly buried in the earth or * For further details regarding the external struc- ture of the annelida the reader may consult the excellent work of M. Savigny, intitled " Systeme des Annelides," principally of those found on the coasts of Egypt and Syria ; the article ' Vers ' of the Dictionnaire des Sciences Naturelles, torn. lvii. by M. De Blainville; and a more recent publica- tion on the same subject inserted in the Annales des Sciences Naturelles, torn, xxviii , xxix, and xxx, and in the second volume of the ' Rceheiches pour servir a 1'Hist. Nat. du littoral de la France, par MM. Audouin et Milne Edwards.' enclosed in tubes formed by the mucus which is secreted by the skin, and which, while hard- ening, commonly agglutinates together frag- ments of shells and sand. The formation of these sheaths is very quick. I have seen them fabricated in the course of a few hours. Some- times they are of extreme tenuity, occasionally they are as tough as thick leather, and there are some which possess very considerable hardness and are composed in great proportion of carbonate of lime, like the shells of mol- lusca. In the greater part of these animals locomotion is produced by general undulations of the body determined by contractions of a layer of muscular fibres extending from one ring to another, and fixed to the inner surface of the skin. But in other species the change of place is effected by the action of the feet, of which we have spoken ; or by the contrac- tion of the tentaculae which surround the mouth, as in the terebellae, and which, by shortening themselves, drag on the body of the animal in the same manner as the arms of the cephalopods : lastly, by the action of the suckers with which the extremities of the body are furnished. The bristles {Jig. 63 and 64, c,) with which the feet of the annelida are provided, do not serve merely as little levers to facilitate their move- ments, but are also offensive arms, and their structure is very curious. They differ con- siderably from the hairs of other articulate animals, which are nothing more than small tubular prolongations of the epidermic layer. By their mode of connexion with the integu- ments and their mode of formation they ap- pear to approach the hair of mammalia, but their disposition is of a more complicated na- ture. They are inclosed in sheaths provided with muscular fibres, by the aid of which the animal can protrude and retract them again : in general, also, they are not merely simple conical filaments, but their extremity is often shaped like a harpoon, a lance, or a barbed arrow, and the annelidan uses it to inflict a wound upon its enemies.* Sensation. — Tactile sensibility is considerable in these animals, and it seems to reside prin- cipally in the antennae, the cirri, and the tentacula. They do not appear to possess a sense of hearing, and there are many among them which do not manifest any sign of sen- sibility to light ; but in others, eyes (Jig. 62, a,) exist, the number of which is sometimes very considerable, but the structure very simple. They are coloured points, (generally black,) and situated on the dorsal aspect of the head or on the cephalic sucker. In the setiferous anne- lida there are never more than two pairs, but in the hirudinidae or leeches their number often increases to eight or ten. The anatomy of these eyes has recently been studied by Professor Muller of Berlin, and according to his researches it would seem that these organs do not contain a crystalline lens, or a trans- parent body analogous to the vitreous cones of * See Observations sur les Foils des Annelides ronsideres comme nioyen de Defense, par MM. Audouin ct Milne Edwards, op. cit. torn. ii. p. 31, 168 ANNELIDA. the Crustacea and insecta, but consist simply of a terminal ganglion of the optic nerve covered by a layer of black pigment and placed imme- diately beneath the integument, which is thin and transparent at that part.* Nervous system. — In like manner the ner- vous system of the annelida Fig. 65. is very simple. It occupies the middle line of the ventral aspect of the body, and con- sists of a double series of mi- nute ganglions of medullary matter, more or less inti- mately united or even blended together, and equal in number to the number of rings. (See Jig. 65. repre- senting the nervous system of the aphrodita aculeata). The ganglions give origin to lateral branches, and are connected together by two chords of communi- cation, sometimes separate, sometimes united into a sin- gle trunk, so as to constitute a longitudinal chain extended through the entire length of the body. The first of these ganglions (a) is lodged in the head, or at least at the ante- rior extremity of the animal, in front of or above the di- gestive tube ; the rest are placed below that canal ; whence it results that the two nervous chords which form the media of communi- cation between the cephalic ganglion and the first of the sub-cesophageal series pass along the sides of the oeso- phagus, and form around that canal a species of collar or ring ; a character which is common to all the articulate animals. f Organs of digestion. — The alimentary canal in the annelida extends from one end of the body to the other, and has an external com- munication at both extremities. The mouth is generally provided with a projectile proboscis, which is formed by the anterior portion of the digestive canal, which can be inverted and pro- truded like the finger of a glove, and possesses muscles for the express object of effecting these movements (see Jig. 66, which represents the •i. Fig. 66. * See Annales des Sciences Nat. torn. xxii. + See Cuvier, Anat. Coraparee, torn. i. ; Trevi- ranus, iiber der stachlichten Aphrodite, Zeitschrift fur Physiologic 3 Band; Moquin Tandon, "Mo- nograph, des Hirudines," Morrem, " Sur le Lom- bric," &c. proboscis of a phyllodoce, and^g- 67, that of a nereis). The surface is frequently beset with small papillae, and its extremity armed with Fig. 67. horny jaws (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 maxilla 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 tenicola 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 terebellse) ; 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, thalassemXe4 iXarrcvv, 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 oft' from their marginal tendinous cord, covered by a reflexion of the lining mem- brane common to the heart and arteries. Hence it follows that the fibres of the middle tunic of the aorta are- not continuous with the muscular fibres of the ventricle, being sepa- rated from them by the tendinous structure above described ; this tendinous connexion is strengthened and supported externally by a layer of dense cellular membrane, which may be regarded as the commencement of the cellular or external tunic of the arterial system. The lining membrane of the heart, after being reflected over the sigmoid valves, extends itself into the aorta, and becomes continuous with the lining membrane of that vessel. The muscular substance of the heart rises in form of a swollen annular border around the commencement of the aorta for a little distance, and is connected to it by dense cellular membrane. The serous layer of the pericardium passes loosely from the surface of the heart over the aorta; a quantity of soft adipose substance, which is absent in the foetus during the earlier months, begins to collect under the serous membrane in this situation, sometimes before, sometimes after birth, and, increasing as life advances, is found in considerable quantity in old age. The fore- going description of the connexion of the aorta with the heart has been determined by my own dissections repeatedly performed, and agrees, in its leading particulars, with the account given of it by M. Beclard* The aorta, arising from the left ventricle of the heart opposite the left side of the body of the fourth thoracic vertebra, ascends at first obliquely forwards, and to the right behind the middle bone of the sternum, until it arrives at the right side opposite the second intercostal space, and behind the sternal articulation of the cartilage of the second rib ; it then stretches backwards and to the left, opposite the junction of the upper and middle portions of the ster- num, on a level with the body of the second thoracic vertebra, and curving downwards it reaches the left side of the body of the third thoracic vertebra, on which there is a slight depression for lodging it; from this point it descends through the posterior mediastinum, * Diet, dc Medecine, art. Aorte- Elemens d'Anat. Gencrale, par Beclard. Paris, 1823. advancing in its course downwards from the left side to the front of the bodies of the ver- tebrae ; it passes through the aortic opening of the diaphragm, enters the abdomen, and on the body of the fourth abdominal vertebra gives off the two primitive iliac arteries, in which it seems at first view to terminate; the aorta, however, does not end here, but is continued, although greatly reduced in size, under the name of the middle sacral artery, as far as the extremity of the os coccygis. The aorta is usually divided by anatomists into three portions; the curved portion fiom the heart to the third thoracic vertebra is called the Arch of the aorta ; the remaining portion of the vessel, to which the name of descending aorta has been sometimes given, is called Thoracic aorta above the diaphragm, and Ab- dominal aorta below that muscle. The Arch of the aorta is divided into three portions, for the purpose of describing its nu- merous important relations to surrounding parts with greater accuracy ; these are, first, the ascending or anterior limb ; second, the trans- verse portion ; and, thirdly, the descending or posterior limb. The commencement of the aorta is covered anteriorly and to the left by the pulmonary artery, on the right by the right auricular appendage, the tip of which overlaps it in front, and behind it rests on the sinus of the left auricle. The ascending limb of the arch lies first in front of the right pulmonary artery, as that vessel crosses behind it in its course to the right lung, and then it gets in front of the right bronchus, and the cluster of bron- chial glands which fill up the angle formed by the bifurcation of the trachea ; it is bounded on the right side by the superior vena cava, and on the left by the pulmonary artery ; an- teriorly it is separated from the sternum by the anterior margins of both lungs, which here approximate, and by the narrowest part of the anterior mediastinum, where the attached sur- faces of the opposite pleurae touch. This portion of the aorta is contained within the bag of the pericardium, the serous layer of which invests it in every part except where it lies in contact with the pulmonary artery. The transverse portion of the arch is shorter than the ascending limb. The three great arte- ries of the head and upper extremities arise from its superior sides ; inferiorly it rests on the left bronchial tube ; in front it has the cellular membrane of the anterior mediastinum, the thymus gland, and the inferior part of the vena innominata ; behind it rests on the trachea a little above its bifurcation, and on the left re- current nerve. The posterior limb is the shortest portion of the arch; it lies immediately behind the division of the pulmonary artery, which is connected to it by a ligament, the remains of the ductus arteriosus ; and it is crossed by the left par vagum; on the right side it is in con- tact with the oesophagus, thoracic duct, and left side of the body of the third thoracic ver- tebra ; the rest of the circumference of the thoracic aorta is covered by the left pleura, and is in contact with the internal surface of the left lung. In the generality of adults having AORTA. 180 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 thoracic 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 IJaller, 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 innominuta, the leftc arotid and left subclavian, which, arising from the transverse portion of the arch, are distributed to the head, neck, and upper extremities, and the primitive 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 parietes of the chest and abdomen ; the coronary arteries which supply the heart arise from the aorta immediately after its origin ; the bronchial arteries which supply the substance of the lungs, and the intercostal arteries supplying the parietes of the chest arise from the thoracic aorta; the coeliac, su- perior and inferior mesenteric, which supply the digestive organs ; the renal arteries which supply the kidnies ; the spermatic going to the organs of generation, the inferior phrenic sup- plying the diaphragm, and the lumbar arteries going to the parietes of the abdomen and lum- bar region of the spine, are the vessels of this order which arise from the abdominal portion of the aorta. 3rd order. — Branches of much smaller size are sent from the aorta to se- * Experimental Inquiry on some parts of the Animal Structure. London, 1740. 190 AORTA. condary parts which lie in its vicinity, as the thymus, the pericardium, the oesophagus, the lenal capsules, ureters, &c. 4th order. — Small arterial twigs lost in the neighbouring cellular substance, lymphatic glands, and in the coats of the aorta itself. Development. ■ — The aorta appears to be formed in the fcetus prior to the heart and sub- sequently to the system of the vena porta, with which, according to Baer, Rathke, and Meckel, it is connected by a small dilatation described by Dr. Allen Thomson* as a curved tube, which is the rudiment of the heart. (See Ovum.) Whilst the heart has but a single ventricle, the aorta and the pulmonary artery form a common trunk, which afterwards becomes divided by the de- delopment of the contiguous portions of the circumference of both vessels ; during the remaining periods of intra-uterine life, and for a short time after birth, the pulmonary artery communicates with the aorta by the duc- tus arteriosus, which appears as a continuation of the trunk of the 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 fcetus 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 fcetus 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. t Osservazioni in Chirurgia. Torino, 1784. and left trunk, from each of which arose a subclavian, an external and an internal carotid: after the two trunks had run for a space of four inches distinct, they joined to form the descending aorta. Hommel, a Norwegian ana- tomist,* relates a case in which the transverse portion of the arch of the aorta divided into two trunks, one of which passed before and the other behind the trachea, after which they joined to form the descending aorta, having encircled the trachea with a sort of ring : this anomalous division of the arch of the aorta is the more remarkable as it approaches the con- dition of the vessel which is constant in all known reptiles. 2d. The arch of the aorta is sometimes absent, in consequence of the vessel dividing, immediately after its origin, into two great trunks, one of which gives off the arte- ries of the head and upper extremities, whilst the other becomes the descending aorta. f This distribution is similar to that in the horse, rhinoceros, and other pachydermata, in the ruminantia, and some of the rodentia. 3rd. Varieties in the course of the arch sometimes, although rarely, occur, as, for instance, when the arch of the aorta, instead of crossing to the left in the usual manner, curves over the right bronchus, and gets to the right side of the spine, whence it either immediately crosses behind the trachea and oesophagus to the left, or continues its course along the right side of the spine to the lower part of the thorax ; in cases of complete transposition of the vis- cera, where the heart is in the right side of the chest, the arch of the aorta is also reversed, in which case its thoracic portion descends along the right side of the spine.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. t Vide Abhandlungen des Josephinischen Medi- cinisch-Chirurgischen Akademie. Band, i. S. 271. Taf. 6. Wien. 1787. J Meckel Handbuch der Menschlichen Anatomie. Band iii. Halle and Berlin, 1817. Abernethy in Phil. Trans. 1793. § Desault in Journal de Chirurgie, torn. ii. Dr. Goodison in Dublin Hosp. Reports. Brasdor Recueil Periodiqu« de la Societe de Medecine. Paris, torn. iii. || Handbuch der Menschlichen Anatomie. Band iii. Halle and Berlin, 1817. AORTA. 191 kind, the number of branches is most fre- quently increased to four, by the left vertebral arising from the arch between the left carotid and left subclavian, as in the phoca vitulina ; next to this in frequency is the instance of the inferior thyroid arising from the arch between the innominata and left carotid, then the in- ternal mammary, and, lastly, the most un- usual is the thymic artery : it is more unusual to find the number of branches 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 two carotids, or, as more rarely happens, between the left carotid and left subclavian. The number of branches arising from the arch will be in- creased to five or upwards, when two or more of the above-mentioned anomalous branches arise from it at the same time. Of the second kind of anomaly, or that by diminution of the number of branches, the most frequent is where these are reduced to two, of which there occur the following varieties : a. the in- nominata sometimes gives off the left carotid as an additional branch, and the left subcla- vian arises separately, as in many quadrumana, several of the carnivora, as the lion, cat, dog, weazel, several rodentia, &c. ; b. sometimes there are two arteriae innominate, 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- clavians ; d. the right subclavian may arise distinct, and a common trunk give oft" the two carotids and left subclavian ; the origin of a single trunk from the arch of the aorta sup- plying the arteries of the head and upper extremities is equivalent to a division of the aorta into an ascending and descending trunk, already noticed. The third kind of anomaly partakes of the characters of the two pre- ceding, although the number of branches is the same as in the normal state : its varieties are, a, the left vertebral arising from the arch, whilst the left carotid comes from the inno- minata ; b, the two carotids may arise from a common trunk between the origins of the right and left subclavians, as in the elephant ; c, the right subclavian and right carotid may arise as distinct branches, whilst the left carotid and left subclavian come from a common trunk, forming a complete inversion of the usual order ; 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 cceliac and dia- phragmatic may arise above the diaphragm ; one or both of the diaphragmatics may be given off by the cceliac ; sometimes the cceliac and superior mesenteric arise by a common trunk as in the tortoise ; sometimes there are two or more renal arteries on one or both sides, and sometimes the primitive iliacs are given off much higher than usual, in which case they are sometimes connected by a cross branch before they divide into the external and in- ternal iliacs : it sometimes happens, when the iliacs are given oft' higher than usual, that the inferior mesenteric arises from the left of them. The diseased conditions of the aorta are described in the articles Artery and Heart. The aorta, as Beclard remarks,* is more sub- ject than any other artery to the ovoid dila- tation in its ascending, and the lateral dila- tation in its descending portion ; it is also very subject to osseous or calcareous deposits, to fissures and ulcerations, to tubercles and small abscesses in its parietes, and to aneurism. Wounds of the aorta are constantly mortal. Laennec has observed a particular lesion of this vessel ; it was a fissure of the internal and middle coats, from which the external tunic was extensively separated by a quantity of blood which had been effused between it and the middle tunic. The late Mr. Shekelton has described, in the Dublin Hospital Reports, a form of aneurism of the lower part of the abdominal aorta, in which the blood forced its way through the internal and middle coats, dissected the middle from the external for the space of four inches, and then burst into a lower part of the canal of the artery, forming a new channel which eventually superseded the old one, which the pressure of the tumour obliterated. Granular excrescences are sometimes formed on the valves of the aorta, which Corvisart conjectured to be of venereal origin. The in- ternal tunic of the aorta sometimes presents a red appearance, not peculiar, however, to this vessel, and occurring in certain forms of fever. Obliteration or constriction of the aorta is a condition rarely met with ; its existence may be traced either to pressure on the vessel from without, morbid thickening of its coats, or the formation of coagula internally ; this latter occurrence being most usually a consequence of the spontaneous cure of aneurism. Aneurisms of the aorta produce various effects on surrounding parts ; thus the heart, lungs, trachea, oesophagus, pulmonary artery, large veins, thoracic duct, and the various organs in the abdomen placed in their vicinity, may suffer derangement of their functions, displacement, atrophy or partial destruction, according to the degree of pressure to which they are subjected. Aneurisms occurring in the ascending por- tion of the aorta, which is within the pericar- dium, are often attended during life by many symptoms very similar to those of disease of the heart itself, while their pressure may produce a diminution of the calibre of the pulmonary artery, obstruct the free passage of the blood through the vena cava superior, and even in- * Dictionnaire dc Medecine, art. Aortc. 192 AORTA teifere 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, oesophagus, or the substance of the lungs. Aneurisms of the thoracic por- tion of the aorta sometimes burst into the left pleura, sometimes into the posterior medi- astinum : they have been known to point at the left side of the spine, after having caused ab- sorption of the heads of the ribs and sides of the bodies of the vertebrae. In two cases observed by Laennec and Mr. Chandler, aneu- rism of the thoracic aorta burst into the spinal canal. Aneurisms of the abdominal aorta most usually burst into the cellular tissue of the lumbar regions behind the peritoneum, seldom into the sac of that membrane. An aneurism of the abdominal aorta has been observed to make its way backwards by the side of the spine, and point in such a situation as to have been at first mistaken for lumbar abscess. Branches of the aorta. I. Branches arising from the arch. — From the arch of the aorta five branches are given off ; two from its com- mencement, the coronary arteries, and three vessels of considerable size (fig. 78 a h c), from the upper part of its transverse portion to supply the head and the upper extremities. The coronary arteries of the heart or the car- diac arteries arise from the aorta close to its origin, and immediately above the free borders of the sigmoid valves ; they are usually two in number, one for each ventricle. The right, anterior or inferior coronary artery is often larger, seldom smaller than the * Dr. Wells in Trans, of a Society for Improve- ment of Medical and Surgical Knowledge, vol. iii. Fig. 78. A B, arch of the aorta. C, thoracic aorta. D, abdominal aorta. E, common iliac artery. g, 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 not arise 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 oesophageal arteries vary in number from vol. r. two to seven : they are inferior to the bronchial in size : they arise from the front of the thoracic aorta, and are distributed to the oesophagus, on which they anastomose freely with descending branches of the inferior thyroid from above, in the middle of the oesophagus with the bronchial, and below with branches of the phrenic and coronary artery of the stomach. The posterior mediastinal arteries are nume- rous and small; they send branches to the oesophagus, thoracic aorta, thoracic duct, ab- sorbents, and cellular membrane of the pos- terior mediastinum, anastomosing with the bronchial, oesophageal, and some branches of the right thoracic intercostal arteries. Inferior or aortic intercostal arteries. — Of the eleven intercostal spaces the two superior are mostly supplied with arteries from the superior intercostal branch of the subclavian ; and as the first aortic intercostal artery frequently supplies the third and fourth intercostal spaces, we often meet with but eight pairs of intercostal arieries 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- tebrae, and in passing the intervertebral hole it sends branches inwards to the spinal cord, which anastomose with the spinal arteries. The continuation of the vessel is distributed to the longissimus dorsi, sacro-lumbalis, and other muscles along the side of the spine, as well as to the integuments of the back. The ante- rior or proper intercostal branch is usually larger than the posterior, and traverses the intercostal space. At first it is situated be- tween the pleura and external intercostal muscle, it shortly divides into two smaller branches, a superior and an inferior, which get between the two layers of intercostal muscles. The inferior branch, usually the smaller, runs forwards along the superior border of the in- ferior rib, and passes obliquely over its surface to the periosteum covering it. The superior branch, larger than the former, enters a groove in the lower edge of the superior rib, about its angle, in company with the intercostal nerve, and passes forwards between the two layers of 0 194 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. Interiorly, 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 cceliac 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 ofthe 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 caliac artery, called, also, cceliac axis, is one of the largest and shortest of the vessels given off by the abdominal aorta. It generally arises from the aorta, between the crura of the diaphragm opposite the junction of the last dorsal and first abdominal vertebra, having the renal capsules and semilunar ganglia on either side of it, with the lobulus Spigelii to the right, the cardiac orifice of the stomach to the left, the superior border of the pancreas inferiorly, and the stomach and lesser omentum in front : it is closely embraced by branches of the solar plexus. The 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 cceliac; 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 coronaiy artery gives off the right hepatic immediately before reaching the cardiac orifice ofthe stomach. The hepatic artery passes forwards and to the right under the lobulus Spigelii to the neck of the gall-bladder. In this part of its course it gives a few twigs to the gastro-hepatic omen- tum and the inferior surface of the liver ; when it reaches the pylorus, it gives two considerable branches called the pyloric and the right gastro- epiploic. The pyloric passes from right to left along the lesser arch of the stomach, where it meets the coronary with which it anastomoses, sending several branches over the anterior and posterior surfaces of the stomach to anastomose with the right gastro-epiploic artery. The right gastro-epiploic artery, much larger than the pyloric, arises after that vessel ; it passes down- wards behind the pylorus, and arrives at the greater arch of the stomach, along which it courses from right to left and anastomoses with the left gastro-epiploic. While passing behind the pylorus, it gives several branches to the pancreas and duodenum, one of which, somewhat larger than the rest,calledpancreatico- 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 ccsliac. 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 (pancreatica magna et parve ), 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 brevia, 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 coeliac, arises from the aorta imme- diately after thecceliac ; 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 inte.-tine, 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-co'.on 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, ccscal, or inferior right colic passes downwards, and to the right towards the ccecum, 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 fcetus 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 ar* three in number, the superior, middle, 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- face of the rectum lodged between the layers of the meso-rectum, here it takes the name of superior hemorrhoidal 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 andquadratus lumborum 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 iliacs, from one of which it arises in some rare 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 ae;ed 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. Bibliography.— Diet, de Medecine, art. Aorie. Beclard, Elemens d'anatomie generate, 8vo. Paris, 1823. Wintringham, Exper. inquiry on some parts of the animal 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. Chirnrg. 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 Iter, period, de la Societe de Medecine, t. iii. 8vo. Paris. Stokes, in Dublin Journal of Med. and Chem. Science, 8vo. * * * * Bayer, Prses. Tiedemann, Diss, de rami* ex area aortae 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 (Elements Physiologiae, 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. Jena?, 1781) ; Herold (Diss. exh. obs. quasd. ad corp. hum. partium struct. Marburgae, 1812); Nevin ( Edinb. Med. Comment. Dec. 2, vol.9); Ryan (De quarundum aiteriar. 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 ej usque vi, &c. 4to. Viteberg. 1810) ; Barhow (Disq. circa originem et decursum arteri- arum, 4to. Lips. 1829); Otto (Seltene Becbach- tungen; 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 aortae prod, in Haller. Disp. Anat. Collect, t. ii.) ; Petsche (Sylloge Obs. Anat. Halae, 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 coeur, 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 magna? 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 primi rami, in Saggi de Padova, t.,i.); Murray, (Sondeibane Stellung einiger grosseren Pulsader-stamme, Ab - hand. der Schwed. Akad. Jahr 1768); Vtcq d'Azyr, 198 AHACHNIDA. (Manque de l'anastomose qui reunit les ileux arteres mesenteriques, Mem. de Paris, 1776); Du Verney, (Sitr les vaissaux omphalo-mesenteriques, Mem. de Paris, 1700) ; Chaussier, (Sur les vaissaux ompha- lo-mesenieriques ; Nouv. Mem. de Dijon, A. 1782. Societ. Philomath, anil); and Tyson,( Unusual con- formation of the emulgents, Philos. Trans. 1678.) (J. Hart.) ARACHNIDA; a^ayyn, aranea ; Eng. urachnidans ; Fr. arachnides; 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- Class ARACHNIDA 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 carry 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, Walckniier, Duges, 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 : — Orders. {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; tnandibula armed with 1 Families. 1st Order. a moveable and perforated claw, emitting a I ARANEIDAZ Arachnida Pulmonaria. poisonous liquid Abdomen inarticulate, terminated by spinnarets Palpi produced, cheliform, or shaped like pin- ' cers Mandibulce provided with a moveable digit . . ^Abdomen articulate, without spinnarets .PEDIPALPI. M. Walcknaer, who has made a special study of the family of araneida or spinning arachnida, and who has published many works on their methodical distribution and their habits of life, has very recently considered them with the express view of arriving at a natural arrange- ment, of them ; the result of his labour may be seen in the following A RACKS' IDA. 199 - £ >»£- § Si _ - • JJ °- = J? ?>° 2 2 5 o.° ^ " '"S'aj^'S'cS Q.-2 32 .2 £ S J§ " J P » O tfi to fi S W S •> » O ofi oBhJO.<[-J' "Y ■gjg iro«.?2 ,2 h < o .2 T3 ^ 2j= si °- 3 C °'6CCS c Sl- Si .S « i « f s 200 ARACIINIDA. .5 oi *• ^r>'13 . a OI 01 --; M o 2 t- - c ttj 01 <; ci o> a ^ •£ Js .a _ _c _u .g ? D • .5 ' _ w t. -a a ^ ^- oi a oi a cs ca g a — c/i cis ^ 3 la S3 •£«>^ ■« »; ^ «i , • „ <3 oi -r; -a s~ a j> o h «a2 Vg 05 S " ce Si 3 c " S ji^ § .a g ^ bo g o> oi ■is dj t3 o a P o oi 'a © 3 © -a -P © U OS OS ,2 OS > fiH ^3 -£ ^ oi o oi ■O (J O 5 »-< oi co — • © co co _ oi to> a B H g CO C cS n oi © p*p-i is OI „ Pi £ « 3 ^ H SdQ.5 0) * G 01 'S o S o. s o Troml (palpi rs Hydrai palpi anc is . • 3 1 & 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, phrynns, theli- phonus, and p/ialangium, 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, (arcmea,) 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 in the thorax of a pholque, pholcus rivulatus, Jig-79.) But in every case the head(rt) is recog- Fis 79 nizable by constant toa ' 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 Pholcus rivulatus. 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 part, 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- 202 ARACHNIDA. tron is distinctly shewn in Jig. 100, e, which represents the inferior surface of the body of the house-spider, (tegenuria 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, (Jig- 79, b.) Continued comparative researches have convinced me that this dorsal plate of the thorax of the araneida 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 ( pleurae) 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 mygale, 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 mygale.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 (he external covering of the animals of these two classes. To those who already possess (hat infor- mation 1 shall observe that a single piece of the Digestive si/stem. — 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 mandibula or forciples (Jig. 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 mandibulce 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 Manes of insects ( epimera ) forms the back-part of the thorax of spiders ; the other piece ( epistemum ) 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. AIIACI1NIDA. 203 Fig. 81. 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 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.) laUum (c) are here 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 arachnidans 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 Treviranus, 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 maxillae ; 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, (araneae,) and we may take the common species (tegenaria domestica ) as * See Description of Egypt, Arachnidans, pi. 8, tig. 7, E, y, y. Savigny at first admitted but two pharyngeal openings, (Memoir sur les Animaux sans Vertebres, p. 57)-, but subsequently admitted three. Fig. 82. Tegenaria domestica. an example, the alimentary canal (Jig. 82 ) com- municates with the mouth between the maxilla; (a a) by an oesophagus, rather short and of a de- licate texture (&). 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 (d) of moderate length, which dilates (e) and adheres, by its parietes, to a kind of epiploon filled with adi- pose granules (./'). Posteriorly the dilated part becomes stronger in texture, insensibly con- tracts^), then undergoes a second dilatation (h) before it opens into the rectum (*). 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 chilifie 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 ARACHNIDA. 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." 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 e 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- posed,especially Scorpio. if we regard as ccecums these kind of lateral ves- sels. For the alimentary canal presents a still more ramified condition in some crustaceans, — we would cite as an example the argulus studied by Jurine;* and in another animal of the same class which M. Milne Edwards and myselff have made known under the name of Nicotho'e, the intestinal canal sends out considerable lateral prolongations. In the leech, and es- pecially the Clepsina, there exist numerous ccecums. Lastly, certain minute arachnidans (acaridae) are remarkable for analogous lateral dilatations. It is to be observed that all these beings are sustained by animal juices, and the great part, for the better gorging of the same, are fixed either momentarily or during their whole life upon the body of their victim. We now come to speak of the epiploon and the fatty globules which it contains. The fat, or the substance which appears as such, is ex- tremely abundant in the bodies of insects and arachnidans. In the latter it assumes the form of granular masses or globules of various co- lours, and sometimes these are united together by a thin membrane. In the araneae the fat is especially abundant in the abdomen, of which, indeed, it determines the form. The use of this fatty apparatus cannot be mistaken, and it has been placed beyond doubt by experiment, that it supplies the place of nourishment to the animal, either when the latter passes the winter in a state of torpidity, like the hibernating ani- mals, or when in particular seasons circum- stances are not favourable for catching prev. 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, Jig. 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- ri trema. 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 Trucheary Arachnidans are less easy to be distinguished, more espe- cially on account of the small size of the species constituting a part of that group. We have here carefully figured them in an Acaroid species ( Ixodes Erinacei), where they are situated below the sides and on the lower part of the abdomen, (Jig. 85, a,) in shape like a spherical tubercle, (Jig. 86, a,) perforated by * Annales du Museum, torn. viii. p. 431. 1806. t Annales de- .Sciences Naturelles, first series, torn. ix. pi. 49. ARACHNIDA. 205 Fig. 84. Fig. 85. Fig. 86. Ixodes Erinacei. an infinite num- ber of small holes, between which in the centre we may remark a larger circular plate (6.) Each little aperture is as it were stellated at the margins (r,) by which the air penetrates the body and gets into the tracheae. These tracheae are ana- logous in struc- ture and posi- tion to those of insects ;they are elastic, ramify after the man- gins of which adhere to the horny circle or peritrema of the stigma before described. We here subjoin figures copied from those of Professor Midler of Berlin, which represent these parts in a scorpion. Fig. 87 shows one of 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- Fig. 87. Fig. 88. the pulmonary branchiae entire, seen in profile: a is the edge by which it adheres to the circum- ference of the stigma; b the simple membrane without folds ; c the folds or leaves. Fig. 88 shows a portion of the same pulmonary branchia laid open : a is the horny margin of the stigma, or peritrema, to which the simple membrane b 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 Uca, Ruricola, &c, of Linnaeus, possess branchiae which are much better adapted for respiration in air than in water. The Cancer Mtxnas, 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 ARAC1INIDA. liave 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 {fig- 89). It is kept in its situation by small ligaments or muscles, (a a), which in insects are called alee 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- j merous vessels are observed to arise from the heart, es- pecially from its posterior part (c c.) These proceed to a ramify indefinitely, . distributing them- e selves over every organ ; and we have no doubt a . . 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 size (d d,) which communicate in a one direction with a the heart, in an- other, by very fine ramifications, with the pulmonary branchiae. In Clu- bione atrox these b two vessels do not Tegenaria domestica. 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 (fig. 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 (eeee) that come from the pul- monary branchiae. Treviranus, to whom we owe these observations, has not, however, at- tempted to explain the manner in which the circulation takes place in the arachnidans, and indeed this is to be determined by physiolo- gical experiment and 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 cardiac vessels of crustaceans. With respect to veins, of which the latter animals are destitute, they are equally wanting in the arachnidans, and are doubtless replaced by cavities of an irregular form which exist between all the organs of the body. Tre- viranus, indeed, has remarked in the abdomen of Tegenaria domestica two small intervals which are discoverable through the integument, and in which he says the blood may be ob- served to be collected. These reservoirs are perhaps the analogues of the venous sinuses of the Crustacea. The nature of the vessels being thus deter- mined, it becomes easy to conceive how the circulation takes place in the arachnidans — the blood, leaving the heart, is distributed through all the arteries to the different organs for their nutrition : this being effected, and the nutrient fluid being thereby converted into ve- nous blood, it begins to circulate through the sinuses before mentioned, and arrives by an insensible course at the pulmonary branchiae. There it is changed by contact with air into arterial blood, and returns to the heart by means of the branchio-cardiac vessels (e d) to be finally again propelled through die 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 Scorpionida we find the following structure (fig. 90): — the first ganglion, which is commonly called the brain (a), and which supplies the nerves to the parts of the mouth (6,c) is intimately blended with the nervous mass giving origin to the nerves of the legs (d). The succeeding ganglia are distinct from one an- other, and are seven in number : the first three (1 2 3) are situated in the abdomen proper; they have this peculiarity, that they are united together and with the ganglion, which may be termed cerebro-thoracic, by three instead of two chords of communication (e), which is the number found in all other articulate animals ; the four 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. ■A / rectly termed the tail. In the Aran- " idee the ganglions are fewer than in the Scorpionid 210 ARACHNID A. but in some cases there exists a well-marked character. The greater part of the araneae of the male sex have, at the extremity of their maxillary palp, a swelling containing a compli- cated structure, which is not found in the female. Until lately this protuberance was considered, notwithstanding its anomalous po- sition, as the penis of the male ; and even now this opinion is maintained by many naturalists. All observers indeed, both ancient and mo- dern, agree in stating that copulation takes place by means of this part. They have repeatedly observed the fact, and have described the pro- cess with all the details that can inspire con- fidence in their observations. Nevertheless it appears to us certain, if the anatomical facts we are about to disclose are accurate, that there is some mistake on their part, and that what they have taken for the act of copulation was in reality only a prelude to it. It is indeed true thit the male spiders are distinguished from the females by the swelling at the extre- mity of the maxillary palp, and that that swel- ling presents a very complicated structure. Treviranus, Savigny, and, earlier than these, Lyonnet, have given detailed figures of it, which may be consulted with advantage: our descrip- tion will be after that of Treviranus, and from observations made on the common spider, Tc- genaria domestica. The male of this species, when arrived at the adult state, presents a considerable dilatation at the extremity of its maxillary palp (jig. 100, a). On carefully observing this swelling, it is per- Fig. 100. ceived to arise from the penultimate joint (6), which is enlarged and spiny. The swelling it- self, or what has been termed penis, (fig. 100 and fig. 101, a,) is a con- cave body from which a membranous, vesi- cular, and glandiform body (c) protrudes, ter- minated by several horny pieces (d), which are curved and pro- ject but slightly in this species, but ac- quire, in others, a con- siderable development, and protrude in the form of long hooks having a much greater complication of structure. In order that this part should be a penis, as has been supposed, and as many naturalists still believe, itought to be perforated for the emission of the prolific liquor. Now, Treviranus is certain that it is not perforated by any foramen, and also that there does not exist in the interior of the palp any excretory duct which could have brought to this part thesecre tion of the testicles. Lastly, and this proof is still more conclusive, on examining carefully the under surface of the abdomen of a male, he discovered at its base, i. e. at the point where it is inserted into the thorax, between the aper- tures of respiration, and at the part correspond- ing to the vulvary opening of the female, two very small orifices, placed in a transverse fissure, which he ascertained to be the true outlets of the male apparatus. He found in the inte- rior of the abdomen two cylindrical dilated vessels, which he determined to be the testes. (Fig. 102, b,b.) These two organs open into two long, slender, tortuous, Fig. 102. excretory canals ( c ), which terminate at the two orifices of which we have spoken ( a ), but without the appear- ance of any superaddition of a firm or horny part that can be compared to a penis. From this description it is certain that what has been regarded as the act of copu- lation, has been only preli- minary, and that the intro- duction of the extremity of the maxillary palp of the male into the vaginal aper- tures of tli e femal e was for th e mere purpose of opening the oviducts in order that the ac- tual coitus should be effect- ed with facility and with- : out doubt instantaneously ; w hich explains why no ob- server has hitherto witness- ed the act.* The remarkable sexual differences which obtain in 3 the aranea? are not found in other arachnidans. Thus in the scorpions the maxil- lary palps have a similar organization in both sexes, being terminated by pincers, both in the male and female, (fig. 84, b.) The external aperture of the male apparatus is placed behind the thorax, and manifests itself by the presence of a valve formed by two semi- circular pieces (fig. 84, c.) The internal struc- ture of these organs is but imperfectly known. Treviranus believes that he could distinguish the testicles which terminated at the extremity in a kind of horny penis. Leon Dufow has given a more detailed description of these or- gans, together with a figure which represents each testis, as being a large network of three meshes formed by cylindrical tubes. The male, like the female scorpion, presents at the inferior part of the body on either side of * Mr. Blackwall denies the accuracy of Trcvi- ranus's opinion, and supports that of Lister and the older observers, as to the sexual function of the maxillary palp, founding his remarks on observa- tions made on various individuals of the genera, Epeira, Theridion, and Agelena. We must refer for the details to the memoir before quoted from the Transactions of the Linnasan Society., — Ed. ARACHNIDA. 211 the valve certain organs of a singular structure which are called combs, pectines, (fig. 84, d,) on account of the disposition of a series of small appendages of which they are formed, and which are arranged on the lower surface one beside the other, like the teeth of a comb. Many speculations have been offered respecting their uses. Many naturalists believe that they render some assistance in the act of impregna- tion. Some suppose that they are extended during progression, and prevent the abdomen of the scorpion from trailing on the ground : others, again, regard them as hygrometrical organs, by means of which the animal judges of the humidity of the atmosphere. These are, however, all mere gratuitous hypotheses un- supported by any observation ; and the fact is that we have yet to learn the use of these pec- tinated appendages. Of the female generative system. — It has been long known that the orifices of the gene- rative organs in female spiders are situated at the base of the abdomen. We observe on that part yfthe body two distinct cavities, (f g.103, a, a, J which are closed by opercular pieces of Fig. 103. a more or less solid texture, and it is at this part that the oviducts terminate. In the tege- naria domestica, these oviducts (b, b) are con- tinued internally in an insensible manner with the ovaries, which consist of a kind of bags (c,c) situated on each side of the intestinal canal, and to whose parietes the ova are attach- ed in a racemose manner. In the epeira diadema the ovaries are divided by two longitudinal membranous septa, and each is again subdivided by a transverse septum. The longitudinal sep- tum has no orifice, but the transverse one is perforated. There is, therefore, no communi- cation between the principal chambers of each of these ovaries, but there is a passage from the anterior to the posterior division, and the ova which are in the former must pass into the lat- ter before being extruded. This structure ex- plains how it happens that the epeira diadema lays its eggs at two distinct periods. Another spider (theridion quadripunctatum, VYalck.) presents a very analogous organization. The female generative apparatus of scorpions has not hitherto been studied with that degree of care which it deserves ; and there is a consi- derable difference among authors with respect to this subject; it therefore requires farther ex- amination. Treviranus and Leon Dufour have described these organs as consisting of three elongated tubes ; of these, two are lateral and mutually communicate at their apices, the third is mesial and communicates with the lateral by three branches which we observe on either side. All of them, lastly, terminate at the vaginal orifice which is concealed by a more or less rounded plate, and is situated on the middle line of the body anterior to the pectines and between the coxae of the fourth pair of legs, at the same point where the penis is placed in the male (jig. 84, c.J Copulation, oviposition, and development of the ova. Metamorphosis, and reproduction of the extremities. — Natural observers have hitherto given but very few details respecting the man- ner in which the male spider approaches the female, in accomplishing the sexual act : and wehave already observed that they have been de- ceived in considering a preliminary step as the entire process. The preliminaries are accom- panied with very curious circumstances, the account of which may be found in all the me- moirs and works which treat of the animals of this class. It will be there seen with what precaution and fear the male makes his ap- proaches to the female, who is always ready to attack and devour him, whether before or after copulation. The majority of the arachnidans deposit their eggs in great numbers. The female guards them with the utmost care, some- times carries them about with her, and always prepares a silken nest for them which is fre- quently covered with a solid exterior. Some arachnidans, as the scorpions for example, are ovo-viviparous ; the ova are developed in the interior of the body of the female who brings forth her young possessing the faculty of loco- motion ; but they rest for a certain time at- tached to the back of the mother, who guards and feeds them, and gives them a kind of edu- cation. The changes which occur in the ova of spiders (araneae) have been studied with much care. We are indebted to M. Heroldt for highly interesting observations on this subject, published in the work entitled " Exercita- tiones de animalium vertebris carentium in ovo formatione," folio, Marburg, 1824, from which an extract is given in the Annales des Sciences Naturelles, first series, vol. xiii. p. 250. From the importance of these re- searches we here present an analysis of them. The exterior covering of the ovum is formed by a very delicate and transparent membrane, in the, composition of which no pore or fibre can be distinguished on microscopical in- spection. Within this membrane there is a liquid matter in which Heroldt has distinguished several essential parts, which in relation to their functions appear to us to correspond to the vitellus, the albumen, and the cicatricula of the egg in birds. An idea of the disposi- tion and size of these parts may be formed by inspecting the subjoined figure (fig. 104), p 2 212 ARACHNIDA. Fig. 104. representing a vertical section of a fecundated ovum at the moment ofexclusion,and before any organ has been de- veloped. The vitellus or yolk (a) forms the greatest part of the contained liquid mat- ter, and the egg is almost entirely filled by it : its colour is gene- rally that of yellow ochre, and sometimes has a saffron tinge. In some species the yolk is grey, white, or reddish brown; and in each case the colour of this part determines the ge- neral tint of the egg. If the yolk be consi- derably magnified, it is seen to be composed of an infinite number of minute globules of various sizes, swimming in the albumen, or surrounded by it, and resembling so many small yolks. The albumen (6) is a transparent crystalline liquid, without distinct organical parts, and consequently not presenting any globules, sur- rounding the vitellus as far as the cicatricula, and intermediate in bulk or quantity to these. If an ovum be opened, and the liquid which it contains be poured out upon glass, the albu- men is seen to surround the globules of the vitellus and cicatricula exactly as the serum of the blood envelopes the crassamentum. In the interior of the egg the albumen is situated, like the cicatricula, externally to the yolk, and fills the interspace between the yolk and the exterior membrane of the egg. It is in this interspace that the first lineaments of the embryo appear, and here the head, thorax, members, integuments, and their appendages, and all the internal organs, without excepting the intestines, are successively developed. The cicatricula or germ (c) is the smallest and most important part of the ovum. It is situated immediately beneath the exterior co- vering, and at the centre of the circumference of the egg. It is distinguished by the naked eye in the form of a little white point. If it be examined with more care, we perceive that it is of a lenticular figure, and is composed of an innumerable quantity of whitish granules. Under the microscope these granules are seen to be of a globular figure, somewhat similar in this respect to those of the yolk, but more opake, and of a smaller diameter. When segregated and diffused they present a striking analogy to the grains of pollen, but with this difference, that the pollen of vegetables is composed of vesicles filled with organic molecules, whilst each of these globules of the cicatricula must be regarded as simple. The cicatricula or germ is the centre of radiation of all the changes which take place in the ovum. All the parts which it contains seem subordinate to it, as we shall see by carefully tracing their development. A remarkable fact observed by Heroldt in the ova of some undetermined species of spiders is this, that in place of a single cicatricula, there appear to be several spread over different points of the surface of the ovum ; but these small germs rapidly coalesce into one mass, which soon assumes the ordinary form of the single cicatricula. The component parts of the ovum being known, we proceed to the metamorphoses which they undergo up to the time when the young spider breaks through the shell. Fig. 105. First period. — The im- pregnated ovum being de- posited, and the temperature being favourable, develop- ment commences. The changes always begin at the margins of the cica- tricula, which appear to be resol ved into granules,which extend into the albumen and vitellus. The centre of the germ remains the same, the only appreciable difference is the enlargement of its circumference: (A, gives the natural size of the ovum.) Second period. — The germ is much larger, its margins are dispersed in numerous granules ; the centre is not yet affected by this tendency to molecular dispersion, but has undergone a notable modification. It changes its situation and begins to move towards the extremity of the ovum, leaving in the place which it for- merly occupied a train of globules; it now, to compare small things with great, bears some resemblance to a comet, the nucleus of which is represented by the centre of the germ ; the tail, which is formed by the dispersion of the globules, is transparent, and the vitellus which it covers may be as distinctly seen through it as the fixed stars through the tail of a comet. Third period. — The nucleus of the germ (jig. 106, a), which has continued to change its place, is arrived near the extremity of the ovum, but has not quite reached it. The tract which it has traversed is marked by an infinity of granules, which are then so much dissemi- nated that they extend al- most to the opposite extre- mity of the ovum. It is then that the kind of comet which it represents is seen at its greatest development, and with all the characters that have been indicated. The movement of the nucleus of the cicatricula authorizes the supposition that that body has not, at least at the earlier periods, a very intimate connexion with the vitellus. Fourth period. — The nucleus of the germ has not gone beyond the point which it had attained, but it presents a new change. The molecules are disseminated into an infinity of granules, nothing remains of the comet but the tail, which is still more extended ; but we see then that the granules dispersed in the albumen have a tendency to reassemble at the point where the germ was originally situated. Fifth period. — The germ of the ovum, which appears to be disseminated in the albumen, has undergone a very curious transformation. Its nucleus has disappeared, all its granules are decomposed into almost imperceptible mo- lecules, which, in destroying the limpidity of the albumen, have given it a clouded appear- ARACHNIDA. 213 ance, through which, however, the globules of the vitellus may be distinguished. A single point remains perfectly transparent, and this is observed at the extremity of the egg (jig. 107, a,) opposite to that which the germ occupied 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 Fig. 107. after its displacement. Heroldtcalls this clouded albumencolliquamentum. Up to this period the vitellus seems not to un- dergo any change ; all that has been hitherto observed takes place in the albumen and in the circular space between the yolk and the shell. Sixth period. — The colliquamentum, or clouded albumen, which was extended over the yolk so as to conceal it, is now concen- trated upon the point last occupied by the nucleus of the germ, and has assumed a pearly colour (Jig. 108). Its consistence is pretty Fin. 108. solid ; it is opake, so that the globules of the yolk can no longer be distin- guished through it, al- _6 though they are elsewhere more conspicuous on ac- count of the retreat of the clouded albumen towards this single point; from this moment the colliqua- mentum, which seems to have changed its nature, receives a new name, and is designated by Heroldt the cambium. The cambium covers more than a fourth part of the circumference of the yolk; its form is already pretty well marked, and two parts may be distinguished 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 be perceived to develope themselves. The smaller division is of a rounded form, and seems, as it were, an appendage to the preceding; it is destined to give origin to the head, the or- gans of sense, and the appendages of those of mastication. So much being premised, we may call, with Heroldt, the larger division cambium thoracicum, the lesser one cambium 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 araneae 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 diudema offers an example of this circumstance ; in other re- spects there is no important difference observable. Seventh period. — The two portions of the cambium, the cephalic and thoracic, have as yet presented only the appearance of an opake and homogeneous mass, but now we Fig. 109. a 6 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 maxilloe, have their limits well defined from this period. With respect to the head, («) 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 the vitellus. It is implanted upon the yolk just as fungi and other parasitic plants are attached to the trunk of a tree : the yolk, then, is subservient to the nutrition of the most exterior parts of the body. Eighth period. — The exterior parts which are developed in the cambium, viz. the feet, the mandibles, and the head, are more neatly de- fined. The ovum (fig. 110) now presents a 214 ARACHNIDA. very important pecu- Fig. 110. liarity, but which was /^ilbs. >n some measure in- ij^yJ^Ex^ dicated in the pre- " ^SIkSx^X s'ze *s s''Snt^y di- minished anteriorly, f?^^Q^^0!^ii-:% a"d tne vitellus con- l^^^l \ sequently is divided l^^^^^g^H \"e into two portions. V^^S^giMpy terior part ( « J is rea- xS " dily distinguishable ^^aiis*^ 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. an obscure straight band (b ) which commences at the thoracic-abdominal constriction, and reaches to the extremity of the ovum, becoming gradually narrower in that direction. This band, which does not give off lateral processes in any part of its course, is to be considered as the rudiment of the heart or dorsal vessel. The fluid which it doubtless contains in its interior is motionless. Heroldt thinks that the forma- tion of the fluid is anterior to that of the parietes in which it is enclosed : he also be- lieves that it is the albumen which gives origin to the circulatory apparatus, and further attri- butes to it the origin of all the integuments. These are, doubtless, important questions to solve, but as they are the result of speculation rather than direct observation, we have deemed it proper to omit the theories by which they are supported, and confine ourselves to a simple enunciation of the facts The eyes (d) are now distinguishable. Ninth period. — The ovum presents a more sensible diminution anteriorly, and is more dis- tinctly divisible into two parts. The anterior and narrow portion constitutes the smaller ex- tremity, and includes the head, the thorax, and their appendages ; the other portion, which is spherical and of much larger size, constitutes the greater extremity and corresponds to the abdomen. At the same time that these modi- fications take place the ovum becomes slightly elongated, and all the parts which can be dis- tinguished therein have proceeded towards their perfection. The legs now present slight traces of a division into joints, and they have increased so far in length that they cover almost the whole of the lower surface of the thorax. Tenth period. — The small extremity, which is still more elongated, is now found to be dis- tinguished from the large one by a true 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. 110, e.) Heroldt imagines this streak to be an indication of the development of the internal parts of the abdomen, viz. the intestinal canal, the secreting vessels of the web, and the genital organs, &c. In proportion as the fcetus increases, the ex- ternal membrane or covering of the egg is ap- plied more exactly to its body, and seems to represent an exterior skin, of which the young spider soon divests itself, almost in the same manner as the caterpillar sheds the skin in which it is enveloped. Eleventh period. — By the progressive in- crease of the foetus the membrane of the egg becomes so much stretched, and is applied so exactly to the surface of the body of the animal that the different parts can be distinctly seen through it, like the nymph or chrysalis of certain coleopterous insects. The essential parts of the thorax are the head and the feet. The head is of a white colour, and is surmounted by eight brown streaks ; the legs, which are also white, are closely applied to the chest, with their extre- mities alternating with each other. One may dis- tinguish in each a hip, a thigh, a leg, and a tarsus. The articulations of the palps and mandibles are also visible through the general envelope of the egg. The inferior streak of the abdomen is much more extended, and seems to be divi- ded into two parts, one large and elliptical in figure, the other small and rounded ; the latter corresponds to the anal aperture ; at this last stage of the development, the foetus or the im- prisoned young spider, as it may be called, gives no sign of motion. Exclusion or hatching of the spider. — At length the spider bursts the egg by tearing through the exterior membrane. De-Geer* has described this phenomenon. The outer mem- brane or pellicle of the ovum becomes fissured along the corslet, and the spider protrudes by this aperture, first the head, the mandibles, the thorax, and abdomen, after which there remains the more difficult operation of extracting the legs and maxillary palps from that part of the outer membrane with which these parts are, as it were, enveloped. This is at length effected, though slowly, by alternately dilating and con- tracting the body and legs, upon which the animal is liberated, and capable of progression. In proportion as the parts are disengaged from the pellicle, it is pushed towards the extremity of the legs, and is reduced to a little white bag which is all that remains. Sometimes the pel- licle is found still slightly adherent to the ab- * Mem. sur les Inscctes, t. vii. p 195. ARACHNIDA. 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 itself of this other covering ; and it is only then that it can be said to see the light. This last operation, or as it may be termed the first moult, takes place after a period, varying according to the de- grees of atmospheric heat and moisture. Some- times it is observed within the first week, at 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 acaridce, 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, ( arunea,) 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, torn i. and ii., 1834. t See Bulletin de la Socicte Philomathiriue, Paris, Avril, 1813. 21.5 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 junction of the femur with the coxa; and the same thing takes place when the body of the spider is held fast, and the leg is pulled off. In both these cases the spider seems not to suffer pain ; it experiences only a very little loss of the internal fluid, and does not die in consequence ; it spins, seizes its prey, and oviposits in the or- dinary manner. The preceding facts are applicable to all spiders, ( aranete,) 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 dpmestica, 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 when 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 &; Way, Obs. concerning the darting of spiders, Phil. Trans. 1669 and 1670. Hombery, Sur les araignees, Mem. de Paris, 1707. Clerck, Vom fangen und Ernahren der Spinnen Abh. d. Schwed. Akad. J. 1761. Boissier de Sauvuyes Obs. sur une araigne, Mem. de Paris, 1758. Ha- gedom, De Araneis, Miscel. Acad. Nat. cur. Dec. II. an 3, 1684. Valentini, Curiosa in araneis ob- servata, ib. Dec. ii. an 7, 1688. Dorthes, Obs. on the structure and cecoaomy of some curious species of aranea ; Trans, of Linn. Soc. vol. ii. Paidlini, 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 van t'Eiland Java ; Verhand. v. h. Bataaf. Genoot. Deel 3. LatreiUe, Sur la famille des araignees mineuses, Soc. Philomathique, an 7. Prevost, Sur les araignees mineuses : Mem. de la Soc. d'Hist. Nat. de Paris, Cah. i. Martyn, 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, Hydra- rachas quas in aquis Danias, &c. 4to. Lips. 1781. Lister, Hist. Animal. Anglias, 4to. Lond. 1678; Germanice cum add. a Martini et Goeze, 8vo. Quedlingb. 1778. Meyer, Ueber ein. Spinnen d. Gbtting. Gegend. 8vo. Gotting. 1760. Treviranus, Ueber den innern Ban der Arachniden, 4to. Nurn- berg, 1812. Heroldt, Exercit. de animal, verteb. carent. formatione in Ovo Pars prima: De genera- tione araneaium, fol. Marb. 1824. Wulckenuer, Faune Parisienne, 2 torn. 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. Lyonnet, Rech. sur l'anatomie et les metamorphoses de ditferentes es- peces d'insectes, 4to. Paris, 1832. Roesel, Insecten- Belustigungen, 4 torn. 4to. Niirnberg, 1746. ( Victor Audouin.) ARM. (Surgical anatomy.) (The arm, Gr. B^a-^ndv. Lat. Bruchium. Fr. Bras. Germ. Oberarm. Ital. B?*accio.) 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. Blackwall, in the paper already referred to, has related an accidental discovery of the power of some spiders to abstract respirahle air from water. Several individuals have preserved an active state of existence under water for six, fouiteen, 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 iir females, in whom it assumes more or less of a conoid form, tapering to- wards its lower part. (See Jig. 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 and 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 children than in men, and in greater quantity in the depressions than over the muscular prominences ; the filaments Aim. of the cutaneous nerves of the 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- brachial 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 brachials 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 brachiaeus 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, brachiaeus 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 brachiaeus 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 brachiaeus 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 foetus, 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 218 ARM. 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 brachials 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 * Mcmoires de l'Academie de Chirurgie, torn. v. ARM, MUSCLES OF THE. 219 arm 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, brachiteus 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 brachials 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 subscapulars, 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 cubiti ( 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 brachials anticus and the front of the elbow-joint, sinks into a triangular hollow between the pronator 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- rocubitul). — 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 directioninwardsoroutwards; inwards when the biceps acts alone, outwards when the brachiosus. 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. brach'ucus externus, 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. Hart.) ARTERY, (normal anatomy): a^r^ia, etna Toy toii mspol tvquv, ab aere servando. Er. ar- tere. Germ. Pukader,Schlagader. Ital. arter ia. 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 Aretseus, 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- clavian, 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, j and repeated by Mr. Hunter,]: 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 * Haller, Elementa Physiologic, t. i. sect. 1. § 17. t Elementa Physiologic, t. i. s. 1, § 3. $ Treatise on the Blood, &c, p. 168 et sen,. 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- rov-, er in a portion of its course of six inches in length, for which space no branch had been given off. 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, &c. 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,! 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 ova, per, no/jta, 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 two 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 ARTERY. The parietes of arteries are divisible into three tunics, 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 lamina? 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 separatee." 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 * Anatomic Generate, p. 325. t Anatomie Generate, torn. 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 poplita;al, 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 thin 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 Ilaller, 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 smal 1 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 some 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 menschlichen Anato- mic 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, nervi 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 Beclard,J 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- * Op. cit. t Experimental Inquiry on some parts of the Animal Structure. Lond. 1740. \ Anatomie Generale, 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 hemorrhage 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,f 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, t Archives Generates de Medecine, t. xx. Aofit, 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, by Magendie; 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 ia 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, Soemmerring, and Versehuir. 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 times 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, Versehuir, and Hastings, and with results directly contrary to those obtained by that very distinguished anatomist. Versehuir* found that the arteries contracted when stimu- * Bissertatio de arteriarum ct venarum vi irrita- bili. Gronigcn 1766. vol. r. 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. Hunter]; 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 appear 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,£w, diffindo ). — This form of articulation is where a thin plate of bone is received into a space or cleft formed by the separation of two laminae of another, as is seen in the insertion of the azygos process of the sphenoid bone into the fis- sure on the superior margin of the vomer ; and in the articulation of the lacrymal bone with the ascending process of the superior maxillary. c. Gomphosis (yo/Aipo?, clavus. Clavatio, conclavatio). — 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 (a^Qi, utrinque, afi^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 orfibro-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 synarthrodial 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. t The articulation of the lower jaw in the whale- bone whale, above referred to, is a joint of this kind. 256 ARTICULATION. an angle with 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- slood 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 ( urticulatio 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 vertebra? 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 {yiyyKv^oi;, cardo, urticulatio 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 of 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. Diarthrosis 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 ECH1NODERMATA. ASPHYXIA. 25? 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 vocabulary 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-ulnae, Shoulder, Spine, Temporo - maxillary, Tibio-fibu- lar, Wrist, and the morbid anatomy under the head Joint. Bibliography. — Havers, Osteologia nova, 8vo. Lond. 1691. Saltxmann,De Articulationibus Artuum, Argent. 1712. Walther, De Articulis, Ligamentis, &c. 4to. Lips. 1728. Neumann, Lehre von d. Articulationen d. mensch. Koerpers, Freiberg. 1745. Isenflamm, Diss, de Ginglymo, 4to. Erlang. 1785. Bonn, De Suturarum co p. hum. fab. et usu, Lips. 1763. Haase, De unguine articulari ejusque vitiis, 4to. Lips. 1774; Ej. De fabrica cartilaginum, 4to. Lips. 1767. Petscliel, De Axungia articulari, Lips. 1740 (Recus. in Halleri Diss. .\nat. 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 Tabellen, 8vo. Lange. 1782. Monro on the Bursae mucosae, fol. Kdinb. 1788. Heysirjers, Diss. Phys. Anat. de fabrica intima articulationum, 8vo. Traj. ad Rhen. 1803. Loschge, Die Knochen, &c. des mensch. Koerp. fol. Erlang. 1804. Bichat, Mem. sur la membrane synoviale des articulations, Mem. de la Soc. Pliilom. An. 6. Dickinson, A syndes- mological chart, 8vo. Lond. 1821. Cooper, B. on the ligaments, 4to. Lond. 1825. Cruveilliicr, Sur les cartilages diarlhrodiaux, Arch. Gen. dc Med. Fcvrier, 1824. Bichat, Anatomic generate. Beclard, Anatomie gent-rale. (The older and likewise the VOL. I. newer systems of anatomy are mostly deficient in syndesmology ; the works of Bichat and lioyer, however, form exceptions, and arc well deserving of a careful perusal : the descriptions in the Trait! 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 1'homme ; Anglice, The whole anatomy of the human body, by R. Willis, fol. Paris and Lond.) (R. B. Todd.) ASPHYXIA. (Gr. Aafpv^x. Fr. Asphixie. Ger. Scheintod, Asphyxie. Ital. Asfissia.) The word Asphyxia, according to its derivation (from a and a(pv^t>, 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 pupre 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 * Sec 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 whicli 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 ceconomy 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- * Do l'lnflucnce des Agens Physiques sur la Vie, p. 410, et seq. t Journal do Physiologic, t. iv. % See Hodgkin's Translation of Edwards, p. 486. § See Cuvier, La Regne Animale, t. i. p. 56; also Marshall Hall, Philosophical Transactions, 1832, p. 339. 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 * 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 girls, 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 five, 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. * Flourens in Annales d'Histoire Naturelle, 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 deatli by asphyxia. The blood 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 we.l founded, is supported. * Bichat, Recherches Physiologiqucs, &c. (4th edit.) p. 338. S 2 260 ASPHYXIA, 1. The first opinion on this subject, whicli 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 are 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.f 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. % 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 * This point lias 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. 82. t Recherches Physiolo^iques, &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' iin- mersion.f And we are therefore well assured that the arterialization 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,} 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. t Recherches, &c. art. 6. ASPHYXIA. 2C1 Dr. Kay,* which we know to hare 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. " 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 bad 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 lied, and after the muscles of its lower extremities have, in 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 thoughtto beasfollows: — that the venousblood, though more or less noxious to all parts of the body which it fully penetrates, is nevertheless transmitted through the lungs 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 onlv 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 venousblood isaccumulated 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 l'Influcncc, &c. p. i. ch. i. and p. iv. ch. 4' i Treatise on Asphyxia, p. 193 ct scq. 262 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 ;f 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. J 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 mamma? 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 Schultze, Amici, Raspail, and otheis 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 inereased,+ 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. J 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 the lungs, is of the nature of an attraction of the venous blood towards the part where it is to * Prevost and Dumas, An. de Chimie, t. xxiii. + See particularly Schrocder Van der Kolk, Com. de Sanguine Coagulante. } Experimcnta circa Statuin Sanguinis, &c. $ 281 & 357. § Mem. sur lc Mouvcment du Sang, p. 336 et seq. 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 Foder6, 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 hybernating 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. J. • Fodere, Med. Legale, § 613. t Phil. Transactions, 1832. X 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 oeconomy. It seems probable, that if we possessed the means of making the artificial respiration ex- actly similar tQ 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 Xv/mjS, 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 an essential constituent. ASPHYXIA. Gallois, 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, («. e. of deatli 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 unequivocal !y proved by Sir B. Iirodie,* 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 the brain and the gradu- ally increasing insensibility, might be recovered by the irtificul 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 Tlie 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 itself into 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 Obscivatious 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 jmneiples 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, Delia morte apparente, 8vo. Firenz. 1780. Coste, Mem. sur les asphyxies, 8vo. Philad. 1780. Previnaire, 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 vapeuis mephitiques dans l'hommc, &c. 8vo. Paris, 1791. Coleman, A dissertation on suspended respi- ration, 8vo. Lond. 1791. Curry on apparent death, 8vo. Lond. 1792. Fotherqill, Preservative plan ; or, hints, &c. 8vo. Lond. 1798. Graf, Dis. sur l'asphyxie, Strasb. 1803. Bichat, Sur la vie ct la mort, Paris, 1805. Guillebout, Indie, des affec- tions qui produisent subitement la mort, &c. 4to. Paris, 1812. Colorini, Suite varie raorti apparenti, 8vo. Pavia, 1813. Lebel, Consid. sur la ma nitre dont la mort arrive dans quelqucs maladies des organes de la respiration, 4to. Paris, 1815. Orfila, Sccours a donner aux personnes empoisonnees on asphyxiees, 12mo. Paris, 1818. White, A disser- tation on death and suspended animation, 8vo. Lond. 1819. Gammer, De causa mortis submer- sorum, Groning. 1761. Recus. in Sandif. Thes. vol. i. Champeaux et Faisole, Expcr. sur la cause de la mort des noyes, 8vo. Lyon. 1768. liu Cheniin d'Etamj, Mem. sur la cause de la mort des noyes : rcponsc a MM, Champeaux ct Faisole, 8vo. Paris, AVES. 265 1770. Fothcrgill, New inquiry into the suspension of vital action, &c. 8vo. Lond. 1795. Cuillau, Mem. sur l'asphyxie par submersion, 8vo. Bordeaux, 1799. Fine, De la submersion, 4to. Paris, 1805. lierger, 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 occonomy, 4to. Leroy, Rechefches sur les asphyxies, 8vo. Paris, 1829. Devergie, Diet, de Med. et Chir. Prat., art. As- phyxie. Royet, in Cyclopajdia of Practical Medi- cine, art. Asphyxia. Kay, on asphyxia, 8vo. Lond. 1834 ( the most complete and able work on this subj et in the English language ). Edwards, Sur l'influencc des agens physiques, Englished by P/rs. Hodgkin and Lister, Appendix, p. 463. (W. P. Alison.) AVES, birds; (Gr. Ofn6s; ; 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 ptilmonary 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- ations 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- 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 type 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, &cc. 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 biliary 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 ibr themselves the mo- 266 AVES. ment they quit the shell ( Aves prtecoces ) ; while in others the young are excluded feeble, naked, and blind, and dependent on their pa- rents for support ( Aves altrices ). Scotoli, in his ' Introduction to Natural History,' published in 1777, proposed a dicho- lomous 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 Retepedes of this author; those which have the legs covered anteriorly with unequal semicircular plates are the Scutipedes. Nitzsch,* 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 uerem (Luft-vogeln) ; the second order em- braces the birds of the earth, Aves terrestres (Erd-vbgeln) ; the third great division includes the birds which frequent the waters, Aves aqua- tics (Wasser-vogeln). 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 the class Aves intone 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 Birds ; this order is termed Raptorcs, 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 Aves 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- logie, B. 12, p. "73. f 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 Blutnenbach, 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 Blain- ville have nine. Temminck (1820) has sixteen. Schceffer 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 JBirds, and which may therefore be considered as the most natural. Orders. I. Raptores, Vig. Syn. Accipitrcs, Linn. Cuv. Birds of Prey or Raveners.f II. Insessores, Vig. Passeres, Linn. Cuv. Perchers. III. Scansores, Illig. Cuv. Climbers. IV. Rasores, lllig. Gallince, Cuv. Scratchers. V. Cursores, Hlig. Brevipennes, Cuv. Coursers. VI. Grallatores, Hlig. Grallce, 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 ciixulation double. Lungs fixed, perforated. Negative characters, no auricles, lips, teeth, epiglottis, diaphragm, fornix, corpus callosum, scrotum. Order I. RAPTORES. 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. f This vvord is proposed by Mr. Kirby as the English for Raptores ; it is the substantive of rave- nous, from the verb to raven. 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 — Fulconidtf, Eaglesand Hawks ; Vulturidm, Vultures ; and Gypdgeranid(e,v/hich 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 Raptoreshzve the eyes directed forwards, and include the Sirigida or owl-tribe. Order II. INSESSORES. Legs slender, short, with three toes before and one behind, the two external toes united by a very short membrane.* The Perchers 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. (FigAU.) The perchers in general have the females smaller and less brilliant in their plumage than the males ; they always live in pairs, build in trees, and display the greatest art in the con- struction of their nests. The young are ex- cluded in a blind and naked state, and wholly dependent for subsistence during a certain * The genus Ceyx, Lactp. ( 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. The brain arrives in this order at its greatest proportional size; the organ of voice here attains its utmost com- plexity, and all the characteristics of the bird, as power of flight, melody of voice, and beauty of plumage are enjoyed in the highest perfection by one or other of the groups of this extensive and varied order. The beak of the lnsessores 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, Dcntirostres ; 2, Conirus- tres ; 3, Tenuiroslres ; 4, Fissirostres. The Ventirostres, (jig. 1 1 5) characterized by their insect food, and the notch near the extremity of the upper man- dible, include the families termed Laniadte or Shrikes ; Merulida, Thrushes; Sylvi- RostnmoJ 'a Shrike ache, Warblers ; Pipi ida, Tits ; and Muscica- pidee, Fly-catchers. The Conirostres (Jig. 116) include the two Fie. 116. Fig. 114. Rostrum of a Crow. orders of M.Temminck, termed Omnivorcs and Granivores ; and are characterized by a strong and conical beak, the margin of which is gene- rally entire ; the greater part are omnivorous, the rest gran ivorous ; these latter are the Hard- billed Birds of Ray. The families of the tribe are the following : Sturnida, Starlings ; Cor- vida?, Crows ; Buccrida;, Ilornbills ; Loxiada, Cross-bills ; Fringillida, Finches, Larks. The Tenuirostres (fig. 1 1 7) or suctorial Fig. 117. birds form, Mr.Vigors observes, " the most interesting group, per- haps, of the animal Rostrumof theOrthorhynehus, world. Deriving their or Straight-billed Humming subsistence for the most 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 * In the Humming-Birds which we have dis- sected, we have found the remains of minute insects in the gizzard. + We have selected the skeleton of the Humming- bird, one of this tribe, as a striking illustration of the 2(58 AVES. This distinguished ornithologist proposes to divide the Tenuirostres into the following- families : Cinnyridce, Sugar-eaters ; Trochilidce, Humming-birds; — in which families the beak and feet are more remarkable for their tenuity and length : and Promeropida, Hoopoes ; Me- Uphagidte, Honey-suckers ; Nectariuiadce, Nec- tar-birds ; — in which the slenderness of the beak and feet is less remarkable. Fig. 118 The Fissirostres, (fig. 118 J, like the Tenuirostres, are distinguished by a habit of feeding on the wing, but as their food, instead of Rostrum of the vegetable juices, consists of Caprirnulgus. 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. Todidte, Todies ; Halcypnida, King-fishers; Meropidee, Bee- eaters; these latter fa- j^v. i 19, 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 Syndactyles by Cuvier. Fig. 119 represents the foot of the King-fisher. Order III. Feet with two toes before and o\ie behind. (P/g. 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 Foot of the Woodpecker. adaptation of the vertebrate skeleton to powers of flight. * There arc peculiar exceptions to the general character in this as in most other orders of birds. SCANSORES. Fig. 120. llJ 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-. tida, Toucans. Order IV. 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. Tuil-fea- Fig. 121. Beak of the Guinea-fowl. t/iers 14 — If 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 part in 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 ; Phasianida, Pheasant, common Fowl ; Tetra- onida, Grouse, Partridge. Order V. CURSORES. Wings very short, not used for flying; legs robust; Sternum without a keel. This order includes the Brevipennes, 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 Strut h ion ida. 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 Cueulidce, the ' Traveller's Friend,"' of South America,' and among the Psittacidai, 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 Trichoglossi of New Holland affoid 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. 26 which have three . toes, all turned for- ward. 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 Ame- ricana.) The Cassowary ( Cas- suarius guleutus.) The Emeu ( Dromaius 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 ineplus, 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 L'urassow. 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 Jthe 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 slender; neck and beak long. Fig. 123. Head and leg of the Ibis. The Waders, — or Gralla, as they were termed by Linnreus 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 Gruidce, 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 Ardeida, or Heron tribe; the Scolo- pacida, Snipe, Woodcock ; the Rallidm, Rail, Coot; and the Charadriadce, 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. OrdoVII. NATATORES. Body closely covered with feathers, and coated with a thick down next the skin. Legs short, placed behind-the pointof equilibrium. Toes united by a membrane or web, which is sometimes divided. 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 Foot, of the Pelican. 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 ave liberated from the egg-coverings. The families of Swimmers are the Anatida, Swan, Goose, Duck; Co- lymbidw, Divers; Alcada, Auks ; Pelecanida, Pelican, Cormorant, Gannet ; Larida, 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 tlian 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. Fig. 125. Skeleton of the Topaz Humming Bird ( Ti The vertebral axis or spine is divisible into a cervical (Jig. 125, a), dorsal (6), sacral (c), and caudal (d) 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 vertebras are the first parts of the osseous : system which make their appearance in the development of the embryo, and they are of all parts of the skeleton the most constant in their existence and general characters. The doi'sal or costal vertebras in birds rarely form more than a fourth part of the entire vertebral column, and in some of the long- necked Grallatorcs, 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 vertebrae 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 ( Aptenodytes, Catarrhactes ) ; but in the Ostrich the bodies of the dorsal ver- tebrae 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- tebrae to the last dorsal, which is anchy- losed to the sacrum. This is an interesting affinity to the Reptilia, in addition to numerous others displayed in the construction of these, singular birds. In most birds the bodies of some of the middle dorsal vertebrae 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 vertebrae 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. II. Earle. The bodies of the anterior dorsal vertebra: send down processes from their inferior or ventral surfaces for the advantageous origin of the recti untici 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 vertebras 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 vertebrae 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 vertebras 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 vertebra?, which already begins to appear in the last dorsal, is, therefore, continued through all the sacral vertebras as far as the caudal region ; and this consolidated mass ( b to c) is united laterally to the iliac bones. Hence it is always difficult to determine the number of vertebras 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 vertebras ; 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 vertebras 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 vertebras, which are not united together as in the mammalia. The first four or five sacral vertebras 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 so continued double to the end. The spinous processes which are prin- cipally developed from the anterior sacral ver- tebras, 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 vertebra? 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 vertebras have also transverse processes. The last caudal vertebra (d, Jig. 12.5) 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, Linnasus termed the rectrices.* In the Toucan the three last caudal vertebras 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 vertebras is provided with a capsule and synovial fluid, the others have a yielding ligamentous mode of connexion. The spinous processes of these vertebras, 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 vertebras because of the singular move- ments observable in the tail of the Toucan ; it can be inflected dorsad till the superior spines of the vertebras 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. m 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- tebras, 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 vertebras 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 cinerea ) 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 vertebras 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 vertebras : the inter-space of these is filled up externally to the vertebral artery by a rudimentary styhform rib, which is sepa- rated in the young bird, but afterwards anchy- losed, and directed backwards parallel to the body of the vertebra. 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 vertebra at the two extremities of the cervical portion of the spine. Inferior spinous processes are also found on the vertebras at the commencement and termination of the neck, but are wanting m a great proportion of the intermediate cervical vertebras. 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 vertebras 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 vertebras 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 vertebras. 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 vertebras; and on the dor- sal or posterior aspect of the spine, the canal remains open for some extent in the intervals of the vertebras, 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 Mr. 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 vertebras 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 vertebras 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 Natatores it is necessary for the purpose of obtaining their food while swimming the waters. The dorsal vertebras are usually less numerous than in mammalia. The caudal vertebras 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 Lecons d'Anatomie Comparee, exhibits the variety that exists with respect to the number of ver- tebras in different species of birds. Table of the number of vertebra in birds. Order. Raptores Vertebra:. Species. Cervical. Dorsal. Sacral. Caudal. Vulture 13 7 11 7 Eagle 13 8 11 8 Osprey 14 8 11 7 Sparrow-hawk .. 11 8 11 8 AVES. 273 Species, Cervical. Dorsal. Sacral. Caudal. Buzzard 11 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 0 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-linch 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 11 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- sow 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 Argala 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 13 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 ( liluimphastos 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. Species. Cervical. Dorsal. Sacral. Caudal Order. Natatores. Pelican 16 7 14 7 Cormorant.... 16 9 14 8 Tern 14 1 Gull 12 i Petrel 14 Catarrhactes Swan ...... Goose Barnacle . . . Duck Sheldrake . . 13 23 15 18 14 16 Scoter 15 Merganser 15 9 9 11 10 10 8 11 9 8 10 14 14 10 11 13 13 14 14 14 15 11 14 13 13 Grebe 14 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 Vertebrat i 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 Fig. 126. Skull of 'i young Ostrich, 274 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 anchylosed into one piece, with a total obliteration of the original har- monia; ; it is necessary, therefore, to examine the skull of the Bird at an early period of ex- istence, and to compare it with the fetal 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. 126,) 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 bone consists of the petrous por- tion, the squamous portion, (d,d,fg.\26, 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,fig. 1 26,) two orbital plates, ( h,Jig. 127,) forming the floor and part of the septum of the orbits, and which rapidly anchylose with the preceding; two cranial portions, or alae 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. The frontal bone (h, 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. The ant-orbital processes fl3, Jig. 127) are elongated and pointed, ex- tending for- wards to join the lachrymal bones, ( o, o, 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-orbi- tal 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 (I, fig. 127) is seen, in the Ostrich, on the ex- 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 inter-orbital septum where this exists, as in the parrots, ( m, fig. 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 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 is 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 a fresh 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. Arutt. 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 Kasores, 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 (\,fig. 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, fig. 126) is situated immediately below the membrana tympani (8, 8, fig. 126.) There is no fissure analogous to the foramen lacerum medius. The carotid foramina (3, 3, fig. 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 fq, 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 bone9 of the Rodentia. They are always moveably connected with the bones of the cranium, and retain much longer than these their separate condition. -pi„ ^28 ^he nasal bones ( n, n, fig. 127, 128) are a large and elongated pair, extend mg from the inner side of the ant-orbital , processes of Skull of a Parrot. ^ tQ the outer side of the ascending processes of (he intermaxillary bones, expanding as they ad- vance forwards, and giving oh0 from their outer sides a process which curves downwards to join the superior maxillary 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 ungucal bones f o, o, fig. 127, 128, I 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 the frontal bone. They are smallest in the Rasores and Natatores,a.nd 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,fig. 126,) 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. Thevomer (q,fig. 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 (m, fig. 125, r, r, fig. 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 2 276 AVES. 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, jig. 128). The two lateral or mandibular processes ( r, r, fig. 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, ( Larida ). The superior maxillary bones ( s, s, fig. 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,fig.\2&, 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- mulgi, 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, fig. 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 quadratum, 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 jaw. 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. 277 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, figs. 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, Jig. 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 ( Grallatorcs 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 ( Rliyncops), Horn- 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 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 coccothraustcs, 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 Ilasorial 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, ( Tetj-ao 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 interna] angular process. This ligament assumes a fibro-cartilaginous 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 portion 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 {0,Jig. 126) from a broad muscular depression on either side; below these are the large occi- pital foramen, (1, fig. 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 pneumogastric and hypoglossal nerves; these depressions are bounded laterally by the mastoid processes. (10, 10, Jig. 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 Struthwnkkc sends outwards and forwards two rounded processes (j j, Jig. 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 tympani, (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 are 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 ate, 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, figs. 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 interorbital 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 fossae 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 Toucans, 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, the nostrils open on the posterior part of the upper mandible, and the remainder of the 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 Ilelmeted Ilornbill ( Buccros Galcutus.) 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 Wood-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 Rasorcs. The skull is remarkable for its length in the majority of 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 fossae 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 aethmoid 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 exulans 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 fossae nearly approximate in the middle line. In these sea-birds and in the Gulls, the lateral lacunae 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 the'aquatic 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 vertebrae, 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 vertebrae remain separate after the true elements of the vertebrae have coalesced. Inan 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 determining the commencement of the dorsal vertebrae. If the moveable ribs had com- menced, as in Mammalia, by extending to the sternum, the determination of their number would have been easy ; but they begin, some- times by a gradual and at others by a sudden elongation,* opposite the furculum, from which point, either one, or two, as in the Humming- bird, (see p, 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 Raptures to be nine pairs, of the Nocturnal eight; in the Insessurcs seven or eight; in the Scansores nine, except the Cuckoo, which has seven or eight ; in the * This is remarkably the case in the Wood- Grouse ( Tetrao Urogallus), where the penultimate and last cervical ribs, instead of gradually enlarg- ing, diminish in size, so that the determination of the first thoracic rib is easy. AVES. 281 Rasores seven or eight ; in the Struthiones the number of ribs varies ; in the Ostrich (Slru- thio ) we find ten pairs, of which the 3d, 4th, 5th, and 6th, are articulated with the sternum ; in the Nandou (lihea) there are nine pairs, of which only the 3d, 4th, 5th, and 6th, are completed by sternal portions ; in the Emeu (Droriiaius ) 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 Grallatores 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 ( Uria 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. 125, h, jig. 129,) which are moveably connected at both their extremities. These are the centres upon which the respiratory motions hinge; the angle between the vertebral and sternal ribs, and between these and the sternum becoming more open in inspiration, and the contrary when the sternum is approximated to the dorsal region in expiration. As the ribs are traced backwards, their vertebral extremities are seen to become gra- dually double or bifurcated from the in- creasing development of the part answering to the cervix and head of the rib in Mam- malia. The spurious cervical ribs may be plainly seen to be articulated, like the pos- terior spurious ribs of the Cetacea, by the tubercle only; and, as they increase in length in the proximity of the thorax, the head of the rib is then seen to be thrown downwards to join a distinct tubercle on the side of the body of the vertebra close to its anterior margin, but without encroaching on the intervertebral space. The comparative immobility of the dorsal vertebrae allows of this mode of articu- lation ; but it is an interesting circumstance that in the Ostrich, where the costal vertebra; preserve their mobility, the heads of the ribs, at least of those of the anterior ones, evidently pass forwards to the intervertebral space. The tubercle of the nb 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 vertebrae, in giving stability to the trunk by means of small osseous splints, detached from the pos- terior margin of each true rib, and directed backwards and upwards to the next in suc- cession, to both of which they are united by means of oblique fibrous ligaments. In birds of powerful flight these connecting pieces are, as might be expected, most developed. In the Raptores they extend beyond and overlap the succeeding posterior rib, and in this order they are anchylosed. In some of the Struthious birds, as the Ostrich and Rhea, they exist from the third to the fifth rib, while in the Emeu and Cassowary there are only rudimentary traces of them. In the Penguins these accessory processes are remarkable for their breadth, but they are never anchylosed to the ribs, and consequently are apt to be lost if care be not taken in pre- paring the skeleton. The sternal ribs (h, h,fig. 129) are of a less flattened form than the vertebral ; they increase in length as they are situated further back ; their costal extremity is simply rounded, while their sternal extremity is extended transversely and divided into two smooth surfaces moveably articulated by two synovial capsules with cor- responding cavities in the sides of the sternum. The first sternal rib is, however, joined by fibro-cartilaginous substance only, while one or two of the posterior pieces are anchylosed with the rib immediately preceding them, and do not reach the sternum. In the Ostrich the last rib abuts against the ilium, to which it is anchylosed. In the Peacock, Pintado, and common Fowl, the vertebral and sternal portions of the last pair of ribs are unconnected with each other ; the latter thus representing the ossified ten- dinous intersections of the rectus abdominis muscle, as in the Crocodile. This analogy is still more striking in the Herons, Storks, and Curlews, and in many of the Nalutores, in which the sternal portions alone exist, and are remarkably elongated. The part of the skeleton which has undergone the most remarkable modifications in relation to the powers and functions of the anterior ex- tremities is the sternum, ( r,s, fig. 125 and 129,) which gives origin to their principal muscles. It is so developed, both in length and breadth, as to extend over the whole of the anterior or ventral aspect of the thoracic and of a great part of the abdominal cavities, reaching in some birds of great powers of flight even to the pubic bones, so as to require removal be- fore the abdominal cavity can be examined. In order to afford origin to the accumulated fasciculi of the pectoral muscles, which other- wise would become blended together over the middle of the sternum, an osseous crest (s, jig. 125, a, jig. 130) is extended down- wards, analogous to the cranial crest which intervenes to the temporal muscles in the carnivorous mammalia ; and as this crest in- dicates in these the powers of the jaw, so the 282 AVES. sternal keel bespeaks the strength of the ante- rior extremity in the bird. Besides the difference of form and deve- lopment of the mesial crest or keel, the ex- tended sternum presents many other varieties in the different orders and families of birds. A zoological arrangement of the class has even been founded on the modifications of this cha- racteristic and important part of the skeleton. In every species the sternum is more or less Fig. 129. Sternum, coracoids, and clavicles of a Woodpecker. quadrilateral, more or less convex outwardly, and each of its margins affords distinctive characters. The anterior margin presents two grooves (b, b, figs. 129, 130) extending along the greater part of either side, and affording a secure articulation to the coracoid bones ; and in many birds it sends forward a process from the middle part where the two grooves meet, as in the Woodpecker and Penguin (e, fig. 129). This mesial process we shall term the manubrial process, since it is analogous to that which extends from the manubrium or first sternal bone of the seal, mole, &c. The lateral margins are straight and excavated anteriorly, to a greater or less extent, for the lodgement of the sternal ribs. In some birds a process (d,Jigs. 129, 130) is given off at each angle of the union of the lateral with the anterior margin- as this process seems to supply the sternal portions of the anterior floating ribs, it may be termed the costal process. The posterior margin is most varied in its contour, and is in general interrupted by fis- sures, (f, /; jigs. 1 29, 130.) which are always symmetrical in their position, but vary in number and depth, so that this margin is some- times represented by the extremities of three or five long processes. In the Diurnal Raptores the sternum is a large elongated parallelogram, convex both in the direction of its length and breadth, but especially in the latter sense. The manubrial process is thick, the contour of the keel convex, and its margin extended laterally. In the Eagles and Secretary-bird the ster- num is entire, but in the Vultures and Hawks it is pierced on either side by a small round aperture situated near the posterior margin. Ossification sometimes extends along the apo- neurotic membrane stretched over this aperture so as to divide it into two, as has been ob- served in the Buzzard; or so as to obliterate it on one side only, as seen by Meckel in the Kite. In the Nocturnal Raptores the sternum is short, convex as in the preceding tribe, but weaker : there is no manubrial process. The keel is less developed, its margin less convex, and not thickened. The posterior margin is concave and presents two fissures, separated by a middle process, except in the common Barn Owl (Strix Jiammea ) 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 Corvida the keel is more excavated at its anterior margin ; the manubrial process is stronger, and is bifurcated at the extremity ; the posterior fissures are shallower; the angular processes directed outwardly and not dilated at the extremity. In the Swallows ( Hirun- do ) the sternum is large and the keel greatly developed ; there are two posterior fissures, but they are still shallower than in the Crows"; the angular processes are not dilated at the extremities. In the Swifts ( Cypselus ) the sternum is entire, and corresponds in its pro- portional magnitude with the superior length and power of wing which characterizes this genus. The manubrial process is wanting, but the costal processes are moderately long and pointed. In the Humming-birds, which sustain them- selves on the wing during the greater part of the day, and hover above the plant while ex- tracting its juices, the sternum {r, s, Jig. 125,) is still further developed as compared with the body ; it approaches to a triangular form, ex- panding posteriorly, where the margin is entire, and rounded. The depth of the keel exceeds that of the entire breadth of the sternum. The coracoid depressions are deep and approxi- mated ; the manubrial process is small, but evident, and directed upwards ; the costal pro- cesses are also present, but of small size. In the Creepers ( Certhia ) and Hoopoes AVES. 203 ( 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 (ff,fig. 129 ). In the Trogons, Hollers ( Coracias), King- fishers, Bee-eaters ( Merups), 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 Raptores, being in some speciessimply perforated on either side near the posterior margin, and in others wholly ossified. It is, however, narrower in proportion to its breadth. The keel is well developed, its inferior margin concave, its an- terior one describing a sigmoid flexure ; their angle of union rounded. The costal depres- sions occupy almost the entire lateral margins of the sternum. The manubrial process is slightly developed, trihedral, and truncate at the extremity. In the Pigeons, which unite the In- sessorial to the Gallinaceous order, the ster- num is narrow, but the keel is deep, with its inferior border convex, and the anterior one curved forwards, thin and trenchant ; the ma- nubrial process is strong and bifurcated; the costal processes short. The posterior margin is cleft by two fissures on either side of the mesial plane, the lateral and superior fissures being the deepest; the mesial ones are occasion- ally converted into a foramen. The costal surface of the lateral margin is, as in the Gallinaceous birds, of very little extent. In the Crown Pigeon the superior fissures are so deep and wide as to convert the rest of the lateral margin into a mere flattened process, which is dilated at the extremity. In the true Rasorcs 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 iidges which converge to it from the anterior margin of the sternum. This margin is con- vex laterally, and largely excavated for the coracoid bones ; the depressions are continuous with each other, and the compressed manubrial process, arching over the canal, converts it into a foramen. The costal processes are prolonged upwards and forwards; the posterior lateral processes pass backwards exterior to the ribs, supporting them in the Capercailzie, like a semi-hoop ; these processes are dilated at their extremities. In the Grallatores or Waders the sternum corresponds in size to the shortness of the thoracic-abdominal cavity. In the Ardeida the grooves of the anterior surface pass reci- procally beyond the middle line, increasing the surface of attachment for the expanded lower and posterior extremities of the coracoid bone. In most of the genera the posterior margin pre^ sents a single fissure on either side ; these in the Storks and Herons are wider at the com- mencement than at the termination. In the Plo- vers, Woodcocks, Avosets, and Oyster-catchers, it occupies the whole breadth of the sternum. In the Curlews, Ibises, and Spoonbills, there are two fissures on either side. In the Coots, and Water-hens the single fissures on either side of the keel are long and narrow, and the lateral portions of the sternum extend back- wards beyond the middle, and become larger towards their extremities. Among the Nututores, the Albatrosses, Petrels, Pelicans, and Cormorants present a strong wide convex sternum, similar to the Storks and Herons ; the keel is moderately developed, but prolonged anteriorly ; the pos- terior margin presents a single slight fissure on either side. In the Penguins, these fissures are of considerable extent (f,f,fig- 130,) ; but the keel of the sternum is well developed, even in the Aptenodytes ; its inferior border is straight. In the Gulls and Sea-swallows the sternum is of large size, wide, 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 Anatidte or Lamellirostral tribe the sternum is thin, but of large size, very convex transversely, and much elongated. The keel is of moderate depth, and of a triangular form, its inferior margin being straight ; there is only one fissure on either side posteriorly.* In the Divers (Colymbus) the portion of sternum intermediate to the two fissures is pro- longed beyond the lateral pieces, and the ma- nubrial process is strongly developed, and of a rounded form ; the whole bone is remarkable for its length. In the Grebes the sternum is characterized by a third mesial fissure of a chevron figure intermediate to the two ordinary fissures of the posterior margin. The sternum of the Cursorial Birds pre- sents few affinities of structure to that of the rest of the class, resembling rather the ex- panded plastron or abdominal plate of the Tortoises. It has neither a keel, nor manu- brial, nor costal processes, and may be com- pared to a square shield. It is most convex in the Rhea, and least so in the Ostrich ; * The modifications of the sternum in relation to the folded trachea will be treated of in the article on the Organs of Voice. 284 AVES. in the latter there may be observed slight indi- cations of the two ordinary posterior fissures. The ossification of the perfect sternum of the Bird commences from five centres, — a middle one which supports the keel, termed by by Geoffroy St. Hilaire the entosternal (a, fig. 129) ; two anterior lateral pieces, the hyoster- ncds (b, b, fig. 129), and two posterior lateral pieces, the hi/posternals (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 episternals of which he supposes the manubrial process to be composed, then nine elements may be reckoned to enter into the composition of the the coracoid element has been err neously re- garded as the clavicle, in consequence of its being moveably articulated with the scapular piece. In the Emeu ( Dromaius ) it is interesting to observe that the clavicle commences by a dis- tinct ossification, and long continues separate ; it does not reach the sternum, but holds the same relative situation as the continuous acro- mial or clavicular process of the scapula in the other Struthious birds. The scapula (t, fig. 125, 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 extremities, constitute a single bone, which, from its peculiar form, is termed the os furcatorium or furculurei. 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 islongitudi- nal,being extended backwards from 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, ( Cypse/us,) it reaches to the last rib, while in the Emeu, on the contrary, it extends over two ribs only. In the Humming-bird (Trochilus) its posterior third is bent down- wards at a slight angle. The coracoid (u,fig.\25,i,figs.l29, 130), or posterior clavicle, is always the strongest of the bones composing the scapular arch : its ex- panded extremity is securely lodged below in the transverse groove at the anterior part of the sternum, from which it extends upwards, outwards, and forwards, but frequently al- most in the vertical position to the shoulder - joint, where it is united at an acute angle with the scapula and clavicle. It thus forms the 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, ( I, Jig. 1 30,) above which it rises, to a greater or less extent, and affords, on its inner side, an arti- cular surface for part of the acromial end of the clavicle : the inner process is short and com- pressed, and is also joined by ligament to the acromial end of the clavicle. Just below the origins of these processes an articular surface extends transversely across the posterior part of the coracoid bone by which it is firmly united by fibro-cartilaginous substance to the scapula. The glenoid cavity resulting from the union of these two bones is not, however, always equal to the reception of the entire head of the hu- merus. In the birds, which Mr. Vigors re- gards as composing the typical orders of the class, viz. the Raptores and Imessores, (the lives aerete of Nitzsch,) a small but distinct bone extends between the scapula and coracoideum along the superior part of the articular cavity for the humerus, which it thus completes. Nitzsch, the discoverer of this element of the scapular apparatus, denominates it the capsular bone, ( Schulterkapselbeine) ; by Meckel it is called the Os 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 Nutatores, 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, jig. 125, b, fig. 130) in birfls, as in the mammalia, are the most variable elements of the scapular apparatus. In the Ground Parrots of Australia ( Pezophorus, II- liger) they are rudimentary or wholly deficient ;* they are represented by short processes in the Emeu, Rhea, and Cassowary; they do not come in contact inferiorly in the Ostrich, although they reach the sternum. In the Toucans they are separate, and do not reach the sternum. In the Hornbills and Screech Owl ( Slrix 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 furctdum, or merrythought. From the point of union a compressed process extends down- wards in the Diurnal Raptores, the Coniros- tral Insessores, the Rasores, most of the Gral- latores, and Natatores, in which a ligament extends from its extremity to the ento-sternum. The process itself reaches the sternum, and is an- chylosed therewith in the Pelicans, Cormorants, Grebes, Petrels, and Tropic-bird; also in the Gigantic Crane, and Storks in general. In the Humming-birds, where the sternum is so disproportionately developed, the furculum ter- minates almost opposite the commencement of the keel, but at some distance before it ; in * Mr. Vigors has noticed the absence of the os furcatorium in Psittacus mitratus, Platycercus eximius, and Psittacula Galgula. those species in which we have examined it, be- longing to the genus Trochilus, Lacip. it is of equal length with the coracoideum, and not shorter, as Meckel asserts. As the principal use of this elastic bony arch is to oppose the forces which tend to press the humeri inwards towards the mesial plane, during the downward stroke of the wing, and restore them to their former position, the clavicles composing it are stronger, and the angle of their union is more open, as the powers of flight are enjoyed in greater perfection; of this adjustment the Swifts, Goat-suckers, and Diurnal Birds of Prey afford the best examples. Notwithstanding the anterior extremity is limited to one function, and the motions of its parts are confined to simple folding and exten- sion, it contains the same number of joints as the arm of the Monkey, or of Man himself. We shall now successively consider the bones of the Brachium, Antibrachium, Carpus, Metacarpus, and Digits. The brachium, or humerus (w, Jig. 125, m, 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, Avvks, and Petrels, 286 AVES. the humerus presents a notable process at the pronation ; all power of flexion, extension, or of outer side, near its lower extremity; and in rotation, is removed from the wrist-joint, so that the Puffin ( Fratercula arctica) an ossiculum the wing strikes firmly, and with the full force of is moveably articulated to this process. the contraction of the depressor muscles, upon Another ossiculum may here be noticed, al- the resisting air. though it belongs rather to the ulna, being The metacarpus is principally formed of two essentially the separated olecranon of that bone, bones, anchylosed together at both extremities This detached sesamoid bone is found attached (r, r, jig. 1 30) ; of these, the one which cor- (like the patella of the knee-joint) to the capsular responds to the radius is always the largest, ligament and the tendons of the extensor mus- and supports the finger which has the greatest cles, in many of the Raptores, and in the Swifts, number of phalanges: a third small rudi- In the Penguins it is double ( n, n, fig. 130.) mental bone is in most birds found an- Of the two bones of the antibrachium chylosed to the outer-side of its proximal (y, jig. 125) the ulnar (o, fig. 130) is always extremity, and this supports the single phalanx the strongest, and especially so in the Stru- of what is usually called the thumb. The thiones: both this and the radius (p,fig- 130) longest or radial finger is generally composed are in general slender and straight bones, of two phalanges (s, s, Jig. 1 30) of moderate slightly enlarged at their extremities, placed length ; to which, in some birds, a third smaller not by the side of, but one in front of the other, phalanx is added. The ulnar finger consists of and so articulated together, and with the hu- a single phalanx only (t,fig. 130). These are merus, as to admit of scarcely any degree of strongly bound together by ligaments and in- pronation or supination, which, as Meckel tegument, so that the wing loses nothing of its justly remarks, adds to that firmness and resist- force, while it preserves in these separated ing power in the anterior member which are bones its analogy with the anterior extremities so necessary during the actions of flight. In in the other vertebrated classes. In Zoology the Penguins, the bones of the fore-arm present the large feathers that are attached to the ulnar the same modifications as the humerus in re- side of the hand, are termed Primaria or pri- lation to the corresponding action in the denser mary feathers; those which are attached to the element, or that of swimming : they are flat- fore-arm Secundaria, or secundaries, and Tec- tened, and are articulated with the anterior trices, or wing-coverts ; those which lie over edge, and not the extremity of the humerus. the humerus are called Scapularia, or scapu- The bones of the hand are extended in laries ; and those which are attached to the length, but restricted in lateral development, thumb, Spuria, or bastard feathers. In some The carpus consists of two bones only, ( q, fig. birds the wing is armed with a spur attached 130,) so wedged in between the antibrachium to a phalanx at the radial side of the so-called and metacarpus, as to limit the motions of the thumb, which, as Nitzsch observes, would hand to those of abduction and adduction therefore seem analogous to the index finger, necessary for the folding up and expansion of The bones of the leg or posterior extremity the wing; the hand is thus fixed in a state of (jig. 131 ) do not exactly correspond, in their divisions or principal lig. 131. groups, to those of the wing, the segment corre- sponding to the carpus being invariably blended with the one that suc- ceeds. The pelvic bones present a remarkable contrast to those of the shoulder, being always anchylosed on either side into one piece, but being with one exception 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 (I jig. 125, Pelvis and bones of the ley of the Diver, or Loon. — Colymbus glacialis. a, jig. 131.) is the only AVES. 287 bone of the pelvis which comes in con- tact with the vertebral column, and it ex- tends from the posterior dorsal vertebrae along the whole of the sacrum, to which it is early united by anchylosis. At its posterior extre- mity it is expanded laterally and becomes anchylosed with the ischium ( c, Jig. 131) pos- terior to the ischiadic notch (e,Jig. 131) which is thus converted into a foramen. The ilium is of a considerable size, of an elongated form, expanded at its extremities and contracted in the middle ; the anterior expan- sion is concave externally, the posterior on the contrary convex. Besides being anchylosed with the ischium and sacrum, the spinous and transverse processes of one or two posterior dorsal vertebrae are commonly joined to it by bony union. In the Penguins, however, where the posterior extremities are ill adapted for 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 f£, fig. 125, b b,Jig. 131 J does not extend to meet its fellow on the mesial line, but is commonly directed backwards like a long bent styliform process (3, Jig. 134), adapted to allow a safe passage to the large and fragile eggs. In general it unites with the ischium so as to complete the obturator fora- men (f, Jig. \3l), behind which another fo- ramen is occasionally formed by a second union with the ischium, as is seen in the Hum- ming-bird ; while in other Birds, as the Stork, it is only united to the ischium at the cotyloid foramen, and the obturator hole communicates with a long fissure and is completed posteri- orly by ligament only. The cotyloid cavity for the head of the thigh-bone is always incomplete at its posterior or internal part, which is closed in the recent state by a strong aponeurosis. The ischium (c, Jig. 131) is a small elon- gated bone, slightly convex externally, ex- tending from the acetabulum backwards, pa- rallel with the ilium. In the Struthious Birds the pelvis is pro- portionally very long, but narrow ; the ossa innominata cover the whole of the sacrum, meeting and joining above that part like the roof of a dwelling. In the Rhea, or Ame- rican Ostrich, the ischiadic bones meet below the sacrum, where they are united for a con- siderable extent by a symphysis, so that the sacrum is closely surrounded, and in fact it3 place is almost supplied by the ossa inno- minata, for the development of the included vertebrae is in consequence so much impeded, that they can scarcely be detected at this part ; beyond which, however, the coccygeal vertebrae suddenly resume their ordinary mag- nitude. This union of the ischia does not take place in the other Struthious birds ; but the Ostrich presents the remarkable exception, among Birds, of the completion of the pelvic circle by the anchyloses of the pubic bones at their inferior extremities. The femur (Q,fig. 125, g,Jig. 131) is a short cylindrical bone, deviating from the straight line by a very slight anterior convexity. The head is a small hemisphere; joined, without the in- tervention of a neck, at a right angle, to the shaft of the bone : it presents at its upper part, a considerable depression for the attachment of the round ligament. The single large trochan- ter generally rises above the articular eminence, and is continuous with the outer side of the shaft. The orifice for the admission of air into the bone is situated anterior to this ca- vity. The femur is most readily characterised by the form of its lower extremity : this pre- sents as usual two condyles, the inner one cor- responding to the tibia, the outer one, which is the largest and the longest, resting both upon the tibia and fibula; upon this condyle a semi- circular rounded eminence is observed extend- ing from the front to the back part, and being lost in a depression at both extremities; the result of this structure is to put the external lateral ligament upon the stretch when the fibula is passing over the middle of the condyle, and that ligament, being elastic, pulls the fibula into the cavity in which the ridge termi- nates, with a jerk — whether the motion be that of flexion or extension, in either of which con- ditions the leg is by this structure the more firmly locked to the thigh. It has been denied that the spring-joint ever exists at the knee, and it is probable that all birds do not possess the requisite structure in the same perfection ; but a common indigenous species, the Water-hen, ( 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,Jig.\25,hh, flg.\3i) is the prin- cipal bone of the leg— the fibula (x.,Jig. 125, i, Jig. 131) appearing as a mere styliform process tapering to a point below, and anchylosed for a greater or less extent to the tibia. The tibia is of a triangular form, especially at its enlarged superior extremity, the articular surface of which is unequal, being flat internally, convex at the centre, and concave externally and in front. The inferior articular surface of the tibia forms a considerable transverse trochlea, above which anteriorly there is a deep depression. In ge- neral an osseous bridge extends transversely across this depression, converting it into a foramen through which the tendon of the Exten- sor communis digitorum passes. In the Divers, Grebes, Guillemots, and Albatrosses the middle and internal crests of the tibia unite superiorly and are extended up- wards into a long pointed process (k, Jig. 131) directed inwards and forwards, anterior to, but not supplying the place of, the patella, (I, Jig. 131) which will be always found as a distinct bone behind this process. The process is most developed in the genus Colymbus, and affords extensive attachments by way of insertion to the extensors of the tibia, and by way of origin to the extensors of the metatarsus ; by means 288 AVES. of the latter disposition the power of the back stroke of the foot is increased. The Tarsus can only be recognized as a distinct segment of the leg when the bones of a very young Bird are examined. But in the Ostrich, even when it has attained a third of its natural size, the Astragalus re- mains ununited to the metatarsus. It is a flattened transversely oval bone, convex in the middle of its upper surface, and irregularly flattened below, where it is adapted to the three still partially separated bones of the metatarsus. A rudiment of the os calcis may be observed in the detached bone which is found in the tendons of the extensors of the foot near their insertion. The Capercailzie ( Tetrao urogallus ) affords a good example of this structure. The process (m, jig. 131) in which the above tendons are inserted, and which is very prominent in the Rasores, 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 (X, 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- tores and Struth'wnes, 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 flex®n of the leg to counteract the effect of the oscillations of the body, and would prove an insurmountable obstruction to the motion of the joint, if there were not a socket within the upper part of the pulley of the tibia to receive it when the leg is in a bent position. The lower edge of the socket is prominent and sharp, and presents a sort of barrier to the admission of the eminence that requires a voluntary muscular exertion of the bird to overcome, which being accomplished it slips in with some force like the end of a dislocated bone."* It must be added, that the elastic lateral ligaments contribute also to jerk the metatarsal tubercle into the tibial cavities, and to resist its displacement. The lower extremity of the metatarsus is divided into three articular eminences, corres- ponding to the ordinary number of anterior toes. These eminences are convex from before backwards, and the middle one, which is the longest, is converted into a pulley by a mesial groove which traverses it in the same direction. The lateral surfaces are simply convex, and very narrow ; of these the internal is the short- est, except in the raptorial birds. At the extre- mities of the grooves which indicate the lateral juxtaposition of the metatarsal pieces, there are ordinarily foramina extending from before back- wards through the bone. A fourth articular surface is observable in most birds on the inner and posterior side of the metatarsal bone; this is situated on an ac- cessory piece which always commences by a separate ossification, although in some birds it afterwards becomes anchylosed with the inner- most of the other juxtaposed components of the metatarsus. When this does not take place, the metatarsus presents a rough, more or less irregular, oval surface, for the firm ligamentous attachment of the accessory bone which sup- ports the back toe, usually termed the hallux or posterior thumb. This articulating surface is important as affording a good distinctive cha- racter for identifying the bones of birds in a fossil state, and the more so as its position is indicative of the powers of grasping or perching — being placed low down, on a level with the anterior toes, in those birds which enjoy the insessorial power in the greatest perfection, and being gradually removed higher and higher in the Waders, until it is at length wholly lost, as in the genus Cursorius, the Bustards, and the Struthious family. In the Petrel, however, this accessory metatarsal bone is wanting, al- though the hallux is present, the two bones of which are therefore united to the principal me- tatarsal bone by long ligaments. The tarso- metatarsal bone is further characterized by sharp longitudinal ridges of bone on the pos- terior surface, which afford attachment to the aponeurotic theca? 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. Number of Phalanges in the First or inner- most toe or Calcar. Second, com- monly called the Hallux 1 Cock (Gal- lus ), Phea- sants ( Pha sianus ), Tur- keys, Pea- cocks ( Pavo and Lopho phorus J . 2 Raptores ,In- sessores, Co-\ lumbidce, Cra- cidcB, Tetrao- nidce,and the rest of the class, except 3 The Genera, Rhea, Dro- maius, Cusu- arius, Otis, Cursorius, Charadrius, HcEmatopus, Arenai ia, Falcinella, Himantopus, Halodroma, Diomedea 4 The Ostrich ( Strut/no ) 1* Third. Fourth 2t 3* 4§ 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 naturj of the claw. Fie- 132. Fifth or outer- most,or little toe. 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 hicalcaratus, 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. \ In the Dentirostral Insessores this toe is united by one or two phalanges to the fourth. § According to Cuvier this toe and the fifth in the Swift ( Cypselus ) have only three phalanges like the third. In ihe Goat-suckers ( Caprimulyus J and Herons ( Ardea ) the claw of this toe is provided with dentations similar to a comb on its inner side. || This toe is stated by Cuvier to have only four phalanges in the Goat-suckers, and we have ascer- tained the correctness of the exception, and that it also obtains in the Rhea. This toe is united to the fourth toe as far as the penultimate joint in the Bee-eaters (Merops), the Motmots ( Prio- nites ), the King-fishers ( Alcedo ), the Todies ( Todus J, and the Hornbills ( Buceros ), which form in consequence the family Syndactyli of Cuvier. In the Scansores this toe is turned backwards, and assists the Hallux in opposing the other toes. The Owls have the power of turning back the outer toe at pleasure. VOL. I. Foot of tlte Goat Of the fossil bones of birds. — -Birds differ from each other in a much less degree than qua- drupeds, less, perhaps, than any other class. The Penguin and the Ostrich have, indeed, but a remote external resemblance with the Eagle or the Swallow, but yet they have never been regarded as other than birds. The Por- pesse and the Whale, on the other hand, al- though their real affinities were pointed out by Aristotle, have been placed by many sub- sequent Zoologists in a very different class from the Lion or the Ape, and in the older systems of Natural History they always ob- tained their position among the true fishes. Osteological characters of the same value with those which serve to distinguish the genera, and for the most part the species of Mammalia, are, therefore, with difficulty found in the Class of Birds. Cuvier has declared that the differences in the skeleton of two species of an ornithological genus are some- times wholly inappreciable, and that the oste- ological characters of Genera can rarely be detected in any other part than in the bones of the mandibles, which do not always con- form in a sufficiently characteristic manner with the modifications of the horny bill. The determination of the fossil bones of this class is, therefore, conjectural, or, at least, it wants much of that demonstrative character which the bones of quadrupedsafford. 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 vertebrae ; in short, that their whole organization was regulated by the same general u 290 AVES. laws of co-existence and all that relates to the nature of the organs and their essential func- tions, as at the present day. They afford no evidence, not even a trace of any part having been lengthened or curtailed, or otherwise pro- gressively modified, either by the operation of external causes or by internal voluntary im- pulse. Myology. — The muscular system of Birds is remarkable for the distinctness and density of the carneous fibres, their deep red colour, and their marked separation from the ten- dons, which are of a brilliant shining colour, and have a peculiar tendency to ossification. This high degree of development results from the rapid circulation of very warm blood, which is highly oxygenated in consequence of the activity and extent of the respiratory func- tion. The energy of the muscular contraction in this class is in the ratio of the activity of the vital functions, but its permanent irrita- bility is proportionally low, as Carus has justly observed. Fig. 133. Muscles of a Sparrow-hawk. These characteristic properties are mani- fested in the greatest degree in the muscles of those families of the Insessores which take their food on the wing, as the Hirundinid/e and Trochilida (Swallows and Humming-birds) ; in the Diurnal Raptores and in the long- winged Palmipedes, as the Albatross, Tropic Bird, &c. In the more heavy and slow- moving Herbivorous families, and in the short- winged Swimmers, as the Penguins, &c. the muscles resemble those of the Reptilia in their softness and pale-colour. The mechanical disposition of the muscular system is admirably adapted to the aerial loco- motion of this class; the principal masses being collected below the centre of gravity, beneath the 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 Opisthotenar, is easily recognizable, occupying the space be- tween the spinous and transverse processes, arising from the anterior margin of the ilium and the transverse processes of the sacrum, and attached by means of long tendons to the transverse processes of the costal vertebrae. It is most developed in those birds which have the greatest mobility in this part of the spine, as in the Penguins, in which the external venter of the muscle is well developed, inserted into the vertebral ends of the ribs, and adapted to support the body in the erect position which these birds assume while standing. On the mesial aspect of this muscle and somewhat covered by it, the Spinalis dorsi may be distinctly traced, passing from the spinous processes behind, to those at the anterior part of the trunk and beginning of the neck. The Cervicalis ascendens (1, jig. 133) is the chief extensor of the neck : it rises from the spines of the anterior dorsal vertebra;, and is inserted by long and separate fasciculi into the posterior articular processes of the second, third, and fourth cervical vertebrae. In this course it receives descending slips of muscle from the spines of the inferior cervical vertebrae, and ascending fasciculi, which furnish tendons to the fifth and sixth vertebrae, and to the atlas, so that it is enabled to extend the neck even while the head is raised. Muscles corresponding to the Intertrans- versales (2) are continued on the neck from the extemal 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- nal colli (3) is seen passing from the trans- verse to the spinous processes. The Longus colli arises from the anterior AVES. 291 spinous processes of the dorsal vertebrae and from the anterior part of the cervical vertebra, and these slips diverge to be inserted into the transverse processes, and their appended styles or spurious ribs. A superadded muscle, which may be re- garded as a continuation of the preceding, and which corresponds to the increased number of the vertebras 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 vertebra, 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 clown 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 vertebra from the second to the sixth, and is inserted into the posterior part of the basis cranii. Anterior to the preceding muscle a portion of the Rectus capitis ariticus major may be seen at 4. This muscle is largely developed, arising from the anterior part of the sixth, seventh, and eighth vertebrae, and inserted into the basis cranii. There are also muscles ana- logous to the 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. When it is remembered that the cervical re- gion of the spine in Birds is subservient and essential to all the movements and functions of the bill, as a prehensile instrument, and a cleanser of the plumage, we cannot sufficiently admire the endowments of length, flexibility, and muscularity, by which it is enabled to fulfil the important functions of an additional extremity. In the caudal region of the spine the fol- lowing muscles present themselves. On the dorsal aspect, the Levator coccygis (10) ex- tends from the transverse processes and lower extremity of the sacrum to the superior spines of the coccyx and the base of the last or plough-share vertebra. This muscle may be regarded as a continuation of the spinalis dorsi. Beneath it are found strong Interspinals mus- cles. The Quadralus coccygis (11) 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 Fubo-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-coccygius (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 Iscliio- 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 pannieulus 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 ; u 2 292 AVES. and into the sides of the lower jaw from the articulation as far forward as the commence- ment of the horny bill. In the Cormorant there projects backwards from the spine or squamous element of the occipital bone, an osseous style about an inch in length, of a trihedral figure and tapering to a point. It is not anchylosed as a process of the occiput, but is moveably articulated to it ; and its description has been referred to this section because it does not constitute a regular part of the skeleton, not representing any essential element of the bony fabric, but is to be regarded like the bony tendons of the legs as an ossification of the intermuscular aponeu- rosis of the temporal muscles to which it affords a more extensive and firmer origin. This, indeed, is its essential use,* for the mus- cles of the upper part of the neck are inserted into the occipital bone, and glide beneath the posterior or superadded fasciculi of the tem- poral muscle. Analogous parts appended to the true spinous processes of the vertebra are met with abundantly in the inferior vertebrate classes, especially in fishes, where they extend frequently above the spines of the whole ver- tebral column, increasing the surface of origin of the lateral series of muscles. The muscle analogous to the Biventer maxilla (18) arises by two portions, the one from the lateral depression of the occiput, the other from the depression behind and below the external meatus audilorius ; they are in- serted into the back part and angle of the lower jaw. A similar disposition of the digastricus is met with in many of the mammalia; even in the Orang-utan (Simla Satyrus ) it is equally devoid of a central tendon, and is unconnected with the os hyoides. The openers and closers of the mandibles present very slight differences of bulk in rela- tion to the development of the parts they are destined to move; their disproportion to the bill is, on the contrary, truly remarkable in the Horn-bills, Toucans, and Pelican, and the bill is but weakly closed in these in comparison with the shorter-billed birds. The upper mandible is moved by three muscles on either side. The first is of a radiated form, arises from the septum of the orbits, and converges to be inserted into the external and posterior end of the pterygoid bone, just where this is articulated to the tympanic bone. It draws forward the pterygoid bone, which pushes against and raises the upper jaw. The second muscle analogous to the External Pterygoid arises from the space between the posterior part of the orbit and external meatus auditorius, and is inserted into the internal process and contiguous surface of the tympanic bone ; it affects the pterygoid process, and con- sequently the upper mandible in the same way as the preceding muscles, and assists in opening the bill. The Pterr/goideus hiternus is a long and * See Yarrell ' On the Anatomy of the Cormo- ant,' Zool. Trans, v. iv. p. 235. slender muscle ; it arises from the pterygoid process and body of the sphenoid, and is in- serted principally into the inner side of the lower jaw and tympanic bone ; it also sends off a small tendon to the membrane of the palate. This muscle draws forward the lower jaw and depresses the upper one. In the Cross-bill ( Loxia curvirostra) there is a remarkable want of symmetry in the muscles of the jaws on the two sides of the head corresponding to their peculiar position. Those of the side towards which the lower jaw is drawn in a stale 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 bone directly backwards to the posterior part of the articular depression of the lower jaw, and is designed to guard against the backward dislo- cation of the lower jaw. The muscles of the ribs. — The levatores costarum arise from the posterior part of the extremities of the transverse processes, and converge to be inserted into the anterior margin of the succeeding posterior rib. Those of the first and second ribs represent the Scalcni, and are of larger size, arising from the last and penultimate cervical vertebras. The Intercostales exlerni appear to be con- tinuations of the Levatores costarum, and are usually divided into an anterior and posterior moiety corresponding to the marked separation and moveable articulation between the vertebral and sternal portions of the ribs ; the anterior division arises from the costal appendage and extends to the anterior extremity of the rib ; to afford a more advantageous origin to this inspiratory muscle would appear, therefore, to be one of the uses of the costal appendages, as well as to strengthen the connection of the ribs to each other. The Internal intercostals commence at the sternal extremities of the ribs, as in mammalia, but extend backwards no farther than the costal appendages; their fibres run in an opposite direction to the external intercostals, and are shorter, the insertion into the posterior suc- ceeding rib being by a thin but wide aponeu- rosis : in the Penguin they are, however, wholly muscular. Two other layers of inter- costal muscles, corresponding to the triangu- laris sterni, and having the same direction of fibres, are extended from before backwards and outwards to the four anterior sternal por- tions of the ribs ; arising from the superior and external angle of the sternum. The muscles of the abdomen are small and AVES. 293 weak, in consequence of the protection which the extended sternum affords to the viscera of that cavity. The External oblique (19) is chiefly remarka- ble for the transverse arrangement of its fibres ; these arise anteriorly by short fleshy digitations from the inferior ribs, and by a large but very thin tendon from the posterior ribs and the edge of the ilium and pubis ; they are inserted by aponeurosis into the anterior margin of the pubis, and join the aponeurosis of the opposite muscle in front of the thin and tendinous i-ectus 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 pubic bones by cameous 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 cameous, and is inserted into the posterior margin of the sternum. A mesial tendon or linea alba sepa- rates the fleshy portions of the two muscles. The Diaphragm arises by fleshy digitations from the sternal ribs ; in the Ostrich these digitations are five in number on either side : the carneous fasciculi do not, however, extend so far upon the central aponeurosis as even to be united laterally to one another, and consequently this muscle has frequently been denied to birds. From the lungs being con- fined to the back part of the thorax, the dia- phragmatic aponeurosis attached to their inferior surface is not extended as a transverse sep- tum between the chest and abdomen, but allows the heart to encroach upon the interspace of the lobes of the liver, as in reptiles. The contraction of the muscle tends directly to dilate the lungs, but is less perfect as an inspiratory action from the aponeurosis or central tendon being perforated by large cribriform apertures for the passage of the air into the abdominal air-cells. The Wing-Muscles. — The muscles of the anterior extremity, especially those inserted into the humerus, are prodigiously developed, and form the most characteristic muscles of the bird. The muscles of the shoulder, however, are but small, and those of the distal segments of the wing still more feeble. The Trapezius (20), the lower half of which seems only to be present in birds, arises from the spines of the lower cervical, and a varying number of the contiguous dorsal 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 Rtwmboidcus 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 anticus (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 Infraspinatus 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 vertebra? above the origin of the gluteus 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 Deltoides (26) is comparatively a small muscle; it arises from the anterior part of the 294 AVES. scapula, and is inserted along tlie middle of the outer side of the humerus ; it brings the wing upward and backward. Birds have the Pectoralis muscle divided, as in many of the mammalia, into three portions, which are so distinct as to be regarded as sepa- rate muscles ; they all arise from the enormous sternum, and act upon the proximal extremity of the humerus. 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 longand wide in the Nata- tm-ts 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 into the humerus. In the Ostrich its origin is limited to the an- terior and external eighth part of the sternum, and it is inserted by a feeble tendon into the commencement of the crest of the humerus, to which it gives a strong rotatory motion for- wards. The second Pectoral niuscle 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-brachialis, which arises from the middle of the posterior surface of the coracoid ; its direction upwards is less vertical than that of the third pectoral, along the outer side of - which it is attached to the anterior tuberosity of the humerus. This muscle is wanting in the Struthionidee, 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 Carus Extensor plica alaris (30, a b) and forms one of the most powerful flexors of the cubit. It is divided into two portions, of which the anterior and shorter arises from the internal tuberosity of the humerus ; the posterior and longer from the clavicular ex- tremity of the coracoid bone. In the Ostrich and Rhea, however, both portions arise from the coracoid. The posterior muscle (b ) sends down a long and thin tendon which runs pa- rallel with the humerus, and is inserted, gene- rally by a bifurcate extremity, into both the radius and ulna. The anterior muscle (a ) terminates in a small tendon, which runs AVES. 205 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 ligamentum nucha? ; 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,~jfig. 133.) An analogous structure is met with in the wing of the bat. A lesser flexor of the fore-arm, and stretcher of the alar membrane (31) arises, as a portion of the serratus magnus from the ribs, and ter- minates in an aponeurosis inserted into the alar membrane and fascia of the fore-arm ; it is re- presented in the figure as turned aside. The Extensor metacarpi radialis longus (32) is the first muscle which detaches itself from the external condyle of the humerus (e), and it forms the radial border of the muscular mass of the fore-arm ; it terminates in a large tendon about the middle of the fore-arm, and this tendon passes along a groove of the radius, over the carpus, to the phalanx of the so called thumb, or spurious wing, into the radial margin of which it is inserted. It raises the hand, draws it forwards towards the radial margin of the fore-arm, and retains it in the same plane. In the Penguin this muscle is extremely feeble, and the tendon is lost in that of the tensor plica 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, Fhasianidce, and Gruidce. The muscle analogous to the Extensor carpi ulnaris (34) comes off from the inferior extre- mity of the outer condyle of the humerus, passes along the middle of the exterior surface of the fore-arm, and its tendon, after passing through a pulley at the distal end of the ulna, is inserted into the ulnar phalanx. It draws the hand towards the ulnar edge of the fore- arm, and is the principal abductor or folder of the pinion. The Flexor metacarpi radialis (35) is a short and weak muscle, which arises from the inferior part of the ulna, descends along the internal side of that bone, winds round its lower extre- mity and the radial edge of the carpus, passes beneath the tendon of the radial extensors, and is inserted, external to the latter, high up into the dorsal aspect of the radial phalanx of the metacarpus. In the Ostrich it arises from the lower third of the ulna. In the Penguin it is wanting. The Flexor metacarpi ulnaris (36) arises beneath the fore-arm from the internal pulley of the ulna, continues fleshy to the pinion, and is inserted, first into the ulnar carpal bone, then into the ulnar phalanx. The latter insertion is wanting both in the Ostrich and Penguin. The muscles of the pinion or hand are few, and very distinct from one another; the thumb or spurious wing is moved by four small mus- cles, viz. two extensors, an abductor, which draws the thumb forwards, and an adductor. The second digit receives three short muscles, two of which are extensors, and the third an abductor, in this action it is aided by one and opposed by another of the extensors. The lesser digit receives an abductor, which comes from the ulnar edge of the preceding phalanx. Muscles of the lower extremity. — Notwith- standing the simplicity of the motions of the lower or posterior extremity, the muscles of this part are numerous, and present several peculiarities in birds. The femur can be moved freely forward and backward, but its rotation is limited by a strong ligamentum teres, and the structure of the hip-joint does not permit it to be carried under the body, or far outwards. In consequence of the form of the pelvis, the psoas magnus and parvus, the obturator externus and the quadratics 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, (J", Jig. 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 Gluiaus medius: Carus calls it the Gluteus maximus. But the latter, according to Meckel, is represented by the posterior part of what Carus terms the Rcctusjbnoris lutissimus (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 Glutaus minor of quadrupeds. It is wanting in many of the Natator-es, and arrives at its greatest degree of development in the Raptorial Order. A third muscle, still smaller and longer than 296 AVES. the preceding and situated beneath it, which arises from the outer margin of the ilium, and is inserted into that part of the femur which corresponds to the lesser trochanter, is regarded by Meckel as the Iliacus internus, which Cu- vier states to be wanting in Birds. It is, how- ever, present in most, and is seen highly deve- loped in the Ostrich. The muscles analogous to the Pyramidalis and Gemellus superior exist in Birds. There are most commonly three adductors of the thigh. The inferior, external, and posterior one arises from the middle of the external sur- face of the anterior margin of the ischio-pubic bone, and is inserted into the greater part of the lower half of the femur at 38. The second and third adductors are situated internally to the preceding ; the latter of these may be compared to the Pectineus. The Sartorius (39) arises from the anterior point of the ilium, and passes down to be attached to the head of the tibia ; it is an ex- tensor of the leg upon the thigh. The Rectus femoris (40) arises by a thin but wide aponeurosis from the spines of the sacrum, after a short course it joins the Crurmis and Vasti (42), and is inserted into the head of the fibula. It corresponds according to Meckel with the Tensor vagina femoris and the Gluteus magnus. The Gracilis (41) arises from the superior part of the pubis, descends along the inner side of the thigh and towards the lower extre- mity of this part, is continued into a long and strong tendon, which passes in front of the knee-joint, and over the extensor tendon of the leg to the outer side of the fibula, whence it pro- ceeds inwards, anterior to the tendon of the pero- neal flexor, to become united to the outer origin of the flexor perforatus of the toes. Meckel con- siders that the muscle now described represents the Rectus femoris 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 mightbecalled the Semimembranosus (44) : the third flexor is in the middle (45), it comes from the ischium, and as it descends it receives a broad fleshy slip from the back of the femur. It is inserted on the back of the tibia, the tendon covering those of the extensors of the heel. The muscles of the feet present in Birds essential resemblances to the same parts in Reptiles. They are divided into muscles of the tarsus, of the metatarsus, and of the toes, the latter being subdivided into long and short. The principal points in which they differ from the same muscles in Reptiles and the Mammalia are the following : their origins and carneous portions are not situated on the foot but higher up on the tibia and even on the femur. The great length of the metatarsus occasions the smaller muscles to be of a greater proportional length than in other animals. The muscular portions are most developed in the Raptores, 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 flexor digitorum, proceeds to be inserted into both the outer and inner margins of the tarso- metatarsal bone. The Tibialis anticus (48) arises from the an- terior part of the upper extremity of the tibia, below which its tendon passes through an aponeurotic loop extended from the outer to the inner margin of the tibia. It has also a second origin, by means of a slender tendon, from the anterior part of the external condyle of the femur. It is generally inserted pretty high up into the tarso-metatarsal bone between the outer and inner margins ; but in the Psit- tacida it is attached lower down to the internal border, so as to turn the foot inwards as well as raise it, a disposition which is extremely favor- able 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 perforatus 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 toes where they bifurcate to give passage to the ten- dons of the flexor perforans. The Flexor pollicis (51) arises, by its anterior head, from the anterior and upper part of the tibia, and by its posterior head from the ex- AVES. 297 ternal 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 perforans (52) arises as two distinct muscles, the one from the back of the femur and the other from the back of the tibia and fibula ; the tendons of these two portions unite behind the metatarsal bone, and send off tendons to the last phalanges of the toes, which perforate those of the flexor sublimis. The Extensor longus 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 ail the joints of the legs. Birds which have sharp claws, as the Accipitres, Sj-c, retract them when they hop, to prevent their being blunted. The Cat tribe, among mammalia, have a me- chanism effecting a similar purpose. Some birds derive assistance in terrestrial progression by the flapping of the wings, and this is especially the case with the Ostrich, which runs by the alternate advancement of its legs. The act of climbing is performed by means of a peculiar disposition of the toes, aided by prehension with the beak, as in the Maccaws and Parrots, or by the prop formed by the stiff tail-feathers, as in the Woodpeckers. The act of swimming is rendered easy to birds by the specific levity of their body, arising from the extension of the air-cells ; by the shape of the chest, which resembles the bottom of a boat; and by the conversion of the hinder extremities into oars in con- sequence of the membranes uniting the toes together. The effect of these web-feet in water is further assisted by the toes, having their membranes lying close together when carried forwards, whilst, on the contrary, they are ex- panded in striking backwards. The oar-like action of the hinder legs is still further favoured by their backward position ; and by the meta- tarsus and toes being placed almost on the same perpendicular or vertical line with the tibia, an arrangement, however, which is unfavourable for walking. Sailing. — Some birds, as the Swan, partially expand their wings to the wind while swimming, and thus move along the waters by means of sails as well as oars. The act of diving is performed by the rapid and forcible action of the wings, beating the water as in flight, by the feet striking the waters backwards and upwards, and assisted probably by the compression of the air-cells. Flight, the most important and characteristic mode of locomotion in birds, results principally from the construction and form of the anterior extremities, which have already been described. The form of the body has also especial reference to this power, the tiunk being an oval with the large end forwards. The spine being short and inflexible, the muscles act to great advantage, and the centre of gravity is more easily changed from above the feet as in the stationary position, to between the wings as during flight. The head of the bird is generally small, and the beak pointed, which is a commodious form for dividing the air. The long and flexible neck compensates for the want of hands and the rigidity of the trunk, and contributes to change the centre of gravity, according to the required mode of progression, by simply projecting the head forwards, or drawing it back. The position of the great pectoral muscles, as before observed, always tends to keep the centre of gravity at the in- ferior part of the body. The power which birds enjoy of raising and supporting them- selves in the air is undoubtedly aided by the lightness of the body. The large cavities in the bones diminish their weight without taking away from their strength, — a hollow cylinder being stronger than a solid one of the same weight and length. But the specific levity principally depends on the great air-cells, which occupy almost every part of the body, and which are all in communication with the lungs. The air which birds inspire distends these cells, being expanded by the great heat of the body. Lastly, the feathers, and especi- ally the quills, from their lightness and elastic firmness, contribute powerfully to the act of flying by the great extent which they give to the wings, the length and breadth of which are fur- ther increased by the expanded integument situated in the bend of the arm and in the axilla. When a bird commences its flight it springs into the air, either leaping from the ground, or precipitating itself from some elevated point. During this action it raises the humerus, and with it the entire wing, as yet unfolded ; it next spreads it horizontally by an extension or ad- duction of the fore-arm and hand ; the greatest extent ofsurface of'thewing beingthus acquired, 298 AVES. it is-rapicHy and forcibly depressed; the resistance of the nir thus suddenly struck occasions a reaction on the body of the bird, which is thereby raised in the same manner as in leap- ing from the ground. The impulse being once given, the bird folds the wings by bending the different joints, and raises it preparatory to another stroke. Velocity of flight depends upon the rapidity with which the strokes of the wings suc- ceed each other. A simple downward stroke would only tend to raise the bird in the air; to carry it forwards the wings require to be moved in an oblique plane, so as to strike backwards as well as downwards. The turn- ing in flight to the right or to the left is prin- cipally effected by an inequality in the vibra- tions of the wings. To wheel to the right the left wing must be plied with greater frequency or force, and vice versa. The outspread tail contributes to sustain the posterior part of the body ; when depressed during a rapid forward flight, the anterior part of the body is raised, and flight retarded ; when the tail is raised the anterior part of the body is lowered. Some birds bend the tail to one side, using it as a rudder when the hori- zontal course of flight is required to be changed. The first launch of the bird into the air is pro- duced by an ordinary leap from the ground, and depends, in some degree, on the length of the legs. Those birds which have very short legs and very long wings, as the Swallows, &c, cannot leap high enough to gain the requisite space for the expansion of their wings, and consequently have much difficulty in raising themselves from the ground, and generally pre- fer throwing themselves from some high point. The manner of flight varies exceedingly in different birds, some dart forward by jerks, closing their wings every three or four strokes ; the Woodpeckers, Wagtails, and most of the small Insessores are characterized by this kind of undulatory motion : other birds, as the Swal- low, Crow, &c. fly smooth and even : the Kite and Kestrel Hawk and the great Albatross some- times appear to buoy themselves in the air with- out any perceptible motion of the wings. The rapidity with which a strong Bird of Prey flies in pursuit of his quarry is inconceivably great. The anecdote of the Falcon belonging to Henry IV. King of France, which flew in one day from Fontainbleau to Malta, a distance of 1350 miles, is well known, and many similar instances are on record. The flight of a Hawk, when its powers are fully exerted, is calculated at one hundred and fifty miles an hour. The Eider-Duck's usual flight has been ascertained to be at the rate of ninety miles an hour. The famous Race-horse Eclipse is said to have gone at the rate of a mile in a minute for a very short distance; but this speed, if it could be continued, would not be half so great as that which many birds put in practice during their long journeys of migration. Of the Nervous System. — There is a remark- able uniformity in the form and structure of the brain (fig. 1 34, 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-2 ward and visible masses, since the two hemi- spheres, ( a, a,) the two optic lobes, (b, b,) the cerebellum, ( c,) and medulla oblongata, ( d,) s 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. 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, jig. 135) are rounded tubercles, situated be- low and behind the hemispheres, in the la- teral interspace betv/een these and the cerebel- lum. The cerebellum is , , composed of the middle Base of the brain of a , . r , , • r Pigeon. *°"e onV> and ls ol 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 Rodent ia, Marsupiata, and Edentata. The optic lobes are also devoid of the transverse fissure which bisects the optic lobes of mammalia. The cerebellum is marked by close and transverse anfractuosities, such as characterize the corresponding portion of the cerebellum in mammalia, called the vermiform process. Fig. 136. Brain of a Pigeon. When the cerebral hemispheres are divari- cated from each other, (Jig. 136,; they are i seen to be disunited through the whole of their vertical extent, and to be joined only by the round anterior commissure of the brain (k,Jtg. 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 strise which diverge from the commissure. These surfaces are composed of an extremely 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 (7c ) is pro- longed on either side into the substance of the hemispheres, as in man and quadrupeds. The optic thalami (I ) are of small size, and not united by a soft commissure: between them is the cavity called third ventricle (m); and above and behind they give off the peduncles of the pineal gland. This body does not hang freely suspended by the pedicles, but seems to form a rounded and thickened anterior border of the valvulaVieussenii or lamelliform commis- sure of the optic lobes. Cams describes the pineal gland as adhering firmly to the conflu- ence of the great veins situated at the anterior orifice of the aqueduct of Sylvius. In Pigeons he states that it is composed of many segments, but that in general it is of a simple and conical form ; the figure which he gives of it, from the Turkey, exhibits a pyriform shape.* The valve which closes the upper part of the passage from the third to the fourth ventricle, is a thin lamella of great width, in consequence of the distance to which the optic lobes are sepa- rated from one another. Anteriorly the third ventricle communicates with the infundibulum. The fourth ventricle ( n ) resembles that in the brain in mammalia, but is of less width ; its floor is indented with the longitudinal fissure called calamus scriptorius. Besides the cavities or ventricles above men- tioned, there are also two others situated in the optic lobes (o), or bigeminal bodies, each of which, when laid open, is seen to be occupied by a convex body (p) projecting from the posterior and internal side of the lobe; these ventricles communicate with the others in the aqueduct of Sylvius. As there is no transverse furrow in the optic lobes, they cannot be distinguished into the protuberances called ' nates ' and ' testes ' in fig. 6 Anat. Comparce, nouv. ed. i. p. 88, pi. xv. 300 AVES. the human brain ; they have most resemblance, however, to the latter bodies. With respect to the substance of which the brain of birds is composed, we may observe that the bodies analogous to the corpora striata do not merit that name, as there are no alterna- ting stria? of grey and white matter. In this respect the bird's brain resembles that of the cold-blooded ovipara and of the human fetus. The substance of the cerebellum does present the admixture of the two substances, or arbor vita (q ), but in a less complicated degree than in mammalia. The brain in birds is invested with the same membranes as are described in Mammalia. Medulla spinalis. — -The spinal cord is con- tinued from the foramen magnum to the canal formed by the coccygeal 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,Jig. 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.\ZA) 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 nerve3 cor- respond in number to those of the Mammalia. The principal difference of form and structure is presented in the olfactory or first pair (\, fig. 135.) 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. 135, 137,) are in general of remarkable size ; they arise from the whole of the outer surface of the optic lobes, and form in front of the infundibulum, a perfect union, or cliiasma, ( 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. 1 37, 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 fossa?. 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 Anatidte and other Water-fowl, where the upper mandible is notched on the edge, each denticu- lation receives four or five nervous filaments, and the nerve is proportionally of large size. The inferior maxillary nerve separates from the superior, and proceeds obliquely down- wards, dispensing branches to the pterygoid and quadrangular muscles of the jaws ; the trunk proceeds outwards to the lower jaw where it divides into two branches an internal and an external. The internal, which is a con- tinuation of the trunk, penetrates the maxillary canal, and is continued to the anterior end of that mandible. In the Anatidce 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, or portio mollis, is large, very soft and pulpy, and of reddish colour ; it is received into a deep depression on the internal surface of the cranium (at 7, fig. 137), whence it penetrates by several small foramina to the labyrinth. The pneumogastric nerve, or nei~vus vagus, generally passes out of the cranium in two or three filaments, which afterwards rejoin. -On leaving the skull, this nerve communicates with the lingual and glosso-pharyngeal nerves, and is situated between them, the lingual being placed in front. Each nerve of the par vagum passes as a distinct strong cord along the neck in company with the jugular vein, and de- scending into the chest forms the cardiac and pulmonary plexuses, as in Mammalia. The two nerves unite behind the hearl, and proceed along the oesophagus to terminate in anasto- moses with the great sympathetic nerve. The glosso-pharyngeal nerve of the eighth pair passes out of the cranium through the foramen behind the ear, which corresponds to the foramen lacerum postering, 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 parietes 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 desceudens noni, which accompanies the jugular vein to the chest. The trunk of the hypoglossal next crosses the glosso-pharyngeal nerve, then passes beneath the cornu of the os hyoides, and ad- vances towards the superior larynx, where it terminates by dividing into two principal branches, which are distributed, the one to the anterior and inferior, the other to the superior and internal parts, of the tongue. Spinal nerves. — These correspond in number to the vertebra? of the spine. They arise, as in the other vertebrata by two roots, the ganglion on the posterior of which is proportionally very large. In the sacral region of the spine, the anterior and posterior roots escape by distinct foramina, and can be separately divided with- out laying open the bony canal, but they are deeply seated and well protected by the anchy- losed processes of the sacrum and the extended iliac bones. The cervical nerves vary considerably in number, the known extremes being from ten to twenty-three, corresponding to the number of 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 (u' u", fig. \ M) 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 sacrul 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 AVES. which is analogous to the ulnar nerve, and the other soon divides again into nerves which are similar to the median and musculo-cutaneous. The median dips down amongst the muscles on the middle of the fore-arm, to which it gives branches, and afterwards runs along the inter- osseous space, passes under the annular ligament of the carpus, and is distributed to the short muscles of the digiti. The branch analogous to the musculo-cutaneous nerve, is expanded upon the muscles on the upper edge of the radius. " The ulnar nerve, although it appears to be incorporated with the median on the upper arm, can be easily separated from it, and traced to its proper origin in the brachial plexus. After this nerve leaves the median, it turns over the end of the foramen to get upon the edge of the ulna. It gives filaments to the muscles in this situation ; but its chief branch runs down superficially upon the ligaments of the quills in company with a vein, and goes ultimately to be lost upon the ulnar edge of the hand. " The third cord furnished by the brachial plexus, supplies the place of the radial nerve. It detaches several filaments to the muscles on the inside and back of the scapula. It gives off also the articular nerve, and then winds round the humerus between the extensor mus- cles, to which it furnishes some large filaments. On coming to the outside of the humerus, it sends a branch between the integuments of the fold of the wing. The nerve now turns round the neck of the radius, beneath the muscles, and forms two branches ; of which one passes under the muscles to the outer side of the ulna, along which it runs superficially to the hand ; the other branch passes on the radial side, but more deeply amongst the muscles, goes under the annular ligament of the carpus, proceeds between the branches of the metacarpus, and is finally lost on the back of the digiti." The same anatomist describes the course of the nerves of the posterior extremities as follows. " Although Cuvier has given a more accurate description of the nerves of the lower extremity than those of the wing, it nevertheless needs correction in several particulars. " The obturutor 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 tibial and the peroneal nerves. " The tibial nerve, even before it arrives in the ham, separates into several branches, which pass on each side of the bloodvessels, and are chiefly distributed to the muscles on the back of the leg. Two of these branches, however, are differently disposed of ; the one accom- panies the posterior tibial artery down the leg, passes over the internal part of the pulley, and is lost in small filaments and anastomoses, with a branch of the peroneal nerve on the inner side of the metatarsus ; the other branch runs down on the peroneal side of the leg, along the deep- seated flexors of the toes, passes in a sheath formed for it on the outer edge of the moveable pulley of the heel, and proceeds under the flexor tendons along the metatarsal bone, to be distributed to the internal part of the two ex- ternal toes. " The peroneal nerve is directed to the outer part of the leg ; it dips above the gastrocnemii muscles, and runs through the same liga- mentous pulley that transmits the tendon of the biceps muscle; it then detaches some large filaments to the muscles on the anterior part of the leg, under which it divides into two branches, which proceed close together, in com- pany with the anterior tibial artery to the fore part of the ankle-joint, at which place they separate; one passes superficially over the outer part of the joint, the other goes first under the transverse ligament which binds down the tendon of the tibialis anticus muscle on the tibia, and then over the inner part of the joint, below which it divides into two branches, the one is distributed to the inner side of the metatarsus and the tibial side of the pollex, and to the next toe ; the other turns towards the centre of the metatarsal bone, and pene- trates the tendon of the tibialis anticus just at its insertion, and then rejoins the branch of the peroneal nerve it accompanied down the leg. They continue'their course together again in the anterior furrow of the metatarsal bone ; and at the root of the toes, separate once more, and proceed to die interspaces of the three anterior toes, and each divides into two fila- ments, which run along the sides of the toes to the nail." — Rees' Ci/clopadia, 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 the cardiac plexus of the par vagum ; three other filaments proceed inwardly to the projection formed by the bodies of the vertebrae to produce the commencement of the splanchnic nerve ; lastly, the sixth and seventh serve to unite the first ganglion with the second, one passing above, the other below the head of 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 coeliac axis, they surround it and form one, two, or three ganglions from which an immense number of filaments are thrown off, which surround the different arteries of the abdomen. These gang- lions are evidently the analogues of the semi- lunar ganglions of man, and the filaments pro- ceeding from them correspond to the solar plexus. The trunk of the sympathetic con- tinues along the bodies of the vertebras, but the ganglions become less marked after the ribs cease to be given off ; two or three filaments are given off from each of these small swell- ings, which, by uniting with the filaments of the opposite side, form a plexus around the aorta. The termination of the sympathetic may be readily traced along the coccyx, where four pairs of ganglions are observable in the Swan, the last of which join to form a ganglion impar. Fig. 137. Cerebral nerves, eyes, fyc. in situ of a Goose. 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 ismain- tained by a circle of osseous plates or scales (f, fig.i 37) interposed between the exterior and mid- dle layers. These plates vary from thirteen to twenty in number, and are situated immedi- ately behind the cornea, with their edges over- lapping each other. They are in general thin, and of an oblong quadrate figure, becoming elongated from before backwards in proportion as the bird possesses the power of changing the convexity of the cornea. In the nocturnal Ruptores 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 Eishes, 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- Fig. 138. sembles in its structure that of mammalia; it is copiously covered with a black pigment, similar to that in the human eye. Opposite the bony circle the choroid separates into two layers; the exter- nal layer is the thin- nest, and adheres at first firmly to the sclerotica, after which it is produced freely inwards to form, or be continuous with, the iris. The iris ( e,fig. 138) is delicate in its texture, which under the lens appears composed of a fine net-work of interlacing fibres, but it is remarkable for the activity and extent of its movements, which seem in many birds to be voluntary. The contraction and dilatation of the pupil, inde- pendent of any change in the quantity of light to which the eye is exposed, is most conspicu- ous and remarkable in the Parrot tribe, but we have observed it also in the Cassowary and some other birds. The colour of the iris is subject to many varieties, which frequently display great bril- liancy, 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 plies radiating towards the anterior part of the chrystalline lens, where they termi- nate in slightly projecting ciliary processes, ( d, _/?g.l38,)the extremities of which adhere firmly to the capsule of the chrystalline. These processes are the most numerous, close set, and delicate in the Owl ; they are proportionally larger and looser in the Ostrich. The chief peculiarity in the eye of the Bird is the marsupium or 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 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 retina, enter the eye between the lamina? of the retina, along the whole extent of the oblique slit above men- tioned, and immediately enter or compose the folds of the marsupial membrane, upon which they form most delicate and beautiful arbore- scent ramifications. The marsupium is lodged like a wedge in the substance of the vitreous humour, in a vertical plane, directed obliquely forwards. In those species in which the marsupium is widest, the angle next the cornea reaches the inferior edge of the capsule of the chrystalline ; but where it is narrow, the whole anterior surface is in contact with the same point. This con- tact is so close in some birds, as the Vulture, AVES. 305 Parrot, Turkey, Cassowary, Stork, Goose, and Swan, that the 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 lamina? of the hyaloid membrane which form the cells for the lodgment of the vitreous hu- mour. In these cases the marsupium can have no influence on the movements of the lens, unless it be endowed with an erectile property, and be so far extended as to push forward the lens. The researches of Bauer* have shewn that there is no muscular structure in the marsupium, and its changes of form, if such occur in the living bird, must be effected by changes in the condition of the vessels of which it is almost exclusively com- posed. The form of the marsupium varies in differ- ent birds ; it is broader than it is long in the Stork, Heron, Turkey, and Swan; and of the contrary dimensions in the Owl, Ostrich, and Cassowary. The plicae of the membrane are perpendicular to the terminal line of the optic nerve ; they are of a rounded figure in most species, but in the Ostrich and Cassowary they are compressed, and so far inclined from the plane of the membrane, that their convergence towards its extremity gives it a resemblance to a close-drawn purse.f The folds vary in num- ber, being four in the Cassowary, seven in the Great Horned Owl, eight in the Goose, from ten to twelve in the Duck and Vulture, fifteen in the Ostrich, sixteen in the Stork, and still more numerous in the Insessorial Birds, amounting to twenty-eight, according 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 une bourse qui abou- tissoit en pointe vers le bord du Christallin le plus prochain de l'entree du nerf optique. Cette bourse, qui estoit large de six lignes par le bas, a la sortie du nerf optique, et qui iilloit en poiute vers le haut, estoit attachee par sa pointe aubord du Chrystallin, par le moyen de la membrane qui le couvroit du eoste de 1'humeur vitree, et qui couvroit aussi toute la bourse qui estoit noir mais d'un autre noir que n'est celuy de la choroide." — Duvernoy, in ' Me- moires pour servir a 1'Hist. Nat. des Animaux,' p. 375. X Croonian Lecture, Phil. Trans. 1796. VOL. I. it does not extend to the chrystalline,, and by the manner of its attachment in those cases in which it does; since, as in these the mar- supium adheres to the side of the chrystalline, it can only move it obliquely. Some physiologists have supposed that this black membrane was extended towards 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 to the vitreous humour. The chrystalline lens is remarkable for its flat- tened form, especially in the high-soaring Birds of Prey ; it is also of a soft texture, and is without any hard nucleus, as in the eyes of Fishes and Reptiles. In the Cormorant and other birds which seek their food in water, the chrystalline is of a rounder figure, and this is peculiarly the case in the near- sighted Owls which hunt for prey in obscure x 30G 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 cunal of Petit. The vessels of the lens are derived from those of the marsupium, which, as we have before observed, are ramifications of the analogue of the arteria centralis retina?. With respect to this vessel we may here observe, that it is not continued as a simple branch from its origin to the marsupium, — such a course would be in- consistent with the important functions it is destined to fulfil in the present Class. Imme- diately before penetrating the coats of the eye it breaks into numerous subdivisions, the aggre- gate of which is much greater than the trunk whence they proceed, and these again unite, forming a plexus (e,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, Jig. 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. Fig. 139. The Eye-ball is moved in Birds by four straight and two oblique muscles. The Recti muscles a- rise from the cir- cumference of the optic foramen and expand, as they pass forward, to be inserted into the soft middle part of the scle- Muscles of the eye. rotic. We have not been able to trace their insertion distinctly to the osseous circle ; their aponeurosis cannot be reflected for- wards from the sclerotica without lacerating that membrane. The Ob/iqui both arise very near together from the anterior parietes of the orbit, and go * Meckel's Archiven, 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 uttollcns ; b' 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 palpebral 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 ( Caprimulgus) the eye-lids are closed principally by the depres- sion of the upper one. There are but few birds that possess eye-lashes ; of these the Ostrich is an example, as also the Horn-bills and the Owls, in which they are arranged in a double series ; but in these they are rather to be considered as feathers with short barbs, than true eye-lashes. The third eye-lid, or membrana nictitans, is a thin membrane, transparent in some birds, in others of a pearly white colour, which, when not in action, lies folded back by virtue of its own elasticity on the inner or nasal side of the globe of the eye, with which it is in close contact. Two muscles are especially provided to effect its movements, but are so placed as to cause no obstruction to the admission of light to the eye during their actions. One of these is called the Quadratus nictitantis, (g,Jig- 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 quadiatus, 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- diatus, 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, fig. 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 membrane. Its duct (I, fig. 140) is long, and passes to the nose along an osseous groove, behind the lachrymal bone. Its structure is simple, like that of the salivary glands in the same class, being com- posed of ramified follicles from which the * Nouv. Bullet, des Sc. par la Soc. Philomath, iii. an 6. p. 267. t Nitzsch, Meckel's Archrv. 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 thaf-dn the higher Reptiles, especially the Crocodile. There is no concha, or projecting Fig. 141. Organ of hearing. Owl. auricle in this class, for collecting and con- densing the rays of sound ; but to compen- sate for this deficiency, the labyrinth, and especially the semicircular canals, are of large size in proportion to the cranium. In those Birds, however, which enjoy the locomotive or visual faculties in a less perfect degree than in the rest of the class, there is found a peculiar arrangement of the feathers around the external meatus auditorius, which serves in some degree the office of an external ear. The Ostrich and Bustard (d,jig. 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 flammed). 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, fig. 141) is more or less of an oval shape ; it has the same structure as in Mammals, but is extremely delicate ; it is convex, externally, as in the Reptiles, not concave, as in most Mammals. The cavity of the tympanum is widest at its outer part, and very irregular in the rest of its extent. It communicates by the usual fora- mina with the internal ear, and is connected with the fauces by means of the Eustachian tube. It also communicates by three other apertures with the cells of the bones of the cranium. " These," Macartney observes, " are widened into something like canals, where the holes open into them. The largest of the foramina is in the back of the tympa- num, and leads to the posterior cells, and communicates above the foramen magnum with the cellular canal of the other side. The second opening is placed at the anterior part of the tympanum, and conducts to the cells on the lower and anterior part of the cranium. The third foramen is continued amongst the cells which surround the labyrinth. Thus each tympanum has a communication with the interior of all parts of the cranium, and with each other, from which they might be reckoned as making only one cavity. The end of the tympanic bone, also, where it contributes to form the parietes of the tym- panum, has a foramen by which it derives its supply of air. The auditory cells of the cra- nium of birds are analogous to the mastoid of the human subject ; but from their extent they multiply sound much more. They are of the greatest magnitude in the nocturnal birds of prey; the Night-jar ( Caprimulgus ) has them also very large : they diminish in size in other birds, in which the posterior canals have no direct communication with each other; they are little observable in the Struthious Birds, and are wanting in the Parrots, but in their place the cavity of the tympanum is enlarged posteriorly.'' The Eustachian tube ( e, e, fig. 141) is very large in birds ; it is an osseous canal, and ter- minates by a small aperture close to the one of the other side, within the fissure of the posterior nares. In the Swan the Eustachian passages, after having reached the base of the skull, pass forwards for about half an inch and then unite to form one common tube, which gradually expands until it termi- nates just behind the posterior apertures of the nose. The foramina, which lead from the tym- panum into the labyrinth, are situated within a fossa. They do not merit the distinctions of foramen ovale and foramen rotundum, being both oval, and only separated by a small bony process. The ossicula auditus are supplied by a sin- gle bone, analogous to the stapes, and some cartilaginous processes representing the rudi- ments of a malleus and incus. The ossiculum consists of a stalk or pedicle, crowned by an oval plate, which is applied to the foramen that leads into the vestibule of the labyrinth. At the other extremity it is united to two or three cartilaginous processes, which form a tri- angle that is attached to the membrana tym- pani. The elongated stapes, or tympanic ossicle, is moved by one muscle (jf, fig- 141), which comes from the occiput and penetrating the cavity, is affixed to the triangle that is con- nected to the membrana tympani. This muscle, 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, Jig. 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 ampullae (/), on which the nerves are distributed in the same manner as in mam- malia. The place of the cochlea is supplied by a short obtuse osseous conical tube {n, Jig. 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 scahv, the anterior of which communicates with the vestibule and is not closed ; the posterior scala is shorter, and communicates with the tym- panum by the foramen rotundum, which is closed by a membrane. Besides these parts the cochlea still contains a trace of the cretaceous substance which forms so conspicuous a part of the organization of the internal ear in Fishes. The Struthious birds manifest their close relation to the Reptilia by having the tube corresponding to the cochlea, very small in proportion to the other parts. The seventh cerebral nerve is received into a fossa, and there divides into five branches ; one is the facial, or porlio dura, and the others are sent to the semicircular canals and the tube. The facial nerve receives a filament from the par vagum, which traverses the ear, and is afterwards distributed to the palate. Comparetti has described two canals leading * In the Inscssores this canal is generally the smallest of the three. from the labyrinth of birds, which correspond with the aqueducts of the mammalia.* Organ of Smell. — The close affinity subsist- ing between the cold and warm-blooded ovipara is no where more strongly manifested than in the olfactory organs. The external nostrils are simple perforations, having no moveable^ar- 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 Australia 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 liasores the nostrils are partially defended by a scale. In the Corvida they are protected by a bunch of stiff feathers directed forwards. In the Petrels the nostrils are produced in a tubular form, parallel to one another for a short distance along the upper part of the mandible, with the orifices turned forwards ( a, Jig. 142.) The septum narium is, in general, complete, and is partly osseous, partly cartilaginous. It is perforated in the Swan just opposite the external nostrils. The surface of the septum is very irregular in this bird, and the pituitary membrane which covers it is highly vascular. The outer side of each of the nasal passages gives attachment to three turbinated lamina?. 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, Lecons d'Anat. Comp. torn, ii., and Macartney in Rces' Cyclopaedia, Ait. 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 lamina differ in regard to tex- ture. In the Cassowary and Albatross they are said to be membranous. Cuvier states that they appeared to him to be bony in the Horn- bill and Toucan. We have found this to be the case in the recent Toucan. The organ of smell in this singular species is confined to the base of its enormousbeakjf 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, Natatores, Ruptores, Scanso?'es, Insessores, Rasores. There is still, however, much obscurity with reference to the extent to which Birds make use of their olfactory organs. It has been generally asserted that birds of prey are gifted with a highly acute sense of smell, and that they can discover by means of it the carcass of a dead animal at great distances ; but those who have witnessed the rapidity with which the Vultures descend from invisible heights of the atmosphere to the carcass of an animal, too recently killed to attract them by putrefactive exhalations, have generally been led to consider them as being directed to their quarry by sight. " That this is the case," Dr. 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 far from guiding them to their prey from any distance, it affords them no indication of its presence even whencloseathand. The following experiments appear to be perfect- ly conclusive on this subject. Having pro- cured the skin of a deer, Mr. Audubon stuffed it full of hay ; after the whole had become perfectly dry and hard, he placed it in the mid- dle of an open field, laying it down on its back in the attitude of a dead animal. In the course of a few minutes afterwards he observed a vulture flying towards and alighting near it. Quite unsuspicious of the deception, the bird immediately proceeded to attack it as usual in the most vulnerable points. Failing in this object, he next with much exertion tore open the seams of the skin where it had been stitched together, and appeared earnestly intent on get- ting at the flesh, which he expected to find within, and of the absence of which not one of his senses was able to inform him. Find- ing that his efforts, which were long reiterated, led to no other result than the pulling out large quantities of hay, he at length, though with evident reluctance, gave up the attempt, and took flight in pursuit of other game to which he was led by the sight alone, and which he was not long in discovering and securing. " Another experiment, the converse of the first, was next tried. A large dead hog was concealed in a narrow and winding ravine, about twenty feet deeper than the surface of the earth around it, and filled with briers and high cane. This was done in the month of July, in a tropical climate, where putrefaction takes place with great rapidity ; yet, although many vultures were seen from time to time sailing in all directions over the spot where the putrid carcass was lying, covered only with twigs of cane, none ever discovered it; but in the meanwhile several dogs had found their way to it and had devoured large quantities of the flesh."* * See Roget, Bridgewater Treatise, vol. ii. p. 406. AVES. 311 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 papilla; except at its base (o, fig. 1 52) near the aper- ture of the larynx ; these papillae are not, how- ever, supplied by a true gustatory nerve, but by filaments of the glossopharyngeal. No branch of the fifth pair goes to the tongue. The tongue is proportionally largest and most fleshy in the Parrot tribe, and the food is detained in the mouth longer in these than in other birds. It is triturated and commi- nuted by the mandibles certainly, and turned about by the tongue, which here seems to ex- ercise a gustatory faculty, since indigestible parts, as the coat of kernels, &c. are rejected. In the Lories the extremity of the tongue is provided with numerous long and delicate pa- pillae or filaments projecting forwards. Organs of Touch. — With respect to the tactile instruments, but few observations can be made in the class of Birds. The anterior extremities have their digital extremities undivided and entirely unfitted for the exercise of this sense, and the posterior extremities are but little better organized for the purpose. The integument covering the toes is very sparingly supplied with nerves, and is of a texture scarcely fitted for ascertaining the superficial qualities of bodies. However, the villi on the under sur- face of the toes are observed to be remarkably long in the Capercailzie (Tetrao uragallus), but this is probably for the purpose of enabling them to grasp with more security the frosted branches of the Norwegian pine-trees. The Parrots seem to use their feet more like instru- ments of touch, but in them the action may be merely prehensile. The only organ of touch respecting which there can be no doubt is the bill. Even where this is covered with a hard sheath of horn, some filaments of the fifth pair (c,fig. 150) may be traced terminating in small papillae ; but in the Lamelli-rostral water-birds the bill is covered by a softer substance, and is plentifully supplied by branches of the fifth pair of nerves. (See Nerves.) In the Woodcocks and Snipes the long bill is so organized that it is used as a probe in marshes and soft ground to feel for the small worms and slugs that constitute their food. The cire in the Falconida, the wattles of the Wattle-birds (Pliiledon carunculatus and Glaucopis cinerea) and of the Cock, the ca- runcles of the King-Vulture and Turkey, may also be regarded in some degree as organs of touch. Organs of Digestion. — The digestive function in birds is necessarily extremely powerful and rapid in order to supply the waste occasioned by their extensive, frequent, and energetic mo- tions, and in accordance with the rapidity of their circulation and their high state of irrita- bility. * The parts to be considered with reference to this function are the rostrum or beak, the tongue, the oesophagus, the stomach which is always divided into a glandular and muscular portion, the intestines, and the cloaca. The glandular organs of the digestive system are the salivary glands, the proventricular fol- licles, the liver, pancreas, and spleen. The beak consists of the maxillary and inter- maxillary bones, which in place of teeth are provided with a sheath of horny fibrous mate- rial, exactly similar to that of which the claws are composed : this sheath is moulded to the shape of the osseous mandibles, being formed by a softvascular substancecoveringthese parts, and its margins are frequently provided with horny processes or laminae secreted by distinct pulps, and analogous in this respect to the whalebone laminae of the Whale : M. Geofiioy St. Hilaire has described a structure in the bill of birds which presents a closer approach to a dentary system. In a foetus of a Perroquet nearly ready for hatching, he found that the margins of the bill were beset with tubercles arranged in a re-- gular order and having all the exterior appear- ances of teeth : these tubercles were not, indeed, implanted in the jaw-bones, but formed part and parcel of the exterior sheath of the bill. Under each tubercle, however, there was a ge- latinous pulp, analogous to the pulps which secrete teeth, but resting on the edge of the maxillary bones, and every pulp was supplied by vessels and nerves traversing a canal in the substance of the bone. These tubercles form the first margins of the mandibles, and their remains are indicated by canals in the horny sheath subsequently formed, which contain a softer material, and which commence from small foramina in the margin of the bone. The different degrees of hardness and varieties of form of the beak exercise, Cuvier observes,! 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. Ceteris 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 ei g pounds of fish daily. + Anatomic C'omparte, torn. ii. p. 192. 3f2 AVES. general form produces infinite variety in the application of the force. A compressed beak with sharp edges and a hooked extremity characterizes both the Birds of Prey properly so called, which destroy the smaller quadrupeds and birds (fig. 112); and also the carnivorous species of a different order that live on fish, as the Petrels (Jig. 142), Al- Fig. 14,. ((((/ of being as deep as it is long), and the Skimmer ( Rliyncops), in which the still more singular structure obtains of an inequality in the length of the two mandibles, the upper one being con- siderably the shortest ; so that this bird can only get its food, which consists of floating marine animals, by pushing them before it as it skims along the surface of the water. Fig. 144. Bill of the Petrel. batrosses, Frigate-bird, and Tropic-bird. But in the 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.il 5.) As the bill becomes narrower and straighter, it characterizes birds of a voracious habit, but lesss daring in their attacks on other birds, such as the Crows, Magpies, &c, (Jig. 116) ; and the compressed knife-shaped bill is asso- ciated with similar habits in the Water-birds, as the Gulls, Grebes, Dabchicks, &c. Another kind of strong and trenchant bill, which is more elongated and without a hook, serves to cut and break, but not to tear : this form of bill characterizes the Waders which frequent the water and prey upon animals that make resistance in that element, as reptiles, fishes, &c. In the He- rons and Bitterns the. bill is straight ; in the Ibls it is curved down- wards (Jig. 123); in the Jabiru (fig. 143) it is curved in the contrary direction. Bill of the Shimmer. 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 [(Jig. 145), which is also ser- rated at the edges. Some speciesofFly- catcher and Tody have this form of beak on a small scale . ml °f the Boat-bill. Of the blunt-edged bills we may first notice those which are flattened horizontally. When a bill of this description is long and strong, as in the Pelecan (fig. 146), it selves 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.) 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, the more conical ones of Geese and Swans, and that of the Flamingo,* of which the extremities * It is singular that it should ever have been supposed that the upper mandible was alone move- able, and the lower mandible perfectly immoveable, in the Flamingo, since precisely the contrary is the AVES. 313 of the mandibles are bent downwards abruptly (Jig. 148), have all transverse horny lamina; Fig. 148. which are nearly allied to the Anatidte, the la- teral laminas are developed into small conical tooth-like processes, which serve to hold fast the fishes, which the Goosander destroys in great numbers. Fig. 149. Bill of tJie Flamingo. arranged along their edges, which, when the bird has seized any object in the water, serve, like the whalebone laminre of the Whale, to give passage to the superfluous fluid. The aquatic habits of all these birds are in harmony with this structure. In the Goosanders (Mergus), Bill of the Goosander. The bills of the Toucans and Ilornbills 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. Bill of the Toucan. bine, with great bulk, a due degree of strength and remarkable lightness, and their structure is consequently of a most beautiful and delicate kind. The external parietes are extremely thin, especially in the upper beak : they are elastic, and yield in a slight degree to moderate pressure, but present considerable resistance if the force be increased for the pur- pose of crushing the beak. At the points of the mandibles the outer walls are nearly a line in thickness ; at other parts in the upper beak case. In the specimen which we dissected (see Proceedings of the Zoological Society, Part ii. p. 141) the upper mandible was so firmly fixed to the cranium as only to be moved with that part, while the lower mandible was freely moveable when the head was fixed. The Flamingo is remark- able for applying the upper mandible to the soil, which it shovels backwards in searching for its food. they are much thinner, varying from one- thirtieth to one-fiftieth part of an inch, and in the lower beak are from one-twentieth to one- thirtieth of an inch in thickness. On making a longitudinal section of the upper mandible (a, Jig. 150) in the Rhamphastos Touco, its base is seen to include a conical cavity about two inches in length and one inch in diameter, with the apex directed forwards. The walls of this cone consist of a most beautiful osseous net-work, intercepting irregular angular spaces, varying in diameter from half a line to two lines. From the parietes of the cone a net- work of bony fibres is continued to the outer parietes of the mandible, the fibres which imme- diately support the latter being almost invariably at right angles to the part in which they are in- serted. The whole of the mandible anterior to the cone is occupied with a similar net-work, the meshes of which are largest in the centre of 314 AVES. the beak, in consequence of the union which takes place between different small fibres as they pass from the circumference inwards. It is worthy of observation that the principle of the cylinder is introduced into this elaborate structure : the smallest of the supporting pdlars 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 {m,fig. 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 Hornbills and Toucans is so thin that it often becomes irregularly notched at the edge from use. The Hornbills have, besides, upon their enormous beak, horn-like prominences of the same structure and of different forms, the use of which is not known. The Trogons, Touracos, Buccos, &c. exhibit forms of the bill which are intermediate to that of the large but feeble bill of the Toucans, and the short, but hard, strong, and broad bill of the Parrot-tribe, which is also hooked, so as to assist in climbing, like a third foot: {fig. 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 RamphastidcB, 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 Buff'on 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, I have never met with a more interesting or beautiful ex- ample of the adaptation of means to an end than is to be found in the tongue, the beak, and its muscles, in the Cross-bill." * The tongue, as has been already observed, can hardly be considered as an organ of taste in Birds, since, like the mandibles, it is gene- rally sheathed with horn. It is principally adapted to fulfil the offices of a prehensile organ in association with the beak, and it pre- sents almost as many varieties of form. Orni- thologists have not yet perhaps derived all the advantages which a study of the modifications of the tongue might afford in determining the natural affinities of birds. The os hyoides very much resembles that of Reptiles. Its parts have been minutely studied by Geoffroy St. Hilaire, who has bestowed upon them separate names: ( a, 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 in the Swan and other Lamelli-rostres. * Zool. Journal, vol. iv. p. 464. AVES. 315 Fig. 151. 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. Cranium and tongue of a Woodpecker. One of the most remarkable structures which the tongue presents in this class is met with in the Flamingo, where it is remarkable botli 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 Tongtte of tfie Toucan. may almost be considered as a distinct row. At the posterior part of the tongue there are two groups of smaller recumbent spines di- rected towards the glottis. The substance of the tongue is not muscular, but is chiefly composed of an abundant elastic cellular sub- stance, permeated by an oily fat. In the 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 Pelecunida, the tongue is remarkably short. In the Parrots it is thick and fleshy, serves admirably to keep steady the nut or seed upon which the strength of the mandibles is exerted, and is applied to the kernel so extracted, as if to ascertain its sapid qualities. The following are the muscles of the tongue in birds. 1st. The Genio-hyoideus of Vicq d'Azyr, or the Mylo-hyoideus according to Cuvier. This is a thin layer of fibres attached to the lower and inner border of the lower jaw, and running transversely to a mesial tendon which separates them, and extends to the uro-hyal. It raises the tongue towards the palate. 2d. The Stylo-hyoideus arises from the upper and back part of the lower jaw, and divides into three or more portions : the posterior descends obliquely forwards, and is inserted into the tendinous commissure of the preceding mus- cle; the middle portion is inserted into the ' uro-hyal :' the anterior fasciculus is inserted into the side of the basi-hyal above the trans- verse hyo-glossus. The actions of these dif- ferent portions vary according to their insertion ; the first and second depress the apex of the tongue by raising its posterior appendage, (uro-hyal,) the third raises the tongue and os hyoides, and draws it to one side when it acts singly. 3d. The Genio-hyoideus arises by two fleshy 316 AVES. bands from the lower and internal edge of the lower jaw ; these unite and surround the cerato- hyals or cornua of the os hyoides ; and as they draw forward the os hyoides, protrude the tongue from the beak. 4th. The Cerato-hyoideus passes from the cerato-hyal to the uro-hyal, and is therefore subservient to the lateral movements of the tongue. 5th. The Sterno-hyoidei are replaced by a slip of muscle which extends from the anterior surface of the upper larynx to be attached to the base of the glosso-hyal. 6th. A small and short muscle is single or azygos ; it passes from the basi-hyal to the under part of the glosso-hyal ; it depresses the tip of the tongue and elevates its base. 7th. A short muscle which arises from the junction of the basi-hyal with the cerato- and uro-hyals, and is inserted into the upper and outer angle of the base of the glosso-hyal. All these muscles are remarkably large in the Woodpecker, in which there is a singular pair of muscles that may be termed Ceralo- tracheales, (k, 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- Torujue and salivary ylands, Woodpecker. 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 mouth. The structure of these glands is shown at i, k, Jig. 154. Besides the preceding, which may be con- sidered as the true salivary glands, there are numerous accessory follicles in different parts of the oral apparatus of birds. In the Water- hen ( Gallinula chloropus ) there is a series of coecal glandular tubes along each side of the tongue ; and it is interesting to note that glan- AVES. 317 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- chiae of Fishes. In the Goose the corresponding follicles are longer and wider, and are situated near the sides of the tongue. In the Raven these mucous follicles are narrower but longer. The food, after being embued with the secre- tion of the preceding glands, is poised upon the tongue and swallowed partly by means of the pressure of the tongue against the palate, partly by a sudden upward jerk of the head. The posterior apertures of the nostrils being generally in the form of narrow fissures are undefended by a soft palate or uvula ; and the laryngeal aperture, which is of a similar form, is in like manner unprovided with an epi- glottis, but is defended by the retroverted 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^/^.155). In the male there is a membranous sac extending for some way down the an- terior part of the neck capable of holding several quarts of water ; it communicates with the mouth by an aperture be- neath the tongue. It is not found ex- cept in the mature bird. It is sup- posed to serve the purpose of provid- ing the female and young during the breeding season Fig. 155. Futicial bug of the Bustard. * See Meckel's Archiven, 1826, p. 613. with water, and hence may not be developed to its full extent except at that period. The Swift presents an analogous dilatation of the membrane of the fauces at the base of the lower jaw and upper part of the throat: it is most developed at the period of rearing the young, when it is generally found distended with insects in the old birds that are shot while on the wing. This receptacle is of a rounded form, and communicates with the fauces by a wider opening than that of the 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 the piscivorous birds it is of great capacity, enabling the latter to swallow the fishes entire, and serving also in many Waders and Swim- mers as a temporary repository of food. When the Cormorant has by accident swal- lowed a large fish, which sticks in the gullet, it has the power of inflating that part to its utmost, and while in that state the head and neck are shaken violently, in order to promote its passage. In the Gannet the oesophagus is ex- tremely capacious, and, as the skin which covers it is equally dilatable, five or six herrings may be contained therein. In both these species it forms one continued canal with the stomach. In the Flamingo, on the contrary, the dia- meter of the gullet does not exceed half an inch, being suited to the smallness of the objects which constitute the food of this species. Besides deglutition the oesophagus is fre- quently concerned in regurgitation ; and in the Birds in which this phenomenon occurs, the muscular coat of the gullet is well deve- loped, as in the Ruminant Mammalia. The Raptores, for example, habitually regurgi- tate the bones, feathers, and other indiges- tible parts of their prey, which, in the lan- guage of the falconer, are called ' castings.' A Toucan, which was preserved some years alive in this country, was frequently observed to regurgitate partially digested food, and after submitting it to a rude kind of mastication by its enormous beak, again to swallow it. The oesophagus possesses an external cel- lular covering, a muscular coat, an internal vascular tunic, and a cuticular lining. The muscular coat consists of two layers of fibres ; in the external stratum they are trans- verse ( a, 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 oesophagus does not preserve a uni- form width, but undergoes a lateral dilatation anterior to the furculum at the lower part of the neck. This pouch is termed the ingluvies or crop (b, Jig. 156). 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 the Pigeon it is double, consisting of two lateral oval cavities (b c,Jig. 158). The dilatation of the oesophagus to form the crop is more gradual in the Ducks than in the Gallinaceous birds. The crop is wanting in the Swans and Geese. The disposition of the muscular fibres of the crop is the same as in the oesophagus, but the muciparous follicles of the lining membrane are larger and more numerous. 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 Crop 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 * Animal Economy, p. 235. AVES. 319 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 ' ( ventriculm succenturiatus, bulbus glandulosus, echinus, infundilndum, the ' 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. fig. 159). Hence it is .fig. 159. by some compara- tive anatomists re- garded as a part of the oesophagus. The proventri- culus varies, how- ever, in form and magnitude in dif- ferent birds. In the Rasores it is larger than the oeso- phagus, but much smaller than the gizzard. In the Psittacida and Ardeidcc (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 Part of the proventriculus of a Swan dissected. 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. Eagle. Ostrich. The gastric glands are variously arranged. Among the Raptores, we find them in the Golden Eagle disposed in the form of a broad compact belt ; in the Sparrow-Hawk this belt is slightly divided into four distinct portions. In the Insessores the glands are generally arranged in a continuous zone around the pro- ventriculus; but in some of the Syndactyli, as the Hornbill, the circle is composed of the blending together of two large oval groups. Among the Scansores the Parrots have the gastric glands disposed in a continuous white circle, which is at some distance from the small gizzard. In the Woodpeckers the glands are arranged in a triangular form, with the apex towards the gizzard. In the Toucan they are dispersed over the whole proventriculus, but are more closely aggregated near the gizzard ; the lining membrane of the cavity is reticulate, and the orifices of the glands are in the inter- spaces of the meshes. Among the Rasores the Pigeon shows its affinity to the Passerine Birds in having the gas- tric glands of a simple structure, and arranged 320 AVES. in a zonular form : they are chiefly remarkable for their large cavity and wide orifice. In the Common Fowl and Turkey the glands are more complex, and form a complete circle. In the Cursores the arrangement of the glands is different in almost every genus. In the Ostrich they are of an extremely complicated structure, and are extended in unusual numbers over an oval space on the left side of the proventriculus, which reaches from the top to the bottom of the cavity, and is about four inches broad. The Rhea differs from the other Struthious birds in having the solvent glands aggregated into a single circular patch, which occupies the posterior side of the proventricular cavity. In the Emeu the gastric glands are scattered over the whole inner surface of the proven- triculus, and are of large size ; they terminate towards the gizzard in two oblique lines. In the Cassowary the glands are dispersed over the proventriculus with a similar degree of uniformity ; but they are smaller, and their lower boundary is transverse. Among the Grallatores, the Marabou, or Gigantic Crane, ( Ciconia Argala and Ma- rabou,) has the nearest affinity to the Rhea in the structure and disposition of the gastric glands ; they are each composed of an aggre- gate of five or six follicles, terminating in the proventriculus by a common aperture; and they are disposed in two compact oval masses, one on the anterior, the other on the posterior surface of the cavity. In the Heron ( Ardea cineria ) the solvent glands are of more sim- ple structure, and are more dispersed over the proventriculus; but still they are most nume- rous on the anterior and posterior surfaces. In the Flamingo the gastric glands are short and simple follicles, arranged in two large oval groups, which blend together at their edges. The Natatores present considerable differ- ences among themselves in the disposition of the solvent glands. In the Cormorant ( Pha- lacrocorax carbo ) they are arranged in two circular spots, the one anterior and the other posterior; while in the closely allied genus the Sula, or Gannet, they form a complete belt of great width, and consequently are extremely numerous. In this respect the Gannet, or Solan Goose, has a nearer affinity to the Pelecan, with which both birds weregenerically associated by Linnffius. 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 lojver 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 sacrad of the liver, on the left side and dorsal aspect of the abdomen, generally resting on the mass of intestines ; although, according to Blumen- bach, the Nutcracker and Toucan, as well as the Cuckoo, differ in having the gizzard situated on the abdominal part of the cavity. Hence this peculiarity not being restricted to the Cuc- koo affords no explanation, as has been sup- posed, why it should not incubate. In the Owl, also, the gizzard adheres to the membrane cover- ing the internal surface of the abdominal muscles. In all birds the gizzard forms a more or less lengthened sac, having at its upper part two apertures ; one of these is of large size, com- municating with the proventriculus (a, fig. 161, 162), the second is in close proximity with, and to the right side of the preceding, leading to the duodenum (b, fig. 161); below these apertures the cavity extends to form a cul-de- sac (c, 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. Gizzard of a Swan. AVKS. 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 Raptures 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, fig. 156), and there are some longitudinal fibres beneath the radiating or external layer. In the Removes 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 intermedin {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. Gizzard of a Swan. 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 plainly seen : — and it is worthy of observation that the fibres are not perpendicular to the plane of the muscles but vol. r. oblique, and in opposite directions, on the two sides. Elsewhere the cuticular lining is dis- posed in ridges and prominences (A, fig. 161, 162), which vary in different birds, but are pretty constant in the same species. Cams* has recently figured the gizzard of a Petrel ( Frocellaria glaciulis ), 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 Euphones, among the Tana- gers, the muscular or pyloric division of the stomach is remarkably small and not sepa- rated from the duodenum by a narrow pylorus.^ The parieles of the gizzard, like those of other muscular cavities, become thickened when stimulated to contract on their contents with greater force than usual. In the 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. * Tabulae A natomiam Comparativam illustrantes, fol. pars iv. 1835. t Thus we find in Parrots, where the gizzard is remarkably small, that a crop is present. A like receptacle exists also in the Flamingo, in which the gizzard is small but strong. ± Car us lit 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. GaJlinaceous 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 Redi'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,+ that the action of the great lateral muscles of the gizzard was rotatory. Harvey appears to have first investigated, by means of the ear, as it were in anticipation of the art of auscultation, the actions which are going on in the interior of an animal body, in reference to the motions of the gizzard. He observes, ( De Generatione Animalium, in Opera Omnia, 4to. p. 208,) " Fal- conibus, aquilis, aliisque avibus ex preda viven- tibus, si aurem prope admoveris dum ventricu- lus jejunus est, manifestos intus strepitus, lapillomm 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 euticular lining was plainly discernible. Sec Proceedings of Zool. Soc. 1834, p. 9. Grebe, there is a small but distinct cavity inter- posed between the gizzard and intestine. An analogous structure is found in the Crocodile. The intestines reach from the stomach to the cloaca ; in relative length they are much shorter than in the mammalia. In the Toucan, for example, the whole intestinal canal scarcely equals twice the length of the body, in- cluding the bill. The canal is divided into small and large intestines, sometimes by an internal valve, sometimes by the insertion of a single caecum, but most generally by those of two cceca, which are always opposite to one another. In a few instances there is no such distinction. The small intestines and cceca 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, (f f, fig. 163,) Fig. 163. Abdominal viscera of a Pigeon. which fold receives the pancreas (g- 163) they are as short as in the Insessorial order, and are sometimes wanting altogether, as in the Crown- pigeon. In the Guan (Penelope cristata ) each caecum is about three inches in length; while in the Grouse each coecum measures a yard long, being thus upwards of three times the length of the entire body. The internal surface of these extraordinary appendages to the alimen- tary canal is further increased in the Grouse by being disposed in eight longitudinal folds, which extend from their blind extremities to within five inches of their termination in the rectum. We have always found the cceca in this species filled with a homogeneous pulta- ceous matter without any trace of the heather buds, the remains of which are abundant in the fcecal matter contained in the ordinary tract of the intestines. In the Peacock the cceca measure each about one foot in length; in the Partridge about four inches ; in the common Fowl and other Phdsiunidm the cceca are each about one- third the length of the body ; they commence by a narrow pedicle, which extends about half their length, and then they begin to dilate into reservoirs for the chyme {g,fig- 157). In the Cursores the cceca again present very different degrees of development. In the Emeu they are narrow and short. In the Cas- sowary they are wholly deficient; while in the Ostrich they are wide and upwards of two feet in length, and their secreting and absorbing parietes are further increased by being pro- duced into a spiral valve, analogous to that which exists in the long coecum of the Hare and Rabbit. In the Grallatores the two cceca are gene- rally short where present; they attain their greatest development in this order in the De- moiselle, where the length of each ccecum is five inches; and they are also large in the Fla- mingo, where they each measure nearly four inches, and are dilated at their extremities, presenting with the gizzard, crop, lamellated beak, and webbed feet, the nearest approach to the Anatida. of the following order. In the Natatores the cceca, where they are present, vary in length according to the nature of the food, being very short in the fish-eating Penguin, Pelecan, Gull, &c. and long in the Duck, Goose, and other vegetable feeding Lamellirustres. In the crested Grebe ( Podiceps cristatus ), Yarrell detected two cceca, each measuring 3-16ths of an inch in length. In the Canada Goose the same indefatigable observer found the cceca each nine inches in length, and in the White-fronted Goose the same parts mea- sured severally thirteen inches. They have the same length in the Black Swan. In the Wild Swan the cceca measure each ten inches in length, while in the tame species they are each fifteen inches long. As digestion may be supposed to go on less actively in the somnolent, night-flying Owls, than in the high-soaring Diurnal Birds of Prey, an additional complexity of the alimentary canal for the purpose of retaining the chyme somewhat longer in its passage, might naturally be expected; and the enlarged cceca of the Nocturnal Raptores afford the requisite adjust- ment in this case. For, although the nature of the food is the same in the Owl* as in the Hawk, yet the differences of habit of life call for corresponding differences in the mechanism for its assimilation. In the Rasorial Order t where the nature of the food differs so widely from that of the Birds of Prey, the principal modification of the digestive apparatus obtains in the more complex structure of the crop, proventriculus, and above all the gizzard ; but with respect to the cceca, as great differences obtain in their development as in the Raptores. Now these differences are explicable on the same prin- ciple as has just been applied towards the elucidation of the differences in the size of the cceca in the Raptores. Where the difference in the locomotive powers is so great in the Dove-tribe and the common Fowl ; where the circulating and respiratory systems must be so actively exercised to enable the Pigeon to take its daily flights and in some species their an- nual migrations — a less complicated intestinal canal may naturally be supposed with such increased energy in the animal and vital func- tions to do the business of digestion, than in the more sluggish and terrestrial vegetable feeders ; and accordingly we find that the requisite complexity of the intestinal canal is obtained by an increased development of the ccecal processes in them, while in the Colum- bidce the cceca remain as little developed as in the Insessores, which they resemble in powers of flight. If we regard the coeca as excretive organs, their differences in the above orders may be in like manner explained by their relations to the locomotive and respiratory functions. In the Cursores the development of cceca seems to have reference to the quantity of food, and the ease with which it may be obtained, according to the geographical position of the species. In the Cassowary, which is a native * The indigestible parts of the prey of the Owl do not pass into the intestine, but are regularly cast or regurgitated from the stomach ; the length of the coeca cannot, therefore, be accounted for on Macartney's supposition of their being receivers of those parts. AVES. 325 of the fertile districts of a tropical country, ve- getable food of a more easily digestible nature may be selected, and it need not be detained un- necessarily long, where a fresh supply can be so readily procured. But in the Ostrich, which dwells amidst arid sands and barren deserts, every contrivance has been adopted in the struc- ture of the digestive apparatus to extract the whole of the nutritious matter of the food which is swallowed. In the Grallatores, where no material dif- ferences of locomotive powers or means of obtaining food exist, the cceca present in their development a direct relation to the nature of the food, and are most developed in the Gruklce. The same holds good in the Natatores. Why the increased extent of intestinal sur- face in the above different cases should be chiefly obtained by the elongation of the cceca, will appear from the following considerations. In consequence of the stones and other foreign bodies which birds swallow, it is necessary that there should be a free passage for these through the intestinal canal, which is therefore generally short and of pretty uniform diameter. In the Omnivorous birds of the tropics, as theHornbills, Toucans, Touracos, and Parrots, which dwell among ever-bearing fruit-trees, the rapid pas- sage of the food is not inconsistent with the extraction of a due supply of nourishment, but is compensated by the unfailing abundance of the supply. But where a greater quantity of the chyle is to be extracted from the food, and where, from the nature of the latter, a greater proportion of foreign substances is required for its tritura- tion,— while the advantages of a short intestinal tract are obtained, the chyme is at the same time prevented from being prematurely expelled by the superaddition of the two ccecal bags which communicate with the intestines by orifices that are too small to admit pebbles or undigested seeds, but which allow the chyme to pass in. Here, therefore, it is detained, and chylification assisted by the secretion of the ccecal parietes, and the due proportion of nutri- ment extracted. The large intestine is seldom more than a tenth part of the length of the body, and, except in the Ostrich and Bustard, is continued straight from the cceca to the cloaca ; it may therefore be termed the rectum rather than the colon. It is usually wider than the small in- testine, and its villi are coarser, shorter, and less numerous. The rectum ( a, Jig. 1 64) terminates by a valvular circular orifice (b), in a more or less dilated cavity, which is the remains of the allantois, and now forms a rudimental urinary bladder, (c d). The ureters {h h), and efferent parts of the generative ap- paratus (J", g,) open into a transverse groove at the lower part of the urinary dilatation, and beyond this is the external cavity which lodges, as in the Reptiles and Marsupial and Monotrematous Quadrupeds, the anal glands and the exciting organs of generation. The anal follicles in Birds are lodged in a conical glan- dular cavity, which communicates with the pos- terior part of the outer compartment of the cloaca, and has obtained from its discoverer the name of Bursa Fabricji (k). Derthold considers tlris part as a subdivision of the urinary bladder in Birds, and Geoffroy St. Ililaire as the analogue of Cowper's glands. Cloaca of the Condor. Digestive glands. — The liver is large in Birds, and proportionally larger in the Aquatic species than in Birds of Prey. In the former Posterior mew of the biliary and pancreatic due in the Hornbill. 326 AVES. it bears a proportion of one-tenth, in some of the latter of one-tvventy-ninth part of the entire body. The liver (m m, fig- 163,165) is situated a little above the middle of the thoracic-abdo- minal cavity, with its convex surface towards the abdominal parietes,and its concavity turned towards the subjacent viscera : the right lobe covers the duodenum, pancreas, and part of the small intestines ; the left lobe covers the pro- ventriculus and part of the gizzard ; and the apex of the heart is received between the upper ends of these principal lobes. The liver is, as it were, moulded upon all these parts, and pre- sents corresponding depressions where it comes in contact with them. It is generally divided into two nearly equal lobes, which are often separated for a short extent, and connected together by a narrow isthmus of the glandular substance. In some birds, however, as in the Pigeon, Cormorant, Swan, and Goose, there is a third, smaller lohe, situated at the back of the liver between the lateral lobes, which from its situ- ation appears analogous to the lobulus Spigelii of Mammalia. In the Common Fowl the left lobe is occasionally cleft so deeply as to form two lobes on that side. In some species the right lobe exceeds the left in size ; this is most remarkable in the Bustard, in which the right lobe extends into the pelvis. In the Eagle, however, the left lobe has been observed to be the largest. Each lobe is invested by a double membranous tunic, one embracing it closely, the other surrounding it loosely, like the peri- cardium of the heart. They are formed by laminae of the peritoneum, which seems to split at the exterior thin edge of the liver into four layers, two being continued upon the anterior and posterior surfaces adhering to them, the other two forming the loose exterior cap- sule. The principal ligament of the liver is formed by a large and strong duplicature of the peri- toneum, which divides the abdomen longitu- dinally like the thoracic mediastinum in Mam- malia. It is reflected from the linea alba and middle line of the sternum upon the pericar- dium, and passes deeply into the interspace of the lobes of the liver ; it is attached to these lobes through their whole extent, and connects them below to the gizzard on one side and to the duodenal fold on the other: the lateral and posterior parts of the liver are attached to the contiguous air-cells ; and the whole viscus is thus kept steady in its situation during the rapid and violent movements of the bird. The ligament first described is analogous to the fal- ciform ligament of Mammalia; and, although there is no free margin inclosing a round liga- ment, yet the remains of the umbilical vein may be traced within the duplicature of the membranes forming the septum. As the mus- cular septum between the thorax and abdomen is wanting, there is consequently no coronary ligament; but the numerous membranous pro- cesses which pass from the liver to the sur- rounding parts amply compensate for its ab- sence. The liver is of a lighter colour in Birds of flight than in the heavier Water-fowl. Each lobe has its hepatic artery and vena porta?. The hepatic arteries are proportionally small, but the portal veins are of great size, being formed not only by the veins of the intestinal canal, pancreas, and spleen, but also by the inferior emulgent and sacral veins. The blood, which has circulated in the liver, is returned to the inferior cava by two venae hepaticae. There are occasionally some smaller hepatic veins in addition to the two principal ones. The coats of the portal and hepatic veins ap- pear to be equally attached to the substance of the liver. The biliary secretion is carried oat of the liver by two and sometimes three ducts ; one of these terminates directly in the intestine, and is a 'he- patic duct ' n,fig. 165); the other enters the gall-bladder, and is a ' cyst-hepatic duct ' (o',fig. 165); the cystic bile is conveyed to the duo- denum by a ' cystic duct ' ( o, fig 165). Where, as in a few instances, the gall-bladder does not exist, both hepatic ducts terminate separately in the duodenum (n, n, fig. 163); but in no case is there a single ductus communis cho- ledochus as in Mammalia. The gall-bladder ( p, fig. 1 65) is situated near the mesial edge of the concave or under side of the right lobe, and is commonly lodged in a shallow depression of the liver; but some- times, as in the Eagle, Bustard, and Cormorant, only a very small part of the bag is attached to the liver. It lias the same structure as in Mamma- lia, manifesting no visible muscular tunic, and having its inner surface delicately reticulated. The gall-bladder is present in all the Rap- tores, lnsessores, and Natatores. It is want- ing in a great proportion of the Scansores, as in the Genus Rhamphastos and in the whole of the Psittacidcc and Cuculida. Among the Rasores the gall-bladder is constantly deficient in the Columbid/e or Dove-tribe alone, in which the coeca are shorter than in any other vege- table feeder: (n n, fig. 163, are the two he- patic ducts terminating apart from one another in the Pigeon.) The gall-bladder is occasion- ally absent, according to the French Acade- micians, in the Guinea-fowl; and they also found it wanting in two out of six Demoi- selles ( Anthropoides Virgo ). The gall-blad- der is small and sometimes absent in the Bittern: it is always wanting in the Ostrich. The bile, as before observed, passes directly into the gall-bladder, and not by regurgitation from a ductus choledochus ; the cyst-hepatic duct arises from the right lobe, and is con- tinued in some birds along that side of the bag which is in contact with the liver, where it penetrates the coats of the cyst and terminates about one-third from the lower or posterior end. In the Horn-bill we found it passing over the upper end of the bladder to the anterior or free surface, and the cystic duct continued from the point where the cyst-hepatic duct opened into the bladder ; so that the cystic duct had a communicaton both with the reservoir and the cyst-hepatic duct; being somewhat ana- logous to the ductus communis choledochus; AVES. 327 (see fig. 165, wliere x represents the orifice by which the bile passes both in and out of the gall-bladder.) In the Goose the cyst-hepatic duct termi- nates by a very small orifice, surrounded by a smooth projection of the inner mem- brane, which, aided by the obliquity of die duct, acts as a valve and prevents any re- gurgitation towards the liver. The cystic duct here passes abruptly from the posterior ex- tremity of the gall-bladder, which is not pro- longed into a neck. The duct makes a turn round the end of the bag, and is so closely ap- plied to it, as to require a careful examination to determine the true place of its commencement. The hepatic duct ( n, Jig. 165) arises by two branches from the large lateral lobes of the liver, which unite in the fissure or ' gates' of the gland. Two hepatic ducts have been found in the Curassow ; but these and the cystic duct terminate separately in the duodenum. The place of termination of the cystic and hepatic duct is generally, as shown in Jig. 163 and 165, pretty close together at the end of the fold of the duodenum ; but in the Ostrich one of the hepatic ducts, which is very large and short, terminates in the commencement of the duodenum about an inch from the pylorus; while the other enters with the pancreatic duct at the termination of the duodenum. Both the cystic and hepatic ducts undergo a slight thickening in their coats just before their termination ; and it is remarkable that, in some of the Marsupiata, as the Kangaroo, the termination of the ductus choledochus is si- milarly thickened and glandular. The passage of the bile-ducts in birds through the coats of the intestine is oblique, as in the Mam- malia, and they terminate upon a valvular prominence of the lining membrane of the gut. The Pancreas (q, q, Jig. 163, 165) consists of two and sometimes of three distinct por- tions in Birds ; but these are so closely ap- plied together at some point of their surface as to appear like one continuous gland. It is of a narrow, elongated, trihedral form, lodged in the interspace of the duodenal fold, and generally folded upon itself like the duodenum, as in the Hornbill (Jig. 165). The structure of the pancreas is conglome- rate, like that of the salivary glands, but the ultimate follicles are differently disposed. In the salivary glands these are irregularly branched, while those of the pancreas in Birds diverge in the same plane from digitated and pinnatifid groups.* The ducts ( r r, Jig. 163, 165) formed by the reiterated union of the efferent branches from the component follicles of the pancreas are in general two in number, which terminate separately in close proximity to the hepatic and cystic ducts ; but occasionally there are three pancreatic ducts, as in the common Fowl, Pigeon, Raven, and Horn-bill ; in which case the third duct commonly terminates at a dis- tance from the other two : in the Horn-bill it proceeds from an enlarged lobe of the pan- * Miiller dc Gland. Struct. Pen. fol. p. 66. creas at the end of the duodenal fold, and entering that part, as at r, Jig. 165. The Spleen ( s, s, Jig. 163, 165) is compara- tively of small size in Birds; it is generally of a round or oval figure, but sometimes presents an elongated and vermiform shape, as in the Sea-Gull, or is broad and flat as in the Cor- morant. It is situated beneath the liver, on the right side of the proventriculus. It is, however, somewhat loosely connected to the surrounding parts, so that its position has been differently described by different authors. We have generally been able to trace a pro- cess of the pancreas passing into close contact with it, and connected to it by a continuation of vessels, as in the Horn-bill (Jig. 165, q, s), where it has been turned aside to show the hepatic and pancreatic ducts. The texture of the spleen is much closer in Birds than in Mammalia; but a minute examination proves that the blood of the splenic artery is ulti- mately deposited in cells, from which the splenic veins arise. These veins in the Swan and some other Lamellirostres form a network on the exterior surface of the spleen, as in the Chelonian Reptiles. Absorbents. — The presumed absence of ab- sorbent vessels in the Oviparous Vertebrata was cited by the supporters of the theory of venous absorption in the time of William Hunter as strong evidence in favour of their views ; and the same assertion has again been repeated in the present day by Majendie,* who, in sub- sequently admittingt the existence of lympha- tics in Birds, still contends against their being the exclusive instruments of the function of absorption. Traces of the lymphatic system in the pre- sent class appear to have been observed by Swammerdam| as early as 1676, who sent his preparation ' Lymphaticum peculiare ex ab- domine Gallinee' to the Royal Society of Lon- don ; the lacteals were afterwards noticed in the Stork by Jacobasus§ in 1677, and traces of lymphatics are described by Lang|| in 1704, and by Martin Lister^ in 1711. Lymphatic vessels and glands, however, considered as such, according to the Hunterian doctrine of absorption, were first undoubtedly seen by John Hunter in the neck of a Swan, and the lac- teals of Birds were afterwards re-discovered by Hewson, who made the first attempt to give a detailed account of the absorbent system in Birds. Our knowledge of this system has since been greatly enlarged by the labours of Tiedemann,** Fohmann,-t-f Lauth,|J and Panizza.§§ * Journal de Physiol, torn. i. p. 47. t Annates des Sciences Nat. iii. p. 410. X Hirch, Hist, of the Royal Society, iii. p. 312, § Anat. Ciconia? in Acta Hafn. v. p. 247. j| Physiologia Lips. fol. p. 99. •jf Dissertatio de Humoribus, 1711, 8vo. p. 228. ** Anat. und Naturgeschichte der Vbgel, torn. i. p. 533. tf Anat. Untersuchungen liber die Verbindung der Saugadcrn mit den Venen, 1821, p. 136. t% Annales des Sciences Nat. iii. p. 381. Osservazione Antropo-Zootomico Fisiologiche, fol.Pavia, 1830. 326 AVES. The species in which the absorbent system has been investigated are the Buzzard, Wood- pecker, Turkey, Common Fowl, Bittern, He- ron, Stork, Duck, Swan, Wild and Tame Goose, but especially in the latter. The absorbents of Birds differ from those of Mammals in having fewer valves, which are also less perfect, being so loose as fre- quently to permit for a certain extent a retro- grade passage of the injected fluid. The lacteals, lymphatics, and thoracic ducts have very thin parietes, so as easily to be ruptured, but they are composed, as in Mammals, of two tunics, of which the internal is the weakest. The lymph resembles that of Mammals, but the chyle differs essentially in its trans- parency and want of colour. The lacteals have, however, been observed to contain an opake white fluid in a Woodpecker that had been killed after swallowing a quantity of ants. With respect to the disposition of the ab- sorbents, they do not form in Birds two strata, as in Mammals ; at least those only have been observed which correspond to the deep-seated absorbents which accompany the large vessels. The lymphatic glands or ganglions are also much less numerous in Birds than Mammals, being in the former generally restricted in their position to the anterior part of the chest or the root of the neck. In the Penguin, however, a femoral and two axillary absorbent glands have recently been described.* They have the same structure as in Man, but are softer. In other parts of the body the absorbent glands are replaced by plexuses of lymphatic vessels surrounding the principal bloodvessels. It frequently hap- pens, as in Mammalia, that two large absor- bents form by their union a trunk, which is of smaller diameter than either of the vessels composing it. The absorbents of Birds terminate principally by two thoracic ducts, one on either side, which enter the jugular veins by several orifices. But besides these communications, Tiedemann, Fohman, Lauth, and Lippi state that the lym- phatic plexuses of the posterior part of the body communicate with the contiguous sacial and renal veins. And Lauth describes several intercommunications in other parts of the body; these, however, are denied by Panizza, whose careful and elaborate researches seem to prove that the passage of the lymph into the venous system takes place in Birds only in two places in the pelvic region in addition to those by the two thoracic ducts in the neck. The lymphatics of the foot unite to form the vessels which are found running along the sides of each toe (1, 1,fg- 166). In the Pal- mipedes there are anastomosing branches which pass from the lateral vessel of one toe to that of the adjoining toe, forming arches in the uniting web (2). These branches form a small plexus (3) at the anterior part of the digito- metatarsal joint, from which three or four lymphatics are continued. The anterior and internal branches (4) accompany the blood- vessels, and form a network around them ; the posterior and external branches (5) receive * Reid, in Proceedings of Zool. Soc, Sept. 1835. Fig. 166. Absorle?its of a QooseJ* the lymphatics of the sole of the foot, then ascend along the metatarsus, and form at its proximal articulation a close network (6) ; all the vessels then ascend the tibia, forming a plexus (7) around it as far as the middle of the leg ; then they unite into two branches, of which the smaller passes along the anterior part of the depression between the tibia and fibula as far as the knee-joint, where it joins the other branch which accompanies the blood- vessels. The trunk formed by the union of the two preceding branches accompanies the femoral vessels, forming plexuses in its course * From Lauth's Monograph, Annales dcs Sciences Nat. t. iii. pis. 23 and 25. AVES. 329 (8), which receive tributary absorbents from the surrounding muscles, and a large branch (9) corresponding to the deep-seated femoral vessels. The iliac trunk (10) accompanies the great femoral vein into the abdomen, which it enters anterior to the origin of the pubis; it there receives branches from the lateral parts of the pelvis (11) and afterwards separates into two divisions. The posterior division receives some lym- phatics from the anterior lobes of the kidneys, and those of the ovary or testicles; it com- municates anteriorly with a branch from the absorbents which surround the great mesenteric artery, and posteriorly with large vesicular plexuses or receptacles (12, 13) surrounding the aorta and its branches, arid which receives the lymphatics from the renal plexus, and those accompanying the arteria sacra media (14). The sacral or pelvic plexiform vesicles of the lymph are described by Panizza in the Goose as being two in number, situated in the posterior region of the body, in the angle between the tail and the thigh. Each vesicle is little more than half an inch long and a quarter of an inch broad, and is shaped some- what like a kidney-bean. Panizza laid them bare in several living Geese and punctured them, upon which the lymph issued in con- siderable quantity, and coagulated into a jelly like the lymph from ordinary lymphatics. Fluids thrown into the lymphatics leading to the vesicles not only filled these cavities, but passed from them into the veins. There are analogous vesicles in the Reptiles, which are endowed with a pulsatile power, and propel their contents into the pelvic veins per saltum ; but the recent researches of Muller (Archiv. Fur Physiol. 1834, p. 300) show that the pelvic lymphatic vesicles of Birds are not endowed with a power of motion like that belonging to those of Reptiles, he having satisfied himself, by repeated examination of the living Goose, that the alternate contraction and dilatation of these vesicles in this animal, which Panizza conceived to depend on an automatic power within them, corresponds exactly with the motions of respiration, and no longer continues when they are interrupted.* The anterior division of the femoral lym- phatic trunk (1G) accompanies the aorta, upon which it forms a plexus with the branch of the opposite side, and with the intestinal ab- sorbents (15). These vessels, which from the transparency of their contents can scarcely be termed with propriety ' lacteals,' commence from a plexi- form continuous network situated between the mucous and muscular coats of the intestine; they are larger here than when they quit the intestine to pass upon the mesentery. They accompany the branches of the superior mesen- teric artery, there being many absorbents for one artery, which by their anastomoses form plexuses surrounding the bloodvessels. Before reaching the aorta, these absorbents commu- nicate with the inferior or posterior division of * See Allen Thompson, in Edinb. Med. and Surg. Journ. No. 125. the femoral trunk, and with the absorbents of the ovary or testicles, after which they pass upon the aorta (16, 17), where they receive the lymphatics of the pancreas and duodenum, and terminate by uniting around the cceliac axis (18) with the lymphatics of the liver, the proventriculus (c), the gizzard, and the spleen, forming a considerable plexus, from which, according to Lauth, it is by no means rare to see branches passing to terminate in the surrounding veins. The aortic plexus (19), which may be regarded as analogous to the receptaculum chyli, always gives origin to two thoracic ducts (20, 20) of varying calibre, but often, as in the Goose, exceeding a line in diameter. They are situated at their origin behind the oeso- phagus () crosses z 2 840 AVES. the fore-arm, just below the articulation in company with the nerve, and running along the inferior edge of the ulna, receives a branch from between the basis of each quill, is con- tinued along the ligament which sustains the rest of the quills to the extremity of the wing, receiving many veins of the joints from the opposite side of the 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 (q). " The inferior vena cava (k), before it enters the auricle (a), receives as usual the hepatic veins (s) ; these are numerous, and open into the cava as it passes behind the liver, or more frequently within the substance of that viscus in the back part. We have reckoned in the Cock two large and two small hepatic veins from the right lobe, and one large branch from the left lobe, besides six minute veins, which came indifferently from both lobes. " The trunk of the vena cava is very short in the abdomen ; it separates into two great branches analogous to the primary iliac veins (t), opposite to the renal capsules ; these turn to each side, and experience a very singular dis- tribution. On coming near the edge of the pelvis each of these two veins forms two branches ; one of which collects the blood of the lower extremity, as hereafter described ; the other passes straight downwards imbedded in the substance of the kidney, and admits the several emulgent veins, which are very large, and are seen to pass for some way obliquely in the kidney before their termination. Some- times the emulgent veins are double, as in the figure, (it). The descending branch of the iliac also receives the ovarian veins, and when arrived at the lower end of the kidney, divides into three branches ; one transmits the blood of the muscles of the tail and parts adjacent; another accom- panies the ureter to the side of the rectum, and is distributed about the anus and parts of gene- ration, answering to the hemorrhoidal veins; the third (v,v) passes inwards to the middle line between the kidneys, and there unites with the corresponding branch of the opposite side.* The vessel which is in this manner produced (z) receives all the blood of the rectum from the anus to the origin of the coeca, anastomosing below with the branches of the haemorrhoidal veins ; and at the upper part of the rectum, it becomes continuous with the trunk of the veins of the small intestines (.r), forming the most remarkable anastomosis in the body, both on account of its consequences and the size of the vessels by which it is effected. By means of diis communication, the blood of the viscera and the external parts of the body flows al- most indifferently into the vena cava and vena porta? (w) ; for the anastomosing vessels are suf- ficiently large to admit the ready passage of a considerable column of blood in proportion to the whole mass which circulates in the body * It is these branches which Professor Jacobson supposes to carry venous blood into the kidneys, for the purpose of supplying material for the uri- nary secretion. of the bird ; for instance, in the Goose the com- municating veins of the pelvis are equal in size to a goose-quill, and in the Ostrich and Cassowary they are as thick as a finger. The advantage which appears to result from this remarkable union of vessels, is the prevention of congestion, or the overloading either the heart or liver with blood, as the one organ has the power of relieving the other. It would seem from this, as well as several other pro- visions of the same kind, that the circulation would be more liable to obstruction in birds than other animals.* It is difficult to say, how- ever, to what cause such an effect ought to be ascribed. Is it from the compression sus- tained by the heart and other viscera, by means of the air-cells during respiration ? or, is the mode of progression by flight capable of impeding the motion of the blood ? " The anastomosis of the pelvic veins, in being the means of conveying common venous blood into the liver, goes to prove that the blood of the vena portae does not require any peculiar preparation by circulation in the spleen or other viscera, which has been conceived as necessary by some physiologists to tit it for the secretion of bile. " The vena port cb (w) belongs almost exclu- sively to the right or principal lobe of the liver. It is formed by three branches. The splenic vein is the smallest, and is added to the vena portae, just as it penetrates the liver on the side of the hepatic duct. The next is made of two branches; of which one returns the blood of the posterior gastric artery, and therefore may be called the posterior gastric vein ; and the other is furnished by the pancreas and duode- num, and therefore is the pancreatic vein. The third and largest branch of the vena portae is the mesenteric vein (x), which not only collects the blood from all the small intestines, but likewise receives the injerior mesenteric (z), or vein of the rectum, which forms the com- munication that has been described with the pelvic veins. " The veins of the left lobe of the liver are furnished in the goose by those which accom- any the anterior gastric artery, and some ranches from the head of the duodenum. " The anterior gastric veins produce two small trunks, which enter at the two extremities of the fissure, in the concave surface of the left lobe of the liver, as it lies upon the edge of the gizzard ; the veins from the head of the duodenum furnish a small vessel which passes backwards to penetrate the posterior part of the fissure in the left lobe. " In the cock the veins that the left lobe of the liver derives from the anterior gastric, are more numerous than in the goose. " The veins of the zone of gastric glands, and of the lower portion of the oesophagus, do not * Besides their anastomoses the principal vis- ceral veins are remarkable for their large size in the Diving Birds. Cuvier (Lecons d'Anat. Comp. iv. p. 274) has especially noticed the dilatation of the inferior cava of the Grebes ( Colymbus ), which reservoir he compares with that formed by the hepatic veins in the Seal. AVES. 341 contribute to the secretory vessels of the liver, but proceed to the superior part of that viscus, to terminate in the vena cava, as does also the umbilical vein. " The vein which returns the blood of the inferior extremities is divided in the pelvis into two branches, which correspond with the femoral and ischiadic arteries ; the one passes through the ischiadic foramen, and the other through the hole upon the anterior margin of the pelvis; but the proportion they bear to each other in magnitude is the very reverse of what occurs in the arteries ; for the anterior vein is the principal one, whilst the other is not a very considerable vessel, and receives its supply of blood from the muscles at the pos- terior part of the joint. " The femoral vein {a a), immediately without the pelvis, gives branches on both sides, which receive the blood of the extensor and adductor muscles at their superior part : the trunk passes obliquely under the accessory muscle of the flexor digitorum, and over the os femoris, where itliessuperricially ; itthen winds underthe adductor muscles, and gets into the ham (b b), where it receives many muscular branches, and comes into company with the artery and nerve. It here divides into the tibial (c c) and peroneal veins. The first is joined by some branches from the surface of the joint answer- ing to the articular arteries; it also receives the anterior tibial vein which accompanies the artery of the same name. The tibial vein pro- ceeds down the leg along with the artery on the inside of the deep-seated flexors of the heel : it turns over the fore part of the articu- lation of the tibia with the metatarsal bone, in order to get upon the inner side of the me- tatarsus ; above the origin of the pollex, it receives a communicating branch from the peroneal vein, and immediately after two branches from the toes : one of them comes from the inside of the internal toe ; the other arises from the inside of the external and mid- dle toes, unites at the root of the toes in the sole of the foot, and is joined by a branch from the pollex, before its termination in the internal vein of the metatarsus. " The peroneal vein derives its principal branches along with those of the peroneal artery, from the muscles on the outside of the leg. The trunk of the vein comes out from the peroneal muscles, and passes superficially over the joint at the heel, and along the outside of the metatarsus ; near the pollex, or great toe, it sends a branch rourftl the back of the leg, to communicate with the tibial vein ; after which it is continued upon the outside of the external toe to the extremity, receiving anas- tomosing branches from the tibial vein. " Where the veins run superficially upon the upper and lower extremities, they seem to supply the place of the branches of the cepha- lic, basilic, and the two saphc.na ; but the analogy is lost upon the upper arm and thigh, these branches forming deep-seated trunks; this constitutes the greatest peculiarity in the distribution of the veins in the extremities of birds.'' Respiratory organs. — In the course of this article we have frequently had occasion to allude to the extent and activity of the respiratory func- tion in the Class of Birds ;* nevertheless the organs subservient to this function manifest more of the peculiarities of the Reptilian than of the Mammalian type of formation. The lungs are confined, as in the Tortoise, to the back part of the thoracic-abdominal cavity, being firmly attached to the ribs and their interspaces ; and, as in the Serpent, they communicate with large membranous cells which extend into the abdomen and serve as reservoirs of air. In those aquatic Birds, which are deprived of the power of flight, as the Penguins, the air receptacles are confined to the abdomen ; but in the rest of the class they extend along the sides of the neck, and, escaping at the chest and pelvis, accompany the muscles of the extre- mities. They also penetrate the medullary cavities and diploe of the bones, extending in different species through different proportions of the osseous system, until in some birds, as the Horn-bill, every bone of the skeleton is permeated by air. There is, indeed, no class of Animals which are so thoroughly penetrated by the me- dium in which they live and move as that of Birds. The lungs (w, Jig. 172) are two in number, of a lengthened, flattened,oval shape, extending along each side of the spine from the second dorsal vertebra to the kidneys, and laterally to the junc- tion of the vertebral with the sternal ribs. They are not suspended freely as in Mammalia, but are 1 confined to the back part! of the chest by cellular membrane,and the pleura is reflected over the sternal surface only, to which the strong aponeurosis of the S diaphragmatic muscles is attached. They are con- sequently smooth and even on the anterior m9ht lun9 °f a Goose. surface, but posteriorly are accurately moulded to the inequalities of the ribs and intercostal spaces. The lungs in general are of a bright red colour, and of a loose spongy texture. The bronchi (u,fig. 163; a, Jig. 172) penetrate their mesial and anterior surfaces about one-third from the upper extremities; they divide into four, five, or six branches, which diverge as they run along the anterior surface ; some in- complete cartilaginous rings are found through their entire extent. The orifices of the air-cells of the lungs (c c, Jig. 172) open upon the posterior parietes of the bronchial tubes, while the extremities of these tubes terminate by wide openings {b b, Jig. 172) in the thoracic and abdominal air- receptacles. These orifices are oblique, and * .According to Lavoisier, two Sparrows consume as much oxygen in a given lime as one Guinea-pig. 342 AVES. are partially covered by a slight projection of membrane. The pulmonary artery divides, almost im- mediately after its origin, into two branches, one to each lung; the ramifications of each artery form plexuses upon the air-cells, and freely anastomose with the pulmonary veins ; these leave the lung by a single trunk, and the two pulmonary veins unite into one belore terminating in the left auricle. The thoracic-abdominal cavity is subdivided and intersected by a number of membranes ; the greater part of the cells thus formed are filled with air. The texture of their parietes possesses considerable firmness in the larger birds, as the Ostrich and Cassowary, in which they were described by the French Academi- cians as so many distinct bags. The innermost layer of the air-receptacles can be separated from the outer layer, and is a continuation of the lining membrane of the bronchial tube; the outer layer is a serous membrane, and appears to form the cells by a series of reflections of what may be regarded as the pleura or peritoneum. These large membranous receptacles into which the extremities of the bronchial tubes open are disposed with sufficient general regu- larity to admit of a definite description and nomenclature. Fig. 173. Air- receptacles of a Swan. The first or inter-clavicular air-cell (a, Jig. 173) extends from the anterior part of each lung, forwards to the interspace of the fur- culum, anterior to which it dilates in the Gannet and many other birds into a large globular receptacle. In the Vultures it is di- vided into two lateral receptacles, between which the large crop is situated. A thin fan- shaped muscle is extended from the anterior edge of the furculum, over the interclavicular air-cell in these and some other birds The anterior thoracic cell (6) contains the lower larynx and bronchi, and the great vessels with their primary branches to the head and wings. It is traversed by numerous mem- branous septa, which connect the different vessels together, and maintain them in their situations. The air passes into the posterior part of this receptacle by two openings at the anterior part of the lungs. The deep-seated air-cells of the neck are continued from it anteriorly. The lateral thoracic cells (d) are continued on each side from a foramen on the inner edge of the lung, situated just opposite the base of the heart ; they are covered by the anterior tho- racic air-cell, and from them the air passes into the axillary and subscapular cells, into those of the wing, and into the humerus (e). They also communicate with the cellula cordis posterior (c), behind the heart and bronchi, which cell is often subdivided into several small ones. The cellula hepatica are of much larger size ; they are two in number, of a pyramidal figure, with their bases applied to the lateral thoracic cells, and their apices reaching to the pelvis : they cover the lower portions of the lungs and the lobes of the liver ; they receive air from several foramina situated near and at the external edge of the lungs. The cellula abdominales commence be- neath the cellulae hepatica? at the inferior ex- tremity of the lungs, where the longest branches of the bronchia open freely into them. (A bristle is passed through one of these openings in the figure.) They are distinguished into right (f) and left (h) ; the former is gene- rally the largest receptacle in the body; it ex- tends from the last ribs to the anus, and covers the greater part of the small intestines, the supra-renal gland, and kidney of the same side. The left abdominal cell (A) contains the intestines of its own side, and is attached to the gizzard. In some large Birds, as the Gannet, it is separated from the right recep- tacle by a mediastinal membrane {g) which is continued from the gizzard to the anus. Both the abdominal receptacles transmit air to the pelvic cells (i, k) of their respec- tive sides, and to several small and extremely delicate cells between and behind the coils of intestine. One of these is continued round the fold of the duodenum and pancreas to the gizzard, and has been termed the duodenal cell. From the inguinal cell are continued the in- termuscular glutaal and femoral cells, which surround the head of the femur, and commu- cate with that bone by an aperture (/) situated AVES. 343 immediately anterior to the great trochanter, except in those Birds in which the femur retains its medulla. The cervical air-cells are continued from the large clavicular cell, and form in the Argala a singular appendage or pouch, contained in a loose fold of integument, which the bird can inflate at pleasure. In the Pelecan and Gannet extensive air- cells are situated beneath almost the whole of the integument of the body, which is united to the subjacent muscles only here and there by the septa of the cells and the vessels and nerves which are supported by the septa in their pas- sage to the skin. The large pectoral muscles and those of the thigh present a singular ap- pearance, being, as it were, cleanly dissected on every side, having the air-cavities above and beneath them. The axillary vessels and nerves are also seen passing bare and unsupported by any surrounding substance through these cavi- ties. Numerous strips of panniculus carnosus pass from various parts of the surface of the muscles to be firmly attached to the skin ; a beautiful fan-shaped muscle is spread over the inter-clavicular or furcular air-cell. The use of these muscles appears to be to produce a rapid collapse of the superficial air-cells, and an expulsion of the air, when the bird is about to descend, in order to increase its specific gravity, and enable it to dart with rapidity upon a living prey. The air-receptacles of the thoracic-abdominal cavity present varieties in their relative sizes and modes of attachment in different birds. In the Raptores they are principally attached pos- teriorly to the ribs, the diaphragmatic aponeu- rosis covering the lungs, and to the kidneys ; while in the Grallatores they have anterior attachments to the intestines in many places. The singular extension of the respiratory into the osseous system was discovered almost simultaneously by Hunter and Camper, and ably investigated by them through the whole class of Birds. The air-cells and lungs can be inflated from the bones, and Mr. Hunter injected the medullary cavities of the bones from the trachea. It is stated that if the femur into which the air is admitted be broken, the bird shall not be able to raise itself in flight. It is certain that if the trachea be tied, and an opening be made into the humerus, the bird will respire by that opening for a short period, and may be killed by inhaling noxious gases through it.* If an air-bone of a living bird, similarly perforated, be held in water, bubbles will rise from it, and a motion of the contained * " I cut the wing through the os humeri in a Fowl, and tying up the trachea found that the air passed to and from the lungs by the canal in this bone. The same experiment was made with the os femoris of a young Hawk, and was attended with a similar result. But the passage of air through the divided parts, in both these experiments, espe- cially in the last, was attended with more difficulty than in the former one ; it was indeed so great, as to render it impossible for the animal to live longer than evidently to prove that it breathed through the cut bone."— Hunter's Animal (Economy, p. 94. air will be exhibited, synchronous with the motions of inspiration and expiration. The proportion in which the skeleton is permeated by air varies in different Birds. In the Penguin ( Aptenodytes), which we have examined for this purpose, air is not admitted into any of thebones. Its chief progression being in water, the specific levity of the body gained by the substitution of air for marrow would be rather a detriment than an advantage. The condition of the osseous system, therefore, which all birds present at the early periods of exist- ence, is here retained through life. In the large Struthious Birds, which are re- markable for the rapidity of their course, the thigh-bones and bones of the pelvis, the ver- tebral column, ribs, sternum and scapular arch, the cranium and lower jaw, have all air admitted into their cavities or cancellous struc- ture. The humeri and other bones of the wings, the tibiae and distal bones of the legs, retain their marrow. With the exception of the Woodcock, all Birds of Flight have air admitted to the humerus. The Pigeon tribe, with the exception of the Crown Pigeon, have no air in the femur, which retains its marrow. In the Owls also the femur is filled with marrow; but in the Diurnal Birds of Prey, as in almost all other Birds of Flight, the femur is filled with air. In the Pelecan and Gannet the air enters all the bones with the exception of the phalanges of the toes. In the Hornbill even these are permeated by air. Mr. Hunter* has given the following cha- racters as distinguishing the bones which receive air. They may be known — " first, by their less specific gravity ; secondly, by their retain- ing little or no oil, and, consequently, being more easily cleaned, and when cleaned, ap- pearing much whiter than common bones : thirdly, by having no marrow, or even any bloody pulpy substance in their cells ; fourthly, by not being in general so hard and firm as other bones ; and, fifthly, by the passage that allows the air to enter the bones, which can easily be perceived." We have reserved for this section the de- scription of the foramina by which the air penetrates the different bones. These openings may be readily distinguished in the recent bone, since they are not filled up by blood- vessels or nerves, but have their external edges rounded off. In the dorsal vertebrae the air-orifices are small, numerous, and irregular; situated along the sides of the bodies, and the roots of the spinous processes, the air passes into them directly from the lungs. In the two or three lower cervical vertebrae the air-holes are in the same situation, but receive the air from tho lower cervical or clavicular air-cells : in the remainder of these vertebrae the air-holes are situated within the canal lodging the vertebral artery, and communicate with the lateral air- cells of the neck. * Animal (Economy, p. 91. 344 AVES. The air-holes of the vertebral ribs are situated at the internal surface of their vertebral extre- mities, and appear like tnose of the contiguous vertebrae to have an immediate communication with the lungs. The sternal ribs, or ossified costal cartilages, have also internal cavities which receive air from the lateral thoracic cells by means of orifices placed at their sternal ex- tremities. The orifices by which air is admitted to the sternum are exceedingly numerous, but are principally situated along the mesial line of the internal surface, opposite the origin of the keel, forming a reticulation at that part; the largest foramen is near the anterior part of the bone ; some smaller ones occur at the costal margins. All these orifices commu- nicate with the thoracic air-receptacles. The scapula is perforated by several holes at the articular extremity, which admit air into its cancellous structure from the axillary cell. The coracoid has small air-holes at both ex- tremities ; the largest is situated on its inner surface, where it is connected with the clavicle or furculum. The furculum receives air principally by a small hole in the inner side of each of its scapular extremities, which communicates with the clavicular air-cell- The air-hole of the humerus is of large size, and situated at the back part of the head of the bone, below the curved inferior process. It communicates with the axillary air-cell, and transmits the air to the cavity of the bone by several cribriform foramina. The air-holes of the pelvic bones are situated irregularly on the inner surface upon which the kidneys rest, and must therefore receive air from continuations of the abdominal receptacles around the kidneys. The air-hole, or rather air-depression of the femur, is situated at the anterior part of the base of the trochanter; it receives air from the glutaal cell, and transmits it by several small foramina into the interior of the bone. In the Ostrich, the air-holes are situated at the posterior part of the bone at both of its extre- mities. The cavities of the long bones into which air is thus admitted are proportionally larger than in the corresponding bones of Mammalia, and are characterized by small transverse osseous columns which cross in different di- rections from side to side, and are more nu- merous near the extremities of the bone ; they abut against and strengthen, like cross-beams, the parietes of the bone. We have sometimes succeeded in filling with fine size-injection the minute arteries which ramify on the membrane lining these cavities, but the vascularity of this membrane is by no means very remarkable. The lower jaw receives its air by means of an orifice situated upon each ramus behind the tympano-maxillary articulation. Mr. Hunter was in doubt as to whether the lower jaw derived its supply of air from the Eustachian tube or the trachea where it passes along the neck.* In a Pelecan which we dissected for the purpose we found it to be supplied by an air-tell which surrounded the joint, and was con- tinuous with the upper cervical air-cells. The bones of the cranium and upper jaw have com- munications with the Eustachian tube, but not with the nasal passages, which are every where lined with an impervious pituitary membrane. Various explanations have been given of the final intention of the condition of the respiratory system above described. The extension of this system by means of continuous air-receptacles throughout the body is subservient to the function of respiration, not only by a change in the blood of the pulmonary circulation effected by the air of the cells on its re-passage through the bronchial tubes, but also, and more especially, by the change which the blood undergoes in the ca- pillaries of the systemic circulation, which are in contact with the air-receptacles. The free outlet to the air by the bronchial tubes does not, therefore, afford an argument against the use of the air-cells as subsidiary respiratory organs, but rather supports that opinion, since the inlet of atmospheric oxygenated air to be diffused over the body must be equally free. A second use may be ascribed to the air- cells as aiding mechanically the actions of respiration in Birds. During the act of inspi- ration the sternum is depressed, the angle between the vertebral and sternal ribs made less acute, and the thoracic cavity proportion- ally enlarged ; the air then rushes into the lungs and into the thoracic receptacles, while those of the abdomen become flaccid : when the sternum is raised or approximated towards the spine, part of the air is expelled from the lungs and thoracic cells by the trachea, and part driven into the abdominal receptacles, which are thus alternately enlarged and dimi- nished with those of the thorax. Hence the lungs, notwithstanding their fixed condition, are subject to due compression through the medium of the contiguous air-receptacles, and are affected equally and regularly by every motion of the sternum and ribs. A third use, and perhaps the one which is most closely related to the peculiar exigences of the bird, is that of rendering the whole body specifically lighter; this must necessarily follow from the dessication of the marrow and offier fluids in those spaces which are occupied by the air-cells, and by the rarefaction of the contained air from the heat of the body. Agreeably to this view of the func tion of the air-cells, it is found that the quantity of air admitted into the system is in proportion to the rapidity and continuance of the bird's motion; and that the air is especially distributed to those members which are most employed in loco- motion ; thus the air is admitted into the wing- bones of the Owl, but not into the femur; while in the Ostrich the air penetrates the femur, but not the humerus or other bones of the wing. A fourth use of the air-receptacles, which has not hitherto been suspected, relates to the * Loc. cit. p. 93. AVES. 315 mechanical assistance which they afford to the muscles of the wings. This was first suggested to us by observing that an inflation of the air- cells in a Gigantic Crane ( Ciconia Argala ) was followed by an extension of the wings, as the air found its way along the brachial and anti-brachial cells.* In large birds, therefore, which, like the Argala, hover with a sailing motion for a long-continued period in the upper regions of the air, the muscular exertion of keeping the wings outstretched will be les- sened by the tendency of the distended air-cells to maintain that condition. It is not meant to advance this as any other than a secondary and probably partial use of the air-cells. In the same light may be regarded the use as- signed to them by Hunter, of contributing to sustain the song of Birds, and to impart to it tone and strength. It is no argument against this function that the air-cells exist in birds which are not provided with the mechanism necessary to produce tuneful notes; since it was not pre- tended by Hunter that this was the exclusive and only office of the air-cells. The latest writer on this subject has indeed proposed this suggestion of Mr. Hunter as a novel idea.f Air-passages. — The air-passages in birds commence by a simple superior larynx, from which a long trachea extends to the anterior aperture of the thorax, where it divides into the two bronchi, one to each lung. At the place of its division there exists, in most birds, a complicated mechanism of bones and carti- lages moved by appropriate muscles, and constituting the true organ of voice : this part is termed the inferior larynx. The tendency to ossification, which is ex- emplified in the bony condition of the costal cartilages and tendons of the muscles, is again manifested in the framework of the larynx and the rings of the trachea, which, instead of being cartilaginous, as in Reptiles and Mam- mals, are in most birds of a bony texture. The superior larynx (fig. 151, 174, 175,) is situated behind the root of the tongue, and rests upon the uro-hyal element of the os hy- oides, to which it is attached by dense cellular texture. It is composed of several bony and cartila- ginous pieces, varying in number from four to ten. The largest of these pieces constitutes the anterior part of the larynx. It is of an oval or triangular form, according as its superior termination is more or less pointed : it is regarded by Cuvier as analogous to the anterior part of the cricoid cartilage, (Lecons d'Anat. Comp. iv. p. 489,) but by Carus it is considered as representing the thyroid cartilage (f, fig. 151). The cricoid cartilage in birds consists of the three osseous pieces, which are situated at the posterior * On relating this fact to Mr. Clift, he suggested another use of the air-cells which is more generally applicable, namely, that of assisting the actions of the muscles by compressing and bracing them, in a manner analogous to the action of the fascia? of the extremities in Man. t Jacquemin, Mcmoire stir la pneumatieite des ciseaux, 1835. and inferior part of the upper larynx ; the middle one (g,fig- 151) is of an oblong form, and varies in size, being larger than the lateral ones in the Anatid Acquired Of conformation Absence. jrality. Septa. Extrophy or extroversion. Jersislance of the urachus. /• Sacculi or cysts. \ Capacity, increase of. \ decrease of. (.Introversion. f Hernia?, inguinal. •1 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 found to terminate directly in the urethra, in others they have been inserted into the rectum, in others they have communicated with the vagina. Of the first species we have the fol- lowing examples : Lieutaud * mentions the case of a man, aged thirty-five, in whom the ureters, the capacity of which was much aug- * Hist. Anat. Med. Liber primus. Obs. 1361. femoral, •perineal, vaginal. "Inflammation with its consequences. Idiopathic softening. Rupture. Fistula?. Hamiorrhage. Fungoid tumours. Varices. LScirrhus. « Paralysis. ■'.""( Spasm. merited, 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 | 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- X Rachit. congenit. Nov. Eph. Ac. Nat. Cur„ vol. i. obs. 38. 390 BLADDER, ABNORMAL ANATOMY. scribed under the head : " Uretra in intestinum patens." Of the third species, cases are cited by Ilaller* and by Schrader.y In these cases tliere was no other malformation. In the foregoing enumeration we have purposely avoided the introduction of cases of general monstrosity in which the urinary bladder was absent. Plurality. — There are upon record a certain number of cases in which two or more urinary bladders are said to have existed. Of these some appear to me to have been cases in which the plurality was maintained merely because the organ was divided into compartments, either as a consequence of arrested develop- ment or of the formation of pouches, by the protrusion, or hernia of the mucous membrane of the organ. The following case related by Blasius belongs, I apprehend, to the former species. A person died phthisical, having a " double bladder." When the external sur- face was examined, it appeared to be an unique organ, but upon being opened a membranous septum was discovered, by which the organ was divided into two distinct cavities. The narrator adds, that by dissection he separated the one from the other, so that the longitudinal septum was formed by the parietes of the two bladders, which were in contact, and had become united the one to the other. There is a case of a similar nature described by Brom- field ; and many more are recorded by Mor- gagni and others. We know of no instance in the human sub- ject, with the exception of that related by Molinetti,J in which a plurality of urinary blad- ders distinct from each other existed. In this case there does not appear to have been any thing abnormal in the organisation except in so far as concerned the urinary organs. " A woman had five urinary bladders, as many kidneys, and six ureters, two of which were inserted into a bladder which was much larger than the others ! ! the remaining four ureters terminated in as many small bladders, which poured their urine by particular canals into the larger bladder." Another but less carefully described case of the same kind is mentioned by Fantoni, in his Anat. Corp. Hum. diss. 7; and in the Acta Physico-Medica Academia; Caesareae Nat. Curios, vol. i. obs. * Element. Physiologic, vol. vii. p. 297. t Nov. Ephem. Acad. cur. Nat. vol. i. obs. 38, et die 42, obs. 68. [The Editor has in his posses- sion the preparation of a female foetus which lived some days, where the ureters opened through the abdominal parietes on each side of the pubic region in the form of little pouches or sacs, in which was a continuation of their lining membrane. The urine, as it distilled from the kidney, accumulated in each of these sacs (in very small quantity, as they were incapable of containing more than a drop or two,) prior to its oozing out upon the raw cutaneous surface. This latter was deficient of cuticle for a surface about an inch and a half in diameter ; the pubic bones and the inferior fourth of the recti and tendinous expansions of the oblicpri were absent. There was also only about an inch of large intestine (coecum). — Ed.] Dissert. Anat. Pathol, lib. vi. cap. 7. 83, may be found a well-marked case 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. Oilaire, 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 cava?, and so on. Now if there exist two vagina;, two bladders, two uteri, at a certain epoch of embryotic life, the evolution of these organs should necessarily present three successive periods : a first, characterised by their du- 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 in man and the mammalia. We can therefore 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, 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 entire of each pouch is invested by a layer of mus- cular fibres ; in the latter, it will be found that BLADDER, ABNORMAL ANATOMY. 391 in one of the two compartments no such mus- cular investment is present. Extrophy or 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 " Iiernia" 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 fcetus, 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- * Acad, des Sciences, 1761, torn. cxiv. in 12ino. 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 tliat 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. Iluxham and Oliver and Mr. Bonnet, of a woman who lived at Lautglasse 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/}- 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 t his affection was incompatible with long life. The child of which Highmore speaks} 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,H Mowatt,'** Innes,ff and Labourdette,JJ 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,|||| Denman, Roose,^ * Phil. Transact, vol. xxiii. 1723, p. 408, 413, and vol. xxxiii. p. 142. t Hist. Anat. cent. iv. hist. 30, p. 293. i Disquis. Anat. part iv. cap. 7. § Acad, des Sciences, tome cxiv. in 12mo. p. 67. H Malattie Spettanti alia Chirurg. 1786. f Morbid Anat. p. 309. ** Mem. de Desgranges. tt Arch. Gcncr. vol. ii. p. 286. Journal de Scdillot. ^ Theses de Strasbourg, 4to. 1832. jlll Edinburgh Med. and Surg. Journal, vol. i, f % De nativo vesica urinaria: invcrs, ixc. p. 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's! 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 foetus 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 do 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. He 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 be 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 foetus 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 of 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. 393 extroversion of tlie 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 the 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 Geoffrey St. Ililaire, 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 the sex was undetermined. Ex- trophy of the bladder is a very serious af- fliction, because of the incontinence of urine which 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 Ilaller 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 Vanderuiel, vol. ii. p. 56. Bartholin, cent, ii. hist. 65, the Edinburgh Essays, vol. iii. p. 257, the Journal lincyclopediquc, August, 1756, the Journal de Medccine of Paris, t. v. p. 108, et t. xxvii. p. 26, the Memoirs of the Academy of Sci- ences of Paris, 1761, where wo find an observation of Lemery 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 ( Edinb. Med. and Surg. Jouvn. 1805), and Velpeau (Mem de l'Acad. Royalc de Med. torn, iii.) 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 dilatation 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 Konigf 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. \ ACQUIRED CHANGES. Sacculi 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 Bcaucaire in 1550. t Phil. Trans, v. 16. t Mem. de l'Acad. des Sciences, 1769. 394 BLADDER, ABNORMAL ANATOMY. 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 * Heisler. t De Seii. &c. rp. xlii. art. 18. Franco.* Since Franco, it has been described by by many others, particularly by Alexander Mon- rof and Houstet.| 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. Covillard§ 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 habita, Koenig)** novem chopines ab ischuria, La Motte;)ft 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 remarked that in calculous patients the bladder closely 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 viscus could scarcely have contained anything more. * Traite des hemics, chap. xxxi. p. 107, Lyon, 1561. t Essays and Observations of the Medical So- ciety of Edinburgh, vol. vi. p. 257. X Mem. de l'Acad. des Sciences de Paris, ann. 1702. $ Obs. 11. | Mem. de l'Acad. de Chir., t. i. p. 411. Mem. de l'Acad. des Sciences, an 1702. *" Lith. spec. Epist. 11. tl Traite. des Accouchmens, Obs. 44. if De Sed. rp. xlii. art. 20. BLADDER, ABNORMAL ANATOMY. 395 Tho bladder is also very small in cases of incontinence of urine and in vesical fistula?. 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 Mauchartf 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 % 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, Smcllie, Black, t Ephemerkk'S Acad. Nat. dir., cent. ix. obs. 41. X Traitc des Maladies des Voies Uiinaires, t. i. o. 399. Edit. 1830. $ Mem. de l'Acad. de Chir., t. ii. p. 36. 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 hernia? 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 Hernies, 1688; Mery, Mem. de l'Acad. des Sciences, 1713; Pelit, meme ouvrage, 1717; Le Dran, Garcngeot, and La Faye. Heister and Platncr, Instit. Chir. J. G. Gnnzii, Obs. an. Chir. de Hernia, Lipsix, 1744 ; Monro, Levret, Sharp, Pott, Scarpa, Lawrence, and others. + Hist. Anat., cent, xviii. 396 BLADDER, ABNORMAL ANATOMY. 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 hernias 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 vesica! 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 cantharides 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 Traite des Mai. Chir. tome ii. p. 368. BLADDER, ABNORMAL AN ATOM Y. 397 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 the 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 deatli 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. W hen 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 itself on the external surface of the bladder, or upon the interior. Sometimes it is pre- * See Baillie, Wardrop's edition, vol. ii. p. 259, and Nauche, Maladies des Voies Urinaires, p. 27. 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 llecueil 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 were 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 has 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. eit. t See Hunter, Hey, and others. 398 BLADDER, ABNORMAL ANATOMY. membrane a uniform deep red colour. More- over, dark brown or black patches are found to occupy portions of various extent of the 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, winch 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, de la Societe Anatomiquc. range the 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 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- stance, similar in appearance to that of the un- impregnated uterus; the vessels which surround the organ are dilated, varicose, and form on the external surface considerable plexuses, 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 first 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,f 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 lluid. 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 die 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 * Lib. xvii. ch. 59. t Eph. Nat. Cur. D. 11. an 11. obs. 129. t A case of the kind is detailed by M. Destrees in the Journal General de Medecine. tome lxviij. p. 206. § Med. Prat. torn. i. || Repertoire General, tome iv. part i. Faits relatifs aux lesions de la membrane muqueuse 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 maybe 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 hypogastnum, 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 fistula? 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 the bladder is sometimes established without abscess, without external inflammation. Sometimes the urine does not escape by the rectum, while fa?cal 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 fistula? 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 fistula? 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 ob- stacle to the passage of urine along the urethra. The pubic and inguinal fistula? 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, 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 body which excite the pressure of the abdo- minal muscles. In consequence of the habit which the bladder has acquired of remaining * See Van-dcr-Wiel, Littre, Tenon, and Roux. BLADDER, ABNORMAL ANATOMY. 401 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 : jet 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 anything 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 hematuria; these points appeared to him to be vascular orifices.'* 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 hema- turia, but there was no stone in the bladder. As there was no appearance of disease about the kidneys, it was attributed to the rupture of some varicose vessels in the neighbourhood of the neck of the organ. After death the bladder was found of great size, and within the trigone was a fungous rounded ulceration, six lines in diameter, surrounded with varicose veins and small fungous excrescences. Ordi- narily, however, gravel or calculi appear to be the exciting causes of this disease. * Loc. cit. tome ii. p. 52. VOL. I. 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 pediculuted 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 Glakd. 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 Lusitanus J 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 Krankheiten d. Nieren und Harnblase, 4to. Berlin, 1800, tab. Hi. f Cent. ii. obs. 65. | Prax. Med. Ader. lib. ii. obs. 71. <> Loc. cit. tome ii. p. 77. {| Diss, de Dysuria. ^ Anat. cent. ii. Hist. 52. p. 243. De Sed. pp. lxvi. ait. 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 parietes 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. Baillie, 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 hemorrhoids, 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. De 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 haemor- rhage, in fact assume somewhat of an erectile character. Scirrhus and Cancer. — Cancer primitively affecting the membranes of the bladder is an 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 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 to the accomplishment of excretion. Under many circumstances it may contract with too much force ; in a still greater number its contracti- lity is enfeebled and ultimately destroyed. Apoplexy, hemiplegia, paraplegia, concussion, * Traite des Maladies des voies utinaires, tome i. p. 466. Edit, de 1821. t Traite des Maladies des voies urinaires, 3d edit, p. 177. X Obs. sur les maladies des organes genito- urinaires, p. 8. § Traite des Mai. de la vessie et de l'uretre, trad, de H. Hollard, 1824. BLADDER, ABNORMAL ANATOMY. 403 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,! 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.|| Zuber If 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 urinaria? morbis, 4to. Argent. 1771. Adams on stone and gravel, diseases oi the bladder, &c. 8vc>. Lond. 1772. Lentin, Krankheiten der Harn- blase der Alten, in Ej. Beytrage iii. Bd. 1780. Trqja, Mali della vesica orinaiia, 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. Ital. vol. iii. et vol. v. 1780. Chopart, Des ma- * Elementa Physiologiae, art. Vesica, t Oratio de signis morborum ex corporis situ, partiumque positione patendis, Ticini, 1788. | Path. Anat. chap. xiii. § See cases related by Ploucquet, Bibl. Med. Pract. || Petri Gassendi Tychonis Brahei vita, Paris, 1654, in 4to. p. 206. H Diss, de Morbis vesicae. 2 D 2 404 BLOOD. ladies des voies urinaires, 8vo. Paris, 1791. Mac- heath 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, 1719. SJierwen on diseased and contracted urinary bladder,8vo. Lond. 1799. Walter, Einige Krankliciten der Nieren und Harnblase un- tersucht, 4to. Beil. 1800. Bell, Engravings of morbid parts, fol. Lond. 1803. Schmidt, Ueber derj. Krank. der Harnblase, &c. 8vo. Wicn.1806. Soeni- mering, Ueber tddtliclien Krankheiten der Harn- tjlase, 4to. Frit, a M. 1809. Nauclie, Des mal. de la vessie, &c. 8vo. Paris, 1810. Wudd, Cases of diseased bladder, Lond. 1815. Howship on the diseases of the urinary organs. 8vo. Lond. 1816. Coquin du 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- tharding, De hemorrhoid, vesicae, Rost. 1754 (Kec. in Haller Disp. Pathol, t. vii.). Ludwig, De ischuria ex tumoribus vesicae, 4to. Lips. 1767, in Ej. Advers. Med. vol. ii. * * * * Sahmann, De hernia vesicae urinariae, Argent. 1732 ( Kec. in Haller Di*p. Chir. t. iii.) Camper, De vesica? herniis, in Ej. Demonst. Anat. Pathol, lib. ii. Sandifort, De hernia vesica?, in Ej. Obs. Anat. Pathol, lib. i. Robse, De nativo vesicas urin. inversa; 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. Raiffer, Diss, sur la cysto- cele ou hernie de la vessie urinaire, 4to. Paris, 1805. Beugin, Diss, sur la cystocele, 4to. Paris. 1805. Issnflamm, Beschreibung, &c. angebornen, vorgefallenen, ungestiilpten Harnblase, &c. 8vo. Dorpat. 1806. Fuclis, Hist. anat. prolapsus nativi vesicas urinaria? inversa?, 4to. Jena?, 1813. * * * * Cases of double bladder, by Bordenave, in Mem. de Chirurg. t. ii. ; by Lebenwaldt, in Miscell. Acad. Mat. 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 Hcilkunde, B. 2 ; by Labourdctte , 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 Kec. Period, t. i. ; and by Cttsack, in Dub. Hosp. Rep. vol. ii. (Benjamin Phillips.) BLOOD, (Gr. al'^a.. Lat. sanguis. Ft. 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 of 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 the 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 modern 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,! 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, I have satisfied myself that they differed in size * Vide Hewson on the Hlood, and Prevost and Dumas, Examen du Sang et de son action dans les diverses phenomenes de la Vie, in Biljlioth. I'nivers. 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 jluviatilis ) 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 die 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 ^ 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 Nalurelles, torn. 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 (jij 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 315TOiWns of a line and one 367Ti5Jro5ths 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 ^^Ljihs of a line); a se- cond observation, however,gives a much smaller diameter (lSf^ths 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 SST^jjths 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-,B5j!;ths of a line in diameter, which is considerably different from our mean ; and Dr. Young did not esti- mate them at more than 16 To3rot'ls °f a bne.J It is also possible that both of these eminent individuals have measured the central nuclei of globules divested of their vesicular envelope. Tiie 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-makeis 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 lQ-jg^ths, the se- cond 5 1-nHxio tns °f a bne. From all that has gone before, then, and particularly from those researches which have been conducted under circumstances the most favourable to accurate conclusions, we may assume 'the mean diameter of the globules of the human blood to be about the Sly^jpuths, or in vulgar fractions the 5j3th 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 to the Croonian Lecture, Philos. Trans. 1818. t Loc. cit. % Youns;, Elem. of Med. literature, 8vo. Lond. 1818. BLOOD. 407 NAMES OF THE ANIMALS. REPTILIA. Testudo terrestris, L. . . Colubra berus, L. . . Anguis J'ragilis, L. . . Coluber Razomouskii . Lacerta grisea, L. . . Salamundra cincta, L. Salamandra cristata, L. Rana buf'o, L Rana esculenta, L. . Rana temporaria, L. . . PISCES. Gadus lota, L. . . . Ci/prinus phoscinus, L. Cobitis barbatula, L. Mureena anguilla, L. MAMMALIA. Man Canis familiaris, L Sus scrofa, L Mus ponellus. L Mus avellunus, L Lepus cuniculus, L Erinaceus Europeus, L Simia Subaa, L Equus asinus, L Felis catus, _L . . \ Mus musculus . . ...... S Equus caballus, L -\ Equus hybridus, L. ........ f Bos taurus, L . . i Ovis arks, L ' Antelope rupicapra, L Capra hircus, L Cervus elaphus, L. ...... A VES. Strix fiammea, L. Columba domestica, i. Didus ineptus, L. Anas boschas, L. . . Phasianus gallus, L. . Pavo cristatus, L. . . Anas anser, L. . . . Corvus corax, L. . Fringilla carduelis, L. Fringilla domestica Parus major, L. . . ] Diameter of the globules in vulgar fractions of an English line. Great diam. 1 1 500 503 5T3 Small diam: id. id. id. id. id. &3 Diameter of the globules in decimal fractions of an English line. 0,000231 0,000328 0,000335 0,000220 0,000196 0,000181 0,000104 Great diam. 0,000526 0,000500 0,000488 0,000463 0,000458 0,000316 0,000757 0,000657 0,000598 0,000658 0,000598 0,001132 0,000877 0,000526 Small diam. 0,000231 id.. id. id. id. id. 0,000512 0,000316 0,000342 0,000316 0,000354 0,000704 0,000526 0,000319 From my own observations I am inclined to think that the globules of the blood of the frog have a mean long diameter of about 96-n5i5Ijthsofaline; but the individual differences observable among the several globules ranged between 87-,^ and 100TO^6ths of a line. In the blood of the water-newt (Salamandra cristata) I have obtained in my measurements of the long diameters of the globules the following ex- treme individual varieties: minimum loe^jths of aline, maximum 127T7ij0i5ths. 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 (testacies Jluviatilis ) I have found their mean diameter to be TO-j^ttis of a line. Several, however, were measured which were no more than eT^^lis of a line across, and others which were as much as 72ToOTotns- I" trie ovster I "ave 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 60-n^gths, others only 54^5^8, and some no more than ^Oiggooths of a line 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. Delia 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 Cocur, &c. Annales des Sciences Nat. 1 Serie., t. iii. f 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 lieptilia, 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 Muller,t who does not appear to have been acquainted with this observation of mine, has lately arrived at 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 under the pressure of the moving column of 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 the central nucleus, it is more difficult to be satis- fied of its occurrence; and Dr. Young has 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 Natur. t. ix. t Observations sur l'analyse de la T.ymphe du Sang, &c. Annales des Sciences Naturelles, 2 Serie, Zoologie, t. i. p. 559. X Vide Magendie, Physiologie, t. ii. BLOOD. 4 09 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. IJodgkin 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- 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 hatrachia, 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- 410 BLOOD. jection of so much pure water, and death is do 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 alvme 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, caseum, 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, not 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.f The careful examination of the blood of two strong and healthy men afforded the following results. * BiH. Univers. de Geneve, and An. de Chemie, 2de Seric, t. xxiii. t Journal de 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 . Sub - carbonate of ~ lime .... Sub - carbonate of magnesia . . . Phosphate of lime . Phosphate of mag- nesia .... Phosphate of iron . Peroxide of iron Loss Total . . . 1st Analysis. 780.145 2.100 65.090 133.000 2.430 1.310 1.790 1.265 8.370 2 100 2.400 1000.000 2d Analysis. 785.590 3.565 69.415 119.626 4.300 2.270 1.920 2.010 7.304 1.414 2.586 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 hemutine, and can be readily shown to have the greatest analogy to albumen, from * Ann. de Chimie, 2de Seric, t. lii. 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 glubuline.* 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. * Ann. de Chimie, 2de Serie, t. xlv. t On animal fluids, in Med. Chirurg. Trans, vol. iii. 412 BLOOD. Names of the Animals. Weight of the solid particles in 1000 parts of blood. Composit Albumen. on of the Water. Mean temperature* Normal pulse per Normal number of inspirations per minute. Birds. 15.57 55 y4o 42 centigr. 136 34 Common fowl . . 15.71 75 925 41.5 140 30 Duck 15.01 99 901 42.5 110 21 r~t 14.66 66 934 • • 13.26 68 932 41 200 22 Mammalia. Monkey .... 14.61 92 908 oo.o 90 30 12.92 100 900 OA o9 72 18 Guinea-pig . . . 12.80 100 900 38 140 , 36 Dog 12.38 74 926 37.4 90 28 12.04 96 904 38.5 100 24 10.20 93 907 39.2 84 24 Calf 9.12 99 901 Rabbit 9.38 109 891 38 120 36 9.20 99 901 36.8 56 16 9.00 38 • * Reptilia. Fr°g 6.90 50 950 9. in water. 20 lortoise . . , . 15.06 96 904 7.5 that of the air. • • 3 Fishes. Trout 6.38 77 923 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 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 influence on the composition of the blood : M. Lecanu found in regard to The blood of man (in 1000 parts.) Solid particles. Water. Maximum ... 148 805 Minimum ... 115 778 Mean 132 791 The blood of woman. Maximum ... 129 853 Minimum ... 68 790 Mean ..... 99 821 The quantity of albumen did not appear to 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. Sanguine tempe- Lymphatic tempe- rament rament. Solid particles Water Solid particles Waler Maximum 148 801 117 805 Minimum 121 778 115 795 Mean . 136 786 116 800 W omen. Maximum 129 796' 129 827 Minimum 121 790 92 790 Mean . 126 793 117 802 * Ann. dc 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 hemorrhagic 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; but under certain circumstancesitsphysical 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 clot 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- logists. The experiments of Hunter and of many others show that the coagulation of the blood depends mainly on the cessation of the motion to which it is constantly subjected in the course of the circulation ; for this condition alone suffices to make it coagulate even in the interior of the vascular system, and we are of opinion that the great physiologist just quoted erred in attributing vital properties to the blood. Rest, then, cessation from motion, is that which contributes most generally and most essentially to cause coagulation of the blood ; other circumstances, however, such as its cooling, its being brought into contact with the air, &c. may also contribute to accelerate this phenomenon, which appears, from the experiments of Dr. John Davy, to be unac- companied with any evolution of caloric. 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 * Journal de Phavmacie, 1831. * Ann. de Chimie, f. 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 Miiller 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 death ; 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 buffi/ 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, ceteris 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 Miiller 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 father a less capacity for caloric,* and a somewhat in- ferior specific gravity (1,049 : 1,051); we are, however, led to think that in the normal state the contrary of the latter proposition will be found to obtain, for Messrs. Prevost and Du- mas have shown that in this case arterial blood contains a larger proportion of globules than venous blood.f When 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 ; % 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 ha:morrhage.§ 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, 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. t Ann. de Chimie, t. xxiii. p. 67. f Bichat, sur la Vie et la Moit. See also the article ASPHYXIA. § M. Edwards, Influence des Agens Physiques sur la Vie, translated by Dr. Hodgkin. BLOOD, MORBID CONDITIONS OF THE 415 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, lias 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, Baueiyj- 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. Joum.-May, 1828. § Ann. de Chimie, Here 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 a 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. Hemorrhages 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 ol 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 hec 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 mechanical im- * Pi-ucis d'Anatomie Pathologique, p. 526._^;f^- t Elemcnta Physiologic, torn. ii. p. 5,-'r"i pediment which the encumbered tissue or the rigid fibre offers to the circulation. The state of anemia, 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 cedema, and, in extreme cases, effusion into all the serous cavities. Neither plethora nor anemia 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 from 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- tioiV% tfee. crassamentum, being, after twelve "lococoioiouionNOi 05to^1 2 ™ u o 3 p . «J 3*3 £ bore 2 3 S g o c -c bo C "3 £ .3 "" o e £ C 03 r-< ^ rf< o p -P. .3 « 3 cr1 . 5 s . > O n! o B *3 -a „r a 3 0>0>01OlOlOlOOOOOOO© 0>-HON»ltiSS03tOSTtnoOi OOOOOOOOOOOOOO' RRRRRRR~~~~-~ COCD'-0»C0^1^N.OKKOOO t>-c~co»oG>cococoto a «S „T S S ce d Ph > > Cm Q Q rfCOiN-fMOOtl-fOtO'O o -H ctf erf.*!: VOL. I. ggs-sssg-s 2 J,: Ph bo n fH (LI KS 2 E 418 BLOOD, MORBID CONDITIONS OF THE. The specific gravity of morbid serum has 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 hemorrhages, the specific gravity of serum has been observed as low as 1013,+ 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 1-129, 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 »ot 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 109°. 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, cateris ■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. t Firioht's Reports, vol. i. p. 85. \ O'Shan^hnessy'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 in 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 quality 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 Haen saw the blood in a dis- solved state, and in the plague the bkod is said not to coagulate. In some persons there exists a state of con- stitution, bordering no doubt upon passive he- morrhagic disease, in which the blood is ob- served either to coagulate very imperfectly or not at all. Alarming hemorrhages from the slightest wounds are the consequence of such a diathesis, and the most powerful styptics will not always succeed in preventing their fatal termination. Dr. Wardrop, in a small work just published, has collected together several interesting cases of this kind, and from some of 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. Andral, 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 fevers, 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- BLOOD, MORBID CONDITIONS OF THE. 419 tractility, so as to contain a large portion of fluid, or from its holding 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 mote 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 hemorrhage 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, * Thackrah, p. 188. especially at the bottom, and of less than ordi- cohesion. In extreme cases, such an nary 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 1-024, 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 2 E 2 314 420 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 I 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 Ilaen, 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 houis 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 aboutonehundredandfifty 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 fibrine, 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. 421 man but iu 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 verv 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 * Thackrah on the Blood, p. 85, expt. lii. & liii. 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 where 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 which is formed on the inflamed surface in endocarditis, has 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 I 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 Chimie, new series, p. 363. f See Med.-Chir. Trans, vol. xii. p. 89. t 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, which is precisely that condition when in general we find buffed blood, and therefore, according to Thackrah, an increase in the proportion of fibrine. The hsematosine 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. In 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 destined to contain it. Passive hemorrhages, petechia?, 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 vas- 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 under various forms of disease. Morgagni cites two cases of malignant fever in which the serum was milky. Ilewson, besides enumerating in- stances to be met with in authors, gives three cases sent him by medical friends : one of amenorrhrea 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. BLOOD, MORBID CONDITIONS OF THE. 423 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 Ilaller'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 inappre- 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 blood and rendering it rose-coloured, while it would give the serum the appearance of milk." If the albumen had really been coagulated by * Annates dc Chimic, 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 haematosine. 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 found after death deposited in a crys- talized form, as was observed by Sir Everard Home, who, in dissecting an aneurysmal tumour, found a mass of crystals, w hich 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 1 2*41 Ditto 1373 Average 9-62 Mr. Jennings, in his report on the blood in the Transactions of the Provincial Medical As- sociation for 1 834, 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-l, which is Le- canu'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 Jhe 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 coaguluin 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 buffy 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. Magenclie has artificially produced an analo- gous state of blood by injecting putrid liquids into the veins of animals, and the speedily fatal 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, torn. iii. p. 83. t On the Blood, &c. page 209. BLOOD, MORBID CONDITIONS OF THE. 425 alkaline salts were found diminished in the fol- lowing proportions : — In healthy serum, according to Lecanu, salts 8-10 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 to become thick, muddy, and of a greenish hue, would impart to it a fine scarlet tint that would remain permanent until it began to putrefy. Since the modern advances in ani- mal chemistry, opportunities for examining the blood in true scurvy have been very rare ; and * Jennins's Report. it is therefore the more to be regretted that Drs. Latham and Koget, 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 hemorrhagica, 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,f 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 ajjparent not only in the serum, but still mr^-e 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 colouring 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 minutiae 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. | 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, " 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 maimer 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 giavity 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 '88 Fahr. was 1-041 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-mor- tem examination to have granulated kidneys. Urine reddish brown, very scanty, coagulable; 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. I examined her blood, and found it to contain 0-43 per cent, 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- BLOOD, MORBID CONDITIONS OF THE. 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 thai) 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 drying, to only 50 grains instead of 78 (Le- canu's healthy standard), and it contained fully as much urea as the urine itself, the 1000 grains yielding nearly 15 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 in 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 urea was obtained in abundance from the fluid of the pericardium. In a third the effusion collected after death from the pleura of a man who had suffered from general dropsy and mot- 427 tied 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 liollo, 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 * -Annales 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 haematosine 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 we 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 be 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. Foy, 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 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- 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- rhage occurs, whether by the rupture of a large vessel or by a general oozing from the mucous membrane into the stomach or bowels, we shall find the fluid ejected assume the appearance of 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 haemalemesis 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 BLOOD, MORBID CONDITIONS OF THE. 429 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. llertwich 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 other on her check, inflammations ensued which rapidly terminated in gangrene. Although in all these instances there can be no doubt that the blood was in a poisonous state, there is no reason to suppose that this could have been foretold by any thing remark- able in its appearance or sensible qualities. Scarcely more successful in general has been the search for extraneous poisons, which never- theless have appeared from collateral circum- stances to have entered the circulation, or have even been purposely introduced into it. Dr.Chris- tisonj has cited a sufficient number of cases where poisons swallowed have been afterwards found in the blood, to shew that we must not infer their absence from our inability in most cases to abstract them in a separate form ; and he further demonstrates how erroneous such an inference might be by stating that Dr. Coindet and himself, after destroying a dog in thirty seconds by injecting 83 grains of oxalic acid into the femoral vein, endeavoured in vain to * Duncan's Medical Commentaries, vol. xix. p. 213. t Edinb. Med. and Surg. Journ. for April 1807. Med.-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, 1 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 be detected in it, and others where those which are always present 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. Bibliography. — (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. Lond. 1684, and Analytical observ. on milk found in veins instead of blood, Phil. Trans. 1665. Albinus, De Massae Sanguinis corpusculis, 4to. 1688 (Kecus. in Haller Disp. Anat. t. ii.) ; Ejus, De Pravitate Sanguinis, 4to. Pranc. 1689. De Sandris, De naturali et pra;ter- naturali sanguinis statu, 4to. Bon. 1696. De Haen, De sanguine humana, in Ej. Ratione medendi. N. Davies, Exper. to promote the analysis of the blood, 8vo. Lond. 1760. Fontanq, Nuove osserv. sopra i globetti rossi del sangue, 8vo. Lucca, 1768. Hcwson, Exper. inquiry into the properties of the blood, 8vo. Lond. 1771-78. Spallanzani, Penomeni 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 rnechanisme et les pioduits 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. Gotting. 1788. Deyeux Sr 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 destitute, Prag. 4to. 1798. Tollard, Diss, sur la fibrine, 4to. Strasb. 1803. Le Gallois, Le sang est il identique dans tons les vaisseaux, 8vo. Par. 1805. Henke, Uber die vitalitat des Blutes,8vo. Berl. 1806. Bostoclt, Med. -Chir. Trans, vol. i. Dowler on the products of inflammation, Mi d. Chir. Trans, vol. xii. Thaekrah on the properties of the blood, 8vo. Lond. 1819. Wilson, Lectures on the blood, &c. Lond. 1819. Kolk, Sanguinis cnagulantis 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, des Blutes, 8vo. Leipz. 1823. Sto/ier, in Pathological Observations, Dublin, 1823. Scudamore, Essay on the blood, Lond. 1824. Mi- chaelis, De partibus constitutivis sing, partium sang, art. et veil. 8vo. Berol. 1827. Babington on fatty matter in the blood, Med. -Chir. Trans, vol. xvi. Cltristisvn 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. Seyalas, in ibid, t. xii. Gendrin, Recherches sur les fievres, and Hist. anat. des inflammations. Andral, Pathological anatomy, by Townsend. Denis, Rech. exper. sur le sang hum. 1830. Stevens on the blood, 8vo. Lond. 1832. O' Shaughnessy , Report on the chemical pathology of cholera, Lond. 1832. Prevost If Dunuts, Examen du sang, &c. Bibliotheq. Univ. de Genev. t. xvii. See also Rudolphi, Blumenbach, Spreugel, Adelon, &c. in their systems of physiology. ( B. G. Babington.) BONE, (general anatomy in the normal state.) Gr. oartov. Lat. os. Fr. os. Germ. der Knochen. 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 sup- 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 in the grave as if they constituted the essential element of our frame. We 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 more 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 of a horse's rib as a bow. This elasticity frequently saves them from fractures, and lessens the shock which would otherwise be communicated to the nervous centres and delicate structures they defend. It is possessed by every bone, and may be demonstrated in the oldest and most rigid by cutting them into thin slices. Shape. — Bones assume every variety of shape, as might be expected from the use made of BONE, NORMAL ANATOMY. 431 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. tlie 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 vertebra? 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 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 diploe between {fig. 186, b). In very thin bones the diplue 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 Jig. 186, where A is the head and neck of the femur, and 13 the upper extremities of the tibia and fibula : a indicates the com- pact tissue ; 6 the reticular ; at c it may be seen how thin is the layer of compact tissue cover- ing the head of the femur. 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, Sec. 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 igitur, ossa coagmentari filamentis, et fibris per longum ductis in rete implicitis, qua affuso osseo succo ferrumi- nantur in solidam densamque ossis naturam." (Op. Posth. p. 47. Lond. 1636.) He also allowed the existence of lamella?, though he does not put forward its lamellar structure in a prominent way.* Gagliardi adopted his no- * We arc told by an interesting writer that Mal- pighi compared these lamellae to the leaves of a book. Could this writer have taken " libri," 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. Fcetfis os^a, et cranium precipue, fila- mentorum progressum exhibent ; haec 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, (lamellae, squamulas, 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 the plates, others longitu- dinally through the entire length of the bone.f Leuwenhoeck thought that the filaments of Mal- pighi were hollow tubulin Duhamel observed concentric layers as in wood.§ Haller says, " Fi- brosum est (os) sive in laminas et fila divisum quae sulcis 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. "If 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 lamellated 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 parum a libri natura distorts, cujus potiores areae et tota fibrarum compages exsudante osseo succo repletur et tumet." Here we have a tissue of fibres and filaments run- ning in various directions, and forming a net-work not unlike a book I ! 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, lamellae, and bracteae : " Successivis increments nova fibrarum plana su- perinducuntur, quae prasexistenti lamellae osseo agglutinata succo, debitam molem et firmitatem excitant. Patent autem singula plana resolutione facta per longum ossium maceratione ; integrae namque osseae reticulares bracteee evelluntur. In abortibus verd 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 situati, et inflexi angulum effor- inantes." The inner plates, forming the spongy substance, differed from the outer, and were of three kinds, the corrugated, the perforated or cri- briform, and the reticulated. These had a system of nails peculiar to them : " alia sine cuspide, plurima ramusculos rescissos efformant, nonnulla breviora." — Anatome Ossium. Lugd. Bat. 1723. f Observationes de Ossibus, Auctore Cloptone Havers. Amstel. 1731. t Opera Omnia, Lugd. Bat. 1722. 4 Mem. de l'Academie Roy. des Sciences, 1739, 41, 42, 43. |j Opera Minora, torn. ii. Laus. 1767. f Monro's Works, Edin. 1781. BLOOD, NORMAL ANATOMY. 433 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 osseuses ne me paroissent point exister dans la nature." " Considerons le tissu compact comme un assemblage de fibres rapprochees mais nullement separees par couche."" Blumenbach 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 Leuwenhoeck as to die 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."j 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 Medico-Chirurgical Trans, vols. vi. and°vii. i 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, Leuwenhoeck, 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 as a part of the living si/stem. 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- cartilage 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 die 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 bursae, 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 434 BONE, NORMAL ANATOMY. 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 matet, and might be traced as one continuous membrane over every bone in the body. Boer- haave asserts (Praelectiones Academics) 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 off 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 areolae 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 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 areolae 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 vessels 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 of the canal in a beautiful network on its lining BONE, NORMAL ANATOMY. 435 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- verney.* 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 foetus. 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 use ? Doubtless it is to the general system a store of nutriment, which is absorbed, in cases of wasting or marasmus, for the general good ; but to the bone itself perhaps it is of no more use than so much of any other soft animal substance would be — it fills a space which in the mechanism of the bone was not to be occupied with calcareous matter. Marrow was lighter than the heavy earth of bone, and could at any time be used for the necessities of the animal. We see young bones filled with a gelatinous fluid, and in birds air takes its place — a proof that marrow is no wise essen- tial to the existence of the osseous system. Various other uses have been assigned to the marrow, which will not bear examination. 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 was 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 are 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 * Memoires de l'Acad. des Sc. 1700. * Bell's Anatomy. 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 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. have been investigated by Dupuytren,* and their course in some of the bones, espe- cially the flat bones, splendidly figured by Breschet.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 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 the spongy tissue by numberless radicles, re- ceive branches like other veins in their course, and, after issuing from the compact tissue by 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 indeed settles the question. Lymphatics have not been found in the inte- rior of the osseous substance; but they may be seen on the surface. J In a tissue such as that of bone it would be no easy matter to * Propositions sur quelques points d'Anatomie, de Physiologie, et d'Anatomie Pathologique. Par. 1803. f Recherches Anal, sur le systeme veineux. Par. 1829. X Beclard. Grainger. BONE, NORMAL ANATOMY. 407 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 1 736,* 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 R. Nesbit, M.D. p. 31. Lond. 1736. + Mcmoires dc l'Acadcmie Royalc des Sciences, 1758. this last has the properties of coagulated albu- men.* Berzelius,t 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- ~\ ble in water 32-17 V 33"30 Vessels 1-13 3 Subphosphate of lime with a little fluate of lime 53-04 57-35 Carbonate of lime 11-30 3 85 Phosphate of magnesia .. 1-16 2'05 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. Barros gives the following table :— Phosphate of lime. Carbonate of lime. Lion 95 0 2 5 Sheep 83 0 19-3 Fowl 88-9 10-4 Frog 95 2 2-4 Fish 91-9 5-3 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.!; 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. \ 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 JRadiata, 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 lamina 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, 't rans. 1674 and 1678. Malpighi, De ossium structura, in Ej. Anat. Plantar, lol. Lond. 1675, et in Ej. Op. Posth. Venet. 1743, Lond. 1697. Havers, Osteologia nova, 8vo. Lond. 1681. Gagli- ardi, Anatome ossium, 8vo. Lugd. Bat. 1723. De La Sane, Mem. i. et ii. sur l'organization des Os. Mem. de Paris, 1751. Albinus, De construc- lione ossium, in Annot. Acad. lib. vii. Scarpa, De penitiori ossium structura Com. 4to. Lips. 1799 ; 4to. Pans, 1804; Ticin. 1827, s. t. : De anat. et pathol. oss. Malacarne, Auct. ad osteologiam, &c. Ludwigii et Scarpa;, Padov. 1801. Caldani, Mem. sulla struttura della ossa umana e bovina, 4to. Padov. 1804. Howsldp, 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. Speransa, Consid. sul. tessitura organ, delle ossa, Bolog. 1B19. Ilmoni, Physiol, syst. oss. spec. i. et ii. 4to. Aboa;, 1825,-6. See also the various systems of general and descriptive anatomy and 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 time 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 njore 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. BONE, PATHOLOGICAL CONDITIONS OF. 439 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. Ilibes,* 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: — DISEASES OF THE OSSEOUS SYSTEM. Class i. Derangements of internal functions. a. Deficiency of the calca- reous deposit Rachitis. b. Superabundance of the calcareous deposit ..Fragility. c. Absorption of the calca- reous deposit Mollities. d. Absorption of both con- stituents Atrophy. Class ir. Inflammation. a. Simple inflammation ..Adhesion Union of fracture. Suppuration Abscess in bone. Ulceration Caries. Mortification Exfoliation. Death with regeneration Necrosis. b. 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 hi. Structural diseases. a. Spina ventosa Development of a new cavity within a bone, with unnatural contents. b. Exostosis Growth of a tumour in or from a bone, which may consist of Bone. Cartilage. Both structures mixed. c. Osteo-sarcoma Alteration of structure with deposit of a new material. d. Cancer.f e. Fungus hffimatodes.f f. Bloody cellulated tu- mour within bone. * We refer our readers for a summary of M. Kibes' opinions, &c. to the Dictionnaire des Sciences Medicales, yol. xxxviii. p. 456 et seq. t These diseases are generally, if not alwavs, 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. y^^^HOSPjT^V The early symptorjfsCfcf^ickets are mva^iably those of imperfect of deranged nutrition, pale- ness of skin, flaccim^M--4ihre,-&c. Along with these symptoms or^sftortly 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 which 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 'sf 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 being di- vided by a knife. Meckel % states that the bones of ricketty patients are soft, spongy, flexible, and Gurved, 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, torn, iii. p. 625. + Medico-Cliivurgical Transactions, vol. vii. % Meckel, Manuel d'Anatomie, torn. i. p. 344. BONE, PATHOLOGICAL CONDITIONS OF. 441 they receive more blood. The periosteum has undergone analogous changes. The chemical composition is not the same throughout. Thus, on the onehand, there is notalvvays 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 bone 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.-f 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 pf 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 Chirurgicales, torn. iii. p. 22. 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. Kibes' theory of " a change of action," just as we see the muscle of an old man incompetent 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 haematodes, 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 part is 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 he 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. On 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 Charite.* 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, leav- 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 (Edematous, 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 Surg- ry, vol. iii. p. 30. f The Chirurgical Works of Benjamin Goocli, vol. ii. p. 393. BONE, PATHOLOGICAL CONDITIONS OF. 443 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 laminae 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 the 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 hones had been fractured ; in one the fracture had not united, and in the other there were several fractures which had united very imperfectly. The compact sub- stance of the bone was in some places not * Wilson's Lectures on the Bones and Joints, p. 253. 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. f See Howship's Papers in the Medico-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. Thus 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 out as 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 aneurismal 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, around and between the fragments of a divided bone, which were thus mechanically glued to- * The adhesive ossific inflammation of Hunter. BONE, PATHOLOGICAL CONDITIONS OF. 445 gether. This fluid, which was termed the 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 from 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, arid 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 colour- 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, torn. i. p. 335. may have been detached. At the same time the spicule 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. He 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. Howship'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 union of bone. First, that there is a callus formed like a brace or ferule round the frag- 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 be per- manent is going forward : thus we are 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 the 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- BONE, PATHOLOGICAL CONDITIONS OF. 447 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, and 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 be equally engaged. In process of time this lymph becomes organised, assumes a ligamen- tous rather than a cartilaginous appearance, although, strictly speaking, the new structure possesses not the true characters of either, and finally is converted into bone by the simul- taneous establishment of numerous but irre- gular 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 wonderful 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 I 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 Colles§ 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. X 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 tissi'e 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 it 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, by a remission of pain with an increased sense of weight in the part ; but all these are fal- 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 felt with the finger."* Suppuration on the surface of a bone is of very common occurrence, and so constantly complicated with affections of the periosteum, * Wilson on the Bones and Joints. BONE, PATHOLOGICAL CONDITIONS OF. 449 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 dif- ferences in the results of the inflammation, * Of all the causes that produce these affections of ihe bones, an irregular or protracted use of mer- cuty seems to be the most efficacious. Many sur- geons of the present day doubt whether a suppu- rating node is a true or genuine venereal symptom. We have learned from an experienced army surgeon, who spent many years on the western coast of Africa, where the venereal disease is not known, but where mercury is profusely employed in the treatment of liver complaints and other diseases incident to the climate, that affections of the bones, resembling those considered to be venereal, are of exceeding frequency. It is a remark worthy of attention to the curious in such matters, that nodes, &c. formed no part of the symptoms of syphilis as first observed and described, and that the first practitioner who noticed them (John de Vigo, 1519,) is mentioned by Astryic, (page 158,) as an eminent promoter of the mercurial method of cure, and as having by that means acquired great reputation and riches. + See a paper bv Mr. Crampton, in the Dub. Hosp. Reports, vol. i. } 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, f;nd 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, a id sloughy, and the patient seldom or never recovers. W'here the deposition has taken place after fever, if the patient is young and the con«titu ion has en (bled him to combat the original disease, a recovery very frequently takes place by the process of necrosis. 2 o 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 while 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. 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 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. BONE, PATHOLOGICAL CONDITIONS OF. 451 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 the 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 appear 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 vertebra;, which seems to be connected with what is called a scrofulous state of constitution. In these cases ulceration may be^in 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 G 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 maimer, 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 deianged 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 vertebras 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 vertebrae above and below to come into actual contact, the sound condition of the bony parietes of the spinal sheath effectually preventing this ; and hence, when recovery takes place, it is not by the adhesion of these surfaces, but by the forma- tion of a quantity of new bone which fills up the vacant space, producing a perfect example of true anchylosis. The developement of such a curative pro- cess as this is scarcely to be expected in a scrofulous system, yet is it satisfactory to know that even under such circumstances the case is not utterly hopeless. We have seen repeated instances of angular curvature without the occurrence of abscess, in patients apparently deeply tainted with scrofula, one of which is so very remarkable as to deserve particular notice, because it illustrates a mode of union that frequectly occurs in 'scrofulous cases, and because the preparation is in existence to de- monstrate the fact. In July, 1830, a wretched young girl was brought into the Meath hospital with a very acute angular curvature of the dorsal vertebrae. Almost every joint in her 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 the mud of the street was wiped away after her admission. It need scarcely be added BONE, PATHOLOGICAL CONDITIONS OF. 453 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 die 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 is in fact its true meaning; nevertheless, we are hardy enough to dissent from this applica- tion of the word, and to confine its use to one form of the death of a bone, exfoliation more properly belonging to another. And we do so the more readily because not only do these two affections present different pathological pheno- mena, but there are such practical discrepancies between them that it is essential to every sur- geon to have a distinct and separate notion of each . Exfoliation, then, expresses the death of a portion of bone which is either never replaced, or replaced by a process which is set up after 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. Dillerent 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 why 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 belo .v 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 lirnb 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,t 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 witli 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. + See Ciowther 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 occuirence 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 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, VYeidmann, and other continental surgeons, attribute the process 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 can be separately and distinctly shown. Such is an out'ine of the chief opinions en- tertained on this interesting subject, and it is probable that, to a certain extent, they are all correct. When the periosteum 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 at Park-street, the specimens exhibiting the earliest period of the disease show the periosteum as slightly thickened, smooth on its internal, but more rough and flocculent on its external sur- face, detached from the bone, the surface of which is smooth, and scarcely appears changed from its natural and healthy condition. At a more advanced period, the periosteum is still thicker, but is not softened ; on the contrary, it has nearly the firmness of ligament, and there are small osseous depositions within it ; the bone then being rough and uneven on its surface and evidently having lost its vitality. BONE, PATHOLOGICAL CONDITIONS OF. 455 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 diem, 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 vuth granulation, than when it is only smeared over witli lymph. And here, as in other cases, it may be 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 new 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 spicula of 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 have 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, wUh an extraneous body wo; king to gain the 45C BONE, PATHOLOGICAL CONDITIONS OF. surface and not able to accomplish it quickly, occa.s.on 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. Russell 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. When 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. Regarded 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 repioduction 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 may be 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 tedious 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 of 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 BONE, PATHOLOGICAL CONDITIONS OF. 457 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 have not met with the affection as here described — we have never seen any thing like the rege- neration of a bone thus lost, nor can we con- * Diet, des Sciences Mcdicales, torn. 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 haematodes. 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 stationary, 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. 1823. BONE, PATHOLOGICAL CONDITIONS OF. 459 which a deposit is found between it and the bone, or between the laminae of this membrane. 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 an 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, torn. iii. p. 549. t Diet, des Sciences Medicales, art. Exostose. J Dub. Hosp. Rep. vol. ii. p. 433. the morbid action commences in the; 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. pliere 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. He 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 has 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 laminee 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 heematodes, although like the latter it very frequently attacks 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 aued. In children, particularly about the fingers, the wrists, the fore-arm, &c. nodu- lated swellings are frequently met with of 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 thin, it may BONE, PATHOLOGICAL CONDITIONS OF. 461 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 hsematodes, 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. " In 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 We have taken the above descriptions entirely from preparations in the school of Park-street, Dublin. t Traite des Maladies Chirurgicalcs, torn. iii. which form the walls of the nasal fossa?, 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 may 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 becomesjleshy, 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,} 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, lie 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 * Lecons Orales, torn. iv. p. 636. t Cooper and Travers's Surgical Essays. $ Dub. Hosp. R. 'ports, vol. iv. 462 BONE, PATHOLOGICAL CONDITIONS OF. 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 observation 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. citat. like tumour appearing to spring from 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 of 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 suddenly and quickly increasing : sometimes, on the contrary, it increases rapidly 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 it. It is, generally, firm to the touch, solid and heavy ; but occasionally an examination with the fingers discovers the osseous covering of the tumour to be very thin, and it yields on pressure with a peculiar sensation of elasticity, 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 haematodes. 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. Crampton's case, in which the diseased growth sprung from the roof of the BONE, PATHOLOGICAL CONDITIONS OF. 463 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 hrematodes. 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 oss of the power of resist- ance has preceded the development of the dis- ease in the softer structures. Hut 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 huve 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 hacmatodes 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 sim.lar 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 winch was 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, he left the 464 BONE, PATHOLOGICAL CONDITIONS OF. 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 1826), there is an account of a disease of the tibia related byLallemand 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 both 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 cellulated 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 of 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. Mad 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, Anmerk. viber 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; Anglice by Firrell. Sandifort, Museum anatomicum. Weidmann, De nrcrosi ossium, fol. Frfti. a M. 1793. Augustin, De spina ventosa ossium, 4to. Halae, 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, rie callo ossium, 4to. Norimb. 1707. Bohmer, Diss, de ossium callo, 4to. Lips. 1748. Troja, De novornm ossium, &c. regenera- tione, 8vo. Lutet. Paris. 1775. Russel, Essay on necrosis, 8vo. Edinb. 1794. Koehler, Ex- per. circa regenerationem ossium, 8vo. Gotting. 1786. Bonn u. Marriyues, Abhand. uber die Natur nnd Erzeugung d. Callus, &c. 8vo. Leipz. 1786. Lebel, 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 re- generat. ossium, 4to. Berol. 1824. * * * * Spondli, Diss, de sensibilitate ossium morbosa, 4to. Gotting. 1814. Observations more or less connected with the subject of the foregoing article will also be found in the surgical works of BromjiM, Gooch, Pott, &c, in Meckel's Handbuch d. anatomie or Manuel d'anatomie, in Wilson's Lectures on the bones and joints, Lloyd on scrofula, Cooper Sf Travers'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- gical Transactions, &c. (W. H. Porter.) THE BRACHIAL OR HUMERAL ARTERY. 465 BRACHIAL OR HUMERAL ARTERY (urteria brachialis, humeraria. Germ, die Ar- marlerie.) 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 brachiaeus 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- chiaeus 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 brachiaeus anticus m uscles, 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 Soemm. 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 thoracica acromialis, 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 subscapular, and one or both of the circumflex arteries, derive their origin from the brachial. 2 B 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. of 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 put 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 anasto- moticus, Haller, collaterale du coude, Ch.) arises generally at nearly a right angle from the inner 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 brachials anticus, and perforates the internal intermuscular ligament, giving branches to the brachiaeus 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- mosis with the posterior ulnar recurrent. Where the anastomotica magna is absent, small branches 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 profundse, and the anasto- motica magna : this last, however, sometimes 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.] t [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 below 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 ill its course, BURSiE MUCOSAE. 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 profunda: 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.) BHAIN. See Bnkephalon, and Nervous System (Comp. Anat.) BURS^, MUCOSA. (Fr. bourses synovi- ales; Germ, die Shleimbeutel.) — 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 anomabms branch, the bi:urcation generally takes place nearer the axilla, than when the radial is the abnormal vessel. — Ed.] 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- carpophalangeal 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 bursae were not distinguished from cellular membrane by Monro and others. That they are different structures, however, or at least that they are independent pf the cellular system, is sufficiently proved by the simple process of inflating their cavities through a small 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, w ithout, however, enveloping it. (See fig. Ill, 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 ii 2 468 BURS/E MUCOSjE. 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 burse* : 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 pophteus 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 bursa? : 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 bursas: 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 bursa? of any size or importance. There is in the trunk a large vesicular bursa, usually found between the latissimus dorsi and scapula, lu 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 pleurae 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 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 the synovial sheath is firmly bound down by a dense unyielding fibrous membrane, a cir- cumstance well worthy of remark ; for, as we shall presently see, it modifies in a very im- 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, Sec. Having thus considered the forms and rela- tions of the different sorts of bursa?, we may next proceed to offer a few remarks applicable alike to all, upon their structure, contents, uses, 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. BURS7E MUC0S7E. 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 bursa? 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 bursas is in all cases the same ; they serve to 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. — Bursae 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 bursas 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- cosa.— Bursae mucosae, superficial as well as deep, are not unfiequently 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 eff usion 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 bursa?. 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 bursae 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 buisae; 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 piesence of matter. Monro seems to regard, in certain cases at least, the communication above alluded to be- tween certain bursse 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 lifetime 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 that of SYNOVIAL MEM- BRANE. C John E. Brenan.) CARNIVORA ( caro, camis, 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 ol ject of research, and in which the nomenclature of a system is of little importance, compared with the developement 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 Zoopuaga 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- riiana 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 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. 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 the ccecum is either very small or altogether wanting. The animals of this order differ in the form 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 com- posed are perhaps as follow : — 1. Ursidje, typical genus Ursus, bear. 2. Mustelidje, do. Mustela, marten. 3. Canidje, do. Canis, dog, wolf. 4. Felidje, do. Felis. cat. 5. Phocidje, 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 than any of the others. Skeleton.- — -The structure of the skeleton in the cat tribe exhibits, in the greatest imaginable degree, all the requisites of fleetness, activity, and power, for the purpose of pursuing, sur- prising, overpowering, and tearing the living Fig. prey on which, in a state of nature, they wholly subsist. In the less typical forms we find these attributes possessed to a modified extent, but still admirably adapted to their respective habits. As an example of the typical structure, the skeleton of the lion (Jig. 189) shews, in the 189. configuration of the bones, in their articulation, and in the developement of the different points of muscular attachment, such a combination of lightness of form with vast power, as must strike every one as being exactly equivalent to the natural requirements of the animal. The spine is flexile, yet of great strength, and the extent and robustness of the lumbar portion of the vertebral column seematonce adapted forthe exercise of that flexibility, and for the location of powerful muscles. The ribs are narrow and far asunder; the limbs long, powerful, and so constructed as to afford the greatest facility and extent of motion, an object which is greatly promoted by placing the point of rest Fig, at the extremity of the toes ; the whole of the feet, excepting that part, being thus made sub- servient to the object in question. The cra- nium is broad and short, and fitted for the exercise of almost incalculable force in holding and tearing their food. In the weasel tribe the legs are shorter, the vertebral column elongated and in the highest degree slender and flexible, the lumbar region being as long even as the dorsal, a structure by which they are enabled to creep with almost a serpentine motion in quest of the small and sometimes subterraneous animals on which they subsist. In the bear tribe (Jig. 190) there is a still 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 developemenl 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 is less Fig. 193. I* 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 Phocidse 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, (fig. 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 mustelidse, &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 13 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 mucli 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 necessary 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, answeringto 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. vitulina 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 alse 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 ihe 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 tubercularform,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 (fig. 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 masseter. 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 bone, 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 vertebrae, the atlas and dentata or axis, have already been alluded to. The first is exceed- ingly broad and robust, with strong transverse 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 coatis, 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 clogs. The transverse processes are also very large and strong ; but the most im- portant circumstance connected with the cha- racter of these vertebra 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 great 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 Huminantia 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 vertebras, 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 tribe3 par- 476 CARNIVORA. ticularly in the Badger. The acromion is small and slight in all the true Curnivora, 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- telidte, 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, Ruminantid, 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 (fig. 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 rest, 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 fig. 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. The tibia and fibula,* (fig. 196, I, m; fig. 197, i, k; fig. 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, (fig. 196, f,g,h,i,k,fig.l97, e,f,g,h,fig.\W,f,g,h,k,) the os calcis has a very long and robust tube- rosity both in the digitigrade (fig- 196, k) and plantigrade (fig. 197, /)) 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 are 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 Jig. 198, that of the seal ( Phoca vitulina ), the natatory. CARNIVORA. 477 Fig. 197. The metatarsal bones (fig. 196, 107, 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 (fig. 196, 1 97, 1 98, 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 mustelid/s 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 tinlike 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 (fig. 197) we tind 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 are elongated for that purpose. In the Lion (fig. 196) 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 (fig. 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 Si/stem. — 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 vertebra; 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 Ruminantia, 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 arid 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 lorn 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 mo- 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 cacum exists, but is very small and short in the cats : (fig. 200 shews that of the Lion.) In the dogs it is spi- Fig. 200. ral. The whole canal is almost destitute of val- vule connive/ites, nor is the large intestine tucked up into sacs as in other orders. The mustelida generally have no cacum nor valvula coll. A short comparative view of the structure thus hastily sketched, with that of the digestive system in the typical herbiyora, 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 maxillary 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 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 cme of the pancreatic ducts. In the otter, the common duct forms a second reser- voir near the duodenum. The gall-bladder 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 plantigradesi The pancreas is similar in its general struc- ture to that of the other mammifcra. 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 discovery 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 PLverard Home that two ducts go from the receptuculum 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 be 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 mammij'era in the ascending series, the brain of the Carnivora (Jig. 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 tubercuta 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 qua- 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. Dog A • Man A . O* 5*7 . Crystalline. Vitreous. e 9 ■ ■ 51 • • • 2T 4 24 • • 51 • • • « 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 seal 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, puchydermata, and some if not all the ro- dentia. The organ of hearing is developed to a very considerable degree in most of the Carnivora. 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 Canida. There is in these, as well as in many other mammiferous animals, especially the ro- dentia, a remarkable hollow appendage to the CARNIVORA. 481 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. The 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 v*>ry 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 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. 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 482 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 si/stem. — 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 mustelidte it consists of a thin layer only, whilst in the dogs and cats it forms a large and conspicuous bulb around the urethra. Cowpers glands also are found in many of these animals, but are wanting in the planti- grades, in the mustelida, 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 ursidtE and the mustelidte ; 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 cavernosum. 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 part in 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. The placenta consists, in the cat, the dog, the marten, and others, of a perfect zone sur- rounding the fcetus, 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,) (arteria carotis; Gr. xa^am; ; 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 xapoq, 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 circular 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 urtcr'ue soporiferte. 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 I mean that portion which extends from the origin of the artery to a point on a level with the sterno-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 of 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-hvoideus ; 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- tric 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- minata; 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, snperficialis vel anterior, Samm. 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 between the ear and the ramus of the lower jaw. At first it is superficial, merely covered by the integuments, platysma and cervical 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-pharyn- 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 also 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. The 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 external carotid artery the writer follows that of Meckel. See his Anatoraie Descriptive, &c. trans- lated 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 inferiorly. 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, and 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 486 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 franum, 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 frsenum 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. Branches.— 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 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 smaller branches given off anteriorly to the 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 facial 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 pinnulis), 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, lalerales nasi, and /, 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. Irregularities 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 the usual origin of the inferior coronary ; in this case the transverse facial branch of the temporal generally furnishes 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 externa! 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, splenitis 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 amis, 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. uurkularis 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 oft' 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 * Surgical 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 the 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 off 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 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 which 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, 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 thp 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.] CAROTID ARTERY. 489 frontal branches 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 the 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, I. the superior palatine, m. the vidian, n. the pterygo-pulutine, 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, spinusa ) 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 in 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. brandies 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. t. 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 /. 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-pulatine artery may be con- sidered the termination of the internal maxil- iary ; it enters by the spheno-palatine hole into the posterior part of the nasal fossse, and divides into two principal branches ; an external and an internal; the internal branch passing across the roof of the nasal fossa3 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, (carotis in- terna seu cerebralis, Samm. cerebrate anterieure, 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 vertebra, and making a few contortions along the side of the pharynx, enters the foramen caroticum 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 caroticum : 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 ami- 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- wards it 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 lacerum orbitaleof 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 mala?, 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 retinae, passes forwards along the superior wall of the orbit above the levator palpebrae supe- rioris and superior rectus, giving branches to these 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 artery 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 twoy 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 retinae 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 palpebral 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 fossa; 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 arises 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 frontal 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- 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 artery 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 in 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 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 cms 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. 493 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 direction. All these branches extend to the superior surface of the cerebrum, and anasto- mose with those of the media cerebri and the posterior cerebri, which is furnished by the ver- tebral . Besides these large branches into which the arteria callosa divides superiorly, it gives off from its inferior and concave side a vast number of smaller branches, which penetrate the corpus callosum. Sometimes, instead of being connected by the communicating branch, the anterior cerebral arteries of opposite sides unite, forming a single trunk, which runs forward for some little dis- tance, and then divides into a right and left branch ; this junction is the more remarkable, on account of its analogy to the union of the two vertebral arteries in forming the single trunk 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 ARTERY. 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 in 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 co- agulum 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,f 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. t Arch. Gen. de Med. t. xix. p. 118. $ 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. 350. 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 lift carotid was tied, 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 ; 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 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 and atheromatous deposits are very often met with. In the lower part of the common ca- 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 aorta projects upwards into the neck, compressing and obliterating the carotid, and simulating all 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 aneurismal dilatations of it after it has entered the cranium, and as it lies by the side of the sella Turcica. * 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 an ticus 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."f 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 sterno- 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 the 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. cartilugo, quasi car- nilogo; Gr,voy£jro{j Fr. cartilage ; Germ. Knor- pel ; Ital. cartilagine) 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 * Anatomic Generale, torn. iii. Par. 1812. t Manuel d'Anatomie, torn. 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 alse 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 FlBRO-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 organi- 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 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 the 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 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 ab- 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. t 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 lobulated, 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 ; Haller 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. Haller 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 was 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 va 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 498 CARTILAGE. 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. He 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-seious 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 were 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 Charite 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 * Andral'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 5 100-0 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." t By boiling costal and si/narthrodiul 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 Traite de Chimie, torn. vii. Par. 1833. CARTILAGE. • 409 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 diarthrodiaux 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 syphilis, 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 moit 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. The 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. («) 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 opening is made quite through into the cavity of the joint. When this opening is effected, the mat- ter, which in this form of ulcer is always pre- 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. (b) 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, sem transparent, 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. Hame, 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- veilkier, Obs. sur les cartilages diarthrodiaux, et les maladies des articulations, Archives Gen. de Med. t. iv. 1824; Ej. Usure des cartilages articu- laires, Nouv. Biblioth. Med. t. i. Observations on accidental or loose cartilages may be found, by Cruikshanh, 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 Journ. de Chirurg. t. ii. ; by Abernethy, in his Surg. Observations ; by Laennec, in the art. Car- tilages jlccidentels of the Diet, des Sc. Med. ; by Cruveil/iier, 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, Brodie, Schreger, Wilson, and Scott. — Vide Bibliography of Articulation. ( Charles Benson.) CAVITY, in anatomy, (cavitas; Yt.cavit'e; Germ. Holile; 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 tho- racic and abdominal cavities, from which the viscera have been removed. A simple reference to it and to^g. 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 they, 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. 1 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. 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. It rarely happens that we 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 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 hypochondrium 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 orean be in a state of tumescence. 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 mujus,) 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 ccecum or caput coli, 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 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 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 pregnancy, aud in cases of ovarian dropsy, 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-hepatic 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 venacava 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 of a considerable portion of the small intestine through the foramen of Winslow into the cavity of the omentum, from which it escaped through a lacerated opening in the transverse mesocolon which firmly constricted a knuckle of the intestine and occasioned mortification of h.— Anat. Tovoa. p. 442. t See cases recorded by Andral, Clin. Med. t. iv. and 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 coeliac 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.f 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 (hat 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 porta?, 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 wh ich 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 the 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 cceliac 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 portse and the conflux of the splenic and superior mesenteric veins, the superior mesenteric artery, 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, ai$ 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 be 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.* 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 ; /*, 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 constriction from the artery. Such a constriction can hardly * Sf.c an interesting paper by Dr. Hart, in the Dub. Hosp". Reports, vol. v. t Diet. Pract. Med. art. Epigastrium, CAVITY. 505 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 lamina? 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 form a triangular enclosure, the basis of which is formed by the bodies of the vertebra;. In this space we find the aorta, and lower down the primitive iliac arteries, the commencement of the thoracic duct, the receptaculum chyli, and several tributary lymphatics and lacteals with their ganglions, the vena cava ascendens, and the left renal vein, the lumbar arteries and veins, and many nervous ramifications from the sympathetic, and more on the sides the lumbar ganglia of the same nerve; here also we notice the fibrous insertions of the crura of the diaphragm, and the anterior common ligament of the vertebrae. Each lamina of the VOL. I. 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 musculocutaneous 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 ccecum, 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 from 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 50:6 CAVITY. in it, whether originating in the wall or in the ccecum. There is no part of the intestinal canal in which accumulations are more likely to take place than in the ccecum ; and it is now pretty well ascertained by the researches of various observers that inflammation is often pro- pagated from the ccecum distended with har- dened feces 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 coecum.* 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 ccecum, and percussion em- ployed here will often afford considerable assistance in forming a diagnosis. The ver- miform appendix of the ccecum 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 ccecum, 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 ccecum 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 the rectum with its mesorectum, the middle sacral 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- tum, however, is sometimes, though rarely, found in front of the uterus. The diaphragm 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 ; the peritoneum no longer descends into the pelvic excavation, the bladder and the rectum are strongly compressed, and are in some de- gree impeded in performing their functions; the uterus itself is inclined to one side, in con- sequence of the projection of the vertebral 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 can 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 contained viscera. The most remarkable characteristic of the abdomen at the earliest period is its very great capacity when compared with the other cavities; this arises from thegreatdevelopmentof its contained organs. This great size, however, is manifest entirely in the umbilical region, for neither the epigastric nor the hypogastric can be said to exceed their proportional magnitude in the adult. On the contrary, both these * Blandin, Anat. Topog. p. 431. CAVITY. 507 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 smallpartof the umbilical 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 then at different heights along the inner side of the iliac fossa; ; 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 foetus 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 foetus 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. torn. v. Blandin, Anat. Topog. and Meckel, Anat. Gen. Desc. et Path. torn. iii. 2 I 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 of 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- phulos or congenital umbilical hernia. Both, as Isidore Geoffioy St. Ililaire 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 Hmnaines, pp. 183 & seqq. plate 15. place at an early period of fcetal 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 it is closed having been arrested. This mode 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 hernise 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 pyrami- 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. lxxii.) in wbich 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. Phys. Dub. vol. i. New Series. See also several other cases referred to in Meckel, Handbuch Der Pathol. Anatomie, Band. i. p. 97 — 139. t See Fried, de foetu intestinis plane ntidis 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 will 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. Sucli 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 Translocations 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 mucosas, 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 510 CELLULAR TISSUE. strictm, t. cellulitis 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- 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- 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- 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, 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 it should constitute, as some authorities have con- tended that it does, a species of atmosphere 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 areola1 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 serositu. 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 sni 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, the 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 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 it 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 th.° 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 the 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 irtfiam mat ion, 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. Ulceration. — 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- emia,* 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. Haslings. 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 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 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 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 hyperemia, 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 scirrhus ; 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 iardaceous, 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 cede- * Compend. 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 516 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 cases occurring in one year in the Hos- pice des Enfans Trouves 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 areola; 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 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 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 with 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 jiluriu 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 tissu muq., in his works by Richerand. W. Hunter, in Med. Obs. and Inq. vol. ii. p. 17. Holier, Elementa Physiolog. The systems of Portal, Bichat, Meckel, Beclard, Craigie, and Grainger, Blandin § 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. Hodykin, Annals of Phil. Aug. 1827. The systems of physiology by Blumenhach, 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. De Blainville , De 1'organis. des ariimaux. 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 Cbirurgical Knowledge, vol. iii. Breschet, Recher. sur les hydrop. actives, &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 et seq. Cyclop, of Pract. Med. art. Anasarca. Diet, de Med. et de Chir. Prat. art. Acephalocystes , Anasarqne, Emphyseme, Entozoaires, Inflammation. Mayo, Outlines of human patho- logy. Lobstein, Traite d'anat. pathol. p. 201. Duncan, in Trans, of Med. Chir. Soc. Edin. vol. i. (JR. D. Grainger.) CEPHALOPODA— (x6(pax„, caput, pes); Eng. Cephalopods; Fr. Cephalopodes ; Germ. Kopffusslern, Blackfische, Tinten-fische ; Ital. Scppie, Polpi. Syn. MaXanloc, Aristotle; Mottia, Pliny; the genera Nautilus, Argo- nauta, and Sepia, Linne ; Octopodia, Schneider; Mollusca brachiata, Poli ; Mollusca Cephalo- poda, Cuvier ; Cephalopoda, Lamarck, Leach ; Brachiocephula, Cephalophores, De Blainville ; Pterygia, Latreille, (including the Pteropoda of Cuvier); Antliobrachionuphora, 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 feet (C), or principal organs of loco- motion. Characters of the Cluss. — 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, Jigs. 206, et seq.) and containing the respiratory, circulating, gene- rative, and principal digestive viscera : the mantle sometimes supports a pair of fins (J>, 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 branchial 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 Jig.208. The shell covers the posterior part of the body, the arms are anterior and directed forwards; the letters A, B, C, are along the dorsal or upper surface, the letter i is beneath the ventral or lower surface. t A third order of Cephalopods (the Celluhcea of De Blainville) has been proposed to include an extensive series of minute poly thalamous shells, of exquisite beauty in their form and sculpture, which differ from the camerated shells of our Tetrabran- chiate order in the absence of a siphon, but which 518 CEPHALOPODA. In the first of these, which is most closely allied to the Gasteropodous Mol- lusks, the branchiae are four in number, and the order is therefore termed Tetra- branchitita : in the higher division, which approaches nearest to the Vertebrate ani- mals, the branchiae are two in number, and the order is called Dibrunc/iiata. Order I. TETRABRANCHIATA. Syn. Pu/t/thalamaces, Blainville ; Sip/io- nifera, D'Orbigny ; minus the Spirulidcc and Selemnitidie. The Tetr abranchiate Cephalopods, of which the Pearly Nautilus (Jig. 205) may be regarded as the type, are provided with a large external uni- valve shell, sym- metrical in form like the body of the animal which it protects, straight, or con- voluted on a ver- tical plane, and divided by a se- ries of partitions («, a) into nume- rous chambers (i,6),of which the last-formed (&') is the largest, and alone contains the body of the animal : a dilatable and contractile tube (c, c) is continued from the posterior part of the M. D'Orbigny believes to be constructed by mol- luscous animals of a grade of organization which entitles them to rank with the Cephalopodous class. For this group of animals M. De Haan has pro- posed the name of Asiphonoidea ; but M. D'Orbigny, observing that the chambers of their shells com- municate together by means of one or more fora- mina, has substituted the positive term Foraminifera, and they are placed by Cuvier at the end of the Cephalopodous class under that denomination in the last edition of the Regne Animal. Strong evidence has, however, been recently ad- duced to prove that these minute shells owe their existence to animals which have no pretensions to rank with the Cephalopods ; but before we give the account of M. Dujardin, who is the author of this view, we shall first quote M. D'Orbigny's own description of the animal of the shells, the struc- ture of which he has so ably s'udied and so happily demonstrated by means of enlarged models. " The Cephalopods of the Foraminiferous Order have a bursiform body, in the posterior part of which the shell is lodged ; the body of the animal sometimes presents a great size compared to that of the head, to which it is occasionally subservient as a means of protection, entirely surrounding it in the anterior folds of the skin. The head is small, scarcely, if at all, distinct from the body, terminated by numerous tentacles forming many rows around the moulh, which is central. The animal seems to adhere very slightly to the shell ; it rapidly passes into a state of decomposition after death, when the slightest touch is sufficient to detach it from the shell, in which nothing is left but a coloured liquid which fills all its chambers. The food of these animals consists of different species of Polyps." M. De Blainville, however, states, in the Ap- pendix to his Manuel de Malacologie, page 649, that the animal of one of the microscopic genera con- Fig. 205. The Pearly Nautilus, Nautilus Pompilius, Linn. animal through all the partitions and cham- bers of the shell ; but the attachment of the shell to the body is effected by means of tained in his order Cellulacea, viz. Miliola, has no relation whatever in its structure to a Cephalopod, or Cryptodibranche. And more recently M. Dujar- din has read a memoir, entitled ' Sur les Symplec- tomeres, ou pretendm Cephalopodes mieroscopiques ,' in which the results of numerous and apparently careful observations on the soft parts of different genera of the animals in question are directly op- posed to those of M. D'Orbigny. M. Dujardin carefully studied the Miliolae.Vortici- alias, Rotalias, Truncatulina?, Ciistellariae, Mellonia?, &c. in the recent and living state ; and found that the shell'was not internal, and that the animal, which is absolutely deprived of organs of locomotion and even of respiration, is composed of a succession of joints or lobes, which go on increasing successively, and enveloping each other. The only period when the soft parts of the animal are visible externally, is when a new joint is produced which has not com- pleted the formation of its chamber. On breaking the shell, the composition of the animal is found to be as simple as in the Planariae or Hydras, or any other animals of the Acrite sub-kingdom ; and on dissolving the shell by means of a mixture of alcohol and very weak nitric acid, the entire body is obtained, which is formed of a succession of articulations, occupying all the chambers; and presenting different aspects in different genera, which accord with the peculiarities of the shell. From these observations it necessarily follows that the Foraminifera of JYI. D'Orbigny cannot be arranged with the Cephalopods, or even placed in the Molluscous Series. M. Dujardin, therefore, proposes to consider them as a distinct class of Invertebrata, under the name of Symplectomeres ; and until further and better evidence be adduced to the contrary, we shall regard these minute ani- mals as having only , in the form and structure of their shells, a remote analogical relation to the Cephalopods. CEPHALOPODA. 619 two strong lateral muscles (rf*), which are in- serted into the walls of the last chamber. The numerous hollow arms (e, e) and retrac- tile tentacles (/,/), mentioned in the general characters of the class are peculiar to this order, and the head is further provided with a large ligamento-muscular plate, or flattened disc, (g,) which, besides acting as a defence to the open- ing of the shell, serves also, in all probability, as an organ for creeping along the ground, like the foot in the Gasteropods. There are no fins or analogous organs for swimming. The jaws of the Tetrabranchiata are strength- ened by a dense, exterior, calcareous coating, and have thick dentated margins. The eyes are pedunculated (h,fig- 205) and of a simple structure. There is no organ of hearing. The gills are four in number, and without branchial hearts. The circulating system is provided with but one ventricle, which is systemic or propels arterial blood. There is no ink-bag. The inferior parietes of the funnel (i, fig. 205) are divided longitudinally. Order II. DIBRANCHIATA. Syn. Cryp- todibrunc/ies, Blainv.; Acetubulifera, D'Orb. ; plus the Spirulidtf and Belemnitida . In the Dibranchiate Cephalopods one genus alone ( Argonauta, jig. 206) has been hitherto found in which the body is protected by an Fig. 206. The Paper Nautilus or Argonaut, Argonauta A rgo, Linn. external shell ( a) ; but this, though symme- trical, and convoluted on a vertical plane, consists of one simple chamber, or is ' mono- thalamous,' and does not adhere to the body of its Cephalopodous occupant, either by a hydraulic pipe or lateral muscles. All the other genera of the Dibranchiate Order are naked ; but they are provided either with an internal siphoniferous polythalamous shell,f or the remains of a shell are found in various stages of degradation lodged in the substance of the dorsal part of the mantle. The arms of the Dibranchiata are, properly speaking, eight in number, (c, 1, 2, 3, 4, fig. 206,) to which, in many genera, two longer tentacles ( d, d,figs. 207, 208) are superadded. Both kinds of prehensile organs are provided with acetabula, or suctorious discs for adhesion ; and hence the order has been termed Acetubu- lifera. The jaws are horny, and their margins tren- chant. The eyes are sessile, (e, e,fg. 207,) and of a more perfect structure. The organ of hearing is distinctly developed. The gills never exceed two in number; but the branchial circulation is aided by two mus- cular ventricles, situated one at the base of each gill ; hence there are three distinct hearts in this order. There is an organ for secreting and expelling an inky fluid, used as a means of concealment. The parietes of the funnel are entire, (i, figs. 206, 208.) Subdivision of the Orders. — In the ancient periods of the globe the Tetrabranchiate Cepha- lopods appear to have abounded in every sea ; one genus only, however, viz. the Nautilus, appears to have escaped the influences which have ren- dered extinct the rest of this once extensive order. Their chambered shells are found, generally in a fossil state, in all the regions of the globe, and at every elevation, charac- terizing the strata of the se- condary formation. In some places they occur in such pro- digious numbers that the rocks appear to be composed almost exclusively of their remains. Some of these fossil shells testify the immense size to which their animal construc- tors must have attained : the shells called ' Cornua Am- monis,' which were formed by Cephalopods resembling the Nautilus, have been found measuring four or five feet in diameter; some of the straight chambered shells, called ' Or- thoceratites,' exceed four feet other species again appear not to have surpassed the size of a grain of rice. As the consideration of these remains, of which the Tetrabranchiate division of Cepha- lopods is almost exclusively composed, would necessarily oblige us to exceed the limits allot- ted to this article, we shall here subjoin merely the characters of the two families into which they naturally resolve themselves, and to which their distribution appears to be limited. lencth * The letter is placed on the portion of broken shell which still adhered to one of the lateral muscles in the specimen taken by Mr. Geo. Bennett, in the New Hebrides Islands. See PI. 1. Memoir on the Pearly Nautilus, 4to. 1832. + This is the case in the Families Spirulidas and Belemnitidce ; the terms Polythalamacea or Sipho- nifera, therefore, do not distinguish the preceding or Tetrabranchiate Order, nor indicate any cha- racters peculiar to that group, or which are of ordi- nal importance : and in other Molluscous classes it may be observed that modifications of the shell fail to afford indications of the primary divisions, which are uniformly based , as in the present arrange- ment of Cephalopods, on the modifications of the respiratory system. 520 CEPHALOPODA. Fam. 1. NAUTILIDJE, Nautilites. Animal, organized as described in the character of the order. Shell external; spiral, or straight; septa smooth, and simple ; the last chamber the largest, and containing the animal: siphon central, or marginal and in- ternal. Ex. Genera Nautilus, Lamarck ; Cli/- menes, Munster ; Campulites, Des- hayes; Lituites, Breyn ; Orthoceratites, Breyn. Fam. 2. AMMONITIDJE, Ammonites, Snake-stones. Animal unknown, presumed to resemble the Nautilus. Shell external ; spiral or straight ; septa sinuous, and with lobated margins ; the last chamber the largest and lodg- ing the animal : siphon central, or mar- ginal and external. Ex. Genera Baculites, Lamarck; Ha- mites, Parkinson ; Scaphites, Parkin- son ; Ammonites, Bruguiere ; Turru- lites, Lamarck. The Dibranchiate Order of Cephalopods also had its representatives in the seas of the ancient world, as the shells called Belemnites, or thunder-stones, the fossil shells of the Sepias discovered by Cuvier, and the horny rings of the acetabula found by Buckland in the fossil faeces of Ichthyosauri, sufficiently testify ; but our knowledge of this order is chiefly founded on observation of existing species. These are extremely numerous; they frequent the seas of every clime, from the ice-bound shores of Boothia Felix to the open main, and floating Sargasso or gulf-weed of the Equator; they seem, however, to be most abundant in temperate lati- tudes. Many species frequent the coasts, creep- ing among the rocks and stones at the bottom ; others are pelagic, swimming well, and are found in the ocean at a great distance from land. The Dibranchiala present great variety of size, and although the bulk of the gigantic species has been undoubtedly exaggerated, yet the organization of this order is favourable to the attainment of dimensions beyond those presented by the individuals of any other group of Invertebrate animals. The remains of the large Uncinated Calamary caught by Banks and Solander in the Southern Ocean, parts of which are still preserved in the Hunterian Museum, and the fragment of the Cephalopod weighing one hundred pounds, taken by the French naturalists in the Atlantic Ocean under the line, and preserved in the Museum of the Garden of Plants at Paris, afford indubitable testimony of the formidable size to which some individuals of this order attain. The species included in the higher divi- sion of Cephalopods very naturally resolve themselves into those which possess the eight ordinary arms, forming the tribe Octopoda ; and into those which have the additional pair of elongated tentacles, forming the tribe De- capoda. The Decapods are further characterized by having a pair of fins attached to the mantle; by having the funnel either adherent at the antero-lateral parts of its base, and without an internal valve, or articulated at the same part by two ball-and-socket joints to the mantle, and provided with a valve internally at its apex ; by having fleshy appendages to the branchial hearts, and glandular appendages to the biliary ducts; by having generally a single oviduct, with detached superadded glands ; and, lastly, by the shell or its rudiment being single, mesial, and dorsal. The Decapodous tribe is that which is most nearly allied to the Tetrabranchiate Order. This affinity is not only indicated by the additional number of external arms, and the frequent de- velopment of an internal circular series of eight short labial tentacles, but by several internal characters ; as the single oviduct and detached glands for secreting the nidamentum ; the valve of the funnel; the laminated rudiment of a chambered shell in the Cuttle-fish, and the fully developed chambered and siphoniferous shell of the Belemnites and Spirula. The observa- tions of Peron and Lamarck having proved that the animal of the Spirula possesses eight short arms and two long tentacles, all provided with acetabula, like the Sepia, we regard it as the type of the first family of the Decapo- dous Tribe, or that which immediately succeeds the Tetrabranchiuta. Tribe DECAPODA. Fam. 1. SPIRULIDM. Animal, corresponding in external form to the Decapodous type ; internal or- ganization unknown, presumed to be Dibranchiate. Shell partly internal ; cylindrical, multilo- cular, discoid ; the whorls separated ; septa transverse, concave next the out- let, and with regular intervals. Siphon marginal and internal, uninter- rupted. Genus Spirula, Lam. The character of the family is also that of the single genus of which it is at present composed. Ex. Spirula Australis, Lam. Fam. 2. BELEMNI TIDJE, Belemnites, Thunder-stones. Animal unknown.* Shell internal, composed of an external calcareous sheath formed by a succes- sion of hollow cones, the exterior being the largest; of an internal horny sheath, also of a conical form, containing at its apex a chambered shell, the septa of * As it is certain that the animals of this family of extinct Cephalopods possessed the ink-bag, they must consequently have been enveloped by a mus- cular mantle ; and we may, therefore, infer that they resembled the Dibranchiates in their locomo- tive and respiratory organs, and consequently in the general plan of their organization. In the structure and position of their siphoniferous came- rated shell they are intermediate to Spirula and Sepia, and as the animal of Spirula is proved to be a Decapod, the probability is very strong that the animal of the Belemnite was of the same type. CEPHALOPODA. 52) which are concave externally and perfo- rated by a marginal and ventral siphon. Genus Belem kites, Lamarck* Fam. 3. SEP IAD jE, Cuttle-fishes. Animal, body oblong, depressed, with two narrow lateral fins extending its whole length. Shell internal, lodged in a sac in the back part of the mantle, composed of an ex- ternal calcareous apex or mucro, of a succession of calcareous laminae with intervening spaces filled with air, and supported by columns, but not perfo- rated by a siphon, and an internal horny layer, corresponding to the anterior horny sheath of the Belemnites. Genus Sepia, Cuv. The character of the family is also that of the single genus at present composing it; we may, however, add under this head that the mantle is free at its an- terior margin ; and that the acetabula are supported by horny hoops with the margin entire, or very minutely denti- culated. Ex. Sepia officinalis, Linn, the common Cuttle-fish. (Fig. 207.) Fig. 207 fam. 4. TEUTHIDM* Calamaries. Animal, body sometimes oblong and de- pressed, generally elongated and cylin- drical ; with a pair of fins varying in their relative size and position, but generally broad, shorterthan thebody,and terminal. Shell internal, rudimental, in the form of athin, straight, elongated, horny lamina; encysted in the substance of the dorsal aspect of the mantle. A. Funnelivith an internal valve, andarti- culuted at its base to two ventro-lateral cartilaginous prominences of the mantle. Genus Sepiotfuthis, Blainville. Body oval, flattened, with narrow lateral fins, extending its whole length ; ante- rior margin of the mantle unattached. Horny hoops of the acetabula with den- ticulated margins. Gladius, or rudi- mental shell, long and wide. Ex. Sepioteuthis loliginijbrmis, Ruppel. Genus Loligo, Cuvier. Body elongated, cylindrical, provided with a pair of rhoinboidal or triangular fins, shorter than the body, and terminal, their apices generally converging to a point, and united to the end of the man- tle; anterior margin of the mantle free. Horny hoops of the acetabula denticu- lated. Gladius long and narrow. Ex. Loligo vulgaris, Cuv. the common Calamary or Pen-fish. ( Fig. 208.) Fig. 208. * Also the fossil genera, Actinocamax , Miller ; Pseudubelus, Blainville. VOL. t. The Calamary, Loligo vulgaris, Cuv. * From the term teu8«c applied by Aristotle to the ten-armed Malakia with an internal horny plate or gladius. 2 M 522 CEPHALOPODA. Genvs Onychoteuthis, Lichtenstein. Body and fins as in the genus Loligo ; ventro-lateral cartilages of the mantle long and narrow ; horny hoops of the tentacular, and sometimes of the bra- chial, acetabula produced into the form of hooks or claws. (Fig. 215.) Gla- dius long, broadest in the middle. Genus Rossia, Owen. Body short and rounded ; cephalic margin of the mantle free; fins advanced, short, circular, ses- sile, distant and subdorsal. Gladius short and narrow. Ex. Rossia palpebrosa, Owen. Genus Sepiola, Leach. Body rounded, short; anterior margin of the mantle adherent to the back of the head ; fins advanced, circular, short, subpeduncu- late, distant and subdorsal. Gladius short and narrow. Ex. Sepiola Rondeletii, Leach. B. Funnel unprovided with an internal valve, and adherent at the antero-lateral parts of its base to the mantle. Genus Loligopsis, Lamarck. Body long and cylindrical, terminated by a pairof conjoined large roundfins,forming generally a circular disc ; anterior border of the mantle adherent to the back part of the head for a small extent. Tenta- cula very long and slender, (frequently mutilated.) Gladius long, narrowest in the middle, dilated posteriorly. Ex. Loligopsis Veranii, Ferussac. ( Fig. 209; D the gladius or rudimental shell.) Genus Cranchia, Leach. Body elon- gated, sacciform; anterior margin of the mantle adherent to the back of the head. Fins short, rounded, subpedun- culate, approximate, dorsal, and sub- terminal. Gladius long and narrow. Ex. Cranchia scabra, Leach. Tribe OCTOPODA. The Dibranchiate Fig. 209. Loligopsis Veranii. CEPHALOPODA. 523 Octopods, besides wanting the long tentacula, are also characterized by the absence of man- tle-fins, and consequently are limited to retro- grade progression while swimming ; their ace- tabula are sessile and unarmed ; they have two oviducts, but without detached glands for secre- ting a nidamentum. Family TEST ACE A. Body oblong, rounded ; mantle adhering posteriorly to the head ; first, or dorsal pairs of arms dilated and membranous at the extremity; fc, 1, fig. 206.) Funnel without a valve, but articulated at its base by two ball-and-socket joints to the inner sides of the mantle. Bran- chial hearts with fleshy appendages. No internal horny or testaceous rudi- ments ; but an external monothalamous, symmetrical shell, containing, but not attached to, the body of the animal; which also deposits its eggs in the cavity of the shell. Genus Argonauta, Linnaeus. On the supposition that the shell is parasitically occupied by the Cephalopod, but formed by some other mollusk, some natu- ralists limit the above generic title to the shell, and call the Cephalopod Ocytho'e.* We shall, however, con- tinue to apply the term Argonauta to the Cephalopod in question, as the evidence, Fig. though strong, is not conclusive of its parasitic nature. The character of the Family is also that of the Genus. Ex. Argonauta Argo, Linn. (fig. 206.) Genus Belerophon, founded on the fossil remains of a shell resembling in family characters that of the Argonauta. Ex. Belerophon apertus, Sowerby. Family NUDA. Body generally rounded, mantle broadly continuous with the back of the head. Arms connected at the base by a broad web : first pair elongated, and gradually narrowing to a point. Funnel without an internal valve or external joints ; branchial hearts without fleshy appen- dages ; biliary ducts without follicular appendages. Shell represented by two short rudimental styles, encysted in the dorso-lateral parts of the mantle. Genus Octopus, Leach. The arms pro- vided with a double alternate series of sessile acetabula. Ex. Octopus vulgaris, Cuv. the Poulp or Preke, (fig. 210, in which this species is represented in the act of creeping on the shore ; its body being carried verti- cally in the reverse position with the head downwards; its back being turned to the spectator, towards whom it is supposed to be advancing.) 210. The Poulp, Octopus vulgaris, Cuv * Should the above suspicion be proved to be well founded, we conceive that it would be more appropriate to retain the term Argonauta, in order to designate the Cephalopod which navigates the frail bark ; and revert to the original name of Cymbium for the shell, which was applied to it by 2 M 2 CEPHALOPODA. Genus Eledone, Leach. The arms pro- vided with a single series of sessile acetabula. Ex. Eledone cirrosa, Leach. Internal cartilaginous parts, or Endo- skeleton. — In the Gasteropodous Mollusks the cerebral orsupra-cesophageat ganglions are pro- tected by a dense membrane which has been compared to a dura mater, hut which may be regarded with more propriety as representing the membranous condition of the skull in the embryo of the vertebrate animal ; and which, in fact, assumes a cartilaginous texture in some of the higher organized Pectinibranchiata, forming in them the unquestionable rudiment of a true internal skeleton. In the present class a thick cranial cartilage not only protects the cephalic masses of the nervous system ; but it is enlarged and extended in different directions, so as to afford a basis of attachment to the principal muscular masses of the body : thus fulfilling the second important function of an internal skeleton. In the Nautilus it consists of one principal cartilage, (jig. 211,) which is situated on the ventral aspect of the oesophagus ; two pro- cesses (a a) extend from the posterior or dorsal angles on each side of the oesophagus as far as the optic gan- glions. A deep semi- circular groove (b) extends along the an- terior part of these processes for the lodg- ment of the optic ganglions and the an- terior nervous collar surrounding the oeso- phagus. Two other processes (c c) arise from the ventral angles of the cartilage and give support to the sides of the base of the funnel. A middle process is extended some way between the two great muscles which are inserted into the shell. The central part or body of the cartilage (d) is excavated for the reception of the venous blood returned from the head and funnel, and from this sinus the great dorsal vein commences. In the Dibranchiate Cephalopods the inter- nal cartilaginous skeleton consists of a greater Gualtieri, when he first separated it generically from the Chambered Nautilus. In either case, as the grounds for constituting the new family of Oc- topoda now proposed are derived from important organic differences, as manifested in the structure of the funnel and the branchial hearts, the claims of the Cephalopod to form the type of such a group would not be destroyed by the proof of the shell forming no part of its structure. We cannot, how- ever, retain both the genera Argonauta and Ocy- thoe, as in the Families Naturelles du Regne Animal of Latreille, p. 168 ■, since, if the shell in question be not secreted by the Cephalopod, its analogy to that of the Carinaria would indicate its real con- structor to belong to the Heteropodous Mollusks. Internal Cartilage or Skeleton of the Nautilus. number of pieces, and has a more important share in the organization and functions of the animal. We shall describe it principally as it exists in the Cuttle-fish ( Sepia Officinalis ). The cranial cartilage (A, Jig. 212) is no longer limited in its position to the under side of the oesophagus, but completely surrounds that tube, which, together with the inferior sali- vary ducts, and the cephalic branches of the aorta, traverses a narrow passage in the centre. It is expanded above into a cavity, which en- closes and protects the brain ; while, below the oesophagus, the dense cartilage is excavated to form the two vestibular cavities of the organ of hearing ; at the sides it is developed into broad and thick concave processes, which form the back part of the orbits. In the subjoined figure A is the cranial car- tilage as seen from above : — a is the superior part which protects the brain. b, b, are the two large optic foramina. c, c, the posterior and inferior thick ex- panded orbital process. d, d, the thin and long anterior and inferior cartilage which supports the eye-ball, and is analogous to the cartilaginous eye pedicle of the Rays and Sharks : these processes are com- pared by Meckel to the superior maxillae ; they do not exist in the Octopods, and are compa- ratively much smaller in the Calamaries than in the Cuttle-fish. e, the anterior aperture of the canal through which the oesophagus passes. f, a process, continued from the anterior part of the cranial cartilage, which expands into a broad transverse plate, with a slight con- cavity directed forwards, and gives attachment to the muscles of the arms: this cartilage Meckel compares to the lower jaw, but the analogy is not more satisfactory than in the preceding instance. The infundibular or nuchal cartilage (B), which is a process of the cranial cartilage in the Nautilus, is in the Dibranchiates, and es- pecially the Cuttle-fish, a distinct piece, of large size, and of a flattened triangular figure, situated above the base of the funnel, with its apex directed forwards and its posterior angles turned backwards : it has a moderately deep furrow along the middle of its upper surface. In the Sagittated Calamary this important car- tilage consists of three portions, a middle elon- gated one, having on its dorsal surface a mesial longitudinal groove, and two lateral longitudinal ridges which are adapted to a corresponding ridge and two grooves in the under part of the sheath of thegladius, which sheath here assumes a dense cartilaginous consistence : from the an- terior extremity of the middle nuchal cartilage two flattened cartilages extend outwards and backwards, and then curve slightly inwards. These correspond to the dilated base of the carti- lage in the Sepia, protect the great lateral nerves of the mantle, and give origin to the lateral muscles which are perforated by the nerves. On each side of the base of the funnel there is a smooth oblong articular cavity which is formed by a distinct cartilage (C) ; it is adapted to receive a corresponding cartilagi- CEPHALOPODA. 525 Fig. 212. 6 i Skeleton of the Cuttle-fish. nous prominence arising from the inner sur- face of the sides of the mantle. This pro- minence in the Sepia is of an oval shape ; but in the Teuthida it forms a narrow, elongated, cartilaginous ridge, and is adapted to a cor- responding groove at the sides of the funnel. In the Calamary the ridge is of the same size with the groove ; but in the Onychoteuthis the ridge or antero-lateral cartilage commences at the anterior margin of the mantle, and extends downwards some way below the termination of the infundibular groove. Rathke* discovered in the corresponding part of the mantle of the * Memoires de l'Acad. Imp. des Sciences de Pctersbourgh, torn. ii. pt. 1 ct 2, p, 154. Loligopsis, viz. on either side and towards the ventral aspect, a thick, opaline, elongated cartilage, extending longitudinally for more than half the length of the mantle, and sup- porting a series of wart-like processes. These lateral tuberculated cartilages in Loligopsis we regard as corresponding to the lateral ridges in the Calamaries and Onychoteuthis above-men- tioned ; but in the Loligopsis they are not arti- culated with the sides of the funnel, which are otherwise attached to the mantle. In all the Decapods, however, this pair of cartilages on the ventro-lateral aspects of the mantle is more or less developed. In the Sepia a longitudinal cartilage is situated on the ventral aspect of the liver. The long lateral fins are, in the same genus, each supported by a narrow, flattened, elon- gated, cartilaginous plate (D, D, jig. 212); pointed at its anterior extremity, obliquely truncate behind ; smooth and gently concave internally (g), but traversed by an irre- gular longitudinal ridge (h) on its external surface. These cartilages form the points of attachment to the powerful muscles of the lateral fins. From the dorsal ridge of each cartilage a number of close-set fibro-cartila- ginous lamina? extend at right angles to the cartilage to near the margin of the fin, with their plane in the direction of the axis of the body : they alternate with the strata of mus- cular fibres, resembling the rays which support the fins of fishes. The analogy of this structure to the cartila- ginous basis of the great pectoral fin of the Ray is so close and satisfactory that we can scarcely hesitate to acknowledge the locomotive appen- dages of the mantle in the Decapodous Cepha- lopoda as representatives of the pectoral fins of fishes, and consequently of the anterior extre- mity of the vertebrated animal. As they are not, however, fixed to a vertebral column, their situation is not constant, being sometimes, as in Rossia, situated towards the anterior part of the body; sometimes, as in Loligo, placed at the posterior extremity ; just as we perceive the ventral fins of Fishes shifting their position, in consequence of a similar want of connexion, so as to occupy, in some species, a position more anterior even than the pectoral fins, with- out losing their essential character, as the ana- logues of the posterior extremities. The cartilages of the fins correspond in length to the parts which they support, and are con- sequently much longer in the Cuttle-fish than in the Calamaries; in the Octopods they are entirely wanting. Locomotive System. — The organs of loco- motion in the Cephalopods are of two kinds, one consisting of appendages developed from the head ; the other of rudimental fin-like ex- tremities developed from the trunk ; the latter organs are confined, as we have seen, to the Decapodous genera of the higher or Dibran- chiate Order. The cephalic processes, which are called digitations, arms, feet, tentacles, and pedun- cles, have no real homology with the loco- motive extremities of the Vcrtebrata ; to these they are analogous only, inasmuch as they 526 CEPHALOPODA. 213. have a similarrelationof subserviency to the loco- motive and prehensile faculties of the animal. Among the Vertebrates traces of organs corre- sponding to these cephalic feet are met with principally in the class of Fishes, in the form of tentacles developed from the lips ; and Schultze, a learned German Naturalist,* has indicated the close affinity which the Cyclo- stomous Fishes bear, in this respect, to the Cephalopods; in one genus, viz. Gastro- branchus, or Myxine, eight free filaments are extended forwards from the circumference of the funnel-shaped orifice of the mouth, repre- senting the eight ordinary arms of the Cepha- lopoda Dibranchiata, but arrested in their de- velopment because of the pre- ponderating size of the caudal extremity of the body, which now forms the sole locomotive organ. The expanded sucker anterior to the jaws of the Lamprey may, in like manner, be considered to represent the united bases of the cephalic feet of the class under consi- deration. In the Nautilus the cephalic organs of prehension and loco- motion consist of slender sub- cylindrical annulated tentacles, which are sheathed and retrac- tile, (fig. 213,) like those of some of theGasteropodousMol- lusks, as Doris, Thetht/s, and Tritonia. Here, however, they astonish the observer by their unexampled number, sur- rounding the mouth in suc- cessive series, and amounting to little short of a hundred. These tentacles are divided into three kinds, according to their situation, viz. ' brachial or digital,' ' ophthalmic,' and ' labial : ' the latter being again subdivided into ' ex- ternal ' and ' internal.' The brachial tentacles are forty in number, and are sup- ported by short conical trihe- dral hollow processes or digita- tions, ( e, e,fig. 205,) of which the two superior or dorsal ones are conjoined and dilated into a muscular disk covering the whole upper part of the head, Cf;g>fig- 2050 the remaining thirty-eight are disposed ir- regularly, nineteen on either side, one over- lapping another, and all directed forwards, con- verging towards the orifice of the oral cavity, in which the jaws and mouth are concealed. The longest of these digitations, when its free extremity only is measured, does not equal one inch ; but externally they appear longer, be- cause they adhere for some way to the sides of the head. The digitations present no trace of Digitation and Tentacle. Nautilus Pom- ■pilius. 1818 Meckel Archiv. fur Physiologic, 15. iv. p. 338. acetabula or suckers, but are perforated at the extremity by a canal ( a, a, Jig. 213,) which is continued far into the substance of the head to near the cerebral ring ; the tentacle (b) which is lodged in this canal, is consequently longer than the digitation from which it is protruded. The labial tentacles, forty-eight in number, extend from orifices situated on the anterior margins of four broad flattened processes, arising from the inner surface of the oral sheath opposite the base of the mandibles. Two of these processes (a, a,fig.2\9) are superior, posterior, and external in situation ; the other two, ( b, b,jig. 219,) which are smaller, are inferior, anterior, and more immediately embrace the jaws, and they are connected to- gether by a lamellated organ ( c,fig.2\9), after- wards to be described. Each of these ' labial' processes is pierced by twelve canals contain- ing the tentacles in question : they differ from the digital tentacles only in relative size, and in being of a softer and more delicate texture. The ophthalmic tentacles seem more ex- pressly designed as instruments of sensation ; they do not possess the strength requisite for prehensile purposes, and are not situated con- veniently for locomotive actions; they are four in number, and project laterally one before and one behind each eye, involuntarily reminding the observer of the antennae in Crustacea, &c. At first sight they seem annulated like the brachial and labial tentacles ; but upon a closer examination, they are found to consist of a num- ber of flattened circular disks closely packed upon a lateral stem, a structure which is sin- gularly analogous to that of the antennae of the Lamellicorn Beetles. In this respect, how- ever, the Pearly Nautilus does not stand alone in the Molluscous series, the retractile tentacula of the Doris present a very similar structure. The fibres of the dense musculo-ligamentous sheath (d} d, fig. 219), which incloses the man- dibles and supports the eyes and digital pro- cesses, arise from the whole of the anterior and outer part of the cartilaginous skeleton above described. They were so densely in- terwoven in the specimen we dissected as to preclude the possibility of ascertaining their exact course or arrangement. The large lateral muscles of the funnel come off principally from the infundibular processes of the internal cartilage. There are also two small round and distinct muscles designed to draw the funnel closer to the head, they pass to their insertion through canals excavated in the sides of the funnel. The fleshy masses which proceed backwards from the posterior part of the skeleton are the two great muscles (b, b, fig. 231 ,) which attach the Nautilus to its shell. These are inserted by obliquely truncated flattened extremities into a layer of horny substance which is closely adherent to the inner surface of the sides of the last chamber of the shell at a little distance from the septum forming its base : where, in recent specimens, these impressions are always to be plainly seen. The part which passes through the perforations of the septa is not a muscular or tendinous chord, as has been conjectured, but a weak membranous tube, CEPHALOPODA. 527 which can lend but a feeble assistance in main- taining the shell in its natural position. The mantle of the Nautilus is very thin and membranous, excepting at its free margin, where it is provided with longitudinal mus- cular fibres for its retraction, and a thin exter- nal stratum of transverse fibres, for the closing of its anterior aperture, during the expulsion of the respiratory currents. The large mandibles (a, b, jig. 217 ; e, f, jig. 219,) are supported upon a fleshy substance (g, Jig. 217), and moved by appropriate mus- cles. The fringed lip (c, Jig, 217) which sur- rounds them is provided with a longitudinal stratum of fibres for its retraction, and an exte- rior orbicular sphincter at its anterior margin. The whole buccal apparatus is attached to the cartilaginous skeleton by four strong retractor muscles, two above (A, A, Jig. 217, 219), and two below [i, i, Jig. 217), and its base is sur- rounded by a transverse stratum of muscular fibres (i, Jig. 219) continued from the external labial processes, across the upper or dorsal aspect of the jaws, which, by the contraction of these fibres, are protruded outwards. The tongue (jig. 236) is a large complex muscular organ, the extremity of which is retracted by two pair of long slender muscles (d) arising from the dense membrane closing the lower part of the mouth ; a third pair of muscles (6) given off from the posterior mar- gins of the lower mandible are inserted into the anterior extremity of the horny lingual rasp hereafter to be described. Other internal muscular parts will be mentioned in the de- scription of the viscera to which they relate. The muscular system of the Dibranchiate Cephalopods, like their internal skeleton, is much more elaborately developed than in the inferior order of which the Nautilus is the type : but the same plan may be observed to go- vern the disposition of all the principal masses. A hollow cone of muscular fibres is attached by a truncated apex to the anterior margin of the cephalic cartilage, or to processes deve- loped therefrom, in order to afford these fibres an increased surface cf origin. The fibres are interlaced, one with another, in a close and compact manner as the cone expands to form the cavity containing the fleshy mass of mouth ; and at the anterior extremity of the mouth they are continued forwards and separate into eight distinct portions, which form the arms. These organs are developed in a kind of inverse proportion to the body, being generally, as Aristotle* twice takes occasion to observe, longest in the short round-bodied Octopi or Poulps, and shortest in the long-bodied Cala- maries, Sepia?, &c. in which the two elongated retractile tentacles (d, jig. 207, 208, 209) are superadded, by way of compensation. These latter organs are rarely continued from the muscular cone inclosing the apparatus of the mouth, but arise from the cephalic cartilage, close together, internal to the origins of the * De Historia Animalium, ( Ed. Schneider, Lip- siae,) lib. iv. c. 1. 8 & 9. ventral pair of brachia; they proceed at first outwards to a large membranous cavity situated anterior to the eyes, and thence emerge between the third and fourth arms on either side. The acetabula or suckers are disposed along the whole extent of the inner surface of the ordinary arms, but are generally confined to the extremities of the tentacles, where they are closely aggregated on the inner aspect. Of the difference between the arms and tentacles Aristotle was well aware, and ac- cordingly, with his usual exactness, he applies to them distinct epithets : no'Ja? oZv o»ri I^E» xai tcirtvt; JixoTuJvouf TTaVTct TrXijv eve? j/evoc wo^TroJoiv. "ijio S' E^oucriv ai rs crwriai xat al tsuSiJej xai oi TEufloi Svo Tioo&oo-xiSai; fAaxfai iff ax fan Tpa- %6rnTa l^ai£pi5f opuflouJi). " After the mouth they have a long and narrow oesophagus, then a large round gizzard similar to that of a bird." — Hist, de Anim. lib. iv. c. 1.9. But it is evident that he also had dissected the Octopus, as he afterwards notices the difference in the position of the ink-bag, which occurs in this genu3 as compared with the Sepia. Loligo, as in the Loligo communis, it is ex- tended into a long pyriform membranous bag, but in the Loligo sagittuta, Sepia, and Octopus, it is elongated and twisted spirally, whence it is compared by Aristotle to the shell of a Whelk (f, Jigs. 220, 221). In each of these Fig. 221. Alimentary canal of the Sagittated Calamary.* genera its cavity is occupied by glandular laminse (g, g); the biliary ducts terminate be- tween two of the largest folds, which make a curve as they pass into the intestine, and are continued, gradually diminishing in size, along the canal, presenting at its commencement two tumid projections, which tend to prevent a regurgitation of bile towards the pylorus. The intestine in the Nautilus makes a loop, or narrow fold upon itself before it is continued forwards to the base of the funnel. In the Octopus it is characterized by a similar fold, but in the Cuttle-fish and Cala- mary the gut is continued in a straight line from the stomach to the vent (i, i, fig. 221), and is consequently very short and simple : in both cases it maintains nearly a uniform diameter to its termination. The internal tunic of the intestine is dis- posed in longitudinal folds, of which the two at its commencement, above described (i, », fig. 220), are the most conspicuous. The lon- gitudinal rugse in the Sepioteuthh and Cala- * Home, Lectures on Comp. Anat. pi. lxxxiii. 536 CEPHALOPODA. mary terminate abruptly where the duct of the ink-bag enters the gut (k, jig. 221), which for the small extent beyond this part is smooth internally. In the Octopods the intestine passes through the muscular septum of the branchial cham- ber, immediately above which it terminates. In the Decapods the rectum and duct of the ink-gland are surrounded by the muscular fibres which connect the pillars of the funnel to one another; in both cases the fibres serve as a sphincter to the anus. Fig. 222. In many Dibran- chiata, especially the Decapods, the termi- nation of the rectum is provided with two lateral fleshy appen- dages ; for which, as far as we know, no use has hitherto been as- signed J In the Sepio- teuthis/ these process- es (a, (a, Jig.222) are of a broad inequilate- ral triangular form, Anal valves, Sepioteuthis. attached to the sides of the transverse anal aperture (b) by their acute angle, from which a ridge extended lon- gitudinally to the middle of the base; when the processes were folded down upon the vent (as in A,fg.222),the ridge fitted into the aper- ture, so as accurately to close it. In the Cuttle-fish the corresponding processes are of a rhomboidal form, with a thicker ridge on the side next the anal aperture, which they in like man- ner are adapted to defend against the entrance of foreign substances by the funnel. In other genera they are not adapted to defend the anus mechanically, being elongated and filiform; but they probably serve to give warning of the presence of foreign bodies, and excite the necessary contraction of the constrictors of the gut ; Rathke compares them to antennae in the Loligopsis, where the anal processes are very long (11, Jig. 223). The apparatus for secreting the inky fluid, formerly regarded as characteristic of the class of Cephalopods, is wanting in the Nautilus, which, as it has a large and strong shell to pro- tect its body, stands less in need of such a means of defence : the ink-bag is, however, present in the Argonauta. The ink-bag (I, Jig. 221) varies in its re- lative position in different Dibranchiata: in the Cuttle-fish it is situated near the bottom of the pallial sac, in front of the testicle or ovary. In the Calamary it is raised close to the termination of the intestine ; we have found it similarly situated in the Argonauta, Sepioteu- this, and Rossia. In the Octopus it is buried in the substance of the liver, a small part only of its parietes appearing on the anterior sur- face of that gland, from which its duct is con- tinued forwards to terminate in this genus im- mediately behind the anus. From this connection of the ink-bag with the liver in the Poulp, Monro was led to sus- pect it to be the gall-bladder. What its real nature may be still remains doubtful ; De Blain- ville and Jacobson regard it as a rudimental urinary apparatus :* Sir Everard Home f com- pares it to the secreting sac which opens into the rectum in Rays and Sharks, and this we consider to be the true homology of the ink- bag. It is interesting, indeed, to observe that corresponding anal glandular cavities in the Mammalia are in many instances modified to serve by the odour of their secretion as a means of defence, just as the part in question operates in the Cephalopods by reason of the colour of the ejected fluid. When the ink-bag is laid open and well cleansed of its contents, its inner surface is seen to be composed of a fine cellular or spongy glandular substance : its exterior coat is of a tough white fibrous texture, and its outer surface commonly exhibits a peculiar glistening or silvery character. The ink-bag probably attains its largest pro- portional size in the genus Sepiola, where it presents a trilobate form. It is of an oblong pyriform shape in Sepia, Sepioteuthis, and Loligo. It is relatively larger in Sepia than in Octopus, and the quantity of water which its contents will discolour is very surprising: it behoves the anatomist, therefore, to be very careful not to puncture this part during the dissection of a Cephalopod. In the living Cephalopods the inky fluid is secreted with amazing rapidity ; we have seen an Octopus, which had previously discoloured the water for a considerable extent around it, immediately after its capture continuing its black ejections several times in quick succes- sion, and ultimately expelling in convulsive jets a colourless fluid, when the powers of secreting the black pigment were exhausted. In every species of Cephalopod which pos- sesses this organ, the tint of the secretion cor- responds, more or less, with the coloured spots on the integument. The Italian pigment, called ' Sepia,' and the Chinese one, com- monly called ' Indian Ink,' both of which are the inspissated contents of the organ above described, afford examples of different shades of this singular secretion. If the Cephalopods are enabled thus to con- ceal themselves during the day, they have also the power, by means of another secretion, to render themselves conspicuous by night by means of a phosphorescent exhalation.^ The Liver. — This gland is remarkable in the Cephalopods, as in the other classes of the Mol- luscous Sub-kingdom, for its great proportional size. In the Nautilus the liver (q, q, Jig. 219) extends, on each side of the crop, from the oesophagus to the gizzard. There is a parallelism of form, as will be afterwards seen, between this gland and the Respiratory organs, * Davy states that the secreted fluid is " a car- bonaceous substance mixed with gelatine ;" but, according to Bizio, this secretion yields on analysis a substance sui generis, which he calls ' Melania.' See Edinb. Philos. Journal, vol. xiv. p. 376. + Lectures on Comp. Anat. vol. i. p. 398. j See Oligerus Jacobaeus de Sepiaeluce, in the Acta Hafniens. vol. v. p. 283. CEPHALOPODA. 637 for it is divided into four lobes, and these are connected by a fifth portion, which passes transversely below the fundus of the crop. All these larger divisions are subdivided into numerous lobules of an angular form, which vary in size from three to five lines. These lobules are immediately invested by a very delicate capsule, and are more loosely sur- rounded by a peritoneal covering common to this gland and the crop. The liver is supplied by large branches which are given off from the aorta, {r,fig. 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. When 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 Luligupsis 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. Rathke, 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 llossia 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 Eledonc 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 * nnp»9«o mniilatus, 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, torn. ii. pt. 1 & 2, p. 149. VOL. I. capsule of the liver, but in the Argonaut and ii» 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 Fig. 223. 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 river of the Octopus, according to Muller,* and Rathke' observed the same structure in the terminal cceca 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. But in the Decapodous tribe they continue tosend Viseera in situ, Lolujopsis. off branches, which Lot. Esclischoltxii. subdivide and form clusters of ccecal 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.! 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 Scpiola, Onychoteuthis, Sepioteuthis, 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. 2 N 538 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- phalopods 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 aflattened 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 the upperor 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 («') 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. 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,) 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 ald',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 laminse, 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 (g ) 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 (I ). 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 thedorsal 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 f 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 eorrespond- ing side ; but previous to opening into the ventricle it dilates into a sinus Ce), 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 /'. 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 E/edunef they * From a consideralion of the different particu- lars given in Aristotle's anatomical description of the Cephalopods, Kbhler supposes the part which he calls (xv'ti^, mytis, to have been the glandular appendages of the veins above described. t Carus, Vergleich. Zootomie, tab. iv. 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 trunks 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 Rathke 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- * 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 urethras. 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 Fig. 226. 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,fg. 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, jig. 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 with cells * From Mayer, Analecten fiir Vergleichendc Anatomie, tab. v. and decussating carnea? columns (k,jig. 226), and where they com- municate with the ve- nous sinus two semi- lunar valves (I) 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 vital 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 lamina? ; and, as they approach the sys- temic ventricle, generally dilate into a sinus (n ) Fig. 227. Systemic Ventricle, Onychoteulhis. 542 CEPHALOPODA. on etch 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 Ouychoteuthis (fig. 227) it is lozenge-shaped, with the long axis in the axis of the body ; giving off the two aortae (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 Dibranchiata 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 columns earner, 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, Jig. 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, (q',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 Onychoteuthis 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, in the highest organized Mollusks, that relation with the anal 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 branchias 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 the provision 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 branchiaa 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 (h k> fig- 225) and most other Dibranchiates. They are composed of a number of triangular vascular lamina; extendingtransversely from each side of a central fleshy stem (h,fig. 225), having an alternate disposition : each lamina is com- posed of smaller transverse laminre, which are again similarly subdivided ; the entire gill thus exhibiting the structure called by botanists ' tri- pinnate,' by which an extensive surface is afford- ed for the minute division of the branchial vessels. CEPHALOPODA. .543 In the Nautilus (fig. 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 branchia? are each composed of thirty-six pairs of triangular lamina? : 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,fig. 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 thin 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 aeetabula. 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. 544 CEPHALOPODA. of repose, and the vesicles are contracted and invisible, the skin be 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 Fiance, 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 Linnaus 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 body turned towards the external wall of theshell, as in the figure (Jig. 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,+ 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 ca^aveous covering, such as the Argonauta shell must have formed if it had been applied to the body of the Ocythoe ub 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, torn. ii. p. 1, t Zoological Journal, vol. iv. CEPHALOPODA. 545 adopts different species as they happen to fall in his way. And further, that the different species of Argonauta, as the A. Argo, A. tuberculata, and A.hians, have each different species of Ocy- thoe. We may add that the light fragile tex- ture of the Argonauta 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 Delia 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. Mr. 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. P. 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, w£p! $£ yivto-ltet; xai &v\av{ris-ia><; T&S orTpanou anpiBai (ASi ovTrta Znrai.f 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. t " 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 hook 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 Dulium. The parasitic occupation of shells by the Octopi for the purpose of depositing the ova in them was not unknown to Aristotle. k«S «7T0ti>it£i o fxh 7n>Xv7rovt Ei{ T«( baXafxa; n eJj mpiy,tov ft rt a\\» xo~\m ofAoiov, &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, Onycoteutliis, and Loligo, it extends the whole length of the posterior part of the mantle. In Scpioteuthis 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. Fig. 228 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, * " Tr, fxii oSv c-r,tsla, xat tn Ttv8lo;. Sub dorso firma pars Sepiae Loligini ac Lolio continetur •, illius sepium, horum gladium vocant — Hist. Animal., lib. iv., c. 1. 12mo. Ed. Schneider. dilated, aliform margin (a, a), partly calca- reous and partly horny, which becomes nar- rower as it advances forwards, and is gradually lost in the sides of the shell. As this margin is inclined towards the ventral aspect, it pro- duces at the posterior and ventral side of the shell a wide and shallow concavity, comparable to the chamber of the Nautilus shell which protects the body of that species : if the free margin of the sepium were in like manner produced beyond the previously deposited layers, it would advance from the posterior and lateral aspects of the animal, and cover the ventral surface, as in the Nautilus, leaving the convexity produced by the chambered portion projecting into the back. The thickened part of the sepium (6) which retains that situation, is in fact composed of a series of thin parallel calcareous plates, successively deposited and extending obliquely forwards from the ventral to the dorsal surface : the last formed plate is the most internal and the broadest, but not the longest also, as in the Nautilus ; its develop- ment being limited to the anterior part of the shell, so that the previously deposited layers appear successively behind it forming irregular sinuous transverse striae (c). The intervals of the plates are occupied by crystalline fibres, passing perpendicularly from one layer to the other : A is a magnified view of this structure. At the posterior part of the sepium, a little anterior to the thin margin, a pointed hooked process projects backwards : this differs in size and shape in different species of Sepia; but it is always characteristic of the peculiar production which has been described, and has served to identify some doubtful fossils. As our present observations are limited to the recent species of Cephalopoda, we pass over the Belemnites, which are fossil internal shells of extinct animals of this order, to speak of that of the Spirula. This is a small recent Cephalopod, respecting the precise form and organization of which nothing is yet satis- factorily known. The only entire specimen which has been brought to Europe was taken by Peron, a French Naturalist, as it floated dead in the Tropical Ocean, between the Mol- luccas and the Isle of France ; it has been de- scribed and figured by Roissy, Peron, and Lamarck ; but both the figures and descrip- tions of these authors differ, and the specimen now no longer exists to determine the accuracy of either of the accounts. All agree, how- ever, in stating that part of the shell was concealed within the body of the animal ; and this fact is confirmed by a mutilated specimen in out own possession, and by one in a similar condition in the British Museum. The shell of the Spirula (fig. 230) is about an inch in diameter, symmetrical, con- voluted on one plane, with the whorls disjoined : it is composed of a succession of small regularly formed Fig. 230. Shell of the Spirula. chambers, separated by partitions {a, a), which CEPHALOPODA. 547 are concave towards the outlet of the shell, and are perforated by a siphon (6), the mem- branous tube of which is protected by a series of funnel-shaped calcareous sheaths (c), which are continued from the hole of one septum into that of the next, throughout the shell. The shell is white, lined with a nacrous layer within, and partially covered by a straw-coloured epidermis without. The organization of the Spirula may be expected to be in some respects intermediate to the Nautilus and Sepia, and an opportunity of investigating its internal struc- ture is therefore highly desirable. According to Lamarck the animal is a Cephalopod with eight feet and two tentacles, like a Cuttle-fish, all provided with suckers ; the body shaped like a purse and terminated behind by two lobes. Although the siphoniferous shells are not confined to the Tetrabranchiate Order, yet it is in this division, as in the Pearly Nautilus for example, that we find this singular testaceous production to have arrived at the maximum of its development : it is covered by an epidermis, and, in the living animal, is also probably partially overlapped by a reflected portion of the thin and extensible mantle ; but no part of it is buried in the substance of the animal, whose entire body, on the contrary, is inclosed in the last large expanded chamber. The re- lative position of the soft parts to this cham- ber we had not the means of determining from the specimen dissected by us, as this had been removed from its shell by Mr. Bennett, its fortunate captor, before it was placed in spirits. According to this able naturalist's statement, however, the ventral surface of the body and funnel was applied to the concavity of the outer expanded wall of the chamber; and the concavity behind the cephalic disk was adapted to the involuted convexity of the shell, and abutted against the ridge which rises from that part.* The camerated portion of the shell, according to Mr. Bennett, contained water or a liquid ; but the size, condition, and con- tents of the membranous tube were not ob- served by him. The external form of the soft parts supported Mr. Bennett's account of their relative position to the shell; but some cir- cumstances appeared to militate against the fluid nature of the contents of the deserted chambers. In the description of this spe- cimen, we accordingly stated our belief that the chambers are naturally filled by a gaseous exhalation or secretion of the animal, and that the liquid is contained in the dilatable siphon which is extended from the posterior part of the animal's body, and passes through the central apertures of the different septa of the shell. From the communication which this siphon has with the pericardial cavity, it can be influenced, as to the quantity of fluid which it * M. De Blainville, in a learned Memoir on the Structure of the Shells of Spirula and Nautilus, states his opinion that the true position of the ani- mal of the latter shell is the reverse of that de- scribed above : this opinion has been adopted by some Naturalists of this country, but the analogies by which it is endeavoured to he supported are too remote and vague to enforce conviction. contains, by the actions of the Nautilus itself. A pneumatic and hydraulic apparatus for effecting the rising and sinking of the shell and its in- habitant is thus established, and Dr. Hooke's ingenious conjecture of the use of the camerated part of the shell is confirmed;* but the relative positions of the gas and water would, accord- ing to the above opinion, be the reverse of what Parkinsonf supposed them to be. The full development of the theory of chambered shells, considered as hydrostatic instruments, is, how- ever, in abler hands than ours; and the reader will be gratified to learn that it forms the sub- ject of a portion of the forthcoming Bridge- water Treatise by Dr. Buckland. Nervous System. — In tracing the develop- ment of the Nervous System through the Heterogangliate or Molluscous type of Orga- nization, we find in the Gasteropodous genera which approach nearest to the Cephalopodous or highest division, that the ganglions which are concentrated about the head, are arranged in three groups : one, which is supraoesopha- geal, supplies the sentient organs, as the eyes and feelers ; a second, which is subcesophageal and anterior, supplies the buccal apparatus ; a third, which is subcesophageal and pos- terior, is the centre from which the sensitive, motive, and plastic nerves of the trunk ori- ginate. The anterior or buccal ganglions are united together, and to the cerebral ganglions, forming a nervous collar around the oesophagus ; a similar collar is formed by the corresponding intercommunicating chords of the posterior subcesophageal ganglia. In the Cephalopods the nervous system is disposed on the same general plan, but the nervous substance is accumulated in a greater degree at the different centres of radiation, according to the superior development of the parts that are to be supplied therefrom. In the Tetrabranchiate Order the principal parts superadded to the structure which we observe in the Gasteropodous Mollusk are those locomotive and prehensile organs which sur- round the buccal apparatus ; and the chief modification of the nervous system is therefore seen in the enlargement of the oral ganglia and collar, and their close approximation to the cerebral ganglion. This part is compara- tively little advanced, since the organs of sense which it immediately supplies, retain the same simple structure as in the inferior class of Mollusks, and are only augmented in bulk. The brain therefore is represented by a thick round tranversely extended chord (1, Jig. 231), communicating at its extremi- ties with the anterior and posterior oesopha- geal collars (3, 4), and with the small optic ganglions (2, 2), which supply the sim- ple pedunculated eyes. Four small pairs of nerves (5) also pass from the supraoesophageal band to the fleshy mass supporting the man- dibles. The cranial cartilage seems in the Nautilus to be principally developed with re- ference to the strong muscular masses to which * Philosophical Experiments and Observations, p. 307. t Organic Remains, vol. iii. p 102. Nervous System of the Pearly Nautilus. it affords a fixed point of attachment, and is not extended upwards so as to inclose the brain : this part is defended by a strong mem- brane which loosely surrounds it ; but the ex- tremities of the transverse band, the optic gan- glions, and the anterior oesophageal collars rest in grooves of the cranial cartilage. The nerves which arise from the anterior collar are very numerous : the larger branches (6, 6) enter respectively the roots of the ten- tacles which are lodged in the digital pro- cesses : the ophthalmic tentacles are also sup- plied from this source (5*); no lateral con- necting filaments are found between these nerves, corresponding to those which associate the corresponding nerves of the Poulp for the simultaneous action of the parts they supply. Below the digital nerves small nerves are given off (12), which enter the external labial processes, and penetrate in a similar manner the roots of the tentacles which are there lodged. The internal labial processes are, however, supplied in a different manner : a larger nerve (7, 7) comes off on each side near the ventral extremity of the ganglion, and after a course of half an inch swells out into a flattened ganglion* (8, 8), from which nu- merous filaments (9, 9) extend into the sub- stance of the process, and are continued into the tentacles as in the preceding case ; a larger twig (10) inclines inwards and distributes fila- ments to the olfactory laminae. The infundi- bular nerves (11) come off near the lower part of the anterior collar. From the ganglions composing the posterior collar (4, 4) arise numerous nerves of a flat- tened form, (13, 13,; which pass in a radiated manner to the inner sides of the shell-muscles * These ganglions I believe, from subsequent examination, to have been also connected with a nervous twig from the fleshy mass of the mouth, derived from the supra-cesophageal ganglion. CEPHALOPODA. 549 which they perforate, but there are no columns prolonged backwards from the lateral parts of the brain to form pallial ganglia as in the higher Cephalopods ; the structure and func- tions of the cloak to which these ganglia are subservient, not being enjoyed by the shell- clad Nautilus. The nerves corresponding to the large visceral nerves of the Dibranchiates are, however, proportionally developed ; for in the organs of plastic life the Nautilus is upon an equality with its naked congeners. These nerves, which combine the functions of the sympathetic and par vagum, consist of a large pair derived from the lower part of the pos- terior oesophageal collar, and extending back- wards on each side of the vena cava ; and of smaller twigs (17) coming off between the origins of the preceding nerves, and forming a plexus upon the parietes of the vein. The larger chords swell into ganglions at the termi- nation of the vena cava, (16, 16,) and send off ramifications to the branchiae, (15, 15,) the contents of the pericardium, and the viscera of digestion and generation. In the Dibranchiate Cephalopods which possess instruments for varied and active loco- motion, where the visual organ is of large size, and attains a complexity of structure equal to that of the Vertebrate animals, where a distinct acoustic organ is developed, and where the whole surface of the body is the seat of sensi- ng. 232. Nervous system of the Cuttle-fish, bility, the centre of nervous impression and volition is proportionally developed, and exhi- bits the highest conditions which the brain pre- sents in the Invertebrate series of animals. Except in some of the smaller species, as the Sepiola, in which the surrounding sub- stance still retains the consistency of a mem- brane, the brain, together with the anterior and posterior oesophageal collars, is entirely surrounded by a thick cartilage. The portion of oesophagus which is thus enclosed is sepa- rated from the surrounding medullary matter by a thin layer of softer substance. The cere- bral cavity is larger than the brain itself, and the intervening space is filled with a gelatinous fluid. In the Cuttle-fish the supra-oesophageal mass is transversely shortened, as compared with the Nautilus, and supports a smooth, rounded, heart-shaped medullary mass, slightly divided into two lateral lobes by a mesial lon- gitudinal furrow (1, fig. 232); from the lower and lateral parts of this body proceed the broad bands of cerebral substance which afterwards dilate into the large reniform optic ganglions (2, 2); upon each of these bands is placed a small spherical medullary body ( k, k). These bodies, which we first discovered in the Sepia, we have since ascertained to exist in Loligo. From the anterior apices of the cerebral lobes small nerves are continued, which almost immediately dilate into a round flattened gan- glion ( a, fig. 233) ; this is closely applied to the back part of the fleshy mass of the mouth above the pharynx ; it sends off nerves to the oral appa- ratus (i, i, fig. 233), and two fila- jnents descend and form a pair of small closely approximated ganglions (8, 8, fig. 232) below the mouth, analogous to the labial ganglions of the Nautilus. From the inferior, lateral, and an- terior parts of the brain two large chords (k, fig. 233) descend, and unite and dilate below the oesopha- gus to form the anterior subceso- phageal ganglion, or pes anserinus of Cuvier, from which the nerves of the feet and tentacles arise. Two still larger bands (I, fig. 233) descend from the brain behind the preceding to form, by a similar enlargement and union, the posterior oesophageal gan- glionic collar. From a comparison of these with the corresponding gan- glions of the Nautilus, it will be seen that by their approximation in the transverse direction the distinction of the ganglions at the lower part of the collar is lost ; and a corre- sponding approximation in the antero- posterior direction, being accompa- nied by an additional accumulation of nervous substance, has produced a blending together of the four gan- glions into one large continuous sub- cesophageal mass. The portions of this mass corresponding to the four ganglions and double oesophageal 550 CEPHALOPODA. collar of the Nautilus, are notwithstanding indicated in a manner not to be mistaken, by the origins of the nerves which it sends off, and by the chords which bring it into communication with the cerebral mass above. We shall now briefly mention the points in which the brain in other Dibranchiata differs from what we have described, after careful examination of this part in the Cuttle-fish. In the Poulp, the brain or supra-oesophageal mass is divided, according to Cuvier, into two parts, an anterior ( a, fig. 233), which is of a flatter and squarer figure and of a whiter colour, compared by Cuvier to the cerebrum, but which seems to be the pharyngeal ganglion more closely approximated to the brain than in the Sepia : and a posterior globular mass (b ), of a grey colour, which he compares to the cerebellum ; the optic nerves (c) are much smaller than in the Cuttle-fish, and do not support the small spherical bodies which exist in the Cuttlefish and Calamary. Fig. 233. Brain and nerves of the Octopus vulgaris. The brain of the Argonauta does not present a rounded form above, but when seen from this aspect, is composed, as in the Octopus, of an anterior white oblong band, flattened trans- versely, and of a posterior raised convex semi- lunar mass, which terminates behind in a semi- lunar border, the extremities of which are con- tinued directly to form the posterior collar of the oesophagus. The nerves of the arms proceed from the anterior and inferior suboesophageal ganglions ( d,fig- 233), corresponding in number to the parts they supply, viz. eight in the Octopoda? and ten in the Decapoda. But, according to Rathke, the Loligopsis offers an exception, the nerves of each lateral series of arms being con- tinued for a short distance from the brain as a single pair. In the Poulp, the eight nerves fe> ei fig- 233) glide along the inner surface of the basis of the feet, which they penetrate re- spectively, running with the great artery in their substance, and forming, as Cuvier has described, a series of closely approximated ganglions, corresponding to each pair of suck- ers, and sending off radiated filaments. In the Genus Eledone, where the arms are narrower, and the suckers are arranged in a single series, the ganglia are relatively smaller. In the peduncles of the Decapoda the nerves are continued of a simple structure as far as the acetabuliferous extremities, where they become enlarged and gangliated. Before forming the ganglionic enlargements in the ordinary arms, each brachial nerve gives off two large chords, one to each side, which traverse the fleshy substance of the base of the feet to join the two corresponding branches of the contiguous arms ; the eight nerves are thus associated by a nervous circle (f,f, fig. 233), which subdivides into two, and forms a small loop at each chord. Behind the origin of the brachial nerves, the large infundibular nerves, a single pair ( g, fig. 233), are given off. The small acoustic nerves (h ) arise below and behind the nerves of the funnel, from the nervous sub- stance that effects, as it were, the junction of the two oesophageal collars below. Next arise the large visceral nerves (14, fig. 232, 233), which, after distributing filaments to the muscles of the neck, descend parallel and close to one another behind the vena cava, give off from their inner sides the small filaments which con- stitute the plexus upon the vein ; they then diverge from each other towards the root of each gill, where they divide into three princi- pal branches : one of these dilates into an elongated ganglion ( c,fig. 232), and enters the fleshy stem of the branchia; the second de- scends to the bottom of the sac ; the third passes to the middle heart. The plexus pre- viously formed upon the vena cava receives additional filaments from the two latter bran- ches ; and a large sympathetic ganglion is formed, which is attached to the parietes of the stomach, near the pyloric orifice.* The most important and interesting nerves are the two largeones,(13,13,./%s.232, 233,)which arise from the posterior and lateral surface of the suboesophageal mass, and extend outwards, downwards, and backwards, perforating the shell muscles, and forming upon the inner parietes of the mantle the large stellated gan- glion ( d, d,fig. 232), from which the nerves of the mantle are derived. In the Octopoda the * See Brandt Medicin. Zoolog. a. a. 0. S. p. 309, tab. xxxii. fig. 23, who first described this ganglion in the Sepia, and Jacob's figures of the Anatomy of the Octopus Vulgaris, pi. xv. fig. 7 ; pi. xiii. figs. 2 & 3, in Ferussac's Monograph on Cephalopods, fol. CEPHALOPODA. 551 nerve terminates in this ganglion, (v, v, Jig. 226,) from which about twenty branches radiate to the mantle ; but in the Decapoda, in which lateral fins are superadded to the trunk, it pre- viously divides into two large branches. Of these the external alone produces the ganglion from which the sensitive nerves are distributed in a radiated manner, as in the Poulp; the other division ( e,Jig. 232), after having been joined by a branch (f) from the ganglion, pierces the fleshy substance of the mantle, and ends in a diverging series of twigs appropriated to the muscles of the fin (g). In proportion as the trunk of the Cephalopod is elongated, these branches become more parallel in their course, and dorsal in their position. The anterior part of the mantle is supplied by small nerves, having a distinct origin from the posterior subcesophageal mass, above the great moto-sensitive chords. With respect to the parts of the central axis of the nervous system of the Vertebrata which are represented by the structures above de- scribed, we may reasonably infer from the fact that the supracesophageal mass in the Dibran- chiate Cephalopods, especially the posterior division, is principally in communication with, and owes its superior development chiefly in relation to the complex organs of vision, that it is analogous to the optic lobes or bigeminal bodies. For if it be regarded, as Cuvier sup- poses, as the cerebellum of the vertebrate brain, we have then to reconcile the anomaly of this part being the seat of origin of the optic nerves. The constancy, again, of the optic lobes in the vertebrate series, and their priority of develop- ment to the cerebellum, leads naturally to the expectation that these would form part of such a brain as the highest invertebrate animal is endowed with. The smaller portion of the brain of the Poulp anterior to the optic lobes appears to represent an olfactory lobe. With respect to the inferior oesophageal mass, as it gives origin to the auditory and respiratory nerves, and those two large moto-sensitive co- lumns, which evidently represent, by their structure and position, the spinal cord of the Vertebrata, we consider it as fulfilling the function of the medulla oblongata, and to be the part of the nervous centre which is most intimately connected with the vital energies of the animal.* Organs of Sense. — The Cephalopodous class is the only one in the Invertebrate series in which distinct organs of sight, hearing, smell, and taste, have been detected, although the en- joyment of these senses is evidently by no means limited to this class. Considerable differences, however, present themselves in the relative complexity, and even as to the existence of the different Organs of Sense in the two orders of Cephalopods : thus, of the senses which relate to distant objects, the Organ of Hearing appears to be wanting in the Nautilus, and the Organ of Vision is comparatively imperfect, * See vol. iii. pt. 1, p. 187. Physiological Cata- logue of the Museum of the Royal College of Sur- geons, 4to. 1835. while those which take cognizance of proximate objects are more distinctly and extensively developed. Organ of Sight. — In the Nautilus the eyes are supported on short pedicles which project outwardly from the sides of the head. They are of a spherical form, slightly flattened ante- riorly ; are large as compared with the pe- dunculated eyes of Gasteropods, but are of small size as compared with the complex visual organs of the Dibranchiates. They presented, in Mr. Bennett's specimen, the simplest con- dition of an organ of vision, consisting only of a darkened globular cavity or camera ob- scura, into which light was admitted by a single orifice, and a nerve expanded at the opposite side to receive the impression ; the mechanism for regulating the admission of the impinging rays was wanting, and every trace of that which modifies their direction had disappeared. The form of the eye was maintained by a tough unyielding sclerotic coat (k,Jig. 231), which became thinner towards the anterior part of the eye, where it was perforated by a circular aper- ture less than a line in diameter (m). The nerves continued from the small oval optic ganglion (2) expand, and immediately line the sclerotic as far as the middle of the globe, forming a strong re- ticulate retina (o), which, together with the rest of the cavity, is lined by a black pigment (»). There was no appearance of vitreous humour or crystalline lens; but both parts would no doubt be found to exist in the recent state. In the Dibranchiata the eyes are sessile, but in some species project beyond the sur- face of the head more than in others ; their complicated structure is truly one of the most remarkable features of the organization of this singular class. The eyeball in the Cuttle-fish is inclosed in a capsule consisting posteriorly of a thick carti- lage (a, a, fig. 234), in its lateral circumference Fig. 234. Section of the Eye of the Cuttlefish. of a strong white fibrous membrane (b, b ), and anteriorly of the cornea (o ). The whole of the inner surface of the cap- sule is lined by a thin serous membrane, as far 552 CEPHALOPODA. as the margin of the thick posterior cartila- ginous orbit, to which it is attached, and is thence reflected forwards (c, c) upon the mus- cles of the eye-ball, also upon the long narrow anterior and inferior ocular cartilage (d, d), and upon the exterior fibrous layer of the sclero- tica ; it is reflected inwards over the anterior thickened margin of the sclerotica, where the large anterior aperture of that membrane re- mains unclosed by the cornea, and consequently passes along its inner surface like the mem- brane of the aqueous humour ; it seems to us, however, not to pass over the anterior part of the capsule of the crystalline lens, but into the groove (p,p) which divides that body into two parts. The serous layer above described can- not be detached from the cornea, but ceases to be demonstrable as a distinct membrane where the external fibrous coat is attached to the cornea. The space between the eye-ball and its capsule, which is thus circumscribed, is filled with a watery fluid, which is most abun- dant in the Calamaries. The cornea is sepa- rated by the same fluid from the eye-ball ; but its tension and slightly convex figure is main- tained by it, as by the aqueous humour in the eye of the vertebrate animal. The motions of the eye-ball are facilitated by the secretion of the serous sac, as the movements of the heart in the pericardium, and in other instances in which serous membranes are developed. The membrane, of which we have just de- scribed the reflections and extent, is regarded by Cuvier as analogous to the tunica conjunc- tiva, but a difficulty arises in this mode of considering it, in consequence of the position of the cornea (o), which, in its structure and connection with the integument, bears a close analogy to the cornea in Fishes. The charac- teristic difference which the cornea presents in the latter class, as compared with that of the Cephalopoda, is its adhesion to the margins of the anterior aperture of the sclerotica, by which the anterior chamber of the eye is limited to a very small space ; while in the Sepia it would seem as if the membrane circum- scribing the anterior chamber had over-passed its usual bounds in consequence of the absence of any such adhesion between the cornea and sclero- tica. When we consider the nature of the membrane in question, and the relations of the fluid it secretes to the cornea and crystal- line, should we not be justified in considering it, notwithstanding its excessive development, as analogous rather to the membrane of the aqueous humour, than to the conjunctiva, the ratio of the development of which is as that of the eye-lids or folds of membrane ex- ternal to the cornea, and of which we have only a slight rudiment in the Sepia? (v.) The space between the cartilaginous orbit and the posterior part of the eye is circum- scribed by a membrane (e, e) which has the character rather of a condensed layer of cellular tissue than of a true serous membrane. In this space is contained the optic ganglion (/), its filaments (g), and the surrounding soft white substance (A), by some considered of an adi- pose, by others of a glandular nature. This cavity is proportionally larger in the Octopus than in the Sepia. The eye-ball of the Cuttle-fish is an irregular spheroid, flattened in the direction of its axis. The vertical diameter is less than the horizontal, but both exceed the diameter of the axis. The eye-ball is remarkable in all the Dibranchiata for its considerable development as compared with the size of the body ; it is proportionally largest in the Calamaries, and smallest in the Octopods. The exterior membrane covering the ante- rior part of the eye-ball (i) receives the inser- tions of the muscles of the eye, and seems as if it were formed by their aponeurotic expan- sions ; it lies immediately beneath the reflected layer of the serous covering, is of a soft texture, and has a pinkish colour with a glistening silver lustre ; in the Poulp it is spotted like the skin. The entire eye-ball is surrounded by a second layer of membrane (Ji, k), having a similar texture and appearance ; these are analogous to the exterior or fibrous layers of the sclerotica in the eyes of Fishes. We next find a cartilaginous layer (I, l) corresponding to the internal cartilaginous sclerotica of the Pla- giostomous Fishes. This coat is very thin, and almost membranous posteriorly, where the fibrils of the optic ganglion penetrate it, and where it presents a cribriform surface of consi- derable extent, in which it may be observed that the orifices of the sieve are of consi- derable size, and not very close together. Anterior to the cribriform surface the cartila- ginous sclerotica increases in thickness, but more so on the lower than the upper side of the eye, and about the middle of the eye- ball it terminates in a slightly thickened mar- gin. A layer of fibrous membrane (rn, m) is continued from this margin, along with the external fibrous layer (/), and assists in forming the soft thick anterior part of the sclerotica, which forms the circumference of the pupillary aperture (w), or that by which light is admitted to the cavity of the eye. The supe- rior part of this aperture is encroached upon by a bilobed curtain-like process, which we have observed to present a semi-transparent texture in the eyes of some Cuttle-fishes, as if it were an abortive formation of a sclerotic cornea : in position it resembles the curtain-like process depending from the iris of the Ray. The inner surface of that part of the sclero- tica which lies anterior to the lens is lined with a dark pigment. The tunic which immediately lines the car- tilaginous sclerotic is not, as in Fishes, a membrana argentea, or a vascular choroid, but consists of an expansion of the ner- vous fibres which are given off from the optic ganglion, connected together by a vascular and cellular tissue (o, o). The ganglion does not resolve itself into these fibres uniformly from the circumference to the centre, but sends them off from its exterior surface only, so that, on making a section of the part, the centre of the ganglion presents a homogeneous pulpy texture, separated by a distinct external layer from the origins of the fibrils, as in the figure,/. CEPHALOPODA. 553 The fibres, after perforating the cartilaginous sclerotica, and expanding into the post-pig- mental retina, extend towards the groove of the crystalline, in a direction chiefly parallel to one another, the tunic formed by them be- coming thinner as they advance forwards ; this is joined by a thin membrane, which extends from the anterior margin of the cartilaginous sclerotica, and forms, with that membrane, a ciliary plicated zone ( p, p, where it is repre- sented as left entire,) which penetrates the groove of the lens. The outer surface of this thick nervous tunic is fibrous and flocculent, and connected to the sclerotica by a fine cel- lular tissue : the anterior or internal surface is perfectly smooth. This surface of the nervous tunic is co- vered by a tolerably consistent layer of a dark purple-brown pigment (q). Cuvier, who re- gards the preceding tunic as the only part analogous to the retina in the eye of the Ce- phalopods, expresses his surprise that this black layer is not an insurmountable obstacle to vision ;* and different theories have been proposed to account for the singular position of the pigment on that supposition. In the eyes of different Sepia which we had immersed in alcohol preparatory to dissection, we have, however, invariably found between the pig- ment and the hyaloid coat a distinct layer of opaque white pulpy matter (?■), of sufficient consistence to be detached in large flakes, and easily preserved and demonstrated in prepara- tions. We confess, however, that we can discover no connection between this layer and the thick nervous expansion behind the pig- ment; but, nevertheless, we cannot but regard it as being composed of the fine pulpy matter of the optic nerve, and as constituting a true pras-pigmental retina. The hyaloid coat, which is remarkably dis- tinct in all the Cephalopods, completely sepa- rates the vitreous humour from the internal white layer above described. It is perfectly transparent, and, though thin, is strong. The vitreous humour does not lose its transparency when preserved in alcohol. The crystalline lens is of large size, and is composed of two completely separated portions : the anterior moiety is the segment of a larger sphere, but forms the smaller part of the lens ; the posterior is a segment of a smaller sphere, and forms the larger part of the lens. Two layers of transparent membrane are continued from the ciliary body between these segments. Each of the segments is composed, as in the lens of higher animals, of concentric laminae, which become denser towards the centre, where the nucleus resists further unravelling of its structure. It is of a brown colour, and pre- serves its transparency in alcohol. The lamina? are composed of denticulated fibres; but the minute description of their texture and arrange- ment will be given in another place. The white substance (h) which surrounds the optic ganglion is divided into lobes, but * " On ne conceit pas comment elle n'est pas un obstacle insurmontable a la vision." — Mem. sur le Poulpe, p. 39. VOL. I. exhibits no distinguishable secerning structure ; the bloodvessels of the eye ramify between these masses ; the smaller twigs accompany the nervous fibrils ; the larger ones pass forwards to the anterior soft margin of the sclerotica. We regard this substance as analogous to the so-called choroid gland in the eyes of Fishes. Cuvier assigns to it the function of defending the nervous ganglion and fibres from surround- ing pressure ; and this is most probably the true final intention of the substance, since it intervenes between the ganglion and the mus- cles of the eye-ball. Of these we find three straight muscles and one oblique. The inferior rectus of each eye arises from a small transverse tendon which adheres to the inferior and anterior border of the cranial cartilage, to which it runs parallel, and is attached at its two extremities to the muscles above mentioned, and also to the base or root of the anterior elongated cartilaginous orbital plate. A second straight muscle arises from the posterior margin of the elongated cartilage above mentioned ; its fibres run parallel to those of the preceding, and are inserted into the external sclerotica. Both these muscles are thin, broad, and fleshy. The oblique muscle arises from the inferior and posterior margin of the external orbital car- tilage, and expands, as it proceeds outwards and forwards, to terminate in the external mem- branous sclerotic. These muscles are readily exposed by dissecting away the orbital capsule from the under part of the eye-ball. A short and strong superior rectus, the ten- don of which is continuous with that of the opposite side, is inserted into the upper part of the sclerotic. A few observations remain to be made on the structures defending the anterior part of the eye- ball. The cornea of the Cuttle-fish is appa- rently entire; it is thickest at its superior mar- gin (t ), where it is implanted in a groove of the integument ; it becomes gradually thinner towards the lower margin, where it is over- lapped by the rudimental eyelid (v). This consists of a narrow semilunar fold of inte- gument, the concavity of which is directed upwards and a little backwards. In the small Cephalopod which Captain Ross discovered in the Arctic Ocean, and which has been named after that distinguished and scien- tific navigator,* the cornea is defended by a continuous circular fold of integument, which can be completely closed by an orbicular sphincter in front of the eye, a structure which is probably required in this species in order to protect the cornea against the spiculee of ice witli which its native seas abound, especially in the summer or thawing season. In the Calamary, on the other hand, there is no tegu- mentary fold. Upon carefully inspecting the cornea of the Cuttle-fish, a minute foramen will be seen near the inner or anterior margin of the cornea, covered by the upper extremity of the fold of integument. The aperture leads ob- * See Appendix to Sir John Ross's Voyage, 4to. p. xii. pi. B. c. 2 o 554 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 Cyclostomous or lower organized cartilaginous Fishes, of an acoustic vestibule, containing a limpid fluid and a calcareous body or otolithe suspended in a delicate sacculusto 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- cesophageal cerebral masses. In the Cuttle-fish the cavities are of a sub-quadrate form, separated only by a thin septum (c ) ; 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. (lnfig.235, the oto- lithe is seen as exposed Jn the sacculus on the right side.) Ill the Octopus vulgaris the vestibules are nearly spherical, and their parietes are smooth ; the otohthes 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 seusorium the vibrations which affect the otolithe and its sac. 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 semitiansparent 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,jig. 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, 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- 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. 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. 555 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 Crunchia 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 papilla?; 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. Male Organs, Poidp, 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 (&), 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 granular 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 (/;). 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 adhesion 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 (/c), which is a short pyramidal body, hollow within, and terminating by a small anterior aperture. 2 0 2 556 CEPHALOPODA. In the Sepiola the part corresponding to that called the prostate 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-adapted as to adhere by the mutual apposition of the suckers. In this act the Poulps are described 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 ((pva-rirrj^a), 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, &c. 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; forin 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 Sepia: 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. 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. The tunics of the ovisacs, as in the Dibranchiata, were glandular, but the internal plica? did not present the reticulate disposition characteristic of the corresponding parts in the Sepia, &c. The exterior thin niembrane (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 laminae. 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 plicae 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 Russia, 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. Female generative Organs, Rossia palpebrosa. ( Natural size. ) 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 incli 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 part* of the oviduct in the former. In the Russia the oviduct (d) 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. fig. 9.) 558 CEPHALOPODA. same structure as in Sepia and Rossia, but the single oviduct is relatively wider than in the 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 ( Loligo 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 Loligo, 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 tire two lateral series of glandular laminae. 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 Rossia 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 (g,g,Jig- 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 9hape 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, 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 " In the description of the anatomy of the Loligop- sis by Dr. Grant, contained in the first volume of the 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 (fig* 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 16 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. Loligines 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 succenturiata or ' supra-renal bodies' of the Vertebrate animals. In the Octopodous Dibranchiates the ovary is a spherical sac with thick parietes (\,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 the 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 strikingdifferences 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- Fig. 240. r ; K Ova of the Argonaut. Fig. 241. ' < ' Sf l Fig. 242. JVg.243. Ova of the Calamary , Loligo Vulgaris." * From Ferussac, Monographie des Cephahpoo'es. .560 CEPHALOPODA. ment 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 ft nit 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 ; 6 is the Fig. 244. Fie. 245. 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 : thepigmentum 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 Sepias, 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,fig. 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 aetions 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 * npos-iritpvxe Y h ■yiyvQij.im anuria, to!? aoi; nara to TreisBiov. ' Adhasret ovo Sepia nascens parte sui priore.' Dc Generatione Animalium, lib. iii. c. 8. Fatal Sepia. CEPHALOPODA. 561 developed and proportionally large to direct its evolutions. Bibliography (Anatomical). Aristotle, Historia de Animalibus, cur. Schneider, Lipsiae, lib. iv. cap. 1, 2, & 4 ; lib. v. cap. 6 & 18 ; lib. vi. cap. 13; lib. viii. cap. 2 & 30 ; lib. ix. cap. 36. De Partibus Animalium, lib. iv. cap. 9. In these several parts of his extraordinary work Aristotle indicates nine different species of Cepha- lopods, with so much precision and so happy a se- lection of their distinctive characters, that modern naturalists have been enabled to identify almost all the species which were studied by the Stagyrite two thousand years ago. Of these we may first mention the Nautilus which adheres to its shell, and which we conceive may have been the Nautilus Pompilius ; second, the Nautilus which does not adhere to its shell, universally allowed to be the Argonauta or Paper Nautilus of the moderns; third, the Cuttle-fish (Sepia offici- nalis); fourth and fifth, the great and small Cala- maiies ( Loligo vulgaris and Loligo media ) ; sixth and seventh, the great and small Poulps ; the former is regarded by Belon and Rondeletius to have been the Sepia octopodia of Linnaeus ; but the small species, which Aristotle states to have been variegated,* has not yet been satisfactorily deter- mined ; eighth, the Bolitcena, a genus of Octopods which Aristotle characterized by its peculiar odour ; this is the Eledona moschata of Leach ; ninth, the Eledone, characterized by the single series of suck- ers, and to which the Eledona cirrosa of Leach corresponds. Respecting the living habits of the Cephalopods, Aristotle is more rich in details than any other zoological author, and Cuvier has justly observed that his knowledge of this class, both zoological and anatomical, is truly astonishing. Swammerdam, Biblia Natura;, seu Historia In- sectorum, 1737, 1738, or ' The Book of Nature,' &c. translated by Thomas Flloyd and J. Hill, London, 1758, fol. Towards the end of this work there is a letter from Swammerdam to Redi, in which are given the first anatomical details, in addition to those of Aristotle, which appeared after the revival of literature : the external parts and struc- ture of the tongue are carefully described ; the viscera and the nerves with less exactness ; and the organs of circulation erroneously. Needham, An account of some new microsco- pical discoveries, 8vo. London, 1745. At page 22 we find the first description of the armed suckers of the Calamaries : Chapter V. contains the curious account of the seminal filaments of the male Cephalopods. Baker, An account of the Sea-Polypus; Philo- sophical Transactions, vol.1. 1758. Bohadsch, Dis- sertatio de veris Sepiarum ovis, 4to. Pragse, 1752. Josephus Theophilus Koelreuter, Polypi marini, Russis Karakatiza recentioribus Graecis oxrvrrovf dicti, descriptio. Nov. Comm. Acad. Petropol. torn. vii. p. 321-343, 1759. Lamorier, Anatomie de la Seche, et principalement des organes avec lesquels elle lance sa liqueur noire ; Mem. de la Soc. de Montpellier, torn. i. p. 293-300, 4to. 1766. John Hunter on the organ of hearing in fish ; Phi- losophical Transactions, 1782. [n this paper we find the first announcement of the existence of an organ of hearing in the class Cephalopoda. Nu- merous preparations in his Collection attest Mr. Hunter's extensive knowledge of the rich and singular organization of the Cephalopods : for his accurate description and beautiful figures of the circulating and respiratory organs, the reader is referred to the second volume of the Descriptive and Illustrated Catalogue to the Hunterian Collec- tion, 4to. and to the first volume of the same work, for the descriptions of his preparations of the hard parts and digestive organs of the Cephalopods : among the latter Mr. Hunter had placed the ' Pan- creas of the Cuttle-fish.' Monro (Secundus). The structure and physiology of fishes explained, &c. fol. Edinburgh, 1785. This work contains (p. 62) the anatomy of the Sagittated - Calamary ( Loligo sagittata, which the author terms the Sepia loligo), and from its organization he ably deduces its true place in the natural system, observing that ' by most authors it has been ranked among Fishes ; by Linnaeus it has been placed among the worms : but perhaps it may most justly be con- sidered as a link connecting the two classes of animals.' Monro confirms the discovery of Hunter of the acoustic organ, and figures the otolithe of the Calamary. He first published the true descrip- tion of the three hearts, and rectified the errors of Swammerdam on this part of the anatomy of the class : he notices the absence of the venae porta;, and some of the peculiarities in the structure of the eye ; but his description of the generative system, and his notice respecting some otherparticu- lars, as the urinary and gall-bladder, are erroneous. Scarpa, Anatomicae disquisitiones de auditu et olfactu, fol. 1789. The anatomical descriptions relative to the Cephalopods are limited chiefly to the organ of hearing, and the course of the nerves ; the account of the latter is incomplete and in part erroneous. Tilesius, in the Beitr'age fur die Zergliederungs- knnst von H. F. Isenflamm, B. 1. Heft. 2. G. Cuvier, Lecons d'Anat. Comparee, 1799 to 1805. These five volumes contain the results of numerous researches on the anatomy of the Cephalopoda, all characterized by the. author's usual depth and accuracy. They are collected together with addi- tional details and beautiful figures in the celebrated ' Memoire sur les Cephalopodes et leur Anatomie,' published in 1817, in the Memoires sur les Mol- lusques, 4to. The type of organization illustrated by these researches is considered in the author's subsequent work (the Regne Animal ), as charac- teristic of the class Cephalopoda ; but the chief pe- culiarities are found only in the Dibranchiate Order. De Blainville, De l'organization des animaux, ou principes d'anatomie comparee, torn. i. 8vo. 1822. Contains observations on the skin and organs of sense of the Cephalopods. Ejusdem, Manuel de la Malacologie, 8vo. 1825. Home (Sir Everard), Lectures on Comparative Anatomy, 4to. 1814-1828. On the distinguishing characters between the ova of the Sepia and those of the Vermes testacea. Philos. Tram. cvii. Leach, (W.E. M.D.) On the genus Ocythoe. Phil. Trans, cvn. Appendix to Tuckey's Voyage to the Congo. Zoological Miscellany, vol. iii. Rathke, Ueber Perothis, &c. (on the anatomy of the Loligopsis); Mem. de l'Acad. Imp. de Peters- bourg, torn. ii. parts 1 & 2, p. 169, 1833. Roget ( P. M. M.D.) Bridgewater Treatise, on Animal and Vegetable Physiology, 8vo. 1834. Robert Grant, M.D. &c. Description of a new species of Octopus ( Oct. ventricosus, Grant); Edinb. Philos. Journal, vol. xvi. p. 309. On the structure and characters of Loligopsis, &c. and on the anatomy of the Sepiola vulgaris. Leach. Transactions of the Zoological Society, part i. 4to. 1833. Lectures, Lancet, 1833-4. Outlines of comparative anatomv parts 1 & 2, 8vo. 1835. J' Belle Chiaje, Memorie snlla storia degli animali senza vertebre del regno di Napoli, 1823-1829 4 vol. 4to. San Giovanni, Giornale Encicl. di Napoli, 1824 - Annales des Sciences Naturelles, torn. xvi. p. 305! (His memoirs on the structure and properties of the colorific stratum of the skin of Cephalopoda are contained in the above works.) J. Coldstream, M.D. see Edinb. New Philosophi- cal Journal, July, 1830, p. 240 ; and, On the deve- lopment of the ova of Sepia officinalis, Proceedings of the Zoological Society, part i. 18-33, p. 86. Mayer, Analekten fur Vergleichenden Anatomie, 4to. 1835. 562 CERUMEN— CETACEA. Firussac, M. le Baron, If A. D'Orbigny, Mono- graphic des Cephalopodes Acetabuliferes, folio, Paris, 1835. This splendid work is published in numbers, of which eleven have appeared. As yet the letter-press extends only to the general intro- duction. Broderip, (W. J.) Observations on the animals hitherto found in the shells of the genus Argonauta, Zoological Journal, vol. iv. p. 57. Richard Owen, Memoir on the Pearly Nautilus (Nautilus Pompilius, Linn.) 4to. 8 plates, 1832. This work contains, besides the description of the structure which characterizes the lower or Tetra- branchiate order of the class, some additional par- ticulars on the structure of the infundibulum, and of the brain, and on the function of the superadded branchial hearts, in the Dibranchiate order of Cephalopods. Descriptive and illustrated Catalogue of the Physiological Series in the Museum of the Royal College of Surgeons, 4to. vol. iii. contains an account of the organs of sight and hearing in the Cephalopods, 1835. Description of a new genus of Cephalopoda (Rossia). Appendix to Sir John Ross's Voyage, 1835. Descriptions of some new species ; and anatomical characters of the Orders, Families, and Genera of the class Cephalopoda, Proceedings of the Zoological Society, March, 1836. (Richard Owen.) CERUMEN, (Germ. Ohrenschmalz.)— This secretion, formed by the glands of the ex- ternal ear, has been examined by Fourcroy and Vauquelin, and more in detail by Ber- zelius.* According to Vauquelin it consists of 0 625 of a brown butyraceous oil, soluble in alcohol, and 0-375 of an albuminous sub- stance, containing a peculiar bitter extrac- tive matter. Berzelius observes, that, when first secreted, cerumen appears as a yellow milky fluid, which gradually acquires a brown- ish colour and viscid consistency. Digested in ether it imparts to it fatty matter, which re- mains when the ethereal solution is distilled off water ; it has a soft consistence, is nearly co- lourless, and contains stearin and elain sepa- rable by alcohol ; it is easily saponified, and the soap which it forms has a rank unpleasant smell and taste; and when decomposed by mu- riatic acid, the fatty acids separate in the form of a white powder, which rises with difficulty to the surface, and fuses at about 105*. The portion which remains after the action of ether imparts a yellow colour to alcohol, and on its evaporation there remains a yellow-brown ex- tractive matter, soluble in water, and leaving after the evaporation of its aqueous solution a yellow, transparent, and shining varnish, which is viscid and inodorous, but intensely bitter; when burned, it exhales a strong animal odour, and leaves an ash of carbonate of potash and carbonate of lime, without any trace of a chlo- ride. It is completely precipitated from its aqueous solution by neutral acetate of lead. That part of cerumen which is not soluble in alcohol yields to water a small proportion of pale yellow matter, which, when obtained by evaporation, has a piquante taste ; it is not precipitable by salts of lead, corrosive subli- mate, or infusion of galls, and contains no traces of phosphoric or chlorine salts. The residue of the cerumen, insoluble in water and * Lehibuch der Thierchemie. alcohol, gelatinises in acetic acid, but is only partially dissolved by it; that which is taken up appears to be albumen; and the undis- solved portion is brown, viscid, and transpa- rent; digested in dilute caustic alkali it imparts a yellow colour, but a small portion only is dissolved ; and as nothing is thrown down by supersaturation with acetic acid and ferrocy- anate of potash, it is not albumen that is taken up : the acid solution, however, is copiously precipitated by infusion of galls, so that it contains some peculiar principle. The residue which resists the action of dilute alcali, when boiled in concentrated solution of caustic pot- ash, becomes brown, and smells like horns imi- larly treated; a part of it seems to form a compound with the alkali insoluble in the ley, but soluble in water, in which respect it re- sembles horn, but it differs from it in not being precipitated from its solution by muriatic acid, nor ferrocyanate of potash, and scarcely by infusion of galls. It appears, therefore, that cerumen is an emulsive combination of a soft fat and albumen, together with a peculiar substance, a yellow and very bitter matter soluble in alcohol, and an extractive substance soluble in water: its saline contents appear to be lactate of lime and alkali, but it contains no chlorides and no soluble phosphates. When cerumen accumulates and hardens in the ear so as to occasion deafness, it is easily softened by filling the meatus with a mixture of olive oil and oil of turpentine, by which its fatty matter is dissolved. ( W. T. Brande.) CERVICAL NERVES. See Spinal Nerves. CETACEA; Gr. x»t», SiXQmi, Aristotle; Eng. Whale tribe, Cetaceans; Fr. Cetac'ts ; Germ. WaM-fische. [An order of mammiferous animals, distin- guished, as regards outward characters, by the absence of hinder extremities, neck, hair, and external ears; and by the presence of a large horizontal caudal fin, and the fin-like form of the anterior extremities, the bones of which are shortened, flattened, and enveloped in a thick unyielding smooth integument. With this con- figuration the Cetaceans are fitted only for aquatic life, and reside habitually in the waters of the sea or of large rivers : their resemblance to the true Fishes is so close that many natu- ralists, since the revival of literature, and the vulgar in all ages, have regarded them as mem- bers of the same class. Aristotle, from his anatomical knowledge, was aware of the essen- tial differences between the Whales and Fishes, but it is not absolutely necessary to seek for internal characters to establish the real distinc- tion which subsists between these different de- nizens of the deep ; the horizontal position of the tail-fin at once distinguishes the cetacean from the fish, in which that fin is vertical. This difference relates to the different nature of the respiration of Ihe Whale, which is by lungs, and consequently necessitates a frequent rising to the surface of the water to breathe the CETACEA. 563 air, and a corresponding modification of the chief organ of locomotion. With the lungs are also associated the pre- sence of warm blood, a double circulation, an epiglottis, and a diaphragm, a true viviparous generation, a nourishment of the young by a mammary secretion, and in short all the essen- tial parts of a mammiferous organization. The order is subdivided as follows : Tribe I. PHYTOPHAGA. Char. Teeth of different kinds ; molars with flattened crowns, corresponding to the vegetable nature of their food. Mamma, two, pectoral. Lips provided with stiff bristles. External nostrils, always two, situated at the extremity or upper part of the rostrum, which is ob- tuse. Genus Manatus, Cuv. Char. Incisors £ (two superior, deciduous in the foetus, not replaced). Molars §§, grinding surface with tri-tuberculate _i_ transverse ridges. . Body with a few scattered bristles. Anterior extremities each provided with four nails. Tail-fin oval. Species 1. Manatus Americanus, Cuv. Trichechus Manatus, Linn. : the Ma- natee. Lamantin d'Amerique, Cuv. 2. Manatus Af'ricanus, Lamantin du Senegal, Cuv. Genus Halicore, Cuv. Char. Incisors g. (In the young animal the two superior permanent incisors are preceded by two deciduous ones ; six or eight deciduous incisors in the lower jaw which have no permanent succes- sors). Molars ||; (in the young ani- mal ||) ; the grinding surface exhibits a rim of enamel at the circumference and a slightly excavated centre of ivory. Body, with a few scattered bristles. Upper lip with bristly mustaches. An- terior extremities without nails. Tail- fin very broad, crescentic. Species 1. Halicore Indicus, Cuv. The Indian Dugong, or, more properly, Duyong. 2. Halicore Tabernaculi, Ruppel. Du- gong of the Red Sea. Genus Rytina, Illiger. Incisors none. Molars \ \, large, lamelliform, of a fibrous structure, with the triturating surface roughened by tortuous furrows. Body, without hairs, but covered by a rough and thick fibrous epidermis. An- terior extremities terminated by an un- guiform callosity. Caudal-Jin crescent- shaped, each angle terminated by a horny plate. Species. Rytina Stellcri, Le Stellere, Cuv. This species inhabits the seas of Kamt- schatka. It was discovered by the Russian naturalist, Steller, after whom it is named ; and is described by him with much zoological and anatomical detail in the Nova Comment. Petrop. t. ii. p. 294, (1751,) under the name of the Manati or Vacca marina. Tribe II. ZOOPHAGA. Char. Teeth of one kind or wanting, not adapted for mastication. Mamma, two, pudendal. External nostrils, double or single, situated on the top of the head. A. with the head of moderate size. Family DELPHINIDiE. Teeth in both jaws, all of simple structure, and gene- rally conical form. No coecum. Genus Delphinorhynchus. Rostrum very long and narrow, continued not abruptly from the forehead. Teeth very small and numerous. Ex. Delphinorhynchus microptertis. (Fred. Cuvier, Cetaces, pi. viii. fig. 1.) Genus Delphintjs. Rostrum narrow, of moderate length, continued abruptly from the forehead. Teeth conical, slightly recurved, numerous. Ex. Delphinus Delphis, the common Dol- phin; Delphinus Tursio, the Spouter or small Bottle-nose Whale of Hunter. For the other numerous species of this genus consult F. Cuvier, Histoire des Cetaces, p. 147 et seq. Genus Inia. Rostrum, as in the genus Delphinus. Teeth mammilliform. Species. Inia Boliviensis ; (Fred. Cuvier, Cetaces, pi. x, bis, and xi, cranium) ; inhabits the great rivers of South Ame- rica. Genus, Phoc^na. Rostrum short, broad. Teeth conical or compressed. Ex. Phocana communis, the common Porpoise ; Phocana orca, the Grampus ; Phocana globiceps, L'Epaulard, Cuv. Phocana leucas, the Beluga,* &c. The following genera seem to form the types of as many distinct families of Zoophagous Cetaceans. Genus Monodon. Rostrum short and broad. No other teeth save two in the upper jaw, in the form of tusks, situated horizontally, and both of which continue in the rudimental condition in the female, while in the male one projects far be- yond the jaws in the line of the axis of the body. Ex. Monodon monoceros, Linn. The Narwhal. Genus Hyperoodon. Rostrum of mo- derate length, extending abruptly from a very elevated cranium. Two small teeth in the lower jaw; small callous tubercles on the palate. Ex. Hyperoodon Dalei ; the great Bottle- nose Whale of Hunter. Genus Platanista. Rostrum very long and compressed, enlarged at the extre- mity. Teeth numerous; in both jaws conical and recurved. Cranium enlar- ged by osseous processes. A coecum. Ex. Platanista Gangetica. The Gangetic Dolphin. * This species has no dorsal fin, and on that ac- count has hy some naturalists been regarded as forming the type of a distinct genus, under the name of Delphitmpterus. 564 CETACEA. jB. With the head of immoderate size, equalling one-third the length of the body. Family I. CATODONTIDiE. Teeth nu- merous, conical, but developed only in the lower jaw. External nostrils or blow-holes confluent ; no coecum. Genus Catodon. No dorsal fin. Ex. Catodon macrocephalus ; Physeter macrocephalus, Shaw. The great Sper- maceti Whale. Genus Physeter. A dorsal fin. Ex. Physeter Tursio, Linn. The High- finned Cachalot, Shaw. Family BALvENIDiE. No teeth ; their place supplied by the plates of baleen or whalebone attached to the upper jaw. Blow-holes distinct; a coecum. Genus Bal^noptera. A dorsal fin ; pectoral integument plicated ; baleen- plates short. C See Jig. 259.) Species. Balcenoptera Boops, Cuv.; the Jubarte or great Rorqual. Balcenoptera rostrata, Lacep. ; the Piked Whale of Sibbald and Hunter, sus- pected by Cuvier to be the young state of the Balcenoptera Boops. Balcenoptera Musculus, Cuv. ; the Me- diterranean Rorqual. Balcenoptera Antarctica, Cuv.; the South- ern or Cape Rorqual. Genus BaLjEna. No dorsal fin; pectoral integument smooth; baleen-plates long. Species. Balcena mysticetus, Linn. The great Whalebone Whale of Hunter; great Mysticete. Baleena Australis,Cuv. The Cape Whale.] Organs of Motion. — Swimming is the principal mode of progression of the Cetaceans, but the Phytophagous species appear to have the power, in order to feed upon marine plants, of crawling and walking at the bottom of the sea by means of their anterior members, which in other Cetaceans are exclusively natatory organs. The head, in all, has so little mobility, that its axis can be but slightly altered, without that of the body altering also. In the form and composition of the skull the Cetaceans of both tribes present many im- portant differences, as compared wtth other mammiferous animals. In the Herbivorous genera the bones are dense and massive, and where they are not anchylosed their connection is of a loose kind. In the Dugong the skull is more especially remarkable for the large size of the intermaxillary bones (a, a, Jigs. 246, 247), which extend backwards as far as the middle of the temporal fossae, and are bent down ante- riorly over the symphysis of the lower jaw, so as to terminate nearly on a level with its infe- rior margin. This extent and shape is required in the Dugong for the lodgement of the perma- nent incisors (b, b), which are developed to a large size, one in each intermaxillary bone, and consequently the nostrils are placed much higher and further from the mouth than in the Manatee, in which, in consequence of the small deciduous incisors having no successors, the Fig. 246. Skeleton of the Dugong. intermaxillary bones are of much smaller size. The form of the bony aperture of the nostrils (c,fig. 247) in both the Dugong and Manatee is a large oval, which in the Dugong, as in the typical Cetaceans, is directed upwards. The entire cranium, and especially the frontal bones CETACEA. 565 Fig. 247. Skull of the Dugong. (d,d),axe consequently proportionally shorter than in the Manatee. The processes of the frontal bone, which form the superior boundary of the orbits, are thinner and more rugose in the Dugong ; the portion of the superior max- illary bone, which serves as the floor of the orbit, is narrower; the malar bone (e,e,Jigs. 246, 247), which forms by its curvature the anterior and inferior margins of the orbit, is more compressed and descends lower down. The lachrymal bone, which is situated at the anterior angle of the orbit (fifig- 246), is of larger relative size than in the Manatee ; but, as in that species, it is imperforate. The zygo- matic process of the temporal bone (g, figs. 246, 247), which, in the Manatee, is propor- tionally thicker than in any other animal, is of more ordinary dimensions in the Dugong, being more compressed, and extended further back- wards. The connexions of the bones of the cranium are the same in both these herbivorous species. The parietal bones (h,Jig. 247) are developed in the fcetus, as usual, each from a distinct centre of ossification ; but, what is very remarkable, the ossification of the inter- parietal bone also proceeds from two lateral and symmetrical points : these four, originally distinct bones, are, however, very early anchy- losed together, and also to the superior occipi- tal bone, which latter junction takes place be- fore the three other elements of the occipital bone have coalesced. The parietal crista; are widely separated from each other. The occiput is narrower, and its crest is less marked than in the Manatee. In the interior of the cranium we may observe that there is no bony tento- rium, and that the cribriform plate of the ethmoid is reduced to two simple depressions, widely separated from one another, and termi- nating anteriorly in two or three small foramina. There is no sella turcica for the pituitary gland. The optic foramen presents the form of a long and narrow canal. The lower jaw (i,fig- 246) corresponds in depth to the curvature and length of the inter- maxillary bones, and is bent downwards at the symphysis in a corresponding direction, pre- senting on the anterior surface of this part three or four rough and shallow alveoli, in two of which Sir Everard Home* discovered a small rudimental incisor. The skull of the true or Zoophagous Ceta- ceans is characterized by the great breadth and elevation of the cranium, by the almost verti- cal direction of the nasal passages, by the de- pressed position of the orbits as compared with the bony nostrils,' — a character which is still more marked in these than in the herbivorous species; and, lastly, by the extreme prolonga- tion of the oral or labial portions of the inter- maxillary and maxillary bones. The superior maxillaries (g,g, Jig. 268) are also developed posteriorly so as to rise anterior to the frontal bones, over which they are expanded, extending as far as the level of the nasal bones, which form almost the summit of the cranium. Such at least is the general configuration of the skull in the Delphinida, which constitute the largest family of the Zoophagous tribe. In the Phocana globiceps, of which the skull is represented in Jig. 248, the cranium is very Fig. 248. Skull of the Romidheaded Porpesse ; Phoccena globiceps. convex behind ; the occipital crest ( a, a) sur- rounds the upper part and descends on each side to the middle of the temporal cristas : the posterior convexity is not formed by the occi- pital bone alone, but also by the interparietal and parietal bones (b, b), the whole being an- chylosed together at a very early period. The parietal bones descend, as in the human sub- ject, between the temporal and the frontal ( c, c), and reach the lateral ala of the posterior sphe- noid. As the parietals terminate behind the * See PI. xiv. Philos. Trans. 1820. 566 CETACEA. transverse superior cranial or occipital ridge, and the superior maxillary bones approach very close to the same part, the frontal bone seems to be represented by a very narrow osseous band traversing the cranium from right to left, and dilating at each extremity to form the roof of the orbit ( c, c ). But when the maxillary bones which have extended over the whole anterior part of the cranium are raised, the frontal bone is then seen to be of much larger size than the external appeaiances indicate. The two nasal bones (d, d) are in the form of oblong rounded tubercles, set deeply in two depressions in the middle of the frontal bone, and in front of which the nasal passages (e, e) are continued vertically downwards. The two intermaxillaries (f,f) form the exter- nal and anterior margin of the nasal apertures. The cribriform plate of the ethmoid consti- tutes the posterior wall of the nasal passages; and in this plate there are three or four small perforations. The remainder of the circum- ference of the bony nostrils is formed by the maxillary bones, of which a small part appears at g : their septum is the vomer, which is joined to the ethmoid as usual. The malar bone is an irregular flattened bone, which assists the frontal in forming the orbit, and, like it, is covered by the maxillary bone : it sends backwards a long and slender process, which articulates with the zygomatic process of the temporal bone, and forms the only bony boundary of the lower part of the orbit. The zygomatic process of the temporal bone is united to the post-orbital process of the frontal, bounding the orbit posteriorly; and thus the zygomatic arch is exclusively formed by the temporal bone : this bone terminates at the temporal ridge, having but a small extent of development on the side of the cranium, and not entering at all into the composition of the posterior convex surface. At the base of the cranium the basilar and the lateral occipitals develop expanded plates, which join the ptery- goideal alee of the sphenoid, and a lamina of the temporal bone, to which the petrous and tympanic bones have a ligamentous attach- ment. The parietal bones also extend behind the temporals, to aid in completing the basilar walls of the cranial cavity, so that the temporal bone is almost excluded from entering into the composition of the cranium, serving merely to clo^yorne small vacancies left by the parietals: thrjHfeturc is of great interest, as we perceive inf^Re commencement of that displacement of the temporal bones from the cranial parietes which is characteristic of the small-brained and cold-blooded classes of Vertebrata. The differences between the Dugong and Manatee in respect to the structure of the cranium, we have seen to resolve themselves almost entirely into the expansion and elonga- tion of the intermaxillary bones in relation to the tusks, which they are destined to support in the former animal ; and we shall find on a com- parison of the skulls of the Delphinida toge- ther, that they also differ from one another, chiefly in the forms and proportions of their maxillary and intermaxillary bones. The Delphinorhynchi are characterized, first, by an extremely narrow rostrum, the length of which is four times greater than that of the cranium ; secondly, by the anterior curvature of the posterior extremities of the intermaxil- laries, which, as it were, draw forwards in the same direction the maxillary, the frontal, and even the occipital bones ; thirdly, by the posi- tion of the nasal bones, which are sunk in between the frontals and intermaxillaries; fourthly, by the very diminutive size of the temporal fosste. The Delphini, properly so called, have also a narrow rostrum, but its length is scarcely three times that of the cranium ; the posterior extremities of the intermaxillary bones, toge- ther with the maxillary and frontal bones, are raised, but not bent forwards; the temporal fossae in some species are as diminutive as in the Delphinorhynchi, but in others gradually recede from that character, and approach, by their expansion, to the form which they exhibit in the next generic type, viz. the Inia. The cranium in this genus, besides the great extent of the temporal fossa, and the strong crista which forms its superior border, is also characterized by the shortness of the orbital fossa. In the Phocana the rostrum is as remarkable for its breadth as it is in the Delphini for its narrowness ; this results from the great lateral development of the intermaxillary and max- illary bones ; but the antero-posterior extension of the bones is diminished, and the length of the rostrum does not exceed that of the cranium. The Narwhals ( Monodon ) manifest their affinity to the Porpesses ( Phoctena ) by the breadth and shortness of the rostrum, but differ from that and every other genus of Cetacea in the development of horizontal tusks in the inter- maxillary bones, of which the left in the male and both in the female remain concealed in a rudimental state within the maxillary bones. The cranium in the genus Hyperoodon, which includes the Great Boltle-noseWhale of Hunter, is at once distinguishable by the remarkable vertical crest which rises from the middle of the maxillary bones, the contour of which pro- cess descends suddenly behind, but extends more gradually and obliquely downwards an- teriorly. The lower jaw in this genus has two rudimental teeth at its anterior part. Lastly, in the Gangetic Dolphin ( Plata- nista ) the cranium presents a marked resem- blance to that of the Delphinorhynchus in the length and narrowness of the rostrum, and in the elevation and anterior curvature of its base; but on pursuing the comparison in detail, the structure and composition of this part of the skeleton presents several fundamental diffe- rences, which at the same time indicate an affinity to the Cachalots ( ' Physeter). The most striking character in the cranium of the Platanista is presented by the maxillary bones, which, after having covered, as in the other Delphinidce, the frontal bones as far as the temporal cristas, give off respectively a large osseous expansion, which arches forwards and forms a capacious vault above the spouting CETACEA. 567 apparatus of the nostrils. In order to consti- tute this part, one of the processes inclines towards the other, so as almost to come in contact with it for the two anterior thirds ; but posteriorly they recede from one another to give passage to the blow-hole. The cavity beneath this singular bony pent-house is occupied by an interlacement of numerous osseous pro- cesses, and by a close and hard fibrous sub- stance.* If we suppose the cranium of a Dolphin to be proportionally very much shortened, the margins of the rostrum to be greatly expanded and raised, so as to render its superior surface concave; the supra-frontal portions of the maxillary bones to be much developed and the margins extended upwards, thus form- ing an immense basin, at the bottom of which lie the external orifices of the bony nostrils ; if also the occipital crest in the Dolphin were raised behind the maxillaries so as to aid them in the formation of the bony cavity, in the basis of which the parietals are almost con- cealed, we should then have the skull of a Cachalot. The rostrum in the Catodontida, not- withstanding its immense size, is formed prin- cipally by the maxillary bones, as the inter- maxillaries and the vomer constitute a compa- ratively small part of the intermediate portion. The nasal passages extend obliquely from below upwards and forwards, but are of very unequal dimensions, the one on the right side not having one-fourth the breadth of that on the left. A corresponding want of symmetry is shown in the nasal bones themselves, and the cranium generally; and this circumstance, it may be remarked, characterizes in a greater or less degree the skull in all the Zoophagous Cetacea. The skull in the Whalebone-Whales ( Bala- nida) is, however, the most symmetrical in its general form; it is characterized by the great relative predominance of the facial over the cranial portion, by the narrowness of the ros- trum, and the curvature of the rami of the lower jaw, which each extend outwards, in a convex sweep, far beyond the sides of the upper max- illa, and converge to the symphysis, but with- out meeting to form a bony union at their ante- rior extremities. In the Mysticete, or common Whalebone- Whale (of which a side view of the skull is given sXjig. 249) the immense maxillary bones (a, a ) are compressed, and disposed each like an expanded arch along the outside of the in- termaxillaries (b ) and the vomer; their inferior surface has two facets separated by an interme- diate longitudinal ridge, to the sides of which the plates of whalebone or baleen are attached (b,Jig. 259). The intermaxillary bones are also laterally compressed, and diverge from each other posteriorly to form the long elliptical bony outlet of the nostrils; this orifice is com- pleted behind by the nasal bones, which are of very small size, and are partially covered by the frontal bones, which project forwards above them in the form of two small points. The tranverse portions of the frontal (c) and max- illary (a*) bones, which contribute to form the orbits, extend obliquely backwards : the tem- poral bone (d ) is of an irregular quadrate form, and extends much further backwards even than the occipital condyles. The occipital bone (e) advances forwards so as to cover almost all the upper part of the cranium, where it presents a general convexity. Each ramus of the lower jaw (f) is convex exter- nally, compressed and somewhat trenchant both at the upper and lower margins. The coronoid process, on which the letter is placed, is in the form of a slightly raised obtuse angle ; the condyloid process (g) forms the large tube- rosity behind. It is articulated to the glenoid cavity by a mass of ligamentous fibres, and not by a capsular ligament surrounding a synovial cavity. The vertebral column of the Cetacea does not differ from that of other mammalia except in the modifications demanded by their peculiar mode of existence. The cervical vertebra, of the normal number of seven, with the exception of the Manatee, are in general extremely thin, and though in some species, such as the Manatee, the Dugong (k, fig. 246), and the Fig. 249. * For a detailed account of the structure of the Platanista, they are found free; others, as the skull in this singular fresh-water Cetacean, see Dolphins and Porpesses, have the first two Cuvier, Ossemens Fossiles, v. pt. i. p. 298. commonly anchylosed together. In the Balse- 568 CETACEA. nopterae the dentata is anchylosed at its upper part to the third cervical vertebra. In the Cachalots they are the six last vertebras which are thus found united to one another, and in the Whales, properly so called, or Balana, all the seven are anchylosed. (See Jig. 250.) Fig. 250. Cervical vertebree of a Whale, Balcena Australia. The dorsal vertebrae (I, fig. 246), the number of which varies according to the species, are characterized by having their spinous processes, bent backwards, elongated from the first to the last, and equalled in length by the transverse processes. Moreover, their posterior articu- lating processes disappear after the first ver- tebra, and the anterior ones soon cease to per- form the functions of parts concerned in the union of the vertebrae to one another. In Jig. 251, which represents the eleventh dorsal vertebra of the Cape Whalebone Whale, a is the spinous ; b, b, the two transverse, which begin to lengthen from this point in the succeeding vertebrae; c, c, the anterior articu- lating processes. Fig. 251. Dorsal vertebra of a Whale. The lumbar vertebra; ( m, fig. 246), the posterior limit of which it is difficult to deter- mine in animals devoid of pelvis, have their spinous ( a, fig. 252) and transverse processes (b) very long. The first are straight and slightly inclined backwards. As it is essential that the Cetaceans should have the posterior part of their vertebral co- lumn left free, to allow of the vigorous in- flexions of the tail required in the act of Lumbar vertebra of a Whale. swimming, none of the vertebra; are anchy- losed together or encumbered by a union with posterior extremities, and hence there are none which can be properly termed sacral, unless we regard the sacrum as represented by the single vertebra, ( n, Jig. 246,) to which, in the Dugong, the pelvic bones are suspended. The caudal vertebrae may then be considered to commence from this point. Most of these vertebrae (o, Jig. 246) are further charac- terized by the chevron bones, ( p, Jigs. 246, 253,) which at first are strong and well deve- loped, but together with the other processes gradually diminish and disappear towards the extremity of the vertebral column, where the centres or bodies of the vertebrae alone appear, and present a depressed flattened form cor- responding to the horizontal position of the caudal fin, which characterises these air-breath- ing inhabitants of the ocean. Fig. 253 represents one of the anterior caudal vertebrae of the Cape Whale : a is the spinous ; b the transverse ; c, c, the represen- tatives of the an- terior oblique pro- cesses; p the in- feriorspinouspro- cesses, or chevron bones. To bones so lit- tle mobile, and so rudimental as the vertebrae of the neck in Cetace- ans, muscles pro- portionately de- veloped should correspond, and such in fact is the case. The cervical muscles in these animals are the same in number as in other Mammals, Caudal vertebra of a Whale. but their short- Fig. 253. CETACEA. 569 ness and thinness, principally in those at- tached to the atlas and the axis, are extreme; and although those which proceed from the other cervical vertebra may be better charac- terized, their action, nevertheless, is not much more extensive. The muscles of the back present no other important modifications than their great deve- lopment and their prolongation even upon the coccygeal vertebrae. Thus the longissimus dorsi and the sacro-lumbalis are attached anteriorly to the skull, and posteriorly transmit their ten- dons, the first to the end of the tail, the second to all the transverse processes of this part of the spine, associating in this way the move- ments of the back with those of the tail. As to the muscles peculiar to the tail, besides those which belong to this organ in all Mammals where it exists as a moveable organ, there are besides, in the Cetaceans, 1st, the antagonists of the sucro-lumbalis below the transverse pro- cesses ; 2nd, a levator Cauda, which takes its rise above the five or six dorsal vertebra?, under the longissimus dorsi, and often in this part blends with it ; it then extends freely as far as the extremity of the tail, where the two muscles unite together again by their tendons ; 3rd, a depressor cauda, of great thickness, which pro- ceeds from the pectoral region, and spreads its tendinous processes upon the ribs, distributes them laterally to the transverse processes, and •below to be inserted into the chevron bones along the two posterior thirds of the tail ; 4th, a muscle which comes from the rudimental bones of the pelvis, and is inserted into the chevron bones of the anterior portion of the tail ; 5th, the great recti muscles and the obliqui ascen- dentes, which, proceeding from the abdomen, attach themselves behind to the sides of the base of the tail. It is in consequence of this great aggre- gation of muscles, which are developed in unexampled proportions as compared with other Mammals, that the tail of the Cetaceans acquires the prodigious strength which it pos- sesses, and by means of which these gigantic animals propel themselves with so much faci- lity and impetuosity through the water, and so readily ascend to the surface to respire, and again seek protection in the deep abysses of the ocean. The sternum (q,fig. 246) is short and large. In the Dugong it is composed of five pieces ; in the Dolphin, the Porpesse, and the Pla- tanist, it is generally composed of only three ; in the Whales it consists of but one. In the subjoined figure (fig. 254) from the Bala- noptera Boops, the Fig. 254. sternum is deeply notched behind, and has a large ridge on its exterior or under surface. The ribs of the Cetaceansarechiefly remarkable for their great curvature, but differ in their rela- tive length, thickness, and mode of connection. vol. r. Their thickness and the density of their tex- ture is most remarkable in the Herbivorous species, especially in the Manatee. In the Dugong, which has eighteen pairs of ribs (r, r, fig. 246), only the first three have car- tilages which join the sternum. In the Del- phinida the first pair of ribs are articulated at their sternal extremities to the anterior angles of the first bone of the sternum ; the second pair join the sternum between the first and second bones ; the third between the second and third, and the fourth, fifth, and in some species the sixth pairs of ribs are joined to the third bone of the sternum; the sternal portions of these ribs are ossified. The anterior ribs are articulated at first by a head to the ver- tebral centres, and by a tubercle to the trans- verse processes ; but as they extend backwards the head disappears, and the ribs are attached only to the extremities of the transverse pro- cesses. In the Bulanida the first pair of ribs are remarkable for their great breadth, especially at the sternal extremity, and these alone join the sternum. In the Balana Capensis the two first, as well as the four last pairs of ribs, are joined only to the transverse processes of the vertebrae. The depressors and elevators of the ribs ap- pear to possess nothing particular, and the same may be said of the diaphragm and the muscles of the abdomen ; but in regard to the movements of these parts, we must remember what M. Mayer says of the muscular fibres, which encircle closely the lungs, and which take part in the actions of inspiration and expiration. [Mr. Hunter observes that, " as the ribs in this tribe do not completely form the cavity of the thorax, the diaphragm has not the same attachments as in the Quadruped, but is con- nected forwards to the abdominal muscles, which are very strong, being a mixture of muscular and tendinous parts. The position of the diaphragm is less transverse than in the Quadruped, passing more obliquely back- ward and coming very low on the spine, and high up before, which makes the chest longest in the direction of the animal at the back, and gives room for the lungs to be con- tinued along the spine."] The anterior members in the Cetaceans do not essentially differ from those of the other Mammalia, but they undergo, in these animals, very great modifications. In the shoulder they are entirely devoid of clavicles. Their scapula is very large in general, but varies in this respect according to the species. In the Herbivorous Cetaceans, as the Dugong (s, fig. 246), the anterior angle is rounded, the posterior is extended backwards, and the posterior margin or costa is concave. The spine is prominent, and so placed as to divide the dorsum of the scapula into a supra-spinal and infra-spinal depression. The acromion is pointed, but much less elongated in the Dugong than in the Manatee. The coracoid process is also more pointed in the Dugong. 2 p 570 CETACEA. In the Zoophagous Cetaceans the spine of the scapula does not project much. The supra-spinal fossa is reduced to a mere groove in the common Dolphin, and entirely dis- appears in the Gangetic species ( Platanista) • the coracoid process does not exist in this last dolphin ; and the same absence is found in the Baltznida, whilst it is seen in the common Dolphin and the Cachalot. Lastly, the acro- mion appears always to exist, but with a different development, in different species. In the scapula of the Whalebone Whale (A, fig. 255) it is marked a. The articular or Fig. 255. Bones of tlie anterior fin of a Whale, Baleena Mysticetus. glenoid cavity (b) is proportionally larger in this species than in the Spermaceti Whale. The muscles of this part of the anterior mem- ber present some remarkable modifications, but with which we are only acquainted as they exist in the common Dolphin. Thus the serratus magnus does not extend as far as the cervical vertebrae, and ends at the ribs ; the pectoralts minor, instead of descending on the ribs, is directed towards the anterior extremity of the sternum. The rhomboideus {a, fig. 256) is not attached to the ridge of the spine, but extends along the superior edge of the scapula ; the trapezius covers the scapula and has no clavicular pro- longation. The levator scapula (b,fig. 256) is attached to the broad transverse process of the first vertebra, and spreads itself over all the ex- ternal surface of the scapula. The rest of the anterior member is com- posed of the humerus, the radius, the carpus, the metacarpus, and the phalanges. In the Dugong the humerus (t, fig. 246) is much shorter and thicker than in the Ma- natee, and the deltoid ridge is more prominent. In the true Cetacea the humerus is always very short. In the Whalebone Whale (B, fig. 255) its length is scarcely double its breadth ; its head is hemispherical and almost parallel to the axis of the bone. The lower extremity is divided into two planes slightly inclined for the ulna and radius. The cubitus and the radius (v) are also very short, and are anchylosed (u,fig. 246) together at both extremities in the Manatee and the Dugong, but they retain in these Cetaceans the rounded form which is peculiar to them in the other Mammalia. In the spouting Ceta- ceans they are compressed, and are united by means of fibro-cartilage with the humerus and the carpus. The olecranon varies in size. In the great Whale it rises in but a small de- gree, while in the Spermaceti Whale it is de- veloped in the form of a hook. The radius ( C> fig- 255), which is broader than the ulna (D, fig. 255), is dilated at its lower ex- tremity. The bones of the carpus are very much flattened, and of an hexagonal form ; they are less in number than in Man, but the number varies according to the species. The Manatee has six, the pisiform being wanting. The Dugong has four (w, fig. 246), of which two are in the first row corresponding respectively to the radius and ulna, and two in the second row, the external one supporting the metacar- pal bones of the pollex and index, the internal bone supporting the medius and annularis; the ulnar or little digit is supported by the ulnar carpal bones of both the first and second row. The pollex (x,fig. 246) is reduced, as in the Manatee, to a small pointed meta- carpal bone. The common Dolphin has only five metacarpal bones ; the Whale has seven : of these four are in the first row, and three in the second (E, fig. 255). The metacarpals (F, fig. 255) are five in number, much flat- tened, and have the general form of phalanges. The phalanges in the Zoophagous Cetaceans partake of the flattened form of the bones of the metacarpus. Their number increases in each finger, comparatively with the normal number, sometimes very much so ; and in many cases there are some which remain cartilaginous. The pollex (G 1, fig. 255) in the great Whale has two bones ; the index CETACEA. 571 Rhomboideus. Levator scapulae. Infra-spinatus. Humero-mastoideus Muscles of the anterior fin of a Dolphin. e. Stevno-mastoideus. /. Costo-humeralis or latissimus dorsi g. Portion of pectoral. h. Splenius. (2) four, the digitus medius (3) five, the annu- laris (4) four, and the digitus parvus (5) three bones ; all are terminated by a cartilaginous dilatation : they form collectively a large and short paddle, obliquely rounded. The muscles which characterize the arm of the Mammalia exist generally also in the Dolphin, and doubtless in the other Cetaceans, but with modifications which have not been so satisfactorily described as could be wished. The great pectoral muscle (a part of which is seen-atg, fig. 256) presents the sternal portion, which is called the musculus communis, or mus- cle common to the two arms. The latis- simus dorsi (f, fig. 256) is represented by a little muscle, the digitations of which are attached to the ribs ; the supra-spinatus and infra- spinatus are nearly of equal size, but the sub- scapularis is very large. The coraco-brachialis is very short. The muscles of the other parts of the arm, that is, of the fore-arm and hand, appear in a rudimental state, and seem to exist less on account of the movements of the parts to which they are attached, than to shew the analogy of the anterior members of the Cetaceans with those of other Mammalia. [In our dissections of the common Porpesse vve have found the supra-spinalis of small size, corresponding to the size of the supra-spinal fossa. It is covered by the deltoid muscle (i). The infraspinatus (c) is consequently of much larger size, but is a thinner muscle : behind this muscle is seen the teres major (k) and minor (/).] As we have already said, the posterior extre- mities are wanting ; all that remains of them are the rudiments of a pelvis. These rudiments are found in the Dugorig to be composed of two pairs of bones (j/, fig. 246) united two and two, and end to end by a cartilage, and Fig. 257. attached by a carti- lage also to one of the vertebra. In the Dolphins they con- sist of two little, long, thin bones which are lodged 111 the flesh, one to the right and the other to the left of the anus. In the Whales, at the extremity of each of these bones (a,a, fig 257), which are regarded as ilia, a second (6) is found articulated, smaller, and curved ; the con- vexity of which is external, and might represent a pubis, or an ischion ; it seems to correspond to the second of these bones in the Dugong. We perceive that the internal construc- tion of the organs of movement in the Ce- taceans does nol vary in the different spe- cies except by mo- difications the im- portance of which we are not able to appreciate. The dif- ferences in their exterior structure, moreover, do not ap- pear to exercise any influence over then- mode of living ; for the chief of these consists in the Manatee having nails to the ends of its pectoral fin, which correspond to the fingers, of which it is in part composed ; and in its tail being oval instead of being extended laterally into two wings. We have in no way considered as forming part of the organs of movement, the protu- berances which are seen upon the back of some species of spouting Cetaceans, some- times in the form of a hump, and sometimes like a fin, more or less elevated. These pro- tuberances, in fact, are nothing more than simple gibbosities, simple prolongations of the skin, filled with dense cellular tissue and fat, and resembling more or less a fin, but devoid of any independent movement, and without any direct connection either with the vertebra; of the back or with the muscular system. Digestive orguns. — The alimentary appa- ratus is one of those, which, in many of ils parts, presents the most important modifica- tions in the Cetaceous Order. The three genera into which the Herbivorous Cetaceans are divided, are characterized by three systems of dentition fundamentally dif- ferent. The Manatees have molares with dou- 2 p 2 Pelvis of the Mysticete Whale. 572 CETACEA, ble or triple ridges, and with the root distinct from the crown, pre- senting a remarkable resemblance to those of some of the Pachy- derms, as the Hippopotamus. The Dugongs have simple elliptical molares, the crown of which, before it is worn, presents two slight fur- rows, which are entirely effaced by age. They are without fangs, properly so called ; and in the up- per jaw are found two long tusks, of which the other Cetaceans of this family are destitute. The Rytina have no molares at all; these teeth are replaced by a horny plate in the middle of each jaw, a structure which seems to connect these animals with the Whalebone Whales. The tongue is short and but little susceptible of movement. The os hyoides is characterized in the Cetacea chiefly by the slight degree or total absence of connection with the larynx, resulting from the elevated position of this organ required by its peculiar relations with the posterior nares. In the Herbivorous order the Dugong pre- sents a simple form of the os hyoides ; the posterior cornua soon anchylose with the body, but send no ligament to the thyroid cartilage. The anterior cornua generally remain cartila- ginous, and form the medium of union be- tween the body or basi-hyal, and the large and long styloid processes. In the Delphinidie the body and posterior cornua of the hyoid bone are of a flattened form. In the Balanitis, as the Piked Whale or Balcenoptera, the body (a, Jig. 258) is a cylindrical bone, extended Fig. 258. Fig. 259. Tongue and Baleen-plates of the Piked Whale, Balcenoptera Boops.* The genio-glossi pass backwards and inwards from the anterior contour of the lower jaw. The tongue itself corresponds to the form of the space included by the rami of the lower jaw, and is consequently of great size in the Cachalots and Balaenidee, rising in the latter like an immense cushion (a, Jig. 259), into the space between the laminae of baleen (b), and affording a great quantity of the finest oil. In the figure it is represented in the Piked Whale, but probably preternaturally enlarged and raised by the extrication of gas caused by putrefaction. It is thick, and its free extremity is generally short, but this is less remarkable in the Phi/tophaga than in the Zoophaga. In the Dugong (Jig. 260) the upper surface of the anterior part of the tongue (a) is beset with cuticular spines, and on each side of its basis there is a remarkable horny retroverted pointed process (6, b). . 260. Hyoid bones of the Piked Whale. transversely, and is slightly curved backwards and upwards; its middle portion supports an- teriorly two processes (6, b) resembling the base of the anterior cornua in the Ruminants ; besides these there are, in this genus, two rounded tubercles on the posterior margin op- posite these processes. The styloid bones (c, c) are cylindrical and slightly curved in two directions ; they are joined by cartilage on each side to the occipital protuberance which represents the mastoid process. The muscles which protrude and retract the tongue are extremely simplified in the Ce- taceans ; the retractors are represented by a single pair, analogous to the stylo-hyoidei, the fibres of which pass from the posterior margin of the stylo-hyal bones to the body of the hyoid. The stylo-glossi pass from the anterior and superior margin of the styloid process to their insertion. The hyoglossi arise from the middle of the convexity of the os hyoides. Tongue of the Dugong. In the Porpesse the surface of the tongue is soft and smooth, and very flat superiorly ; the anterior margin is fringed by a number of short irregular processes {a, Jig. 265). The salivary glands are reduced to the most rudimental condition. In the Phytophagous Cetaceans the stomach is separated into two portions (Jig. 261); one, the cardiac (a), very large, the other, the pyloric (6), of narrower calibre, by a contrac- tion (c) giving origin to two prolongations (d, d), which are tubiform in the Dugongs, and of a pouch-like form in the Manatees. In both species there is a gland at the cardiac extremity of the stomach (c), which in the Dugong, Sir Everard Home (from whose memoir the figure subjoined is taken) describes as " forming a round mass, as in the Beaver. The orifices of these glands are small, and * From Fr. Cuvier, Cetacea, pi. 20. CETACEA. 573 Fie. 261. Stomach of the Dugong. covered over with a membranous bag, which has only one large aperture. The glandular mass is divided into two portions."* Thus the stomach of the Dugong presents peculiarities which are met with singly in animals of the Cetaceous, Pachydermatous, and Rodent Or- ders. Like the stomach of the Whale it is divided into distinct compartments ; like the stomachs of the Hippopotamus and Peccary it has ccecal pouches superadded to and com- municating with it; and like those of the Dor- mouse and Beaver its cardiac compartment is provided with a glandular apparatus : (f is the oesophagus, g the intestine.) The ccecum is simple and cordiform in the Dugong (fig. 262), but is of more irregular Fig. 262. Caecum of the Dugong . figure and bifurcated in the Manatee. The Ry- tina appears also to possess a stomach divided into two portions, of which the cardiac is also larger than the pyloric ; and it has a very large ccecum, divided on its internal surface into * Phil. Tians. 1820, p. 317. numerous cells. A gland, remarkable for its size, is also found in the first portion of the stomach of this species. No sub- stances but fuci have ever been found in the alimentary canals of these animals. The Zoophagous Cetaceans present still greater difler- encesin theiralimen- tary organs than the Phytophaga. In the Dolphins the teeth, which are generally simple and conical, or compressed in both jaws, vary con- siderably in number, and often remain concealed in a rudimen- tary state in the gums- In the Cachalots they are only found in the lower jaw; are simple and oviform ; and their number ap- pears to be in no way certain. The Whales have no true teeth, but at each side of their palate grow, transversely, horny plates, named baleen (the whalebone of commerce), pro- vided on their inner edges with fringe-like beards, amidst which, as in the meshes of a net, the animals which form their food are retained. [The structure, forms, and disposition of the teeth having been given in the characters of the different genera of Cetacea, we have here only to add a few words on the subject of the baleen-plates which form their substitutes in the family of Bala;nidas. Each of these plates consists of a central, coarse, fibrous, and two exterior or lateral compact layers ; the first extends beyond the latter, so that the plate terminates at its lower or free extremity in a fringe, and in looking upwards into the mouth of a Whale when all the baleen-plates are in situ, only their fringed extremities are seen. The base of each baleen-plate has a conical cavity, which is fixed upon a pulp of a cor- responding form, buried deeply in the firm vascular substance of the gum which covers the under surface of the maxillary and inter- maxillary bones ; the sides of the base of the baleen-plate are firmly attached to white horny , lamina? of the gum, which are reflected from one plate to another, and from which the ex- ternal compact layers of the baleen are con- tinued : the pulp appears to be subservient to the secretion of the central coarse fibrous part alone.] Nothing can differ more, or indeed be more contradictory than the descriptions which have been given of the stomachs of the Zoophagous Cetaceans. In many of the species the struc- ture of this part is unknown. It has been more or less fully described in the Ddphino- rhynchus micropterus, the common Dolphin, the Small Bottle-nose ( Dclphinus Tursio), the common Porpoise, the Grampus, the 574 CETACEA. Phocccna globiceps, the carinated Porpoise, the Beluga, the Platanist, the Narwhal, the Great Bottle-nose or Hyperoodon, and the Piked W hale (Bu lanoptcra ). There is bo doubt that the stomachs of all these animals are very complicated ; and although it may be more than probable that they do not resemble each other in their composition, it is to be presumed, however, that it is to their complication we must attribute the essentially different descriptions which have been put forth on this subject. What authorizes this supposition is the di- versity of opinions which exists relative to the number of the stomachs of the common Dolphin and common Porpoise, some counting only three, others four, others five, and others six, &c. Now it is certain that these differences of number proceed simply from the manner in which this organ is viewed. When it is only judged of by its exterior, and its globulous parts alone are called stomach, only three or four can be reckoned; and then the more or less tubular passages, situated amongst those more or less spherical cavities, are considered as mere intercommunicating canals. But if the interior of these stomachs be studied, it is seen that several amongst them have a special organization, and are separated from one another by small openings, which do not invariably establish a direct communica- tion between them : hence the tubular parts cannot be considered as simple passages, but must necessarily be admitted as essential parts of the stomach, which, like the others, impress their peculiar action upon the food. It has also been the case that the dilated sac into which the biliary and pancreatic juices are poured, has not been admitted as belong- ing to the stomach ; but besides its not being without example that in Mammalia the bile may be poured immediately into the stomach, the difference in the nature of the membranes ought to suffice for deciding whether the part which receives these secretions belongs or not to the duodenum. Now in the Dolphins it is evidently at the termination of the last stomach that their duct opens. In this state of things it is impossible to decide with precision in what particulars the Zoophagous Cetaceans differ from one another in the structure of the sto- mach. It appears, however, that this organ in the common Dolphin, the common Porpoise, the Globiceps, and the Platanist, is formed upon the same type, and is composed of five parts ; and if they differ one from another, it is only by modifications of secondary importance. If to these facts we add what Meckel -states re- specting the Narwhal, in which he recognizes five stomachs, and what Hunter says of the Grampus and Piked Whale, in which he like- wise found five, we have three species more to add to the first. In fact, when we consider that only three or four stomachs have been re- cognized in the Carinated Porpesse and the Beluga, which are true Phocarue, and that Baussard saw three, and Hunter seven in the Hyperoodon (Great Bottle-nose Whale), we believe ourselves authorized in thinking that these differences depend entirely upon the manner in which this organ is viewed, and we consider it very probable that the number of stomachs in tliese Cetaceans, as in the others, is five. However, from this small number of facts, and from all the conjectures with which we have been obliged to approach the subject, we shall draw no precise conclusion as to the structure which may be common to the Zoo- phagous Cetaceans. But this undoubted great complication of the stomach in animals which are nourished with the most animalized food, is an anomaly the cause of which it would be very important to investigate ; for from the ascertained facts which we have to reason from, we are not led by any analogy to an explanation of this subject. [In our examinations of the stomach of the Porpesse (fig. 263), we have not been able to 263. Stomach of the Porpesse. distinguish more than four compartments. This complex digestive organ, besides the structure of the internal surface, differs from that of the Ruminant Animals in the compara- tively small size of the first cavity, and the mode of inter-communication of the other compart- ments, which succeed one another, and are not appended to the extremity of the oesopha- gus : instead, therefore, of the oesophagus communicating with all the four cavities, it opens only into the first, and consequently no CETACEA. 575 rumination can take place. The first cavity is continued in the same line with the oesopha- gus, having the same structure, and not being divided from it by any sensible constriction ; its commencement is indicated by the orifice leading into the second stomach, beyond which orifice it is continued in the form of a dilated ovate cavity ( a). It is lined with a cuticle, and its inner surface is beset with small rugae. A number of large irregular projections sur- round the aperture leading to the second ca- vity, and are calculated to prevent the passage into the second of any substances save such as are of very small size. Notwithstanding the nature of the lining membrane the di- gestive processes are considerably advanced in this cavity, which does not act simply as a reservoir. It is probable that the secretion of the second stomach, which is highly glandular, regurgitates into the first and assists in pro- ducing the dissolution of the carneous parts of the fishes, the remains of which are usually found in it. The thick cuticular lining terminates abruptly at the small ori- fice leading into the second stomach (b). The interior of this cavity presents a series of close-set thick longitudinal wavy rugae, laterally indented into one another. The internal layer is thick and of a peculiar structure : according to Sir David Brewster, " it seems, in its wet state, to consist of tubes or fibres perpendicu- lar to the two membranes which inclose them, and the upper surface of one of the membranes is covered with hollows or depressions corres- ponding with the extremities of the tubes or fibres. A more minute examination, conducted in a different way, proves these perpendicular portions to be tubes. In order to dry it, 1 pressed it between folds of paper, and the effect of the compression was to press together nearly all the tubes, and make the whole one dense mass, of a dark brown colour ; but when it be- came dry and slightly indurated, I drew it out as if it had been India-rubber, and the tubes opened, and the mass became white." The membrane next the cavity of the sto- mach is perfectly smooth ; the one external to the fibres is a vascular and cellular tunic, and is inverted by the layer of muscular fibres continued from the preceding cavity. The communication with the third stomacli is near the lower end of this cavity. The third com- partment is a small round vascular cavity, into which the second opens obliquely : it is lined by a smooth and simple villous tunic. It is not visible exteriorly, and does not exceed an inch in length in the Porpesse, but in the Hyperoodun is about five inches long. The fourth cavity (c, c) is long and narrow, and passes in a serpentine course almost like an intestine; the internal surface is smooth and even, but villous. It opens on the right side into the duodenum (d), which is much dilated, and, as in the human subject, is without valvulae conniventes at its commencement. The pylo- rus is a smaller opening than that between' the third and fourth cavities.] Some authors speak affirmatively of a con- siderable bladder, which in the Rorquals, after death, comes up into the mouth and forces the two jaws asunder. Now what is the nature of this vesicular mass, of which other authors say nothing ? To what organic system does it be- long ? This has never been made a subject of enquiry. It has been considered as belonging to the respiratory system, or as an air-bladder analogous to that of fish. Is it not more proba- bly a portion of the stomach distended by the gases formed there ? In general the Spouting Whales have no coecum. However, a trace of this gut has been found in an oval elevation in the Plata- nist ; a caecum exists also in the Piked Whale and in the Whale-bone Whale. The variations in form or affinity of the spleen and the liver appear to have no essential relation with the forms of the stomach. [Mr. Hunter observes that " there is a con- siderable degree of uniformity in the liver in this tribe of animals. In shape it nearly re- sembles the human, but is not so thick at its base nor so sharp at the lower edge, and is probably not so firm in its texture. The right lobe (e, Jig. 263) is the largest and thickest, its falciform ligament broad, and there is a large fissure (g) between the two lobes, in which the round ligament passes. The liver towards the left (f) is very much attached to the sto- mach, the little epiploon being a thick sub- stance. There is no gall-bladder." " The pancreas is a very long, flat body, having its left end attached to the right side of the first cavity of the stomach : it passes across the spine at the root of the mesentery, and near to the pylorus joins the hollow curve of the duodenum, along which it is continued, and adheres to the intestine, its duct entering that of the liver near the termination of the gut." — Phil. Trans. 1787, p. 410. The structure of the biliary organs has a closer resemblance to that of Quadrupeds in the Herbivorous Cetacea, and differs from that above described in the presence of a gall- bladder, besides some minor points. In the Dugong the liver is a transversely- oblong viscus, divided into three lobes with a fourth small process at the root of the left lobe, representing the lobulus Spigelii. It is as usual convex towards the diaphragm, but rather flattened than concave towards the viscera, the anterior margin thick and rounded. Of the three larger lobes the middle one is the smallest, of a square shape, projecting forward, and as it were overhanging the gall-bladder, which is lodged in the middle of the inferior surface. The ligamentum suspensorium is continued upon the middle lobe, immediately above the gall-bladder, the anterior margin of this lobe being notched to receive it, and the remains of the umbilical vein entering the liver an inch above the fundus of the gall-bladder. The two lateral lobes are more than double the size of the cystic lobe, and of these the left is the largest. Both these lobes are concave to- wards the small middle lobe, which they thus surround and conceal. The lobulus Spigelii is of a flattened and square shape, measuring one inch and a quarter in length 576 CETACEA. and one inch in breadth. The gall-bladder is of an elongated form, about an inch in diameter at the broadest part. It does not receive the bile by means of a communication between the cystic and hepatic ducts as in most animals, but that fluid is conveyed directly into it by two distinct hepato-cystic canals in the same manner and situation as the ureters terminate in the urinary bladder. The two orifices are half an inch apart on the same transverse line, and at a distance of three inches from the fundus vesica they are large, readily admitting a full-sized probe. The common ducts, of which they are the terminations, are half an inch in length, and branch off into the lobes on either side. The inner membrane of the gall-bladder is rugous; it has a longer investment of peritoneum than in man. Where it ends it is difficult to say, as it gradually diminishes in size after the entry of the above ducts, and does not appear to be separated from the cystic duct by any marked contraction or valvular structure. The cystic duct is about six inches in length, and two lines in diameter; dilates a little before entering the duodenum, and as it passes between the coats of that intes- tine the canal is provided with a reticular valvular structure of the inner membrane, which may probably supply the deficiency of this structure in the preceding parts of the duct. Three vena cava liepatica from the three lobes of the liver join the vena cava inferior at the upper and posterior edge of the liver, which is not, however, perforated by it as in most quadrupeds. The vena porta, formed in the usual manner, but deriving a very small branch from the spleen, enters the fissure below the gall-bladder. Sir Everard Home takes no notice of the pancreas ; Sir Stamford Raffles merely observes that it lay ' below the duodenum.' It is situated below and behind the pyloric cavity of the stomach. Its length in a Dugong six feet long we found to be seven inches ; it was obtuse and thick at the splenic or left end, where its diameter was two inches, and gradu- ally growing smaller towards the duodenum, it terminated in one uncommonly large duct, which was three lines in diameter and of great length. On laying open this canal the orifices of from twenty to thirty tributary ducts were observable, which were two lines in diameter; the coats of these ducts thick, and terminating in flattened lobules. The spleen, as Sir S. Raffles observes, was very small, of a rounded form ; its length in the larger specimen four inches and a half, its breadth in the middle one inch and a half, from which it tapered to either end; its structure finely reticular. In the Piked Whale the spleen is single and of small proportional size ; in the Porpesse this organ is remarkable for its subdivision into distinct portions, of which one is generally about the size of a walnut (/», Jig. 263) ; the others, to the number of four, five, or six {i, i), are of much smaller size.] The Spouting Whales always feed upon living food. The Dolphins and Cachalots pur- sue or catch fish principally, and large Mollusks, whilst Whales prey upon the numerous little Molluscous and articulated animals and Vermes which swarm, it is said, in the northern seas, and in the number of which are reckoned crustaceans, cuttle-fishes, clios, medusas, sea- anemonies, &c ; but in this respect a difference must be made between the Baleenopterae and the Whales, properly so called ( Balana ), for we are assured that the first also feed upon fish, and are capable of swallowing much larger animals than the latter. Organs of Circulation. — The researches of the anatomist on the circulating system of the Cetaceans have not hitherto been extended to many species. In its essential parts it is similar to that in other Mammalia. But the peculiar nature of Cetaceans, and the great modifications of their organs of movement, have necessarily produced in this system, not only modifications analogous to those of these organs, but vascular developments exclusively characteristic of these animals. It is not known whether the Manatee pre- sents anything particular in regard to the organs of circulation, but the heart of the Dugong (Jig. 264) and of the Rytina is cloven by the Fig. 264. Heart of the Dugong. deep separation of the two ventricles, a cir- cumstance which adds an important link of affinity to those already subsisting between these animals. [In the heart of the Dugong, the ventricles, as Sir Stamford Raffles has correctly described them,* are not completely detached from one another. The auricles are of equal size and of a rounded form. In the right auricle (a), which receives a single superior cava, the coronary vein, and the inferior cava, there is on the auricular side of the orifice of the latter vein a fleshy Eustachian valve, of the size and form which, in such cases, is com- monly seen in the human subject. The valve of the foramen ovale has a reticulate surface at the upper margin, but is entire and im- perforate. The right ventricle (b), in the Du- * Phil. Trans. 1820, p. 174. CETACEA. 577 gong previously mentioned, which was six feet in length, was three inches and a half long and three inches broad at the base ; the thick- ness of its parietes one line and a half; the earner columnar are few, and resemble those in man. The tricuspid and mitral valves are of the usual form and structure, but the latter are broader than in man, measuring each one inch three lines across the base. The diameter of the orifice of the pulmonary artery (c) is one inch and a half. The capacity of this vessel is very great, according with the impediments to the transmission of blood through the lungs which must arise from the submarine habits of this animal. In the left auricle (d) the trans- verse pectinated muscular bands are equally if not more developed than in the right. The trace of the foramen ovale is more evident on this side the septum uuriculare than in the right auricle ; it appeared as an oblique slit directed upwards, about three lines broad, but was com- pletely closed. The parietes of the left ventricle ( e) are half an inch in thickness ; there is nothing unusual in the mitral valve or the carnese columnar connected with it ; the inner surface of the ventricle was as usual smooth below the origin of the aorta (f). The breadth of the semilunar valves here was ten lines, the dia- meter of the orifice being one-third less than that of the pulmonary artery. The ductus ar- teriosus was completely obliterated.] The heart in the Dolphins and Whales does not appear to have undergone any remarkable modifications; but their arterial system pre- sents a very important one in the infinite circumvolutions of arteries, and the vast ple- xuses of vessels, filled with oxygenated blood, which are found particularly under the pleura and between the ribs, on each side of the spine. [Of this remarkable structure, which was discovered by Hunter, we here subjoin the original description. " The general structure of the arteries re- sembles that of other animals; and where parts are nearly similar, the distribution is likewise similar. The aorta forms its usual curve, and sends off the carotid and subclavian ar- teries. " Animals of this (the Whale) tribe, as has been observed, have a greater proportion of blood than any other known, and there are many arteries apparently intended as reservoirs, where a larger quantity of arterial blood seemed to be required in a part, and vascularity could not be the only object. Thus we find, that the intercostal arteries divide into a vast number of branches, which run in a serpentine course between the pleura, ribs, and their muscles, making a thick substance somewhat similar to that formed by the spermatic artery in the Bull. Those vessels, every where lining the sides of the thorax, pass in between the ribs near their articulation, and also behind the ligamentous attachment of the ribs, and anastomose with each other. The medulla spinalis is surrounded with a net-work of arteries in the same man- ner, more especially where it comes out from the brain, where a thick substance is formed by their ramifications and convolutions ; and these vessels most probably anastomose with those of the thorax. " The subclavian artery in the Piked Whale, before it passes over the first rib, sends down into the chest arteries which assist in forming the plexus on the inside of the ribs ; I am not certain but the internal mammary arteries con- tribute to form the anterior part of this plexus. The motion of the blood in such cases must be very slow ; the use of which we do not readily see. The descending aorta sends off the intercostals, which are very large, and gives branches to this plexus ; and when it has reached the abdomen it sends off, as in the quadruped, the different branches to the viscera and the lumbar arteries, which are likewise very large, for the supply of that vast mass of muscles which moves the tail. " In our examination of particular parts, the size of which is generally regulated by that of the whole animal, if we have only been accustomed to see them in those which are small or middle-sized, we behold them with astonishment in animals so far exceeding the common bulk as the Whale. Thus the heart and aorta of the Spermaceti Whale ap- peared prodigious, being too large to be con- tained in a wide tub, the aorta measuring a foot in diameter. When we consider these as applied to the circulation, and figure to our- selves that probably ten or fifteen gallons of blood are thrown out at one stroke, and moved with an immense velocity through a tube of a foot diameter, the whole idea fills the mind with wonder."*] It is to be presumed, as has been done, that this singular complication of vessels is caused by the necessity in which the Cetaceans are often placed of suspending their respiration, and consequently the oxygenation of their blood, during a considerable time. These numeerous arteries form, therefore, a reservoir of oxyge- nated blood, which, re-entering the circula- tion, supports life throughout, where venous blood would only produce death. But how this blood is sent to this general system of arte- ries, or what is the peculiar force which acts upon it to this effect, is a point on which we are still reduced to the most vague conjectures. * Phil. Trans. 1787. p. 415. It must be supposed that M. Breschet, who has recently written on the arterial plexuses of the Cetacea, could only have known the preceding description by extractor refe- rence, or he would not have stated that the structure in question had been 'observee par J. Hunter, mais indiquces trop sommairement pour poiivoir etre des lors comptcs au nombre des taits acquis a la sci- ence,' for we do not find in M. Breschet's paper any essential addition to the original account given by our celebrated anatomist, either with respect to the observation of additional facts, to their clearer description, or to the physiological inferences de- duced from them. It is agreeable to find that M. V. Baer, whose observations on the subdivision of the brachial arteries, and on other par's of the vascular system of the Porpesse, are real additions to the anatomical history of the Cetacea, by no means considers it necessary to depreciate the value of the observations of his predecessors in the same field of enquiry. 578 CETACEA. The disappearance of the posterior members has occasioned that of the vessels which should nourish those members ; and as the tail has attained a considerable development, the arte- ries and veins which belong to this last part of the trunk have been developed in the same proportion. The abdominal aorta does not send off any external iliacs, but is continued underneath the tail in the canal of the inferior processes, from whence its ramifications are dis- tributed to the muscles which move this organ. The modifications of the venous system are in many respects analogous to those of the arteries. The quantity of blood contained in the vascu- lar system appears to be proportionally much greater than in the other Mammalia. [In the Porpesse the veins are almost univer- sally devoid of valves, so that they can be as easily injected from trunks to branches, as in the reverse direction. The plexiform disposi- tion which we have seen to characterize so many parts of the arterial system is still more strongly displayed in the venous. Thus in the system of the anterior vena cava, with the ex- ception of the trunk of that vein itself, and the short jugular veins which join it, an internal and an external jugular branch, and a pair of large subcutaneous veins, all the other parts of the system manifest the plexiform disposition. This is most remark- able in the large venous sinuses surrounding the central axis of the nervous system, which receives the intercostal veins, and by means of which the system of the anterior cava is chiefly brought into com- munication with that of the pos- terior cava ; for, as V. Baer has observed, there is no intercommu- nicating channel analogous to the vena azygos of the higher Mam- malia. Of the venous plexuses belong- ing to the system of the inferior cava, that which is found at the posterior parietes of the abdominal cavity extending from below the kidney to the lower boundary of the abdomen is the most remark- able, and we have selected in illustration of this, the figure from Baer's excellent memoir on the vas- cular system of the Cetacea.* In this figure (fig. 266) the anterior parietes of the abdomen are remo- ved. The two immense lateral de- pressor muscles of the tail are seen at A, A, and B shows their point of convergence to be inserted into the inferior spinous processes, by which the cavity of the abdomen is contracted and defined posteriorly. Just anterior to this commissure is seen the termination of the rec- tum H. C, C, are the two ischia. D, D, the posterior parietes of the chest projecting forwards over the abdomen. On the right side the kidney and the peritoneum are re- moved; on the left side they are seen in situ, and also a part of the left cornu of the uterus G, with the oviduct and ovary K. At p is seen the inferior vena cava cut through, which lies in the interspace of the two great depres- sors of the tail. The trunk of the vena cava seems smaller than it Abdominal venmis plexus and kidney of the Porpesse. * Ueber das Gefass - system des Braunfisrhes, Nova Acta, Phys. Med. Leopold. Carol, torn. xvii. 1835. CETACEA. 579 really is, on account of its deep position and the overlapping of the kidney, E. As it gets beyond this part it is seen to dilate. Two veins, corresponding to the vena iliucaz of Quadrupeds, ( m, rn,J return the blood in part to the tail, and join the vena cava near the kidneys. The vein corresponding to the caudal or sacro-median of Quadrupeds is not a simple vessel, but a plexus, which is surrounded and protected by the inferior spinous processes ; it is seen at,/'. A venous plexus from the intestinal canal (g) terminates in the right iliac vein, which is larger than the left, and thus establishes a com- munication between it and the portal system. h shows a muscular vein, and i the termination of a hypogastric plexus. The more important plexuses which commu- nicate with the iliac veins are, first, the perito- neal plexus (/), which in older individuals, and especially at the season of sexual excitement, is much more considerable than is here repre- sented ; and secondly, the iliac or psoadic plexus (k,k), which forms an immense reser- voir of venous blood. It is situated between the under surface of the depressors of the tail, which represent the psoas muscles, and the peritoneum, reaching from behind the lower extremity of the kidney to the posterior end of the abdomen, and forming a mass of closely interwoven veins, of an inch or more in thick- ness, and serving to bring the subcutaneous veins of the posterior part of the body into communication with the posterior vena cava. This plexus is fed, if we may use the ex- pression, by a, an inferior vein ; b, a lateral ; and c, a superior vein of the tail, which unite to form an ischiadic sub-plexus, d. Laterally the iliac plexus receives from five to seven veins, which return the blood from the dorsal and lateral parietes of the abdomen, and pierce the lateral abdominal muscles to join the plexus at e, e. On its internal or mesial edge the iliac plexus communicates by many and wide aper- tures with the iliac vein. At the anterior part of the abdomen the inferior cava receives the plexus phrenicus, o, o. The condition of the venous system above described, while it is admirably adapted to the mode and sphere of existence of the Cetaceans, presents a beautiful instance of that co-ordinate analogy to the condition of the veins in the embryo of the higher Mammals, which is ex- hibited in the general form of the animals composing this the lowest order of the class.] Organs of Respiration. — The organs and all the essential phenomena of respiration are the same in the Cetaceans as in the other Mammals. They have been made the subject of but few observations. [In the Dugong the lungs are of a very elon- gated and flattened form, resembling those which Daubenton has figured of the Manatee. They are, as Sir Everard Home has observed, one-fourth the length of the animal; those from the animal, eight feet long, which he re- ceived from Sir Stamford Raffles, measuring two feet. They are convex posteriorly or on the dorsal aspect, flattened on the opposite side, and along this surface the principal branches of the bronchi can be seen through the serous covering. The upper end of each lung is obtuse, thick, and narrow ; they gradu- ally become flatter towards the lower extremity, the margin of which is rounded. The whole surface of these lungs presents an appearance somewhat similar to that of the Turtle (Chelonia Mydas), in consequence of the large size of the superficial air-cells, which are a line in diameter (a, a, fig. 268.) The great extent of the lungs down the back, and the high division of the trachea, and consequent length of the bronchi, are further instances of this resemblance. Fig. 267. Cartilages of the bronchus of the Dugong. The cartilages of the bronchial tubes are continued spirally into one another ( fig. 267) : the pulmonary artery lies to the outer side of the bronchus and is deeper seated; the pulmo- nary vein to the inner side, and is superficially situated. The principal branch of the bron- chus (b, fig. 268) runs down near the inner margin of the lung, and continues distinct to within four inches of the end ; it then divides into smaller branches; the larger ramifications are given off from its outer side, c, c. In all the branches the cartilaginous rings continue distinct and strong till their diameter is con- tracted to one or two lines ; the rings passing irregularly into each other as in the main trunks. The lining membrane of the air- tubes is thrown into longitudinal ruga, in- dicating their dilatability. We have before mentioned the large size of the pulmonary artery : in this respect, as well as in the structure of the lung, the Dugong manifests a greater similarity to the reptile than the Porpoise does. In this animal the air-cells in no part of the lung exceed a sixth part of the size of the superficial ones in the Dugong; and 580 CETACEA. Fig. 268. Structure of the lung of the Dugong. the pulmonary artery is proportionally smaller. From the difference that exists in the locomo- tive habits of the two animals arising from the difference in the nature of the food, may be deduced the circumstances which relate to the difference in the respiratory organ. The Por- poise, ever bounding and gambolling on the surface, breathes as it were at will ; whilst the Dugong is compelled to prolonged submersion in order to acquire its food, which from its fixed attachment, and comparatively innutri- tious nature, necessarily demands much time in collecting.] It is said that, in the Dolphins, each lung is surrounded by muscular fibres, which take part also in the acts of inspiration and expi- ration, and that the lobes communicate with each other in such a manner that, air being introduced through one of the bronchi alone, they are all filled with it. Fig. Bui though the diaphragm, the lungs, the bronchi, and the trachea are only found with modifications of a secondary order, the nostrils, which serve intermediately for the passage of the air, between the atmosphere and the respiratory organ, present very im- portant ones. It is especially upon these mo- difications that the exterior distinction between the Herbivorous and the Spouting Whales de- pends, [n the structure of the nostrils, the mechanism by which the phenomenon of the spouting is produced has necessarily caused some changes, which, on the one hand, appear to have necessitated the exclusion of the organ of smell, and, on the other, to have led to the formation of a new organ entirely peculiar to this order of Mammalia. We may be allowed to believe that this organ is essentially the same in the Dolphins, the Cachalots, and the Whales; it has only, 269. Vertical section, shewing the tongue, laryw, and nostrils of the Porpesse. CETACEA. 581 however, been studied with any detail in the Dolphins, and its principal parts consist in the larynx, which ascends as far as the pos- terior nares; in the disposition of the mus- cles of the pharynx, which have the power of binding the anterior part of the respiratory organ ; and in the membranous and fleshy bags placed at the superior part of the nostrils. The orifice of the spouting hole, which is simple in the Dolphins, is situated towards the summit of the head (f, Jig. 269) ; in the Cachalots it is equally simple, and situated at the superior extremity of the snout; and in the Whales it is double, and opens towards the summit of the head, as in the Dolphins, under the form of a crescent, the convexity of which is sometimes forward and sometimes backward . In the Herbivorous Cetaceans, the orifice of the nostrils is found, in the Manatee at the anterior extremity, and in the Dugong at the middle and upper part of the snout. [We here subjoin the detailed description of the spouting apparatus of the Porpesse, from the pen of Baron Cuvier. "If we trace the oesophagus upwards, we find that when it arrives opposite the pharynx ( a, Jig. 269), it appears to divide into two passages, of which one (ft) is continued onwards to the mouth, while the other (c) mounts to the nose: this latter passage is surrounded with mucous glands and fleshy fibres which constitute several muscles. Some of these are longitu- dinal, arising from the circumference of the posterior orifice of the bony nostrils, and de- scending along that canal to the pharynx and its lateral parts; the others are annular and seem to be a continuation of the proper mus- cle of the pharynx ; as the larynx rises into this passage in the form of an obelisk or py- ramid, these annular fibres have the power of grasping it by their contractions. " All this part is provided with mucous fol- licles which pour out their secretion by con- spicuous excretory orifices. The lining mem- brane of the nasal passage having reached the vomer (d), assumes a peculiar texture; it be- comes thin, smooth, and of a black colour, is apparently destitute of vessels and nerves, and is very dry. " The two osseous nasal canals are closed at the superior or external orifice by a fleshy valve in the form of two semicircles, attached to the anterior margin of that orifice, which it closes by means of a very strong muscle lodged above the intermaxillary bones. In order to open it, some foreign body must press against it from below. When this valve is closed, it cuts off all communication between the nasal pas- sages and the cavities above them. These ca- vities are two large membranous pouches (e, e), formed by a dark-coloured mucous skin, much wrinkled when they are empty ; but assuming, when distended, an oval figure, which, in the Porpesse, equals the capacity of a wine-glass. These two pouches are lodged beneath the integument, in front of the nostrils ; they communicate with an intermediate space im- mediately above the nostrils, which open ex- ternally by a transverse semilunar slit. Very strong fleshy fibres form an expansion, which covers all the upper surface of this apparatus ; these fibres radiate from the entire circum- ference of the cranium to unite above the two pouches, and are adapted to compress them forcibly. Let us suppose the Cetacean has taken into its mouth some water which it wishes to eject : it moves its tongue and jaws as if it were about to swallow it ; but, closing its pharynx, it forces the water to mount into the nasal passages, where its progress is accelerated by annular fibres, until it raises the valve and distends the membranous pouches above. Once in the pouches, the water can be re- tained there until the animal wishes to spout. For that purpose, it closes the valve to prevent the descent of the water into the nasal passages, and it forcibly compresses the pouches by means of the muscular expansions which cover them : compelled then to escape by the nar- row crescentic aperture, it is projected to a height corresponding to the force of the pres- sure." Urinary organs. — The Phytophagous Ceta- ceans are not distinguished by a form and structure of the kidney different from that in the Zoophagous tribes ; for, although in the Dugong the kidney has an uniform unbroken external surface, yet in the genus lii/tina, according to Steller, that organ is subdivided into a great number of lobules, as in the Seal and Sea-Otter, and consequently resembles in this respect the typical or true Cetacea. Hun- ter makes the same statement with respect to the Manatee.* In the Dugong the tubuli uriniferi terminate by two lateral series of eleven mammillae in a single elongated pelvis, from which the ureter is continued. In the Porpesse and Whale there is no common pelvis, but the ureter com- mences by more than two hundred branches from as many distinct lobes or renules, of the aggregate of which the entire kidney is formed ( EKfig. 266). Each renule is of a conical figure, having its base towards the circumference, and its apex towards the centre of the kidney ; it is composed of a cortical and medullary substance, the latter terminating in a single mammilla at the apex, where it is surrounded by a long infundibulum, wide at its com- mencement, where it embraces the base of the mammilla, and thence becoming smaller, and uniting with others to form the common ex- cretory .duct. Miiller found that each of the lobules of the kidney in the foetus of the Dolphin con- sisted principally of the convoluted uriniferous ducts extending from the apex to the periphery of the lobule, the intertwinings of the tubuli being greatest in the cortical part (Jig. 270). It is a curious fact that the supra-renal gland in the Porpesse presents a certain resemblance to the kidney in its lobulated exterior ; but the analogy extends no farther, for on making a section of this part, it is seen to be composed of the usual continuous compact substance.] * In the paper on Whales, p. 412. 582 CETACEA. Fig. 270. 4 section of one of the lobes or venules of the kidney of a Dolphin. The Nervous System. — The nervous system, like the greater part of the other organic sys- tems, has in many species of the Cetacea been the subject only of superficial observations. Formed on the plan of that of Mammalia in general, it has followed in its deve- lopment that of the other organs, in all cases in which it was naturally de- pendent on such modifications. Thus the lumbar and sacral nerves do not give origin to those of abdominal members, whilst, on the other hand, the coccygeal nerves are found nume- rous and powerful. The olfactory nerves do not exist, unless, as some authors say, it is in the form of almost imperceptible threads . What appears certain is, that in the common Dol- phin, and in the common Porpesse there are no traces of ethmoidal openings; and if there are holes in the ethmoid of the Whale, they are in very small number, and nothing proves that they give passage to nerves.* In the common Dolphin and Porpesse, the brain is found as richly developed as in any Mammi- ferous quadruped whatever. To judge from the capaciousness of the skull, the other species of this family of Cetacea have not been less liberally gifted than the common Dolphin. The brain of the Cachalots and the Whales has not been made a subject of study, or has been so only in a very super- ficial way. To judge of it by the cranial cavity, one may conclude that in them this organ is reduced to very small dimensions. [The illustrations of the brain of the Cetacea (Jig. 271, 272, 273) are taken from the ex- cellent figures of the brain of the Dolphin ( Delphinus Delphi* ), published by Tiedemann in the second volume of his Zeitschrift fur Physiologie, (pi. xii. p. 251.) The following description embodies the observations of the same author on the brain of the Dolphin, and of Hunter on that of the Balanoptera (Piked Whale). In a young specimen of the Balana rustrata, which measured seventeen feet, Hunter Fig. 272. Fig. 271. Brain of tlie Dolphin, Delphinus Delphis * M. F. Cuvier seems here to have overlooked the fact that Hunter had established the existence of an organ of smell in the Balaenida:. , He observes, Base of the brain of a Dolphin, Delphinus Delphis. found that the brain weighed four pounds eight ounces. In a young Bulana mysticetus nineteen feet long, Scoresby found the weight of the brain to be three pounds twelve ounces. From analogy we may suppose that the brain had here acquired nearly its full development, which gives us, taking the weight of the full grown whale at 11,200 pounds, the ratio of the weight of the brain to that of the body as 53*55 . In the smaller Cetacea, however, the brain is not dimi- nished to a proportionate size, but exhibits a development which may be said to be extraordinary, even in the Dolphin of six feet in length. In tracing the brain according to Tiedemann's method from below upwards, we first observe the " In many of this (the Whale) tribe, there is no organ of smell at all ; and in those which have such an organ, it is not that of a Fish, therefore CETACEA. 583 spinal chord (a, Jig. 272) gently expanding into the medulla oblongata, on the anterior surface of which the corpora pyramidalia (b, Jig. 272) are seen well defined and prominent. At the point where they begin to rise above the surface of the medulla, there is a manifest decussation of their internal fibres ; they pro- ceed through the pons Varoli (c), and are continued into the crura cerebri. The corpora olivaria are situated near the pyramidalia; they do not, however, project from the surface as in the human brain, but are distinguishable by the internal grey sub- stance ( corpus dentatum oliva ). Their medul- lary fibres proceed through the pons and enter the bigeminal bodies, in which they converge and decussate each other. The transverse medullary fibres, which are seen in most Mammalia extending across the under surface of the medulla oblongata imme- diately behind the pons, and which Treviranus has called the trapezium, are wanting in the brain of the Dolphin, as in that of the Orang Utan and the Human subject The two posterior columns of the spinal chord are continued (according to Tiedemann) as the corpora restiformia to the cerebellum. Between these is situated the fourth ventricle, from the floor of which the acoustic nerves take their origin. The very large size of the cerebellum in proportion to the spinal chord and cerebrum, which Hunter noticed in the Piked Whale, is equally remarkable in the Dolphin. The cere- bellum is deeply divided into lobes, of which six may be distinguished on the upper surface of each hemisphere. Of these, two small lobes correspond to the posterior superior lobes of the human cerebellum. On the under surface we remark the posterior inferior lobes (e), the anterior inferior lobes (fj, one lobe corresponding to the amygdaloid lobe of Reil (g), and the Jioccus (A). Each lobe is subdivided by deep fissures into smaller lobes, and these again by shallow anfractu- osities into lamellae. The middle or vermiform portion of the cere- bellum (a, Jig. 273) is not sym- metrical, but inclined, like the cra- nium itself, to the right side. The internal medullary substance of the cerebellum resulting from the di- vergent fibres of the crus, corpus restiforme, and processus ad testes, and the superadded commissural fibres, has a well-marked internal grey substance or corpus Jimbri- probably not calculated to smell water. It becomes difficult therefore to account for the manner in which such animals smell the water ; and why the others should not have had such an organ, which seems to be peculiar to the large and small Whale- bone Whales ( Balcena mysticetus and Balcenoptera rostrata); the organ, in those which have it, is ex- tremely small, when compared with that of other animals, as well as the nerve, which is to receive the impression."— Phil. Trans, pp. 428, 430. atum, and is covered by the usual external layer of similar material. Between the columns which extend from the cerebellum to the bige- minal bodies, the medullary lamella called valvula Vieussenii is situated. The pons or commissure of the cerebellum (c, -fig. 272) is of large size, corresponding to the hemispheres of the part which it seems to associate in action. The cerebrum is extended backwards over the cerebellum, but the posterior parts of the hemispheres diverge from one another so as to expose a part of the cerebellum. The most striking feature of the cerebrum is its great breadth, which exceeds its length, a disposition of this organ peculiar among Mammalia to the Cetaceous order. Each hemisphere is seen at its inferior surface to be divided by the Jissura magna (k, Jig. 272) into an anterior (I) and middle lobe (pi), which latter is con- tinued above the cerebellum into the posterior lobe. The whole external surface of the he- mispheres is divided by deep anfractuosities into convolutions, which are proportionally more numerous and narrower even than in the human brain. This structure seems common to all the Cetacea ; besides the observations of Tiedemann and Cuvier in the common Dol- phin, the numerous convolutions have been remarked by Tyson in the brain of the Por- pesse, and by Scoresby in that of the Mysticete Whale. The crura cerebri (i,Jig. 272) are of large size; the eminentiae mammillares (p) are as usual situated between them, and anterior to these are the infundibulum and pituitary gland (o). The two hemispheres in the Dolphin's brain described by Tiedemann, measured each two inches and eleven and a half lines in length, and were united by a corpus callosum (b,Jig. 273,) of one inch and three lines in length. The chief peculiarity of this part is its position, which is not horizontal, but inclined down- wards and forwards. The bigeminal bodies are of considerable size ; the anterior ones are rounded and lie closer together than the pos- terior. These have an oval form, and are separated by a depression which receives the 584 CETACEA. anterior part of the vermiform process of the cerebellum. The pineal gland is a small flattened body about two lines in length, connected as usual to the thalami optici. These appear in each ventricle in the form of an oval flattened body (i, fig. 273). They are joined together posteriorly by the medullary commissure. Tiedemann did not observe any soft commis- sure. The third ventricle is continued anteriorly into the infundibulum. The corpora striata (rf) are proportionally of small size, as Hunter observed in the brain of the Whale. They are united anteriorly by the anterior commissure. The fornix is also of inconsiderable size. The slender anterior pillars of the fornix proceed to the mammillary bodies, and send forwards two small triangular medullary lamella? to the under surface of the anterior part of the corpus striatum, from which the septum lucidum is continued. The fornix then bends backwards along the under surface of the corpus callosum and above the thalami, and its hinder crura sink down, diverging from each other to form the cornua ammonis (g). These bodies are small, thin, but broad, and exhibited no den- ticulated folds. The taenia fimbriata (h) are attached as usual to the external border of the cornua. The lateral ventricles are capacious though short; they extend, as in the human brain, into an anterior, a middle, and a posterior horn ; the latter, however, is very small. In each ventricle there is a large plexus choroides, which is remarkable for the transverse parallel folds of membrane which support the divisions of the artery. With respect to the cerebral nerves, Tiede- mann states that, although in the Dolphin the brain was removed with every precaution from the skull, yet he could not perceive the slightest trace of the olfactory pair. Hunter and Tyson equally failed to detect them in the Porpesse. Treviranus, however, believed that with the aid of a magnifying glass he had detected very delicate filaments in the situation of the olfac- tory nerves in the Porpesse. But supposing that there was no illusion here, which could hardly have happened to so accurate and close an observer, these fibres represent only a very rudimental condition of the olfactory nerves; and we may observe that the shortness of the anterior lobes of the brain, and the smallness of the striated bodies are closely related to the absence or imperfect development of the first pair of nerves. With respect to the other cerebral nerves, they are relatively larger in proportion to the brain than in man. The optic nerves (2, fig. 272) rise partly from the thalami, partly from the anterior bigeminal bodies and the corpora geniculata; they curve round the crura cerebri, and unite as usual before the pituitary gland. The angle at which the nerves diverge from each other after the decussation is more open than in other Mammalia. The accessory nerves of the eye are of large size, as the third (3), the fourth (4), and the sixth (6) pair. The fifth pair (5), which emerge from the sides of the pons, but arise from the medulla oblongata between the corpora restiformia and olivaria, have a smaller proportional size than in man. The nerves concerned in the actions of respiration, as the facial (7), the pneumogastric (10), and the recurrent (11), are well deve- loped, in relation to the large size of the muscles which effect the respiratory movements in the dense medium of water. The glosso-pharyngeal nerve (9) and the lingual (12) are also very large, corresponding to the vigorous associated actions of the tongue and pharynx, which must take place during deglutition in the Cetacea. But perhaps the most remarkable nerve for its great relative size is the acoustic (8), which certainly testifies to the delicate sense of hear- ing in the Dolphins.] The organs of the senses, with the exception of that of smell, are composed, in all the Cetaceans, of the parts which essentially con- stitute them in terrestrial Mammalia, and are only modified with reference to the habitually aquatic life of the animals of this order. But little inquiry has been made as to their utility in these animals, the length of time they con- tinue serviceable, and the characteristic diffe- rences which might be drawn from them for the distinction of the species. Eye. — The eye of the Herbivorous Cetaceans alone is provided with a lateral lid or membrana nictitans; that of the Spouting Whales is de- void of lachrymal glands ; but its lids are fur- nished below with little glands which secrete a mucous matter, adapted like the tears for lubricating the sclerotica. [Hunter observes that " the eye in this tribe of animals is constructed upon nearly the same principle as that of quadrupeds, dif- fering, however, in some circumstances ; by which it is probably better adapted to see in the medium through which the light is to pass. It is upon the whole small for the size of the animal, which would lead to the supposition that their locomotion is not great; for, I believe, animals that swim are in this respect similar to those that fly ; and as this tribe come to the surface of the medium in which they live, they may be considered in the same view with birds which soar ; and we find, birds that fly to great heights, and move through a considerable space, in search of food, have their eyes larger in proportion to their size. " The eyelids have but little motion, and do not consist of loose cellular membrane, as in quadrupeds, but rather of the common adipose membrane of the body ; the connexion, however, of their circumference with the com- mon integuments is loose, the cellular mem- brane being less loaded with oil, which allows of a slight fold being made upon the sur- rounding parts in opening the eyelids. This is not to an equal degree in them all, being less so in the Porpoise than in the Piked Whale. CETACEA. 585 Fig. 274. Section of the eye of a Whale. " The tunica conjunctiva ( g, g, fig. 274), where it is reflected from the eyelid to the eye- ball, is perforated all round by small orifices of the ducts of a circle of glandular bodies lying behind it. " The lachrymal gland* is small, its use being supplied by those above-mentioned ; and the secretion from them all, I believe to be a mucus similar to what is found in the Turtle and Crocodile. There are neither puncta nor lachrymal duct ( ductus ad nasum ), so that the secretion, whatever it be, is washed off into the water. " The muscles which open the eyelids are very strong ; they take their origin from the head, round the optic nerve, which in some requires their being very long, and are so broad as almost to make one circular muscle round the whole of the interior straight mus- cles of the eye itself. They may be divided into four ; a superior, an inferior, and one at each angle ; as they pass outwards to the eye- lids, they diverge and become broader, and are inserted into the inside of the eyelids almost equally all round. They may be termed the dilatores of the eyelids ; and, before they reach their inseition, give off the external straight muscles, which are small, and inserted into the sclerotic coat before the transverse axis of the eye ; these may be named the elevator, depressor, adductor, and abductor, and may be dissected away from the others as distinct muscles. Besides these four going from the muscles of the eyelid to the eye itself, there are two which are larger, and enclose the optic nerve with the plexus. As these pass outwards they become broad, may in some be divided into four, and are inserted into the sclerotic coat, almost all round the eye, rather behind its transverse axis. " The two oblique muscles are very long ; they pass through the muscles of the eyelids, are continued on to the globe of the eye, between the two sets of straight muscles, and at their insertions are very broad : a circum- * This is analogous rather to the Harderian gland, being situated at the inner or nasal side of the eyeball. VOL. I. stance which gives great variation to the motion of the eye. " The sclerotic coat (a, a, Jig. 274) gives shape to the eye, both externally and internally, as in other animals ; but the external shape and that of the internal cavity are very dissimilar, arising from the great difference in the thick- ness of this coat in different parts. The external figure is round, except that it is a little flat- tened forwards ; but that of the cavity is far otherwise, being made up of sections of various circles, being a little lengthened from the inner side to the outer, a transverse section making a short ellipsis. " In the Piked Whale ( Bulanoptera ros- trata) the long axis is two inches and three quarters, the short axis two inches and one- eighth. " The posterior part of the cavity is a tolerably regular curve, answering to the dif- ference in the two axises ; but forwards, near the cornea, the sclerotic coat turns quickly in, to meet the cornea, which makes this part of the cavity extremely flat, and renders the distance between the anterior part of the scle- rotic coat and the bottom of the eye not above an inch and a quarter. " In the Piked Whale the sclerotic coat, at its posterior part, is very thick : near the ex- treme of the short axis it was half an inch, and at the long axis one-eight of an inch thick. In the Bottle-nose Whale ( Hyperoodon ), the extreme of the short axis was half an inch thick, and the extremes of the long axis about a quarter of an inch, or half the other. " The sclerotic coat becomes thinner as it approaches to its union with the cornea, where it is thin and soft. It is extremely firm in its texture where thick, and from a transverse sec- tion would seem to be composed of tendinous fibres, intermixed with something like carti- lage ; in this section four passages for vessels remain open. This firmness of texture pre- cludes all effect of the straight muscles on the globe of the eye by altering its shape, and adapting its focus to different distances of objects, as has been supposed to be the case in the human eye. " The cornea (b, fig. 274) makes 'rather a longer ellipsis than the ball of the eye ; the side of which are not equally curved, the pp being most considerably so. It is a segmen. of a circle somewhat smaller than that of the eyeball, is soft and very flaccid.* " The tunica choroides resembles that of the quadruped ; and its inner surface is of a silver hue, without any nigrum pigmentum. The pigmentum nigrum only covers the ciliary processes (c, c), and lines the inside of the iris. The retina (e) appears to be nearly similar to that of the quadruped. " The arteries going to the coats of the eye form a plexus passing round the optic nerve, resembling in its appearance that of the sper- matic artery in the Bull and some other ani- mals. * Its laminated texture is well displayed in the Whale ; I/eeuwenhoek counted twenty-two layers. 2 Q 586 CETACEA. " The crystalline humour (d) resembles that of the quadruped ; but whether it is very convex or flattened, I cannot determine ; those I have examined having been kept too long to pre- serve their exact shape and size. The vitreous humour adheres to the retina at the entrance of the optic nerve. The optic nerve (J') is very long in some species, owing to the vast width of the head."* The crystalline lens is of a spherical form, but slightly flattened anteriorly : it is inclosed in a strong and dense capsule, and is placed at a very small distance from the cornea, so that it diminishes the space for the aqueous humour, while it increases that for the vitreous; this exists in a greater degree than is shown in the subjoined figure, as Soemmering, from whose work ' De oculorum sectione horizon- tali' the figure is taken, himself allows. From the peculiar colour and eccentric position of the nucleus of the lens in the Whale's eye, in which it is of a dark colour, and placed in the posterior half of the lens, we are led to suspect that the section of the lens in Soemmering's plate is imaginary.] Ear. — The ear is without any external con- cha ; no doubt a sphincter has the office of closing the entrance of the auditory canal, to preserve the tympanum, which some call fi- brous, and others cartilaginous, from the contact of the water. The Eustachian tube exists according to some anatomists, others deny it. The senses of sight and hearing, not- withstanding their apparent imperfection, appear to be endued with great delicacy. Whale- catchers assert that Whales, Cachalots, &c. see and hear at a great distance, and that, in order to approach them, many precautions are neces- sary ; otherwise these animals would avoid them by a sudden retreat, and it would become necessary to recommence the long and labo- rious chase. We ought, nevertheless, to add that Scoresby, who speaks of the delicacy of hearing of the Whales, states that they remain insensible to the noise of the report of a cannon. [For the most accurate and philosophical description of the Organ of Hearing in the present tribe we again recur to Hunter's ad- mirable paper on the organization of the Cetacea. He observes, that " the ear is con- structed much upon the same principle as in the quadruped ; but as it differs in several respects, which it is necessary to particularize, to convey a perfect idea of it the whole should be described. As this would exceed the limits of this paper, I shall content myself with a general description, taking notice of those ma- terial points in which it differs from that of the quadruped. " This organ consists of the same parts as in the quadruped ; an external opening, with a membrana tympani, and Eustachian tube, a tympanum with its processes, and the small bones. " There is no external projection forming a funnel, but merely an external opening. We * Philos. Trans. 1787, p. 440. can easily assign a reason why there should be no projecting ear, as it would interfere with progressive motion ; but the reason why it is not formed as in birds, is not so evident ; whe- ther the percussions of water could be collected into one point as air, I cannot say. The tym- panum is constructed with irregularities, so much like those of an external ear, that I could suppose it to have a similar effect. " The external opening begins byasmall hole, (a, Jig. 275), scarcely perceptible, situated on Fig. 275. Organ of Hearing, Porpesse. the side of the head a little behind the eye. It is much longer than in other animals, in con- sequence of the size of the head being so much increased beyond the cavity that contains the brain. It passes in a serpentine course (b), at firsthorizontally,thendownwards,and afterwards horizontally again, to the membrana tympani, where it terminates. In its whole length it is composed of different cartilages, which are irre- gular and united together by cellular mem- brane, so as to admit of motion, and probably of lengthening or shortening, as the animal is more or less fat. " The bony part of the organ (r, c) is not so much inclosed in the bones of the skull as in the quadruped, consisting commonly of a distinct bone or bones, closely attached to the skull, but in general readily to be separated from it ; yet in some it sends off, from the posterior part, processes which unite with the skull. It varies in its shape, and is composed of the im- CETACEA. 587 mediate organ (or labyrinth) and the tym- panum. " The immediate organ is, in point of situa- tion to that of the tympanum, superior and in- ternal, as in the quadruped. The tympanum is open at the anterior end, where the Eusta- chian tube begins. " The Eustachian tube opens on the outside of the upper part of the fauces : in some higher in the nose than others ; highest, I believe, in the Porpoise. From the cavity of the tym- panum, where it is rather largest, it passes forwards and inwards, and near its termination appears very much fasciculated, as if glan- dular. (A probe passes through the Eusta- chian tube in the figure, showing its nasal ter- mination at d.) " The Eustachian tube and tympanum com- municate with several sinuses, which passing in various directions surround the bone of the ear. Some of these are cellular, similar to the cells of the mastoid process in the human sub- ject, although not bony. There is a portion of this cellular structure of a particular kind, being white, ligamentous, and each part rather round- ed thau having flat sides.* " One of the sinuses passing out of the tympa- num close to the membrana tympani, goes a little way in the same direction, and commu- nicates with a number of cells. " The whole function of the Eustachian tube is perhaps not known ; but it is evidently a duct from the cavity of the ear, or a passage for the mucus of these parts ; the external opening having a particular form would incline us to believe, that something was conveyed to the tympanum. " The bony part of the organ is very hard and brittle, rendering it even difficult to be cut with a saw, without its chipping into pieces. That part which contains the immediate organ is by much the hardest, and has a very small portion of animal substance in it ; for when steeped in an acid, what remains is very soft, almost like a jelly, and laminated. The bone is not only harder in its substance, but there is on the whole more solid bone than in the cor- responding parts of quadrupeds, it being thick and massy. " The part containing the tympanum is a thin bone, coiled upon itself, attached by one end to the portion which contains the organ ; and this attachment in some is by close contact only, as in the Narwhale ; in others, the bones run into one another, as in the Bottle-nose and Piked Whales ( Hyperoodun and Balanop- tera ). " The concave side of the tympanum is turned towards the organ, its two edges being close to it ; the outer is irregular, and in many only in contact, as in the Porpoise : while in others the union is by bony continuity, as in the Bottle-nose Whale ( Hyper oodon), leaving a passage on which the membrana tympani is * " These communications with the Eustachian tube may he compared to a large bag on the bases of the skull of the Horse and Ass, which is a lateral swell of the membranous part of the tube, and when distended will contain nearly a quart." stretched, and another opening, which is the communication with the sinuses. " The surface of the bone containing the im- mediate organ (the petrous bone, p, fig. 269) opposite to the mouth of the tympanum is very irregular, having a number of eminences and cavities." According to the Baron Cuvier* the petrous bone in the Ddphinidm is permanently lodged between the temporal and contiguous parts of the occipital bone ; it forms the upper and inner part ; the tympanum the lower and outer. The petrous bone is brittle and very thick. It has a larger portion, an irregular ellipsoid, which gives attachment to the tympanum by its outer surface, and which contains the three semicircular canals ; and another smaller por- tion in the form of a quarter of a sphere, which is separated from the first by a pretty deep de- pression, and is occupied internally by the cochlea. The acoustic nerves enter by fora- mina at the bottom of the depression. The tympanum is formed by a thick bony plate folded longitudinally, so as to form a canal, open anteriorly, whence is continued the Eustachian tube. It is closed behind, where it assumes a bilobate figure, and adheres above this part to the outer and posterior part of the petrous bone by a rough process, which is firmly wedged in, but does notanchylose soon. It adheres to it also by a part of the external margin, and it is between these two points of adhesion that we find the very irregular opening of the tympanum. The internal margin leaves a long interval between it and the petrous bone. Beneath the bilobate portion of the tympanum the styloid process passes, which is attached immediately behind it by ligaments to the de- scending plate, which represents the mastoid process. The bone of the ear of the Cachalot displays great relations with that of the Dolphins, only the tympanum is shorter and less lobated behind. The bone of the ear in the Bulanidie differs from that of the Ddphinidce by the enormous thickness of the tympanum (a,fig.276), espe- cially at the inner side. This tympanum is a little more closed anteriorly, but leaves between it and the os petrosum (b) on the inner side a proportionally shorter and wider interspace. It is not bilobed posteriorly. The petrous bone is of a very irregular shape and knotty surface ; it gives off two large rough processes, of which one is situated behind and a little above, and articulates with a corre- sponding process of the tympanum, is wedged between the temporal and lateral occipital bones; and the other, situated anteriorly and below, is articulated by a squamous suture with the part of the temporal which descends to furnish the articulation of the lower jaw. This second process, which in the Balance, is as large as the other, is very small in the Bulte- noptcra ; nevertheless the ear-bone of the Ba- la;na; is fixed more solidly to the cranium than that of the Delphini. * Oss. Foss. vol. v. pt. i. p. 300. 2 q 2 588 CETACEA. A comparison of the ear-bone of Balama Australis with that of Balana Mystketus cor- roborates by differences, slight indeed, the dis- tinction of species between them. " The cavity of the tympanum ( a, a, Jig. 276) is lined with a membrane, which also covers the small bones with their muscles, and appears to have a thin cuticle. This membrane renders the bones, muscles, tendons, &c. very obscure, which are seen distinctly when that is removed. It appears to be a continuation of the periosteum, and the only uniting substance between the small bones. Besides the general lining, there is a plexus of vessels, which is thin and rather broad, and attached by one edge, the rest being loose in the cavity of the tympanum, somewhat like the plexus choroides in the ventricles of the brain. The cavity, we may suppose, intended to increase sound, pro- bably by the vibration of the bone ; and from its particular formation we can easily conceive that the vibrations are conducted, or reflected, towards the immediate organ, it being in some degree a substitute for the external ear. " The external opening being smaller than in any animals of the same size, the membrana tympani is nearly in the same proportion. In the Bottle-nose Whale, the Grampus, and Por- poise, it is smooth and concave externally; but of a particular construction on the inner sur- face ; for a tendinous process passes from it to- wards the malleus, converging as it proceeds from the membrane, and becoming thinner till its insertion into that bone. I could not dis- cover whether it had any muscular fibres which could affect the action of the malleus. In the Piked Whale, the termination of the external opening, instead of being smooth and concave, is projecting, and returns back into the meatus for above an inch in length, is firm in texture, with thick coats, is hollow on its inside, and its mouth communicating with the tympanum ; one side being fixed to the malleus, by a part similar to the tendinous process which goes from the inside of the membrana tympani in the others.''* In the figure fjig.276), which represents the internal ear in the Balaena Mysticetus, the let- ters c, d, e indicate the extent of the membrana tympani, the letter e being placed on the part which forms a convex projection into the tym- panic passage : /'shows the triangular ligamen- tous process which attaches the handle of the malleus (g) to the membrana tympani. This connection between the membrane and the ossicles of the tympanum is denied by Sir Everard Home, who wrote a paper and pub- lished two plates in support of his opinion.f After quoting Mr. Hunter's description of the attachments of the membrana tympani in the Piked Whale, Sir Everard observes, " the fact is, that there is no connexion whatever between the membrana tympani and the malleus, as will be explained ; but as that circumstance forms the great peculiarity in the organ of this species of Whale (Bulana mysticetus, L.) * Hunter in Philos. Trans. 1787, p. 432. f Philos. Trans. 1812, p. 88, pis. I. and II. Fig. 276. Internal car of the Mysticete Whale. I thought it right to quote what he had stated on this subject." So remarkable an anomaly as an absence of any communication between the membrana tympani and the ossicula audi- tus, would of itself, independently of our inte- rest for the character of Hunter as an accurate observer, have induced us to spare no pains to test the conflicting statements with the facts themselves; fortunately in this instance the preparations figured by Sir Everard are pre- served ; we have carefully examined them, and find the following to be the true structure of the parts in question. The membrane marked c in Sir Everard Home's second figure is con- tinuous at d, with e the convex projection of the membrana tympani ; whereas the edge of the shadow is so strong in the figure as to make it appear as if c and e were separate membranes, as indeed Sir Everard de- scribes them to be : they are, on the contrary, parts of the same membrana tympani, the at- tachment of which is extended inwards beyond the circumference of the termination of the bony meatus auditorius. The triangular liga- ment /j which is common to all the Cetacea, is attached not only to the plane portion of the ear-drum, but to the whole of one side of the convex portion which projects into the meatus, and is affected by every motion of that part. It is a thick opaque aponeurosis, and not, as it is represented in the plate, a semitransparent membrane passing clear over the convex part of the drum. " A little way within the membrana tym- pani, are placed the small bones, which are three in number, as in the quadruped, mal- leus (g), incus (h), and stapes (i J; but in the Bottle-nose Whale (Hyperoodon) there is a fourth, placed on the tendon of the stapedius muscle. These bones are as it were suspended between the bone of the tympanum, and that of the immediate organ. " The malleus has two attachments, besides that with the incus ; one close to the bone of CETACEA. 589 the tympanum, which, in the Porpoise, is only by contact, but in others by a bony union ; the other attachment is formed by the tendon, above described, being united to the inner surface of the membrana tympani. Its base articulates with the incus. " The incus is attached by a small process to the tympanum, and is suspended between the malleus and stapes. The process by which it articulates with the stapes is bent towards that bone. " The stapes stands on the vestibulum, by a broad oval base. In many of this tribe, the opening from side to side of the stapes is so small as hardly to give the idea of a stirrup. " The muscles which move these bones are two in number, and tolerably strong. One arises from that projecting part of the tym- panum which goes to form the Eustachian tube, and running backwards is inserted into a small depression on the anterior part of the malleus. The use of this muscle seems to be to tighten the membrana tympani ; but in those which have the malleus anchylosed with the tympanum, we can hardly conjecture its use. The other (o) has its origin from the inner surface of the tympanum, and passing backwards is inserted into the stapes by a tendon, in which I found a bone in the large Bottle-nose. This muscle gives the stapes a lateral motion. What particular use in hearing may be produced by the action of these muscles I will not pretend to say; but we must suppose whatever motion is given to the bones must terminate in the movement of the stapes. " The immediate organ of hearing is contained in a round bony process, and consists of the cochlea and semicircular canals, which some- what resemble the quadruped ; but besides the two spiral turns of the cochlea, there is a third, which makes a ridge within that continued from the foramen rotundum and follows the turns of the canal. " The cochlea (k, jig. 276) is much larger when compared with the semicircular canals, than in the human species and quadruped." Besides its greater relative size, the coch- lea of the Delphinida differs from that of the human subject in the greater pro- portional extent, and especially the form and disposition of the scala vestibuli, which, in- stead of being one compartment of a single tube divided in the direction of its axis, is a complete conical tube. It also forms an oblique sigmoid curve before commencing its spiral turns, which are two and a half in number. The semicircular canals have the same dis- position as in Mammalia, but are relatively smaller. Cuvier, in correcting the error into which Camper had fallen when he denied the existence of the semicircular canals in the Whale, appears to have overlooked the fact that they had previously been discovered in the Cetacea by Hunter. And it is simply be- cause they do not possess any difference of note as compared with other Mammalia, (ex- cept in their relative volume to other parts of the labyrinth which Hunter is careful to point out,) that they are not described by him with the same minuteness and detail as the cochlea and other parts of the organ. It may also be observed that the more extensive researches of Hunter preserved him from the error into which Cuvier has fallen of ascribing to the Cetacea a structure of the cochlea which is peculiar to a small part only of the order. The depression of the gyrations of the cochlea to nearly the same plane, and their limitation to one and a half in number, is certainly not applicable to the Delphinida, and it may be doubted how far it can be with accuracy asserted of the Baltfrns.* The canals which establish a communication between the labyrinth and the interior of the cranium, viz. the aqueductus vestibuli and aqueductus cochlea;, are very large in the Del- phinidtB, especially the latter.] Taste. — This sense probably exists in the Herbivorous Cetaceans, whose tongue, although but slightly moveable, has notwithstanding a complicated and delicate structure. But has this sense a special organ in the Spouting Ce- taceans ? Some doubts may be allowed to exist on this subject. The tongue of the Dol- phin and that of the Porpoise have neither fossulate papillae nor conical papillse ; they only present on their surface slight elevations, of which the middle appears to be perforated, and their edges are fringed, as if for multiplying the sensations of touch. Touch. — The general organ of touch, the skin, has formed, in the Spouting Cetaceans, the subject of important researches, which have given a more extended knowledge of this organ in general than was before possessed. According to the observations of MM. Breschet and Roussel de Vauzeme, there may be distinguished in the skin of the Cetaceans, as in that of other Mammals, six principal constituents which either penetrate or are superimposed on one another, but which are severally destined to fulfil a special function. 1 . The derm or corium ( le derme ), a dense fibrous cellular texture, which contains and protects all the other parts of the skin. In the Whale it is constantly white and opake, and its peripheral surface presents a series of papilla, the intervals of which are occupied by the epidermis, which forms for each a sheath. 2. The papillary bodies (les corps papil- laires ) consist of papillae covered by the derm. They have a nacrous lustre, and are several lines in length in the Whale, but are much shorter in the common Dolphin and Porpesse. These papilla; are composed of fibres pene- trated by vessels ; they originate from the sub- cutaneous nervous plexus and return back again to the same ; the derm serves merely as a sheath to the papillre, the extremities of which exercise the sense of touch. 3. The sudorific apparatus (Vappareil sudo- rifique ) consists of soft, elastic, spiral canals, which extend through the entire thickness of * See Ossem. Foss. vol. v. pt. i. p. 300, and Lc?ons d'Anat. Comparee, vol. ii. p. 467. 590 CETACEA. the derm, and open in the intervals of the papilliE by an orifice generally closed by a small epidermic valve. 4. The inhalent apparatus (I'appareil d'in- halution ) is formed by extremely delicate canals, which are smooth, straight, silvery, branched, and very easily ruptured : they originate in a plexus extended in the dermis beneath the sudorific canals, anastomose to- gether, and are provided with partitions. The lymphatic vessels have no connection with these canals, which communicate directly with the arteries and veins. They are absorbing canals. 5. The mucous apparatus (I'appareil blen~ nogene ). This is composed of secerning glands and excretory ducts, which open be- tween the papillae like the orifices of the pre- ceding canals. It is wholly contained in the derm, and produces a mucous material, which by desiccation (en se dessechant ) becomes the cuticle. In the Whales this cuticle acquires an extreme thickness: it is much thinner in the Dolphins. 6. The colorific apparatus (Vappareil chro- matoghie) is likewise composed of secerning glands and excretory ducts ; it is situated in the first superior (peripheral) layers of the corium on the right and left sides of the outlet of the excretory ducts of the preceding appa- ratus, and it pours out the coloured product at the same point where the mucous matter is excreted, where it stains it. [It may be questioned how far this expla- nation satisfactorily accounts for the formation of cuticle in animals living habitually under water. The whole account is to be received with reserve, and requires to be confirmed by further ob- servations, especially as regards the reflexion of the nervous fibrils and the sudorific and inhalent apparatuses.] We do not stop to examine how far this analysis serves to explain the different phe- nomena which the external teguments of the Mammalia present. But admitting it as it is presented to us, it results that the sensations of touch must be lively and delicate in the Cetacea : the great development of their pa- pillary apparatus leads to this conclusion. Nevertheless, the most generally received opi- nion is that the common Dolphin, notwith- standing the delicacy of its epidermis, has but little tactile sensibility. But is this opinion devoid of foundation ? or is it explicable on the ground of the deposition of fat, which penetrates every part of the skin, and is accu- mulated in a dense layer beneath it, so as to enfeeble the sensibility of the surface, accord- ing to the common belief. This is the opinion to which we have arrived. With respect to the Balaenidse no difficulty exists on account of the thickness and horny texture of the epi- dermis. [According to Hunter's views the reticular network containing the blubber, which he de- scribes as fine in the Porpoise, Spermaceti, and large Whale-bone Whale ( Balcena ), and coarse in the Grampus and small Whale-bone Whale ( Balanoptera ), forms part of the skin ; for he observes that " the cutis seems to be the termination of the cellular membrane of the body more closely united, having smaller interstices and becoming more compact," and that the distinction between the skin and cel- lular membrane is much less obvious in fat than in lean animals; " for the cells of both membrane and skin being loaded with fat, the whole has more the appearance of one uniform substance. This uniformity of the adipose membrane and skin is most observable in the Whale, Seal, Hog, and the Human Species."*] In the Balanoptera the integument covering the ventral surface of the neck, thorax, and anterior part of the abdomen, is disposed in longitudinal folds, about five-eighths of an inch in breadth in the contracted state. The skin is very soft in the insterstices of the folds, and covered there with a thinner cuticle : it possesses great elasticity over the whole of the plicated surface. A panniculus carnosus ad- heres closely to this part of the skin, but is separated by a loose cellular membrane from the deep-seated muscles ; in which space the blubber is in smaller quantity than on the dorsal and lateral parts of the body. Besides the adipose substance which is ac- cumulated beneath the integument, another secretion of a peculiar kind, called Sperma- ceti, which is analogous in many of its pro- perties to the adeps, is met with in certain species of Cetacea, but more particularly in the genera Catodon and Vhyseter, which are hence termed Spermaceti Whales. Of this substance Mr. Hunter gives the following account from a dissection of a recent specimen of one of these Whales. [ " What is called spermaceti is found every where in the body in small quantity, mixed with the common fat of the animal, bearing a very small proportion to the other fat. In the head it is the reverse, for there the quantity of spermaceti is large when compared to that of the oil, although they are mixed, as in the other parts of the body. " As the spermaceti is found in the largest quantity in the head, and in what would ap- pear on a slight view to be the cavity of the skull, from a peculiarity in the shape of that bone, it has been imagined by some to be the brain. " These two kinds of fat in the head are con- tained in cells, or cellular membrane, in the same manner as the fat in other animals ; but besides the common cells there are larger ones, or ligamentous partitions going across, the better to support the vast load of oil, of which the bulk of the head is principally made up. " There are two places in the head where this oil lies ; these are situated along its upper and lower part : between them pass the nos- trils, and a vast number of tendons going to the nose and different parts of the head. " The purest spermaceti is contained in the smallest and least ligamentous cells : it lies above the nostril, all along the upper part of * Ibid. p. 395. CETACEA. 591 the Lead, immediately under tlie skin, and common adipose membrane. These cells re- semble those which contain the common fat in the other parts of the body nearest the skin. That which lies above the roof of the mouth, or between it and the nostril, is more inter- mixed with a ligamentous cellular membrane, and lies in chambers whose partitions are per- pendicular. These chambers are smaller the nearer to the nose, becoming larger and larger towards the back part of the head, where the spermaceti is more pure. " This spermaceti, when extracted cold, has a good deal the appearance of the internal structure of a water melon, and is found in rather solid lumps. " About the nose, or anterior part of the nostril, I discovered a great many vessels, having the appearance of a plexus of veins, some as large as a finger. On examining them, I found they were loaded with the spermaceti and oil ; and that some had corresponding arteries. They were most probably lym- phatics ; therefore I should suppose, that their contents had been absorbed from the cells of the head. We may the more readily suppose this, from finding many of the cells, or cham- bers, almost empty; and as we may reason- ably believe that this animal had been some time out of the seas in which it could procure proper food, it had perhaps lived on the super- abundance of oil. " The solid masses are what are brought home in casks for spermaceti. " I found, by boiling this substance, that I could easily extract the spermaceti and oil which floated on the top from the cellular membrane. When I skimmed off the oily part, and let it stand to cool, I found that the spermaceti crystallised, and the whole became solid; and by laying this cake upon any spongy substance, as chalk, or on a hollow body, the oil drained all off, leaving the sper- maceti pure and white. These crystals were only attached to each other by edges, forming a spongy mass ; and by melting this pure spermaceti, and allowing it to crystallise, it was reduced in appearance to half its bulk, the crystals being smaller and more blended, consequently less distinct. " The spermaceti mixes readily with other oils, while it is in a fluid state, but separates or crystallises whenever it is cooled to a certain degree ; like two rMfferent salts being dissolved in water, one of which will crystallise with a less degree of evaporation than the other ; or, if the water is warm, and fully saturated, one of the salts will crystallise sooner than the other, while the solution is cooling. I wanted to see whether spermaceti mixed equally well with the expressed oils of vegetables when warm, and likewise separated and crystallised when cold, and on trial there seemed to be no difference. When very much diluted with the oil, it is dissolved or melted by a much smaller degree of heat than when alone ; and this is the reason, perhaps, that it is in a fluid state in the living body. If the quantity of spermaceti is small in proportion to the other oil, it is, perhaps, nearly in that proportion longer in crystallising ; and when it does crystallise, the crystals are much smaller than those that are formed where the proportion of spermaceti is greater. From the slowness with which the spermaceti crystallises when much diluted with its oil, from a con- siderable quantity being to be obtained in that way, and from its continuing for years to crys- tallise, one would be induced to think, that perhaps the oil itself is converted into sper- maceti. " It is most likely, that if we could dis- cover the exact form of the different crystals of oils, we should thence be able to ascertain both the different sorts of vegetable oils, much better than by any other means ; in the same manner as we know salts by the forms into which they shoot."*] Okgans of Generation. — The organs con- cerned in the reproduction of the species do not exhibit the same type of conformation in the Phytophagous as in the Zoophagous species. In the former the mamma? are pectoral, in the latter inguinal or rather pudendal, since they are situated on each side of the vulva : in both orders their number never exceeds two. The vulva, which resembles in its form that of the Ruminants, presents nothing peculiar in its structure. The penis is attached to the rudi mental bones of the pelvis; in the Phytophaga the glans is complicated, but in the Zoophaga it is of a simple elongated fusiform shape : in all the species it is provided with a prepuce. [According to Hunter, the parts of generation in both sexes of this order of animals come nearer in form to those of the Ruminants than of any others; and this similarity is, perhaps, more remarkable in the female than in the male; for their situation in the male must vary on account of the modification of the external form of the body. The testicles (a, a, Jigs. 277, 278) retain the situation in which they were formed, as in those quadrupeds in which they never come down into the scrotum. They are situated near the lower part of the abdomen, one on each side, upon the two great depressors of the tail. At this part of the abdomen, the testicles come in contact with the abdominal muscles anteriorly. The vasa deferentia (c, c) pass directly from the epididymis (b, b) behind the bladder (d, d) or between it and the rectum (e) into the urethra (f) ; and there are no bags similar to those called vesicula? seminales in certain other animals. The structure of the penis is nearly the same in them all, and formed much upon the same principle as in the quadruped. It is made up of two crura (g, g), uniting into one corpus cavernosum, and the corpus spongiosum seems first to enter the corpus cavernosum. In the Porpoise, at least, the urethra is found nearly in the centre of the corpus cavernosum ; but towards the glans seems to separate or * Philos. Trans. 1787, p. 390. 592 CETACEA. Fig. 277. £ Male Organs of a Porpesse. emerge from it, and becoming a distinct spongy body, runs along its under surface, as in qua- drupeds (h). The corpus cavernosum in some is broader from the upper part to the lower than from side to side; but in the Porpoise (Jig. 277) it has the appearance of being round, becoming smaller forwards, so as to terminate almost in a point some distance from the end of the penis. The glans does not spread out as in many quadrupeds, but seems to be merely a plexus of veins covering the anterior end of the penis, yet is extended a Fig. 278. Male Organs of a Dolphin. good way further on, and is in some not more than one vein deep. The crura penis are attached to two bones, which are nearly in the same situation and in the same part of the pelvis as those to which the penis is attached in quadrupeds; but these bones are only for the insertion of the crura, and not for the support of any other part, like the pelvis in those animals which have poste- rior extremities, neither do they meet at the fore part, or join the vertebrae of the back. The erectores penis (g, g, Jig. 277) are very strong muscles, having an origin and insertion similar to those of the human subject. The prostatic portion of the urethra (J\ Jig. 278) is surrounded by a muscle of prodigious thickness (k,k), destined to compress and forcibly expel the contents of that part of the canal. The acceleratores muscles (I ) are likewise very strong ; and there is a pair of strong and long muscles ( m, Jig. 277) arising from the anus, and passing forwards to the bulb of the penis, that run along the under surface of the urethra, and are at last lost or inserted in the corpus spongiosum. These muscles draw the penis into the prepuce, and throw that part of the penis that is behind its insertion into a serpentine form. These muscles are common to most animals that draw back the penis into what is called the sheath, and may be called the retractores penis. The female organs in the Phytophagous Cetacea have been described by Steller as they exist in the liytina, and by Home in the Dugong; the latter author has given a figure of the uterus with part of the vagina: (see Jig. 279.) In both species the vagina (a) is characterized by the longitudinal ruga; of its inner surface. The body of the uterus (c) commences by a single os tineas (6) in the Fig. 279. i Uterus of the Dugong. Dugong, and gives off the cornua uteri (d, d) at right angles.* The structure of the Fallo- pian tubes and ovaries is not described. Steller states that in the Rytina they resemble those of the Mare. The vulva he describes as of a tri- angular form, with the clitoris, which is of a gristly texture, and an inch and a half long, * See Home, in Phil. Trans. 1820, p. 321. CETACEA. 593 situated at the anterior broad part of the open- ing, which is eight inches anterior to the anus. In all the females of the zoophagous tribe of Cetacea which Hunter examined, the parts of generation were very uniformly the same ; consisting of the external opening, the vagina, the body and two horns of the uterus, Fallopian tubes, fimbria?, and ovaria. " The external opening is a longitudinal slit, or oblong opening, whose edges meet in two opposite points, and the sides are rounded off, so as to form a kind of sulcus. The skin and parts on each side of this sulcus are of a looser texture than on the common surface of the animal, not being loaded with oil, and allow- ing of such motion of one part on another as admits of dilatation and contraction. The va- gina passes upwards and backwards towards the loins, so that its direction is diagonal re- specting the cavity of the abdomen, and then divides into the two horns, one on each side of the loins ; these afterwards terminating in the Fallopian tubes, to which the ovaria are at- tached. From each ovarium there is a small fold of the peritoneum, which passes up to- wards the kidney of the same side, as in most quadrupeds. " The inside of the vagina is smooth for about one-half of its length, and then begins to form something similar to valves projecting towards the mouth of the vagina, each like an os tincse : these are about six, seven, eight, or nine in number. Where they begin to be formed, they hardly go quite round, but the last are com- plete circles. At this part, too, the vagina becomes smaller, and gradually decreases in width to its termination. From the last pro- jecting part, the passage is continued up to the opening of the two horns, and the inner sur- face of this last part is thrown into longitudinal rugs, which are continued into the horns. Whether this last part is to be reckoned com- mon uterus or vagina, and that the last val- vular part is to be considered as os tincse, I do not know; but from its having the longitudinal ruga?, I am inclined to think it is uterus, this structure appearing to be intended for dis- tinction. " The horns are an equal division of this part; they make a gentle turn outwards, and are of considerable length. Their inner surface is thrown into longitudinal rugae, without any small protuberances for the cotyledons to form upon, as in those of ruminating animals ; and where they terminate the Fallopian tubes begin. " In the Bottle-nose Whale ( Delphinus Tur- sio), where the Fallopian tubes opened into the horns of the uterus, they were surrounded by pendulous bodies hanging loose in the horns. " The Fallopian tubes, at their termination in the uterus, are remarkably small for some in- ches, and then begin to dilate rather suddenly; and the nearer to the mouth the more this dila- tation increases, like the mouth of a French horn, the termination of which is five or six inches in diameter. They are very full of lon- gitudinal rugae through their whole length. " The ovaria are oblong bodies, about five inches in length; one end attached to the mouth of the Fallopian tube, and the other near to the horn of the uterus. They are irre- gular on their external surface, resembling a capsula renalis or pancreas. They have no capsula but what is formed by the long Fallo- pian tube. " How the male and female copulate I do not know ; but it is alleged that their position in the water is erect at that time, which I can readily suppose maybe true; for otherwise, if the connexion is long, it would interfere with the act of respiration, as in any other position the upper surface of the heads of both could not be at the surface of the water at the same time. However, as in the parts of generation they most resemble those of the ruminating kind, it is possible they may likewise resemble them in the duration of the act of copulation, for I believe all the ruminants are quick in this act. " Of their uterine gestation I as yet know nothing, but it is very probable that they have only a single one at a time, there being only two nipples. This seemed to be the case with the Bottle-nose Whale, caught near Berkeley, which had been seen for some days with one young one following it, and they were both caught together. " The glands for the secretion of milk are two, one on each side of the middle line of the belly at its lower part. The posterior ends, from which go out the nipples, are on each side of the opening of the vagina in small sulci. They are flat bodies lying between the external layer of fat and abdominal muscles, and are of considerable length, but only one-fourth of that in breadth. They are thin, that they may not vary the external shape of the animal, and have a principal duct, running in the middle through the whole length of the gland, and collecting the smaller lateral ducts, which are made up of those still smaller. Some of these lateral branches enter the common trunk in the direc- tion of the milk's passage, others in the con- trary direction, especially those nearest to the termination of the trunk in the nipple. The trunk is large, and appears to serve as a reser- voir for the milk,* and terminates externally in a projection, which is the nipple. The lateral portions of the sulcus which incloses the nipple are composed of parts looser in texture than the common adipose membrane, which is pro- bably to admit of the elongation or projection of the nipple. On the outside of this there is another small fissure, which I imagine is like- wise intended to give greater facility to the movements of all these parts. The milk is probably very rich ; for in that caught near Berkeley with its young one, the milk, which was tasted by Mr. Jenner, and Mr. Ludlow, surgeon, at Sodbury, was rich like cow's milk to which cream had been added. " The mode in which these animals must * The description of this structure has lately been reproduced as a new discovery by Geoffroy St. Hilaire. 594 CHEIROPTERA. suck would appear to be very inconvenient for respiration, as either the mother or young one will be prevented from breathing at the time, their nostrils being in opposite directions, there- fore the nose of one must be under water, and the time of sucking can only be between each respiration. The act of sucking must likewise be different from that of land animals; as in them it is performed by the lungs drawing the air from the mouth backwards into themselves, which the fluid follows, by being forced into the mouth from the pressure of the external air on its surface; but in this tribe, the lungs having no connexion with the mouth, sucking must be performed by some action of the mouth itself, and by its having the power of expansion." Much stress has recently been laid on the supposed existence which the muscles sur- rounding the mammary gland afford in the act of suckling by compressing the gland and ejaculating the milk accumulated in the dilated receptacle above described ; but when we con- sider how great the pressure of the surrounding water must be upon the extended surface of the mammary gland, we may readily conceive that when the nipple is grasped by the mouth of the young, and the pressure removed from it by the retraction of the tongue, the milk will be expelled in a copious stream by means of the surrounding pressure alone, independently of muscular aid. The intimate structure of the mammary gland in the Zoophagous Cetacea is essentially the same as in the Ornithorhynchus, being compo- sed of an innumerable quantity of small elon- gated crecal tubes ; these are, however, shorter than in the Ornithorhynchus, and their glandu- lar parietes are firmer ; they are well shown in the figure of the mammary gland of a young Piked Whale, ( Bulauoptera Rostrata,J given by Muller in his pi. xvii. Jig. 2, and according to that author present, after the Ornithorhyn- chus, the simplest structure of the mammary gland in the entire mammiferous series of ani- mals.] BIBLIOGRAPHY. — Aristotle, Historia de animali- bus. Bartlwlinus, Cetonim genera, Historia anato- mica, Cent. iv. p. 272-285 ; De oculo Balaena; et Dentibus, in Acta Hafniens. vol. ii. p. 67-70; De Unicornu observationes novae, 12mo. 1645. Achre- lius, Cetographia, sive Dissertatio Historico-physica de Cetis, Aboae, 1683, 8vo. Ray, An account of the dissection of a Porpesse, Philos. Trans. 1671, vol. vi. p. 2274. Major, De Anatome Phocamae, vel Delphini Septentrionalium, Ephem. Acta Nat. Cur. Dec. 1, Ann. 3, p. 22-32 ; De respiratione Phocasnae, vel Tursionis, Ephem. Acad. Nat. Curios. Dec. i. Ann. 8, p. 4, 5. Tyson, Phocaena, or the anatomy of a Porpess, 4to. 1680. Sibbald, Pha- lainologia nova, &c. Edinb. 1692, 4to. ; Scotia illus- trata, fol. 1684. De la Motte, Anatome Phocapnae, in Klein Hist, piscium naturalis, p. 24-32. Ticho- nius, Monoceros piscis haud monoceros, Hafniae. 1706. Dudley, An essay on the natural history of Whales ; with a particular account of the ambergris found in the Spermaceti Whale, Phil. Trans. 1725. Steller, De Bestiis marinis, Nouveaux Memoires de l'Academie de Petcrsbourg, t. ii. 1751. Daubenton, Descriptions des tetes de Lamantins et de Dugong, Hist. Nat. de Buffon, t. xiii. 1765. Linnceus, Systema Nature, Ed. xii. 1766. Pennant, Brit. Zoology, 1776. Fabricius, ( Otho,) Fauna Grcen- landica, 1780. Pallas, Spicilegia Zoologica, 1767 to 1780. Hunter, Observations on the structure and ceconomy of Whales, Philos. Trans. 1787. Baussard, Memoire sur un Cetace echoue pres de HonHeur, Journal de Physique, 1789. Cuvier, Geo. Sur les narines des Cetaces, Bulletin des Sciences par la Societe Philomathique, Juillet, 1797 ; Lecons d'Ana- lomie Comparee, torn. i. v. 1799-1804; Recherches sur les Ossemens Fossiles, 4to. 2d ed. t. v. pt. i. 1823; Regne Animal, &c. 1817, 2d ed. 1829. Lacepede, Hist. Nat. des Cetaces, 1803. Scoresby, Account of the Balaena Mysticetus, &c, Wernerian Transactions, vol. i. p. 578 ; An account of the Arctic Regions, 1820. Home, Lectures on Compa- rative Anatomy, 4to. 1814-1828. Albers, Icones ad lllustrandam Anatomen Comparatam, fol. Camper, Observations Anatomiques, &c. sur plusieurs es- peces de Cetaces, Paris, 1820. Rudolphi, Memoires de l'Academie de Berlin, 1820. Barclay on the anatomy of the Beluga, Trans. Wernerian Society, vol. iii. Eichwald, Observ. Anatom. sur unjeune Marsouin, Memoires de l'Acad. de Petersb. t. ix. 1824. Blainville, Note sur un Cetace echoue au Havre, Nouveau Bulletin des Sciences, Sept. 1825. Jacob, Anatomy of the Delphini, Dublin Philo- sophical Journal, 1826. Tiedemann, Hirn des Delphins mit dem des Menschens vergleichen, in Zeitschrift fur Physiologie, Band ii. Heft i. 1826. Baer, Anatomie des Braunfisches, Oken's Isis,1826; Uber das Gefass-system des Braunfisches, Nova Acta Phys. Med. t. xvii. pars ii. 1835. Rapp, Natur Weissenschaft abhandlung, 1827 ; Beitrage zur anatomie und physiologie des Wallsfisches, in Meckel's Archiv. fiir Physiologie, 1830. Haber, Sur le soufflage des Cetaces, Isis, 1827. Schegel, Memoire sur le Baleinoptere de la Mer Arctique echoue, 1826, &c, Mem. de lTnstitut Royal des Pays-Bas, 1828. Rousseau, Moustache chez les foetus de Dauphins et Marsouins, Annales des Sciences Naturelles, 1830. D' Orbigny , Notice sur un nouveau genre de Cetaces, Nouv. Annales du Museum, t. iii. 1834. Breschet Sf Roussel de Vauxeme, Recherches anatomiques et physiologiques sur les appareils tegumentaires des animaux, in Annales des Sciences Nat. 1834, and subsequently collected into 1 vol. 8vo. Nouvelles Recherches sur la Peau, Paris, 1836. Owen, Description of the Hunterian anatomical preparations of the Cetacea in the ' Descriptive and Illustrated Catalogue of the Physiological Series in the Museum of the College of Surgeons, London,' 1832-1835. Cuvier, Fr. Histoire naturelle des Cetaces, 8vo. Paris, 1836. ( The preceding article has been derived from the work last named in the Bibliography, with the addition of the extracts from Mr. Hunter's papers and tlie other passages included between brackets.) (F. Cuvier.) C H EI RO PTER A, (from xf^manus, wrc^o », ala,) Bats, Fr. C/iauvesouris,Germ. Fledermdu- ser, an order of mammiferous quadrupeds, consisting of such as have a generally in- sectivorous type of dentition, with the extremi- ties connected together by an aliform expansion of the integuments, for the purpose of flight. The question whether this group, as well as that of the Carnivora and that of the In- sectivora, ought to be considered as forming a single order according to the method of Cuvier, has been already sufficiently adverted to under the head Carnivora; and it needs only to be now observed that if there were sufficient ground for giving to the last-men- tioned group a separate consideration, either on account of expediency and convenience, or on that of natural arrangement, the same CHEIROPTERA. 505 reasons hold good, in the present case, in an equal, if not a superior degree. The distinctions by which the present order is separated from all others are so marked, and the general similarity in the organization of its component groups is so striking, as greatly to facilitate and shorten the necessary detail of the organization. There appears to be a great and obvious objection to the usual location of the remark- able genus Galeopithecus amongst the Cheiro- ptera ; there are so many important parts of its organization in which it clearly resembles the more insectivorous forms of the Quadru- mana, not only in the peculiarities of its osteology, but in many other not less essential points, that I have preferred following the change suggested by Blainville, and subse- quently adopted by Temminck, to the arrange- ment of Cuvier and of most other zoologists. It may undoubtedly be considered as an oscu- Ient form, leading from the Quadrumanous order, by the Makis, &c. to the present group ; but it cannot but be acknowledged by any one who has attentively marked its anatomical structure, that the affinity of this genus to the Quadrumana is more intimate than that by which it approaches the Bats ; though perhaps it would be going too far to say, with Temminck, that it bears the same relation to the Quadrumana as Petaurista to the Mar- supiata, or Pteromys to the Rodent ia. The latter genera are not even on the confines of their respective orders, nor do they offer any important aberration from the typical struc- ture ; but in the present case there are several characters which indicate an interesting ap- proach towards the order from which it has very properly been removed. Omitting, then, the genus Galeopithecus, the Cheiroptera form, without perhaps a single exception, the most distinctly circumscribed and natural group to be found in the whole class of the Mammiferu. The characters by which the order thus restricted is distinguished are as follow : — General form disposed for flight ; an ex- pansion of the integument stretched between the four members, and the fingers of the an- terior extremities, which are greatly elongated for that purpose ; the flying membrane naked, or nearly so, on both sides. Mamma pectoral, clavicles very robust ; fore-arm incapable of rotation, in consequence of the union of the bones of which it is composed. The Cheiroptera consist of two distinct groups ; of which the first, containing the genera Pteropus and Cephalotes, is frugivorous, and distinguished by the molar teeth being obliquely truncated and longitudinally grooved, and by the existence of a third phalanx, which is in general provided with a little nail on the index or second finger, and by the absence or rudimentary condition of the tail. The second, consisting of the insectivorous bats, ( Chauve- souris vraies, Cuv. Vesper tilionida, Gray,) have the molares furnished with acute points, similar to those of other insectivora. Osteology. — The evident object in the general structure of the skeleton of the Cheiroptera (Jig. 280) is to combine as great a degree of lightness as possible with great extension of the anterior extremities, for the purposes of flight. The general form of the head differs in the two grand divisions of the Cheiroptera by the different lengths of the cranium ; and this diversity is exactly conformable with that which exists in other families. The frugivorous group (jig. 281, 282, 283) has a much more elongated form than the insectivorous (fig. 284, 285, 286), arising principally, though not wholly, from the form of the maxillary and intermaxillary bones. The cranium is generally rounded, and rather broad. The posterior aspect more or less con- vex in different groups ; in some overhanging Fig. 280. Skeleton of Pteropus. 596 CHEIROPTERA. fig. 281. the occipital foramen, in others not so. The occipital crest is triangular, stronger in the insectivorous than in the frugivorous form. In many there is also a longitudinal crest. The face is broad. The orbits are not com- plete in either group, and the temporal J'ossa is large, but the zygoma in many very slender ; in some it is horizontal, in others slightly convex above. The nasal opening is very considerable; and in many whole genera, as in Rhinolophus, in Plecotus, and several others, in consequence of the intermaxillary bones not meeting each other, it is not closed at the lower part. In the genus Pteropus, and some others, as is seen in Jig. 282, 283, though the intermaxillary bones meet in front, yet, as the arch is very small and narrow from before backwards, the palatine foramina unite and form a single large opening. From the extreme thinness of the cranial bones, the internal surface corresponds exactly with the external, and there is no vestige of a bony tentorium, which is so strong in many of the Carnivora. The frontal bone in the genus Pteropus presents a prominent orbitar process ; it re- sembles that of Man, and of the Quadrumana, in the circumstance of the two portions be- coming early united. The parietals, also, unlike those of the examples just named, form but a single bone. The temporal bone has a very extensive development of its acoustic portion ; a cha- racter which is of the utmost importance to their peculiar habits, as the organ of hearing Fig. 282. Fig. 283. requires to be extensive in those animals which prey by night, and especially in such as feed upon insects and pursue them on the wing. The occipital bone is remarkable from the narrowness of its body, the transverse direction of the condyles, the short, thin, and convex form of its squamous portion, and particularly from the unparalleled proportionate size of the occipital foramen, which is nearly vertical and rounded. Fig. 284. fig. 285. Fig. 286. Cranium of Pteropus. Cranium of Phyllostoma. The jugal bone is small in most of the bats and very strait. The superior maxillary bone is considerably elongated in this order, particularly in, the frugivorous genera. The difference in this respect which exists between the frugivorous and insectivorous forms is shewn in the cranium of a Pteropus belonging to the former (jig. 281, 282, 283), and a Phyllostoma to the latter group (fig. 284, 285, 286). In the former case, the portion occupied by the teeth fully equals in length the portion of the cranium posterior to it ; in the latter it is little more than as two to three. The number of teeth con- tained in this bone varies considerably. There is, however, always a single canine tooth on each side, which is tolerably robust and sharp. The molares of the insectivorous Bats are always shorter than those of the frugivorous, and are furnished with sharp points, the latter being truncated and longitudinally grooved. They vary in number from a to 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 formulae — \ § \ |. 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 veiy large in this region. These vertebra 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 (Jig. 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 (jig- 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 vertebrae is but six in Noctula, twelve in Ves- pertilio and some others. The number of vertebrae 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 Jig. 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 398 CHEIROPTERA. it would require the 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 inferiorly. 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 fibula 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. Themetatarsal 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 f 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 Pteropns 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- preciable 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 CHYLIFEROUS 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 the aliment than the teeth ; offering, in the Pte- ropus (Jig- 287), a very striking affinity to that Fig. 287. of many true vegetable feeders in some remote orders, and in Plecotus (fig. 288), as complete Fig. 288. 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 rugae 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 itecum. 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 Com- pels 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.) CHYLIFEROUS 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 foocVor the chyle, from the alimentary canal intaftjae san- guiferous vessels. The function of tflpse chy- liferous vessels appears to be performec? by the veins in the invertebrated classes, ajaere the white colour of the blood causes lJPm 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 CHYLIFEROUS SYSTEM. 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- dusae 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 congloba^glands is yet supplied, as in the inferior iJwftebrata, by numerous complicated networks |Blacteal vessels, formed in different parts of t^B course ; and, as in fishes, two or more duct^re 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 R 602 CICATRIX. CHYLIFEROUS 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 not 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 * 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 veiy 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 cutic'.e 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 cuds 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 veiy 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.-)- When the ulcer was small, the cicatrix has sometimes a considerable resem- blance to the scar of small-pox.f 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. | Blight'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. 5 On Mediate Auscultation, translation by Dr. Forbes, 2d edit. p. 300. || Clinique Medicale, torn. 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.f- 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 contiaction 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. 005 which the ulcer was subjected in the process of healing. When these have been considerable, the hardness is correspondingly great, 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 exhalent 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 cedema 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 cica- 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, ah 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.f 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. "J 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 * Lecons de Clinique Chir. torn. 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. 606 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. Dupuytrenf 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 (in 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 Eye 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 * De phenomeno motus vibratorii, &c. 4to. Wratisl. 1835. CILIA. 507 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 (jig. 289), the cilia are usually set round the mouth or spread over the Pig. 289. body generally, in which case they are often d isposed in regular rows. Their struc- ture has been carefully in- vestigated by ProfessorEhren- 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 (Jig. 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 erythropthahna. 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 Fig. 290. 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 votvox, 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 Naturae, 1719, p. 382, Epist. 144. f 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 swiftty 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 :f " 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,! next to Leeuwenhoek, takes notice of the cilia of animalcules. He observed them in many species, and named them fins, or feet, and sometimes fibrillar. 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 fibrillar move themselves very briskly, sometimes with a kind of rotation, atid sometimes in a trembling or vibrating manner,"5f " 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.jj; It appears that he was aware of the true structure of the so-called wheels, and though he often speaks of their * Continuatio Arcanorura Naturae, 1719, p. 386, Epist. 144. f Epistolae Physiologies, 1719, p. 66. Epist. 7. J 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. [I Reprinted in op. cit. ii. p. 267. ir p. 27i. ** P. 273. tt P. 284. i\ 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 Rotijer, 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. SaussureH 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. Wrisbergft observed the currents and eddies produced by the vorticella; 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 Miiller,U 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. t P. 183. X P. 199. j Tom. ii. p. 227. (| Spallanzani, Nouvelles Recherches sur les Decouvertes Microscopiques, &c. 1769, p. 161. % See Letter by Bonnet, in Spallanzani Opus- cules, torn. i. p. 176. ** Elenchus Zoophytorum, 1766. ±r Observationum de Animalculis Infusoriis sa- tura, 1765, p. 52. p. 63. ft Verrmum Terrestrium et Fluviatihum His- toria, 1773, and Animalcula Infusoria, 1788. CILIA. 609 Gleiehen,* in 1778, described the currents produced by the vorticellse. 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 FontanaJ 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.frf 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 .J J 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, fig. 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 * Abhandlung ueber-die Saamen -und Infusions Thierchen, 1778. f See M'uller, Infus. p. 87. % Traite sur le venin de la Vipere, etc. 1781, torn. i. p. 87. § Sur les Rotiferes, Ann. du Musee d'Hist. Nat. 1812, torn. xix. et 1813, torn. xx. |l Salzburg. Med. Chir. Zeitung, 1818, iv. p. 222. H Ueber die Zauberkraft der Infusorien, Nov. Act. Acad. Ca?s. Leop. torn. x. p. 127. ** Hist. Nat. de l'Alcyonella Fluviatile, etc. Mem. de la Soc. d'Hist. Nat. torn. iv. and Chimie Organique, 1833. H Abhandl. d. Akad. der Wiss. zu Berlin fiir 1831. it Wagner, Isis, 1832, p. 383. 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 undulations 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. RoeselJ 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 l'Hist. d'un genre de Polype d'eau douce, 1744, p. 212. •f Of Microscopes, ii. p. 309. j Insecten Belustigungen, torn. iii. 1755, p. 458. § Analecten neuer Beobachtungen und TJnter- suchungen fiir die Naturkunde, 1802, p. 89. 610 CILIA. Polype of a Flustra in its cell. 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- Nt cies which have been classed among the Ser- K 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-thirtyrifth 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 u'ber Polypen, Isis 1828, p. 1225. figure), and they are clearly to be seen oh 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 (Jig. 293, A, B) has a creeping stem Fig. 293. (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 (A). The mouth, or expanded aperture of the animal, is sur- rounded by a prominent lip or border (j, 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 /c, Jc ; 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 Flustra?. 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. Campanularia. 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 hydra? ; 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 (6), 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 quietfor 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. t 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 Sertularia;) 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 Fig. 295. is a transparent horny tube y (a, a), containing a soft mat- ^w|/ 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- \ |i: $ semblance to the circulation of globules observed in plants of the genus Chum. 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 Sertulanae. At the nodous parts of the * Edin. Phil. Journ. t Phil. Trans. 1834, p. 366. 612 CILIA. tube {m, 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 Flustree, 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 Flustree 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- lariffi. 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 Sertularise, 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 Wera. Soc. fol. p. v. p. 488. t On the Structure and Nature of Flustra?. Ed. New Phil. Journal, vol. iii. 1827. X 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 faecal 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 fascal 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. i. and ii. CILIA. 613 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 (Jampanu- 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 swim 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-rlower 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 du mouvement vital devoile, 1826, p. 179, and Annalesdes Sciences Naturelles, 1828, torn. xv. p. 205. t Hist. Nat. des Corallines, p. 116. J Memorie per servire alia storia de' Polypi Marini, Nap. 1785, p. 8, p. 48 of German trans- lation. 6 Edin. New Phil. Journal, vol. i, p. 150. II Isis, 1828, p. 1225, sqq. Isis, 1830, p. 186. wards shown, in the ova of many other ani- mals. 4. Acalepha. — Many species of Medusae are furnished with cilia, or at least with moving organs bearing a close resemblance to the cilia of other animals, though in the Medusa they present several peculiarities. The cilia are found in all the Medusae belonging to the order Ciliograda of Blainville, or Ctenop/iora 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,f 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; he 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 Medusas 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 Medusa?. (See Acaleph^e, p. 48.) 5. Actinia. — In a paper published on the present subject in 1830,1 I mentioned that I had found the ciliary motion in the Actinia or Sea-auemony, but gave no description of it. I have since re-examined various species of Actinias 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. 297 Fig. 297. Actinia. 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. Caes. 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 fe> g> g > g\) Pass fr°m 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 Actiniae, 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-grown 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 the 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.f 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- rent directions, namely, from the base to the point, and from the point to the base ; and (supposing the arm spread out horizontally,) the outward current was along the under part of the tube, and the returning one along the upper: (see//.) I also observed these internal currents of the tentacula in a young specimen of Actinia senilis, which seemed to have been very recently discharged from the parent ; in it also there were radiating currents on the disc, but they stopped at the base of the tentacula. Thus the external currents on the disc and ten- tacula were found in one species, and they occur on the disc in some other species in the young state, but their occurrence in this situa- tion is by no means general in adult Actiniae. The phenomena described are in all proba- bility connected with the processes of nutri- tion and respiration. They bear a striking analogy to those I have observed in the Echino- dermata. The ova of the Actinire were observed by Rathke to revolve round their axis, and occa- sionally to move straightforward s in the water. He could detect no cilia or other moving organs.* 6. Echinodermata.— The animals of this class in which I have observed the ciliary motion, are different species of the Sea-star ( Asterias ), and the Sea-urchin (Echinus ). In proceeding to describe the phenomena in the Asterias, I must first take the liberty of ex- plaining some points in the anatomy of that animal, referring the reader for other details to the proper sources, especially the monograph of Tiedemann.f On the under surface of the Asterias, (I speak of the Asterias rubens in particular, fig. 298, A, B, C, as it is a large species and common on our shores,) we observe the mouth in the centre, and the tubular feet ( I, fig. B) projecting in rows along the under part of the rays. Nearly the whole surface of the animal is beset with three kinds of eminences. First, hard calcareous processes, ( a, fig. C,) placed like studs at some distance from each other. Secondly, claw-like processes (6, b); these sin- gular organs are more thickly set ; they consist of a solid stem of soft substance, bearing at the extremity a sort of pincers or forceps of hard calcareous matter, like the claw of a crab. They resemble analogous organs found on the Sea-urchin, only that the maxillas or pincers in the latter consist of three pieces ; they were named antennas or feelers by Monro, but Mul- ler regarded them as parasitical animals. The third sort of processes (c, c,) are named the respiratory tubes, and are the most important in regard to our present subject. They are short, conical, membranous tubes, communi- cating at their base with the internal cavity of the body, and perforated at their point by an orifice which can be very perfectly closed. Most of them are placed in groups or patches, and, corresponding with each group of tubes, the fibrous membrane forming the wall of the body presents on its inside a pit or shallow depression (e), perforated with holes, through which the tubes communicate with the general cavity. Like the tentacula of the Actiniae, which they resemble in several other respects, they can be distended with water and elon- gated, or emptied, contracted, and shortened. Fig. 298. A, Asterias viewed from above. B, Cross section of a Ray. C, Part of the section at m, fig. A, magnified. * Dorpater Jahrbiich. fur Litt. Stat, und Kunst. Bd. i. Heft. i. p. 84—86, quoted by Purkinje and Valentin, p. 32. I have since seen the indepen- dent motion of the ova when extracted from the animal. It was shown to me by Mr. Graham Dalyell, who had long before observed it. The cilia could be distinctly perceived. f Anatomie der R'ohren Holothurie, &c. Land- shut, 1816. 616 CILIA. In the inside of the body the membranous stomach (g) occupies the middle part, and from it a pair of lobed coeca (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 coeca, attaches each of the cceca by a me- sentery (0,0) to the roof of the ray, lines the fibrous paiietes of tbe body, and is probably reflected over the vesicles of the feet and the ovaries. Each mesentery encloses a space ( °> fi&- B) between its sides, which opens into the general cavity at the root of the coeca. 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, Jig. 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 ray, forwards or towards its point : (see the arrows in Jig. 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 coeca, an advancing one (h ) on the inferior surface, and a retiring one superiorly (h, h, fig. A) in the space ( o,Jig. 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 " ., and"' again partially emptying itself, L<- " j. never per- ceive the fluid entering or ijjr":.ig, at the oxificou described. & \ \j — ,_" — we may so express it, connected by others which run vertically and transversely on the coeca and on the roof and sides of the cavity, (see the arrows in Jig. 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, Jig. 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 coeca; 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 caeca 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 coeca, 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 th'& tubes. There can be little doubt that the - * Anat. *er 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 orgroups, 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,f 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 lamina?. The vessels or spaces within the lamina? 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 lamina? 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 lamina? from their external * Anatomy of Fishes, &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 lamina? 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 was 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 lamina?, though from an observation of Carus, who states that he saw globules circulating within these lamina?, 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,f from which it appears that the 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 Echinodermata. A great part of the body of the Aphrodita aculeate, 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 Natur-wissenschaft, etc. Dres- den, 1829, p. 152. t Muller's Archiv. Band 1, p. 578. 2 s C18 CILIA. Fig. 299. A . Cross section of the Aphrodita aculeata. e B. Alimentary canal and caeca, 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, fig. 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 TAJ, 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 cceca, 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 cceca, 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 ccecal 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 1830, 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. 619 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 alveolate,. 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 Dorsibranchiata, probably as a Sabella. The currents in this worm proceed forwards along the back, be- tween the rows of gills (as marked in Jig. 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. Mollusca. — The ciliary motion prevails very extensively in this division of the animal kingdom. It seems to exist generally in Ihe Gasteropodous and Acephalous Mollusca. There is some uncertainty as to its existence in the Cephalopoda ; I have repeatedly sought for it in that class, but 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 Nudibranchiata, Cyclobranehiuta, Pectinibranchiata, and the aquatic Pulmonifera, in one or more species of each. a. Nudibranchiuta. — -In this order, in which the gills are entirely exposed, the currents can be 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, 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, andy^f 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 Planaris, 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. Cass. Leop. xi. p. 238.) 2 S 2. 620 CILIA. Fie. 301. Denis. 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. Cyclobranchiata. — In the Patella or Limpet (Jig. 302, representing the under surface), the gills form a series of simple Fig. 302. Patella. B. Portion inclosed between the lines c and d, magnified to show a, a, the branchial la- mina?, and b, b, the circular border of the mantle. lamina? (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 (Jig. 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 lamina? 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 lamina? over their surface and along their edges : a, a, are the gills ; b one of the gills magnified, showing its laminae; Chiton, c the same viewed endwise. The arrows mark the direction of the currents. c. Pectinibrancldata. — The common Buc- cinum (fig. 304) may serve as an example of Fig. 304. Buccinum Undatwm. 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 (b) 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 (J', J'); 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 lamina? from the larger series, h the at- tached border, i point, m left, and n right border. Currents pass between these lamina; 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 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 branchiae 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. Pulmonifcru. 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 tentacida of bian- 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 AccphrJa. — 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 (fig. 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. Lcop. 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, f c,) are united at the edge of the gill (<-), 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, h, jig. 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 (/;) 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, ij, 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 (tn, 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 svrface 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, (b, 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 (/;, Jig. C) are exceedingly small ; they extend upon the cross slips, (hjig- 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 ( Ascidia ). — 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 Ascidise 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 Ascidiae on its peduncle, with the opening of the mouth (g) and the funnel (_/') in front. The outer covering is a tough coat ( CILIA. Valentin state the effects which they found to result from the application of various sub- stances, but erroneously conceiving, 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 larvae 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 Beroe a vessel conveying water runs beneath each row * Trans, of Zoological Society of London, vol. i. p. 11. 635 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 water 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 we 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 G3G 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 hy the cilia. — 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 Sertulariae. Indeed both CILIA. 637 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- • As by Baker, Guillot, and others. 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. Amst. 1684. Swammerdam, Biblia Naturae, fol. Leidae, 1737. * Leeuwenhoek , Opera, 4to. Delph. et Lugd. Bat. 1695-1719. * Baker, Of microscopes, &c. 8vo. Lond. 1785. Hales, Haamastaticks, 3d edit. 8vo. Lond. 1769 Ellis, Hist. Nat. des Corallines, 4to. La Haye, 1756, (a translation from the Jing- lish, with the'author's additions). Roesel, Insecten. belustigungeu, vol. iii. 4to. Niirnberg, 1755. *Spal- lanzani, Opuscules de Physique, 8vo. Pavie, 1787. *O.F. Dliiller, Hist, veimium terrestrium et fiuvia- tilium, 4to. Hafniac, 1773, and, Animalcula Infu- soria, 4to. Hafniae, 1786. *Cavolini, Memorie per servire alia stona dei polipi marini, 4to. Napoli, 1785; translated into German by W. Sprengel, Niirnb. 1813. Poli, Testacea utriusque Sicilian, fol. Parmae, 1792. Stiebel, Lymnasi Stagnalis anatome, 4to. Gbtt. 1815, and in Meckel's Deutsches Archiv, fur die Physiologic, Bd i, and li. Ehrman1 638 CIRCULATION. in Abhandl. der kijnigl. 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. Treviranus, Vermischte Schriften, 4to. Bd iii. Bremen, 1820. Hugi, in Isis for 1823. *Carus, Von den aussern Lebens- bedingungen der weiss-und kaltbluetigen Thiere, 4to. Leipz. 1824 ; Nov. Act. Ac. Cces. Leop. 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., Edin. 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. Dutrochet, 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. *Eltrenberg, Ueber Infnsorien, in Abhandl. der k. Acad, der Wissensch. zu Berlin fur 1830 and 1831, Miiller's Archiv. i. 1834. R. Wagner, Isis for 1832. Jo. Miiller, Handbuch der Physiologie, Bd i. 8vo. 1833. H. Rathke, in Dorpater Jahrbucher, &c. Bd i. 1833. *Jos.J. Lister, in Phil. Trans. 1834. *J. E. Purkinje 8f 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, Cireuitus 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 in man. The organs of circulation consist of the heart, arteries, veins, and capillary vessels. We refer the reader to the articles on these different organs for 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 (jig. 312, H) Fig. 312* Circulation in Man. • In all the figures relating to the circulation in different animais 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; «*, the vena cava superior; c, the capillary vessels; P, the pulmonary artery ; p, the pulmonary vein ; B, the branchial artery ; b, the branchial vein ; D, 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 hi 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 cava? ( 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 chyle or imperfectly formed blood, which is the pro- duct of digestion, and which is poured along with the lymph from the 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 (if), and the stream of venous blood brought by them to the right auricle (h!), 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 (P, 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 cceliac artery ; L, vena ports ; I, hepatic vein ; !*, hepatic artery ; K, advehent renal veins ; h, renal veins ; ft*, 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 are merely plans, and that strict anatomical accuracy is not to be looked for in them. 640 CIRCULATION. the pulmonary veins (p). The left auricle (ft) 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 porta?. The blood supplied by the coeliac and me- senteric arteries (J, 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 port?e, 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 ports, being joined in the minute branches by that of the hepatic artery (I*), passes into the smallest ramifica- tions of the hepatic veins, by the principal trunks of -which (/), 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. 4th . 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 the 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 fcetus 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 fcetus, 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 fcetus passes out of its body through the umbilical cord (Jig. 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. Postal circulation seen from behind. continuity of tube exists between the maternal and foetal 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 foetus, after passing through the minute ramifications of the umbilical arte- ries (V, U) in the placenta, returns by the umbilical vein («) 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 porta; ( L), with which the umbilical vein unites, through the sub- stance of the liver, and is then conveyed by means of the hepatic veins (/) into the general current of the returning blood. The right auricle of the heart (It), therefore, receives not only the blood which has circu- lated through the body of the foetus, but also that which has passed through the placenta, consequently a mixture of venous and arterial blood ; — the blood in the superior vena cava (»*) 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 foetus 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 foetus 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 foetus 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 foetal 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 foetal 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 l'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. Miiller in Burdach's Physiologie, vol. iv. and in his Handbuch dcr 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 many 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 blood 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 Garnivora, 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 * Sec 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 porta?, 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 ports, 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 ports, have been ascertained by Professor Jacobson,J 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 ports, 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. X Meckel's Archiv. vol. iii. p. 147. Edin. Med. and Surg. Journ. 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 (fig. 314, i Fig. 314. Heart of Laeerta ocellata. H, If 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 C H'J giving off chiefly the pulmonary ( P ), the left or posterior (ft), the systemic arteries ( A J. 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. Heart of Common Tortoise. 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. * Lecons, vol. iv. p. 221. t Vergleich. Anatomic, vol. v. p. 231. 644 CIRCULATION. mals, 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 cava? (V v*) is directed wholly into the pul- monary vessels ( P ) by the right ventricular compartment ( H' ). Fig. 316. Lacerta ocellata. 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 the 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 coeliac 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- pents again, the arterial and venous blood must be 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 the 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.J In most of the adult Batrachia the ventricle (fig. 317, if J, being single and giving rise to one arterial trunk only ( A), the pulmonary arteries (P',P) 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 (/>), and this mixed blood being propelled into the 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. f See Bojanus' beautiful Anat. Monography of the Tortoise. t In this respect, ^as well as in the mode of origin of the left aortic arch, the Tortoise and Tur- tle differ from one another. CIRCULATION. 645 Fig. 317. Frog. 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. Proteus Mexicanus (Axolotl). 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 (fig. 318, H), which propels its blood into the bulb or commencement of the aortic trunk (.4 ). 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 Batrachian 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 1 Wc omit the consideration of the Amphiuma, Menopoma, and Coecilia. 646 CIRCULATION. heart (A, H) receives the 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 (a) 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 (7c) 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 foetal 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 (ft) 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 side. 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. Fish. through the branches of the aorta (A) in the various parts of the systemic circulation. Dr. Marshall Hall* and J. Mullerf 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. 1831. 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 & A') from the abdominal viscera and posterior parts of the body. The vena porta? 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 Cceur, &c. Bull, de la Soc. Philomathique, 1818-19, p. 148. 648 CIRCULATION. der, and tail. There is, however, considerable variety in regard to the distribution of the posterior abdominal veins in fishes; and com- arative anatomists do not appear as yet to ave 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 portions of the nervous system ; while in all Vertebrate 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 Verlebrata 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, torn, 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. 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. Cuttle-fah. the gills has a dilated contractile portion (£*), 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 (figs. 321 and 322, h, H). 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 vol. r. Helix. 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 Ascidia, Mr. Lister* has recently discovered one of the most remarkable modifications of the circulation with which we * Philos. Trans. 1834, p. 378. 2 u 650 CIRCULATION. are acquainted. Mr. Lister finds thai the dif- ferent Ascidia; 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 ascidia 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 ascidis 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. Articuluta. ■ — 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, and 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 (fig. 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- Lumbricus. 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. — In the leech the principal and most highly contractile longitudinal vessels are placed one on each side (fig. 324, a, a ), arid 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 isremarkablethat 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. Miiller, 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 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 Cams 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 larvae, 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, if J 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. Insects. 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 lamina?, antenna;, 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 larvee 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* x) prevents the passage of the blood in a retrograde direction. There 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 (fig. 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 Carus and others in some of the perfect insects. Carus saw it in the wings of the Semblis developed for flight. The circulation has also been seen by Carus 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 Stomapoda, 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 articula'ed 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 (fig. 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 (7*). 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 {E) 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 Fie, 326. Lobster. 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 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 Holothuria, 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 Holothuria, 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. Planaria. — Next to the Echinodermata in respect of the degree of perfection of their cir- culatory organs, may be mentioned the Plana- rias, 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- vity of the Planaria and some Entozoa was believed to hold the place of organs of circula- tion, the same cavity in which digestion occurs being believed to carry by its ramifications the nutritious fluids to different parts of the body. But Duges has shewn the existence in them of a system of vascular organs resembling considerably those of the Leech, to which animals the Planaria bears, in other parts of its organization also, astriking analogy. The vascular system of the Planaria consists of three principal longitudinal trunks, two lateral and one dorsal or median, which are all united together by numerous minute anasto- Planaria. * Sec the article Arathnida, p. 206. * Annal. des Sciences Natur, xv, p, 160. 654 CIRCULATION. mosing vessels. The larger parts of the longi- tudinal vessels have been observed to contact and dilate; but neither a regular progressive circulation, nor a connection of the vascular with any distinct respiratory system has as yet been detected. Entozoa. — In the Entozoa, organs of circu- lation somewhat similar to those just mentioned in the Planarias have been found by Bojanus and Mehlis in the Distoma and Tristoma, and by Nordmann* in those remarkable small Entozoa inhabiting the aqueous chamber of the eyes of some quadrupeds, the Diplosto- mum, and in the Diplozoon. In the first of these animals, the motion of fluid in the vas- cular system is exceedingly obscure ; but in the Diplozoon (fig. 328), Nordmann saw, with Fig. 328. Diplozoon. a high magnifying power, currents moving in opposite directions in two sets of vessels (n, v) placed on each side of both limbs of the ani- mal. These vessels, termed external and in- ternal, are said to terminate posteriorly in a dilated bag, to which Nordmann gives the name of receptacle of the chyle. The organs of circulation of the Diplozoon differ, there- fore, in this respect from those of the Planaria, to which otherwise they bear considerable si- milarity; for, in the latter animal, the vascular system appears to be entirely closed. Accord- ing to Nordmann and Ehrenberg no contrac- tions or dilatations of the vessels are visible. AcalephtB.— In some of the Medusa tribe, or Acalephse, there appears to be no distinct circulatory apparatus ; and we observe that in these instances, the alimentary cavity is of great extent and is often much ramified on the surface of the animal. In others there are distinct vessels with a * Micographische Beitragc, p. 69. Berlin, 1832. circulation of fluid within them. The distri- bution of this very simple kind of vascular system was first discovered by Eschscholtz, who has described its form particularly in theCestum and Beroe. In the latter animal, it is stated that eight arterial vessels and two veins unite with a large annular vessel which surrounds the mouth, and, according to Eschscholtz's* conjec- ture, another vascular ring, situated at the pos- terior extremity of the body, forms the means of communication between the arteries and veins in that region. Branches pass from the external or arterial vessels, and from the in- ternal or venous vessels to the fins, which organs seem to serve at once for respiration and for locomotion. Although the motion of a yellowish fluid containing globules has been seen in these vessels, the complete circulation does not appear to have been made out in a satisfactory manner. Infusoria. — Some kind of circulation is stated to have been observed by Ehrenberg in some of the Infusoria; but this is an observa- tion which, with every confidence in the ac- curacy of this celebrated microscopic observer, we feel inclined to consider as liable to fallacy, on account of the prevalence of various kinds of ciliary currents in the interior of many of these animals. Polypi. — We would extend the same remark to the last kind of circulation to which we shall allude, viz. those singular currents of fluid, which were discovered by Cavolini and recently observed by Mr. Lister in some of the Polypiferous Zoophytes. According to the latter observer, in each of the divisions of the stem of the Tubularia indivisa, a cur- rent of fluid carrying globules along with it is seen proceeding up one side and down the other. In various Sertulariae, the direction of the current becomes reversed from time to time. Similar phenomena are to be observed in Campanularise and Plumularias. The striking analogy which these currents bear to those occurring in the stems of some plants, as Chara and Caulinia, seem to us to bring them under another class of phenomena than those of the vascular circulation of the higher ani- mals. We do not, however, intend to enter upon the consideration of this subject, as it is already fully treated of under the article Cilia. In concluding our notice of the simpler forms of the circulatory organs, we would re- mark that one of the great difficulties which retards the acquisition of an accurate know- ledge of the function of circulation in the lowest classes of animals, proceeds from oar inability to determine, whether currents moving within enclosed spaces in these animals belong to the circulation of their blood and nutritious fluids, or are connected with respiration, loco- motion, and other processes of their economy ; and this is an obstacle to the progress of the investigation which from its nature we cannot hope soon to see removed. * System der Acalcphen. Berlin, 1829. See the article AcalephiE, p. 43. CIRCULATION. 655 In the Planaria, Medusa, some Entozoa, and Polypi, the subdivided or ramified cceca of the alimentary cavity (Jig 328, I) must obviously contribute to the effect of furnishing a supply of digested matter to the different regions of the body, and of thus rendering a distinct vascular system in them to a certain extent unnecessary. But in these simpler kinds of animals, and even in those of them in which distinct vessels have been discovered, we cannot regard such scattered tubes as the only principal means of distributing the nutri- tious fluids to the different parts of the body. They may assist in bringing this about ; but it is also necessary to suppose the occurrence of an interstitial movement or organic transuda- tion of the fluids, in order to furnish to all the parts the materials for assimilation. III. Phenomena of the circulation and POWERS MOVING THE BLOOD. In proceeding to the third division of our subject, viz. the phenomena of the circulation and the powers by which the blood is moved, we would remark, that, however desirable it might appear in a systematic work of this kind to treat of these two subjects under distinct heads, such a separation would have the effect of detaching inconveniently the facts from the legitimate conclusions which may be drawn from them. We shall first state the phenomena and causes of the motion of the blood which belong strictly to the organs of circulation themselves, and afterwards shall treat of various circumstances connected with the other functions by which the circulation is modified. In this view it is our chief object that the facts adduced should bear upon the explanation of the motion of the blood in the human body, but from the nature of the investigation the facts themselves must be drawn chiefly from experiments made upon the lower animals. Of course those experi- ments and observations which have been made on Mammiferous animals have most value in relation to such a view of the function as that which it is our intention to give. The order which we shall follow is founded on the course which the blood pursues. We shall treat, 1, of the passage of the blood through the heart ; 2, of its flow in the arteries ; 3, of its passage from the arteries to the veins through the ca- pillaries ; and 4, of its flow in the veins. 1. Flow of the blood through the heart. — That the muscular contraction of the heart is, in man and in all animals in which this organ exists, the principal source of the power by which the blood is propelled in its course, seems to be satisfactorily proved by the facts, that whenever the action of the heart ceases or is impeded, the whole circulation ceases, and that, when an obstruction prevents the action of the heart from reaching the blood in any of the bloodvessels, the flow of blood ceases almost instantaneously in all the branches proceeding from the obstructed vessel. The constant and regular persistence of the contractions of this muscular organ from the commencement of life to its termination, the early period at which it begins to act in the foetus, viz. before any re- gular circulation of blood takes place, and the existence of a heart or some similar contractile organ in all those animals in which a regular circulation of blood or nutritious fluids occurs, are confirmatory of the view suggested by direct observation and experiment. Under the article Heart will be found a detailed account of the structure and functions of this organ ; in this place we shall only state, in as few words as we can, what seems to have been best ascer- tained regarding its action, in so far as this appears to have a reference to the force of im- pulsion and direction which it communicates to the blood. The action of the heart may be observed by opening the chest of a living animal, or for a short lime in one immediately after death, or best of all in an animal deprived of sense and motion by poison, and in which artificial respira- tion is maintained ; it has also been seen in chil- dren born with ectopia cordis, or in persons in whom from accident a part of the heart has been exposed to view. When observed under one or other of these circumstances, the action or contraction of the whole heart is seen to consist of two motions, viz. 1, the contraction or systole of the auricular part, and 2, that of the ventricular part of the organ. The con- traction of the auricle immediately precedes that of the ventricle and seems to be continued into it, and the systole of each cavity is imme- diately followed by its diastole or relaxation.* After the relaxation of the ventricle, there is a period of repose, or a pause in the action of the heart, during which motion seems to be nearly suspended. At the moment when the systole of the ventricle takes place, the heart appears to be diminished in all its dimensions, and exactly at the same instant of time, the apex is seen to be moved towards the sternum, in whatever position the animal is placed. This tilting forwards of the apex gives the heart a pulsation against the ribs that can be felt externally. This pulsation probably de- pends on the arrangement of the muscular fibres of the heart, as the raising of the apex occurs when the heart is removed from the body and is empty of blood. At the time of the systole the heart is thicker and more conical in its figure than during the diastole ; when held in the hand it feels hard, and the ventricles appear to have propelled the whole of the blood out of their interior, as far as one can judge from the great diminution in their size. In the inferior animals, as Reptiles and Fishes, its colour is lighter from the expulsion of the blood. During the relaxation or dias- tole, the heart appears to fall away from the * In some of the lower animals, in the fuetus of the Bird at an early period, and in warm- blooded animals when the action of the heart is weakened, as at the approach of death, the con- traction is seen to begin in the venous sinus of the auricle, extend through it to the ventricle, and from one part of the ventricle to another in a gra- dual manner. In the Batrachia, the contraction begins in the veins, and after passing through the auricle and ventricle, extends into the commence- ment of the aorta. 656 CIRCULATION. chest, its parietes become flaccid, and it as- sumes a flattened form. The pulse in the arteries, which is in truth nothing more than the communication of the impulse of the heart along the blood in these vessels, corresponds, at least in the larger arteries near the heart, very exactly in time with the ventricular systole and the beat on the walls of the chest. The action of the heart is accompanied by two sounds, that can be heard on applying the ear to the cardiac region. The first of these sounds is synchronous with the systole of the ventricles, the second with their diastole ; the second follows the first immediately, and is succeeded by an interval of silence. Of the space of time in which a full action of the heart is completed, the systole of the ventricle occu- pies nearly a third, the systole of the auricle less than a quarter ; the dilatation of the ven- tricle and repose taken together must be effected in the remainder. The heart, from its structure and action, may justly be considered as a living or self-moving double forcing-pump, which is continually filled at one part and emptied at another. During one-third of the time of a complete action of the heart, the blood in the arteries is impelled onwards by the direct impulse of the ventricles at their systole. During the other two-thirds of the time, while the ventricle is inactive, the communication between its cavity and the great arteries is stopped by the closure of the semilunar valves, and the blood must, therefore, at this time be propelled by the elastic and other forces of the arteries them- selves. But the heart continues to receive blood from the veins during a longer time than it gives out any of that fluid, for the auricles offer a resistance to the entrance of blood du- ring only a space of less than a quarter of the time employed in a complete action of the heart, and the blood is continually impelled into the auricles as well as the ventricles du- ring the whole time that these cavities are not contracted, although more blood enters the auricles immediately after their relaxation, and more is propelled into the ventricles just be- fore their contraction than in the rest of the time. During the systole of the ventricles, while the stream of blood issues from their cavities into the first adjoining parts of the large arteries, the folds of the semilunar valves are laid close to the inner side of these vessels. As soon as the contractile force of the ventricles ceases, the free edges of the semilunar valves are brought towards the middle of the vessel, and applied firmly against one another so as to close the ventriculo-arterial orifices : this is effected by the pressure of the column of blood acted upon by the elastic coats of the arteries, assisted perhaps by the elasticity of the borders of the valves themselves and by the change of position consequent on dilatation of the ventricles. During the systole of the ventricles, the auriculo-ventricular or tricuspid and mitral valves are closed, so as to prevent in a great measure regurgitation of the blood from the ventricles into the auricles. When the ven- tricles are in the relaxed state, the valves are opened by the stream of blood flowing from the auricles. The circumstance that the free margins of the mitral and tricuspid valves are bound down to the inner walls of the ventricles by the tendinous cords at- tached to the fleshy pillars, and that, by the contraction of these pillars, the free margins of the valves mnst be pulled further down into the ventricle than in the relaxed state, has occasioned to some a difficulty in under- standing their action, and led them to suppose that the columns carneae must necessarily be relaxed at the time of the ventricular systole, and that by contracting while the ventricle is in its diastole, the fleshy pillars contribute to open the valves. The direct observation of the contraction of the column* carneae in the heart of an animal taken from the body, and an attentive observation of the structure of these valves, from which it appears that the tendinous cords passing to opposite flaps of the valves frequently come from the same columnce carneae or point of attachment in the ventricular paries, sufficiently prove that these fleshy pillars actually contract at the same mo- ment as the rest of the parietes of the ven- tricles, and that their contraction, besides drawing the free margins of the valves down- wards into the ventricles, must also tend to make them approach one another more nearly ; and we are therefore entitled to form the con- clusion, that, while the tendons serve to fix the valves, the action of the columnae carneae is to draw these down so as to allow the blood to pass behind them, and to press them to- gether and close them in the same manner as the semilunar valves of the aorta and pulmo- nary artery are shut. The apparently greater facility of the en- trance of blood into the heart at one time than at another, has given rise to the opinion enter- tained by some physiologists that the dilatation of the heart is, like the contraction, accom- panied with the production of a new force, which draws the blood from the veins towards the heart. Some who regard muscular elon- gation as a source of new power have gone so far as to suppose that this force is even greater than that accompanying contraction, but it is manifest that such a view is opposed by every thing we know of muscular action, which leads to the belief that the shortening of muscular fibre ought alone to be considered as an active, and the subsequent elongation as entirely a passive change. Others suppose the ventricles of the heart to dilate in consequence of elas- ticity, in the same manner as a bag of caout- chouc does after being compressed with some degree of force. Attempts have even been made to measure the extent of the force pro- duced during the dilatation of the ventricles, by endeavouring to ascertain the weight which is displaced by this motion of the heart. We would not wish to be understood to deny the possibility of the heart's exerting some slight force in this way during its dilatation, but it appears very clear that a measurement of the CIRCULATION. 657 kind referred to must be so difficult as to be almost useless; indeed, it is very probable that some have mistaken the contraction for the dilatation, and we shall afterwards find that the power of suction, exerted by the heart on the blood, as measured by the force with which the veins are emptied, is very small indeed. It is clear that the blood driven on from behind by a propelling power, or flowing through parts which are pressed upon by neighbouring organs, must enter the heart more easily during the relaxation of the pa- rieles of the ventricle than at any other period during the heart's action, so as to give rise to an appearance of suction, but direct expe- riments make it sufficiently obvious that the force of impulsion from behind is almost the sole cause of the entrance of the blood from the trunks of the great veins into the cavities of the heart. In order to form an estimate of the time in which a given quantity of blood may pass through the heart, or of the time in which the whole quantity of blood contained in the body would take to pass through the heart, several data are required which are not yet furnished by accurate experiments. In the first place, we must know the average quantity of blood contained in the body, and, in the next place, the quantity which is evacuated from the heart at each stroke or systole of the ventricles. Witli regard to the first of these points, a number of calculations have been made which vary greatly in their results. Animals have been bled to death by the section of the larger bloodvessels, and the quantity of blood lost has been measured. The quantity of blood lost in this way seems to have varied from l-10th to l-30th of the weight of the whole body, and Dr. Moulins, who formed his estimates from experiments of this kind, rated the quantity of blood in the human body at eight or nine lbs. only, or l-20th of the weight of an average sized man, taken at 150 or 160 lbs. But it is obvious that when one of the larger bloodvessels is opened, from the suddenness of the flow, the animal faints or dies before the whole or even a considerable proportion of the blood has been lost; and it has been ascertained from numerous obser- vations, that when the blood flows more gra- dually and from small vessels, as occurs in hemorrhages from the nose, stomach, rectum, or uterus, a proportionally much greater quan- tity of blood may be lost than occasions death in animals experimented upon by the section of the larger arteries or veins. Instances are on record in which from ten to twenty lbs. and even greater quantities of blood have flowed from the human body within twenty- four hours.* We feel inclined on these grounds to coincide with the estimate formed by Haller, that the blood forms about a fifth of the weight of the body, or equals from twenty- five to thirty lbs. in a man of the average weight of 150 lbs. It is obvious that this * See Mailer's Elemen'a, and Keill on the An. Eeon. must vary in different individuals from other circumstances besides a difference of stature. In the young, the quantity of blood is con- sidered to be greatest. Of the whole of the blood contained in the body, it is estimated by Haller, and probably with accuracy, that four parts are contained in the arterial and nine in the venous system. In endeavouring to estimate the quantity of blood which passes through the heart in a given time, we must find the capacity of the cavities of the heart, we must ascertain whe- ther the cavities on the two sides are of the same size, and, as it is almost impossible to measure the quantity of blood evacuated from the heart at each stroke, we must find to what extent the ventricles empty themselves during their systole. It is obvious that, so long as the circulation is uniform and no local accumu- lation of blood takes place, the same quantity of blood must pass out of the ventricles into the larger arteries which enters by the veins, and for the same reasons, that the quantity of blood passing through the right and left cavi- ties of the heart must be exactly equal. The circumstance that an equal quantity of blood passes out of the right and left cavities of the heart during their systole does not entitle us to conclude that the capacity of the different auricles and ventricles is the same, because any one of them during its systole may be more or less completely emptied than the rest, and a regurgitation obviously takes place from some of them, so that the whole blood which they contain is not propelled in its onward course. According to some anatomists the au- ricles are larger in capacity than the ventricles, probably in the proportion of three or two and a half to two, and the auricles are by no means completely emptied during their systole. An opinion has very generally prevailed that the cavities on the right side of the heart are some- what larger than those on the left. There is no doubt that in making measurements of the rela- tive capacity of the two sides after death, it is most frequently found so; but it is obvious that some have very much overrated the difference, and there is much reason to believe that the greater capacity of the right auricle and ven- tricle depends in part on the accumulation of blood which generally takes place in most kinds of slow death in the pulmonary arteries, and in part also upon the greater thinness and consequent distensibility of the right ventricle. In men dying suddenly, and in animals killed purposely, in which the pulmonary artery is opened so as to allow of the free egress of the blood from the right side of the heart, the capacity of this ventricle is not greater than that of the left, and the proportions of the capacity of the two sides of the heart usually found after slow death are sometimes reversed when a ligature is placed on the aorta and the pulmonary artery is opened.* Most authors seem to have agreed to follow the estimate of the capacity of the ventricles given by Hales in his Medical Statics. This author esti- * Sabaticr. 658 CIRCULATION. mates the capacity of the left ventricle at 1§ oz. fluid measure, and that of the right at 2 oz. The contemplation of the muscular structure of the left ventricle, and the great diminution in size it undergoes during its sys- tole, would induce us to conclude that it must be completely emptied during the contraction, and that there cannot remain any blood even among the columns carneae. The right ven- tricle does not appear from the quantity of its muscular substance to be so well suited to be emptied, but its position round the left must assist considerably in the diminution of its size during its systole. In some cases of sud- den death in healthy persons, both ventricles have been found completely empty. The whole of the blood issuing from the ventricles into the first parts of the great arte- ries is retained within these arteries by the action of the semilunar valves, and it would appear that in the healthy condition the adap- tation of these valves is such that very little if any blood regurgitates or flows backwards into the ventricles. At the time that the auri- cles contract, a very different phenomenon presents itself, for while a certain quantity of the blood from the auricles passes onwards into the ventricles, some is driven back into the orifices of the great veins. This venous re- gurgitation is particularly evident in the veins connected with the right side of the heart, the orifices of which have no valves or very im- perfect ones ; and it gives rise to a pulsation in their larger branches, synchronous with the systole of the auricle, as may be seen in most thin persons in the jugular vein at the lower part of the neck. It would appear that upon some occasions, even in the state of health, a certain back stroke from the ventricles also is perceptible in the veins, and Hales was of opinion that some of the blood (half an ounce) from the right ventricle flowed back into the auricle during each systole of the ventricle. It must be apparent that immediately after the auricle has ceased to propel its contents into the ventricle, and just when the systole of the ventricle begins, the column of blood extend- ing from the ventricle into the auricle through the auriculo-ventricular orifice must be con- tinuous, and the pressure of the ventricular systole must thus be transmitted upwards until the valves flap together and close that opening. Accordingly, in some persons in health, a ve- nous pulse, synchronous with the ventricular systole, is occasionally seen or felt in the jugu- lar veins, but this appearance is much more commonly a sign of disease ; for the venous pulse which is synchronous with the ventri- cular systole is much increased when an ob- stacle presents itself to the free flow of blood through the pulmonary artery, or when from ossification or other morbid alteration, the auri- culo-ventricular valves do not close accurately the passage in whieh they are placed. We may conclude, from the observations above alluded to, that on an average each of the ventricles of the heart gives out nearly one ounce and a half at each stroke ; and we may now state the general calculation of the time that the blood takes to move through the heart, which is generally founded upon the above data. Let us suppose the heart to beat seventy- five times in a minute, which is nearly the ave- rage number of pulsations in a healthy man in the prime of life, and assume the quantity of blood in the body at 28 lbs. ; and let us sup- pose that 1 1 oz. of blood is expelled from each ventricle into the great arteries connected with them, then 112 oz. or 7 lbs. of blood would pass through each ventricle in a minute, and 28 lbs. in four minutes ; or in three minutes, if the quantity of blood passing through the ventricles at each systole be estimated at two ounces, i. e. a quantity of blood equal to that which we conceive to be contained in the whole body, would flow through the heart in the short space of four minutes, and this quan- tity would run the same course fifteen tiroes in an hour. We must guard against conceiving, on the one hand, that this calculation affords any accurate measure of the quantity of blood which actually passes through the ventricles in a given time, for there are innumerable circum- stances which tend to cause this quantity to vary to a considerable extent ; and on the other hand, it must at all times be borne in mind that we can, from such calculations, estimate only the velocity of the blood in the heart itself, or the time which a certain quantity of blood takes to pass through its cavities, but that we are not furnished with any measure of the time that the whole of the circulating quantity of blood actually takes to pass through its course, for the length of the courses through which the blood has to pass in different parts of the vas- cular system varies to such a degree, that in some places, as for example in the bloodves- sels of the heart itself, the return to the heart must be effected in less than half the time employed by that which is transmitted to the extremities. On comparing the longest or shortest calculations of this kind made by dif- ferent authors, we shall find that the time of a circulation is made to vary from six minutes and a half to one minute. We shall not at present enter upon the con- sideration of the force with which the blood issues from the left ventricle of the heart, as the experiments by which this force is deter- mined being made upon the arteries, come more suitably to be treated of under the arte- rial circulation. 2. Phenomena of the arterial circulation. — In proceeding to consider the phenomena and causes of the flow of blood through the arterial system, we purpose to treat of, 1st, the velocity; 2d, the force of the blood in the arteries ; 3d, the nature of the arterial pulse ; 4th, the vital properties of the arteries; and 5th, the influence exerted by this class of bloodvessels on the cir- culation. We shall find that, in this part of our subject, the difficulty of becoming ac- quainted with the immense variety of circum- stances capable of modifying the flow of the blood, has prevented the explanation of pheno- mena which arc in themselves sufficiently sim- ple and apparent. In our remarks upon the above-mentioned topics, we shall endeavour to CIRCULATION. C59 refer the phenomena of the circulation, as far as we can, to hydraulic principles, which, when correctly applied, must form the only sure guide in conducting a physiological inquiry of this nature. The flow of the blood, as it is expelled from the left ventricle, may be said to be intermit- tent, for it moves only at the time of the ventri- cular systole. Farther on in its course, in the larger as well as the middle sized arteries, the flow of blood is remittent, or is more rapid after each beat of the heart, and by the time it arrives at the capillary vessels and commence- ment of the veins, the velocity is rendered per- fectly uniform. The effect, therefore, produced by the arterial tubes is to convert an intermittent, first into a remittent, and afterwards into a uni- form force. When an opening is made into one of the larger arteries, the jet of blood which issues is regularly increased in velocity at every systole of the ventricle. In the very small ar- teries, this acceleration of the stream becomes less perceptible. We know that it has altoge- ther disappeared in the smallest vessels or ca- pillaries, from microscopic observation of the flow of the blood in them, and the uniformity of the velocity of the stream in the veins is clearly shewn in all instances in which a vein is opened, as in the common operation of bleeding from the arm. Various circumstances shew that in the living body the blood forms an uninterrupted column of fluid in the bloodvessels, and that the whole vascular system is kept in a state of forced dis- tension by the reiterated impulses communi- cated to the blood by the ventricular contrac- tions. Besides the general fulness of the blood- vessels and their connection with the heart, we may mention as proofs of the distended state of the vascular system, the facts, 1st, that, on opening any of the bloodvessels, the blood issues with greater force at the first moment than afterwards ; and 2d, that when we imitate the propulsion of the blood through the arteries and veins by artificial injection of fluids in a dead animal, we observe that the jet from an opened vessel continues to flow for some time after we have ceased to drive the piston of the syringe. The arteries being much stronger than the veins, re-act with greater power than they do against the distending force of the heart. Were the arteries rigid tubes, it is ma- nifest that in a given time just as much blood would pass from their remote extremities into the commencement of the veins, as enters them by the mouth of the aorta; but the arteries must be fuller at one time than another, for the quantity of blood expelled from the ventricle at each systole, must pass suddenly into the first part of the aorta, while an equal quantity of blood, which must necessarily pass from the remote arteries into veins, as it moves uni- formly, must employ the whole period of time occupied by a complete action of the heart in its passage; and consequently it is manifest, that the arterial system must be fuller just after than immediately before the contrac- tion of the ventricle. The arteries are distensi- ble and elastic, they yield a little to every suc- cessive stroke of the ventricle, and during the diastole they re-act by their elasticity, so as to keep up the flow of blood. We have already said, in speaking of the heart, that the muscular contraction of that organ is the chief, if not the only source of the power propelling the blood. It is only in those arteries which are nearest to the heart, however, that the blood can be said to be propelled by the direct impulse of the ven- tricle, for in the rest of the arterial system, the progression of the blood is immediately effected by the elastic power of the arteries, called into operation in consequence of their distension by the action of the heart. In the experiments of artificial injection of the bloodvessels in dead animals already mentioned, as long as we con- tinue to drive the piston of the syringe, and to propel fluids through the arteries into the veins, the arteries are kept in a state of forced disten- sion ; in consequence of this, the fluid issues from an opened artery with a jet accelerated after each successive stroke of the piston, and continues to flow for some time after the pro- pelling power has ceased to act. The unifor- mity of the stream of fluid from the veins, which occurs in the same experiment, is a proof that the continued flow of blood in these tubes may, in the living body, be owing to an impul- sion from the heart, transmitted by the arteries, and that it is caused by the elasticity of the coats of the vessels themselves. a. Velocity of the blood in different arteries. The space of the aorta filled up by the blood propelled from the ventricle at each systole, divided by the time occupied in its propul- sion, constitutes the velocity of the blood in the first part of the aorta. The diameter of the aperture of the aorta at the ventricle being taken as on an average 1-1 2 of an inch,* its area would be one square inch, and consequently 1£ oz. which equal 2-45 cubic inches of blood, would occupy a little more than 2-5 inches of the aorta, supposing its size to be for such an extent of a uniform diameter. As it is satisfactorily ascer- tained by actual measurement, that the blood contained in the smaller vessels is in much greater quantity than that in the larger trunks ; or, in other words, as the capacity of the smaller vessels taken together is greater than that of the larger, it will at once be apparent, that the velocity of the blood must diminish in passing from the larger to the smaller vessels. The arterial and venous vessels may in fact be re- garded as two hollow cones, curved so as to be joined at their apices to the heart, and at then- bases to one another. The veins, being more numerous and wider than the arteries, must be represented by a wider cone. The section of these cones at any place is supposed to give the combined area of the section of the vessels at a corresponding distance from the heart. The estimates made by different authors of the relative velocity of the blood in the larger and smaller vessels, differ in a great degree, * The aperture of the aorta is somewhat less than one inch in diameter in most persons ; we may, however, adopt the above estimate of its size, as the sinus of the aorta is much wider than its aperture. 660 CIRCULATION. and are exceedingly unsatisfactory. Haller, who fully admitted the greater capacity of the smaller arteries, and allowed that the flow of the blood must therefore, from hydraulic prin- ciples, become less rapid in passing from the trunks to their branches, — a proposition which he illustrates by comparing the stream of blood in its passage to a river which enters a lake, — was yet inclined, from the result of his actual observations, to deny that the velocity is much less in the smaller than in the larger arteries. Spallanzani, although admitting more explicitly still than Haller the necessity of such a retarda- tion, seems to have met with the same difficulty in reconciling theory with his attempts to mea- sure the velocity of the blood in the small ves- sels : and both these authors state, that although the circulation was in general comparatively slow in the web of the frog's foot, still in many instances in this situation, and more frequently in the mesentery, they were unable to detect any difference in the rapidity of the flow of the blood in the larger and smaller arteries.* Hales, again, states as the result of his ob- servations and measurements, that the velocity of the blood in the smallest capillaries of the abdominal muscles of the frog, is so small as one or one and a half inch in a minute; and, from the attempts which we ourselves have made at these measurements, we feel inclined to agree with the statement of this able experi- menter, having, upon several occasions, ascer- tained that in those capillaries which admit only two globules of blood, the velocity is not greater than the hundredth part of an inch in a second ; but it seems doubtful whether in all the capillaries the velocity is so small as in those just alluded to, and in the larger capillary vessels of the diameter of six globules, when no unnatural obstruction to the circulation in the limb occurred, independently of the diffi- culty of fixing the eye upon any globule in such a way as to trace its progress along the vessel, the velocity has always appeared so great as to prevent the possibility of measuring it; and we are at a loss to conceive in what manner Haller made the comparison he speaks of between the velocity in the larger and smaller arteries. By means of the microscope, it is easy to see that the velocity is greater in the small arteries than in the corresponding veins, which are both more numerous and considerably larger than the arteries. The results of actual observation of the flow of the blood and of the measurement of the relative capacities of different arteries, afford as yet very unsatisfactory data upon which to found an estimate of the relative velocity of the blood in the trunks and branches of the arte- ries. In the absence of more direct means of calculation, an approximative estimate may be made in another way, viz. by comparing the quantity of blood which occupies a known space of the larger vessels with the whole quan- tity of blood contained in the body. We have already seen that the whole blood * Haller appears to mean here arteries of consi- derable size. in the body may be estimated at nearly thirty pounds : now, let us suppose the aorta and pulmonary arteries, together with their return- ing veins, to form a continuous tube of the length of the two courses of the blood, in the systemic and pulmonic circulations, and of the same diameter as these vessels at their point of junction with the heart; a very simple calcula- tion shews us that such a tube is capable of holding only about six pounds and a quarter, or less than a fourth part of the whole blood of the body ; or in other words, were the aggre- gate capacities of the small vessels no more than equal to that of the larger, they would be capable of holding only a fifth of the blood contained in the body. The velocity of the blood in the commence- ment of the aorta may be considered as two and a half inches in a second, for this is the space occupied by all the blood which is pro- pelled into the aorta from the left ventricle in that time, and according to the arbitrary modes of estimating the relative capacity of the aorta and its branches here employed, the velocity of the blood in the aortic capillaries generally, might be considered as one-fourth of that in the commencement of the aorta, or nearly half an inch in a second, a result widely different from that obtained by Hales. Attempts have also been made to estimate the velocity of the flow of blood, by ob- serving the time which certain substances, when introduced into one part of the vascular system, take to pass to another. The most remarkable series of experiments of this na- ture with which we are acquainted were per- formed by Hering.* This author states that he has been able to detect prussiate of potassa, which he had introduced into one of the jugu- lar veins of a horse, in the blood drawn from the opposite jugular vein in the space of from twenty to thirty seconds ; and he has formed the conclusion from this experiment that the prussiate of potass, in order to gain the jugu- lar vein on the opposite side of the body, had passed in this remarkably short space of time through the whole course of the double circu- lation : that it was first carried to the heart, then passed through the pulmonary arteries and veins, and returned to the heart, from which it must have been transmitted through the ultimate ramifications of the systemic ar- teries before being brought back by the veins, in which it was found on the opposite side of the body. Hering states, as the result of other experiments of a similar nature made upon different bloodvessels, that the prussiate of potassa passed from the jugular vein to the saphena vein in twenty seconds ; to the mas- seteric artery, in fifteen to twenty seconds ; to the external maxillary artery, in ten to twenty- five seconds ; to the metatarsal artery, in twenty to forty seconds. We consider these curious experiments as important in many points of view, but do not feel inclined to concur in the conclusion de- duced from them by their author, that the * Ticdcmann's Zeitschrift, vol. iii. p. 85. CIRCULATION. circulation of the blood, rapid as it may be, takes place in this remarkably short space of time, and we are disposed to suspect that the experiments themselves are liable to several sources of fallacy. The tendency of the prus- siate of potass to permeate the textures of the body, more freely than any other substance known, has been proved by many expe- riments, and it is therefore necessary that Hering's experiments should be performed with some other substances, before they can be re- garded as a correct means of estimating the rapidity of the circulation. The velocity of the blood is generally be- lieved to be greater in the pulmonic than in the systemic circulation, — an opinion founded chiefly on the supposed less capacity of the vessels belonging to the pulmonary trunks. Actual measurements of the velocity of the blood in the capillaries of the lungs of cold- blooded animals by Hales, Spallanzani, and others, would seem to give support to this view, but it must at the same time be re- collected that the course through which the blood passes in the pulmonary or lesser circu- lation, is considerably shorter upon the whole than that of the systemic or greater, — a circum- stance which must diminish to a certain extent the disproportion in the velocity.* b. Force of the blood in the arteries and force of the heart. — Another interesting inquiry con- nected with this subject relates to the force with which the blood is impelled in the arte- ries, and the calculations that have been made of the power of the heart itself, from the ob- servation of the force of the blood in the arte- ries. The experiments made with a view to discover these forces appear sufficiently simple in their nature ; but the calculations founded upon the experiments have differed so widely, as to have furnished a plausible pretext for throwing ridicule on the application of physical laws to the living animal functions. As the arteries and other vessels are kept distended with blood by the action of the heart, it follows that were they rigid tubes, the force of the heart would, in accordance with the laws of propagation of pressure through fluids, be transmitted without loss through the whole column of blood in the arteries at one and the same moment : but in consequence of their yielding to distension, the force of the heart operates upon the blood only through the elastic reaction of the coats of the arteries. When an opening is made into one of the larger arteries, the blood issues with force, and spouts to some distance, but the height to * In reference to the above calculations, it must also be kept in mind, in the first place, that the estimate of the velocity of the blood in the pul- monic circulation in the frog can scarcely with propriety be applied to man, seeing that in the frog the pulmonary artery is only a branch of the aorta; and, in the second place, that in animals with a double circulation, although the quantity of blood which leaves both sides of the heart at each systole be equal, it does not necessarily follow that the whole blood which circulates through the system should in the same time pass through the lungs. which the blood rises when allowed to escape from a simple aperture in an artery varies from many accidental circumstances, and cannot therefore be taken as affording an accurate measure of the force with which the blood moves within the vessels. Hales seems first to have investigated this force in a more accurate and experimental manner, by observing the weight which the blood in one of the arteries of a living animal is capable of sustaining within a tube adapted to it. He remarked that the blood issuing from a simple aperture in the carotid artery of a horse and directed upwards did not rise above three feet,* but that when the blood was allowed to pass into a long glass tube adapted to the same artery it rose very quickly to a much greater height, as to nearly ten feet in some of the experiments. Hales performed similar experiments on the arterial flow in sheep, oxen, dogs, and other animals, and after observing for each the pressure which the blood in the arteries is usually capable of ex- erting, he endeavoured to compute the pres- sure of the blood in the arteries of man, by a comparison of the size of his whole body or heart and bloodvessels with those of the other animals. The pressure of the blood in the aorta of the horse being considered as eleven pounds, Hales estimates in the way above- mentioned the force of the blood in the human aorta at 4 lbs. 6 oz. ; seven and a half feet being the height to which he supposed that the blood would rise in a tube connected with the larger arteries of a man. These experiments of Hales shewed in a very clear manner, that the height to which the blood rises in one of the larger arteries affords us the means of ascertaining directly the amount of pressure which the stream of blood impelled by the heart through the arte- ries is capable of exerting at any part of the arterial system, or in other words it gives us a measure of the statical force of the heart as it operates through the arterial tubes.f According to a well-known law of physics, the heart must be pressed upon in every part of its internal surface by the column of blood which it has raised; so that by multiplying the area of the internal surface of the ventricle into the height of the column of blood sup- ported in the tube connected with an artery, we shall ascertain the pressure which acts backwards on the inner surface of the heart. Hales estimates the inner surface of the ven- tricle of the human heart at fifteen square inches, and multiplying the pressure of a co- * This experiment we have repeated with Mr. Dick's assistance. t These experiments, as well as others subse- quently performed, demonstrate the importance of confining our researches in an inquiry of this nature to the estimation of the statical force operating in the organs of circulation, as the only useful ob- ject of such calculations, — the propriety of which is also sufficiently apparent from the extraordinary results of the attempts to estimate the dynamical power of the heart or the whole force generated in that organ by muscular contraction, by Borelli and Bernouilli, the first of whom calculated this force to equal 180,000, the second 3,000 lbs. 662 CIRCULATION. lumn of blood of seven feet and a half high into the area of the inner surface of the heart : he hence calculates the pressure on the in- ner surface of the human heart to be nearly 51£ lbs. The pressure on the interior of the horse's heart he estimates at 113 lbs. upon similar principles. As pressure applied in any direction to a fluid column is equally transmitted through all its parts, and as the blood in the arteries forms continuous columns which all branch off from the aorta, it might a priori have teen con- cluded that the force of the blood must be the same in all the arteries of any considerable size. Hales, though he does not state this proposition very explicitly, seems yet to have taken it for granted ; for, in estimating the pressure of the heart, he takes into account merely the height of the column without re- ference to the size of the artery. We shall find this proposition to be satisfactorily proved to be correct by direct experiments subse- quently performed. The experiments of Hales were liable to two principal objections : 1st, that the coagulation of the blood in the long glass tube adapted to the artery must have prevented its free motion ; and, 2nd, that the length of the tube, besides giving rise to the necessity of frequently re- moving it and various other inconveniences, must have occasioned a considerable loss of blood in filling from the arteries of small ani- mals. Both these sources of fallacy have been provided against most successfully by M. Poiseuille,* an ingenious ex- Fig. 329. perimenter of Paris, who, by the adoption of a simple con- trivance, has been enabled to measure with great accuracy the arterial pressure of the blood, and has thus confirmed and extended the interesting re- searches of Hales. The instrument employed by Poiseuille, to which he gives the name of Hemadynamome- ter, (fig. 329,) consists of abent glass tube of the form here repre- sented, filled with mercury in the lower bent part (a, d, e). The horizontal part (b), provided with a brass head, is fitted into the artery, and a little of a solu- tion of carbonate of soda is interposed between the mercury and the blood which is allowed to enter the tube for the pur- pose of preventing its coagula- tion. When the blood is al- lowed to press upon the fluid in the horizontal limb, the rise of the mercury towards (c) measured from the level to which it has fallen towards (d) gives the pressure under which the blood moves. Magendie's Journal, vols. viii. & ix. Brcschct's Poiseuille 's He- madynamometer. Repert. d'Anat. et de Physiol. 1826. One of the most important facts established by Poiseuille's experiments is, that the pressure of the blood is within certain limits nearly the same in arteries of very different calibre and at different distances from the heart; as proved by the rise of the mercury of the hemadyna- mometer to nearly an equal height when this instrument was connected with the iliac, caro- tid, radial, facial, and other arteries in some of the lower animals. It is hence apparent, that, in order to ascertain the whole amount of force with which the blood is propelled in the aorta, or the statical force of the heart itself, it is sufficient to measure by means of the tube the momentum of the blood in any one of the arteries. Poiseuille estimates the force with which the blood is propelled in the commencement of the aorta in man at 4 lbs. 3 oz., — a result which agrees remarkably with that obtained by Hales.* Poiseuille, however, considers the pressure backwards within the heart to amount to 13 lbs. only, as he calculates this in a different way from that followed by Hales, viz. by multi- plying the pressure of the blood in the aorta into the surface of a plane passed through the base and apex of the left ventricle, — a mode of calculation which it appears that Dr. Hales had not lost sight of; for, at page 21 of the work on Hemastatics, he proposes it as the " means of estimating the force of the blood which the muscular fibres of the ventricle must resist." Poiseuille estimates the force with which the blood moves in the radial artery of man at four drachms. Hales had remarked that the blood in the tube connected with an artery rose regularly a little way at each systole of the ventricle, and remained always somewhat higher during the straining of the animal, that is, while the muscles of expiration were in action. These phenomena, known to Haller, were demon- strated experimentally by Magendie, and re- ceive a still more decided confirmation from the experiments of Poiseuille made with the hemadynamometer.f We would here remark that, it having been shewn by the above-mentioned experiments that the force of the heart is sensibly the same in the trunks and larger branches of the arte- ries, it is manifest that the angles of rami- fication and the friction of the blood against the sides of the vessels can give rise to very little if any diminution in the force of the heart transmitted by the elasticity of the arterial parittes. We shall afterwards see that the case is very different in the smaller vessels. We would also call the attention of the reader to an interesting application of the fact of the complete transmission of pressure through the fluid contained within the bloodvessels in all directions, in the immense force which the * The power of the heart has also been calcu- lated from the force supposed necessary to raise the foot of one of the legs thrown across the other in the pulsatory movement which is then seen to occur, — one of the most inaccurate methods that could be adopted. t See Part IV. of this article. CIRCULATION. 663 blood occasionally appears to exert within an aneurismal tumour; giving rise to its peculiarly hard pulsation on every side, and assisting the ravages by absorption which are frequently the consequence of the larger internal aneurisms. The pressure in an aneurism is obviously to be measured by the extent of its internal surface multiplied into the force with which the blood moves in the part of the artery where it opens into the aneurismal sac. c. Arterial puke. — The arterial pulse, or suc- cession of beats felt by the finger placed over an artery, depends upon the impulse of the left ventricle being communicated along the arterial tube and the column of blood which it contains. When a ligature is put upon an artery, no pulse is felt beyond the place where the artery is obstructed, but it is distinct up to that place. This experiment at once shews the dependence of the pulse on the systole of the ventricle, and establishes that this phenomenon is not dependent on the progressive motion of the blood, since, in that part of the artery placed on the side of the ligature next to the heart in which the pulse is distinct, the blood is at rest. Nor does the pulse appear in ordinary circumstances to depend upon lateral distension of the arteries, for such distension occurs to so small a degree as is quite insufficient to account for the produc- tion of the pulse. Arthaud,* a French surgeon, was the first who sustained, in opposition to the opinion prevalent at the time he wrote, the view that the arteries are not laterally di- lated at each systole of the heart, and that the pulse is not to be explained by such dilatation. Arthaud shewed that when an artery is laid bare, no perceptible enlargement of its calibre takes place at the time when the heart con- tracts and the pulse is felt. We have already stated that the arterial system being fuller of blood at one time than another must be dilated to admit the blood propelled into the aorta from the ventricle ; and it seems to follow from the observations of Arthaud, which have been ably confirmed by the interesting expe- riments of the late Dr. Parry,f that the en- largement of the capacity of the arteries is effected principally by their elongation. Ac- cording to these experimenters, when one of the larger arteries is laid bare, the eye does not distinguish any lateral enlargement corres- ponding to the systole of the ventricle, and Parry measured with great care the artery at the time of each pulse and between the beats without being able to detect the slightest differences in its size ; but though not percep- tibly distended laterally, the artery undergoes a certain change of place, for at each systole of the ventricle it is propelled in a direction outwards from the heart, and during the di- astole it returns to its former situation. This locomotion of the artery, as it is called, is * Dissert, sur la Dilatation dcs Arteres. Paris, 1770. t Dr. C. H. Parry's Inquiry into the Nature of the Arterial Pulse. Jiath and Lond. 1816. Dr. Chas. Henry Parry's Additional Experiments. Lond. 1819. obviously produced by the distension and elongation of the larger arteries near the heart. A considerable elongation of the arteries may also easily be seen at all sudden incurvations of these vessels. The bend of the curved part is generally increased and projected further out- wards during the systole; and we observe that a straight part of an artery, if fixed at its opposite ends, is bent at the time of the pulse in conse- quence of its elongation. In many persons in a state of health the arteries may be seen to move under the skin, although not exposed. This motion is generally perceived at places where there is a sudden bend of an artery, or where the artery lies upon an unyielding part, as bone, &c, and in some individuals an ap- pearance of dilatation or lateral enlargement even may be perceived in some of the larger arteries. Although these circumstances shew- that the pulse is not attributable to a lateral dilatation of arteries, yet it would appear that such an enlargement does occur in a small degree, for it is occasionally perceptible to the eye in the arteries when laid bare ; and M. Poiseuille,* by means of a small apparatus, capable of being applied round a part of an artery, has proved distinctly the occurrence of lateral enlargement, and estimated its extent in the larger arteries at 1-1 1th of their dia- meter. The finger laid upon an exposed artery does not feel any pulse, unless the artery be com- pressed, and when the arteries are in their na- tural situation covered by the integuments, it is only when they lie upon a hard part, as a bone, and when the sides of the artery are brought nearer to one another by pressure, that the pulse is perceptible. Those instances in which this does not appear to be the case, as well as those in which the dilatation occasionally seems to occur below the integuments, may in like manner depend upon the artery being subjected to pressure of superjacent parts at the place ob- served. It is also sufficiently obvious that the pulse does not depend upon any active change of the artery itself, or upon any vital contraction and dilatation of the vessels, for the exact appear- ance of the living pulse maybe produced in the arteries of a dead animal by injecting water into the arteries with a syringe, if care be taken to imitate with the strokes of the piston the beats of the left ventricle of the heart. A fur- ther proof of this, and an excellent illustration of the nature of the pulse, is obtained from the curious experiment performed by Bichat of connecting the bloodvessels of a living animal with those of a dead one, the result of which is the production of a pulse in the vessels of the dead animal connected with the arteries of the living one. In those instances in which a communication has been established between an artery and a contiguous vein in consequence of a wound, or in what is called Aneurismal Varix, the vein pulsates exactly like an artery. Many have remarked that the pulse in the * Sur la dilatation des Artere3 ; Magendie's Journ. vol. ix. p. 44: and Breschet's Repert. 1828. 664 CIRCULATION. arteries of the extremities is a little later than the beat of the heart on the ribs and the pulse in the arteries in the immediate neighbourhood of the heart. This retardation has of late been more distinctly pointed out by Dr. M'Donnell of Belfast,* and by Weber of Leipsig.f It is much more marked in some persons than in others, and is always most perceptible when the circulation is slowest. With a little atten- tion we can thus observe a distinct succession in the occurrence of the beat of the apex of the heart at the ribs, the pulse in the carotid, facial, radial, and posterior tibial arteries, the interval between each of which, though very small, being yet appreciable by the finger. Weber states that the retardation of the pulse in the foot after that of the beat of the heart amounts to not more than one-seventh part of a second. We have ourselves confirmed by experiments on several individuals the most of these facts relating to the later pulse in the more remote arteries. The cause of the retar- dation is obviously the elasticity and yielding of the arterial panetes ; for were the arteries rigid tubes, it is manifest that the impulse of the heart would be felt at one and the same in- stant of time throughout the whole of the branches ; but as these vessels yield to disten- sion, that part of them to which the distending force is immediately applied is first dilated, and this dilatation does not reach immediately the remote parts. The pulse has been correctly compared to the propagation of an undulation or wave on the surface of water; for the successive im- pulses of the heart are first given to the column of blood in the commencement of the aorta ; this column communicates these impulses to the arterial parietes and tends to distend them. The parietes re-act against this distending force and compress the adjoining part of the column of blood, from which the impulse passes to the next part of the aorta ; and so the pulse, gradu- ally passing on from the trunks to the smaller branches, becomes less and less perceptible as the force of the heart is equalized by the elastic resistance of the coats of these vessels. 1 The pulse is still perceptible in very small arteries: Haller§ states that he was unable to perceive any in small arteries of one-sixth of a line in diameter, — an observation which does not, however, prove the flow of the blood to be uniform or without jerks even in vessels of this size, for Spallanzani || observed pulsations in arteries of this small size; and the microsco- pic observation of the circulation in transparent parts by Haller himself, Spallanzani, and others, shews that the visible impulse of the * At the Meeting of the British Scient. Associat. in Dublin. f De pulsu in omnib. arter. plane non synchro- nico. Annot. Academ. Leipzig, 1834. $ Young's Croonian Lecture on the Functions of the Heart and Arteries, in his Introduction to Me- dical Literature. § Mem. surle Mouvement du Sang. Laus. 1756. Translated. || Exper. sur la Circulation, in French, by Tour- des. Paris, An 8. In English, by Hall. Lond. 1801. heart is communicated to the blood in the smallest of those vessels, which have distinctly the characters of arteries. The pulse being nothing else than the beats of the heart transmitted through the arteries, the consideration of the variations in force or frequency to which it is subject belongs more properly to the subject of the functions of the heart. In this place we shall only mention the mean of the usual number of pulsations of the arteries in the space of a minute as they occur at different periods of life. Child before birth 140—150 Newly-born infant 130—140 Child one year old .120 Two years 108 Three years 95 Seven years 85 Age of puberty. 80 Manhood 75 Old age 60—50 d. Vital properties of the arteries. — In the view we have hitherto taken of the arterial circu- lation we have considered the coats of the arte- ries as endowed with physical powers only, and we have alluded to no other phenomena of the motion of the blood than those which appear to be connected with their elasticity. We have now to direct our attention to the more strictly vital and contractile powers of the arteries, which constitute them an independent source of force, and to examine how far the operation of such powers may modify the flow of the blood. We shall here discuss more in detail the questions whether the heart is to be regard- ed as the only source of the power by which the blood is impelled, and the bloodvessels merely as the modifiers or regulators of the force generated by the heart's contraction — or whether the arteries do not, by their own inde- pendent power, contribute to the propulsion of the blood. Physiologists are very much divided in their opinions upon these questions, some regarding the heart as the sole moving power, some suppo- sing the bloodvessels to be the principal, the heart a subordinate cause of motion ; and others adopting various modifications of these oppo- site views. Many who agrep in considering the heart's action as insufficient to propel the blood through the smaller bloodvessels into the veins, differ as to the cause of the additional power supposed necessary for the maintenance of the circulation ; the larger and middle sized arteries being looked upon by some as highly contractile, and in consequence of this, the agents of propulsion ; the capillaries being re- garded by others as the most efficient promoters of the flow of the blood within the bloodves- sels. We must, for the present, confine our remarks to the first of these, or the opinion that the larger arteries are mainly or in part the agents of the propulsion of the blood. That the arteries have the power of changing, to a certain extent, the quantity of blood which passes through them, and of thus modifying the circulation by their own independent powers, there can be no doubt, from the occurrence of unequal distributions of blood, or of local de- CIRCULATION. 06.5 terminations of that fluid which take place in blushing, inflammation, and other states of the economy in which particular parts of the vas- cular system become more or less filled with blood than usual ; for such variations in the distribution of the blood would be impossible, were an alteration in the powers of the heart alone the only means of modifying the circula- tion. The questions, however, whether such powers as are possessed by the arteries contri- bute upon the whole to the progressive motion of the blood or modify only its distribution, are quite distinct from one another. In its anatomical structure the fibrous coat of the arteries differs considerably from muscu- lar substance, and appears to resemble more nearly the yellow elastic ligamentous tissue. Its fibres are less mixed with cellular substance than those of muscles ; they are also more dry, hard, and friable,' less coloured, and, accord- ing to Hodgkin and Lister,* are destitute of those transverse stria? or lines observed by the microscope in ordinary muscular fibres. The chemical constitution of the middle coat of the arteries differs also from that of muscle, for it is less soluble in acetic acid, and more easily so in mineral acids, and it is believed by Ber- zelius and Young not to contain the animal principle, fibrine, peculiar to muscular flesh. Although we fully admit the importance of these observations as establishing anatomical and chemical distinctions between muscular substance and the texture of the middle coat of the arteries, they do not appear to us to warrant the conclusion too hastily deduced from them by some, that this coat cannot be irritable, or does not possess any of the same properties as muscle, the existence or non-existence of which must be ascertained principally by physiologi- cal evidence. For the transverse stria; cannot be considered as characteristic of all muscular fibres; and were we to reason in this way from the result of anatomical observations only, we should be necessitated to deny the irritability of various other textures, the con- tractility of which from stimulation or without it, is universally admitted, although anatomists have not yet detected muscular fibres in them. The coats of the smaller arteries are generally believed to be proportionally thicker than those of the larger trunks, and John Hunter held the opinion that the yellow fibrous tissue exists in greatest quantity in the larger arteries ; while the smaller vessels, considered more active, are composed of a substance more nearly allied to muscular fibre. The grounds upon which the latter opinion rests are upon the whole not very satisfactory ; and it appears to be opposed by those instances in which, after the closure by ligature of the principal artery of a limb, the smaller collateral vessels which maintain the circulation, after undergoing a rapid enlarge- ment, assume the structure and general appear- ance of the large arteries. The irritability of the smaller arteries, now very generally admitted by physiologists, though * Appendix to the Transl. of Edwards's Work on the Influence of Physical Agents, &c. p. 443. VOL. I. it seems by some to have been inferred from analogy, and to have been rendered probable by Dr. Wilson Philip's observations on the effect of chemical stimuli in removing the dilated state of the capillaries in inflammation, was first distinctly proved experimentally by Dr. Thomson of Edinburgh,'* who caused the arte- ries in the web of the frog's foot to contract powerfully by the application of mechanical irritation as well as by chemical stimuli. His experiments shewed that the nature of the con- traction produced by stimulation of one of the smaller arteries varies considerably, occupying sometimes a greater or less space of the vessel, and being at other times confined to one place, sudden, and frequently so great as completely to stop the passage of blood. They also de- monstrated the fact that the contraction of the small arteries does not follow immediately the application of the stimulus, as occurs in the voluntary muscles, but that a period of from one to three minutes elapses before the contrac- tion begins, and that the vessel remains con- stricted for some time, and then returns to its original state, unless inflammation shall have occurred, in which case it dilates to a greater size than natural. The irritability of the small vessels has been fully established by experi- ments similar to those of Dr. Thomson, by Dr. Wilson Philip,f Dr. Hastings,^ Kaltenbrun- ner,§ and Wedemeyer,§ the last of whom suc- ceeded in causing the small arteries to contract by means of galvanic as well as of mechanical irritation. The constriction which follows the injection of styptic and irritating fluids into the arteries, observed by Hales|| in animals recently dead, and similar experiments by Wedemeyer, may be adduced as another proof of their irrita- bility. The stoppage of hemorrhage from cuts of the small arteries and capillaries, assisted as it is by cold or irritating applications, may be regarded as the effect of the same property. Contractions do not occur so readily or ob- viously in the large as in the very small arte- ries. Verschuir appears to have been the first who observed, in a manner not liable to fallacy, distinct contractions of the larger arteries to occur after the direct application of a stimulus. From an extended series of experiments upon this subject, described in his Inaugural Disser- tation De Vi Arteriarum Contractili, Verschuir was led to adopt the opinion that the arteries are possessed of irritability, or contract in the same manner as muscles do from irritation ; as he observed very obvious and powerful con- tractions to occur when, by means of a sharp point or chemical stimuli, he irritated the coats of the larger arteries of animals. Haller, though considering the middle coat * Lect. on Inflammation. Edin. 1813. t Introduce, to the second part of his work on Fever. X Introduce, to his work on the Inflammation of the Mucous Membrane, &c. § Exper. circa statum Sang, et Vasor. in Inflam- matione. Munich, 1826. || Untersuch. iiber den Kreislauf des Blutes, &c. Hannover, 1828. See also Koch in Meckel's Archiv. 1832, p. 121. H Statical Essays, ii. p. 124. 2 x 666 CIRCULATION. of the arteries as of a muscular nature, was un- successful in producing obvious contractions in them. The repetition of the experiments of Verschuir by many others has been attended with very various results ; some confirming his observations, others having entirely failed in producing any obvious contraction, or not being disposed to consider it of a muscular kind. Among the last may be mentioned Nysten, Bichat, Wedemeyer, and J. Midler. It must be obvious that, laying aside the difference of opinion regarding the nature of the contractions when they are admitted to occur, in a question of this kind a positive re- sult deserves more consideration than a nega- tive one, provided the phenomena stated to have been observed are such as to be appre- ciable by all. Among the experiments favour- able to the view that the large arteries are en- dowed with irritability, maybe mentioned those described by Hastings,* and a series of unpub- lished observations by Dr. Thomson, to which we have access, which seem to prove in a very satisfactory manner the frequent occurrence of contractions in the larger arteries after stimula- tion ; and to point out as a cause of the failure of some at least of the previous experiments, the long time which commonly elapses between the application of the stimulus and the occur- rence of the contraction ; together with the cir- cumstances formerly remarked by Verschuir, that the contraction is not an invariable conse- quence of the stimulation, and that it occurs much more readily in some animals than in others. According to Dr. Thomson the contraction of the larger arteries is in general not percepti- ble before from three to ten minutes after the application of the stimulus. When galvanism is used, the shocks need not be strong, but must be frequently repeated in order to induce contraction. Many have remarked the gradual or sudden contraction of the trunks of arteries which have been laid bare in Man as well as in the lower animals. When exposed, an artery is some- times equally contracted for some length along its tube ; at other times its surface assumes a waved appearance from the occurrence of irre- gular contractions or alternate contractions and dilatations, and not unfrequently the coat of the artery is much constricted at one point only, as if a tight cord had been passed round it. Appearances of this kind, which seem to indicate very distinctly the possession of the property of irritability by the arteries, are well known to many surgeons ; they were noted by Drs. Jones and Thomson, in the experiments upon which Dr. Jones's work on Hemorrhage was founded ; and also by Dr. Parry, who nevertheless refuses to consider them as irri- table contractions. At p. 74 of his work on the Powers of the Arteries, Dr. Parry, referring to Experiment 13th, says, "thus a very narrow ring of the carotid became, while it was under examination, contracted as if a * Inaug. Dissertat. Edin. 1817, et loc. cit. See also Hunter on the Muscularity of the Arteries, Edin. Med. and Surg. Journ. xxii. p. 256. small ligature had been half tightened around it." So also in Experiment 24th, he relates that a part of the carotid artery of a ewe was diminished by a third of its original diameter under exposure, after having been half an hour denuded, while the neighbouring parts had be- come rather dilated, and that while he was pro- ceeding to measure one of these dilated por- tions, he " saw it shrink to nearly the same size as the constricted part." It appears to us manifest, that, whether these irregular diminu- tions of the diameter of the artery, obviously occasioned by a shortening of its fibres, are at- tributed to the exposure of the artery to the air, or the violence done during the dissection of it by the scalpel, they must equally be regarded as the consequence of stimulation of one kind or other, and are therefore of the nature of mus- cular contractions. Hoffmann first noticed the contractions of the arteries from the application of acrid che- mical stimuli to their coats; and it appears from numerous subsequent experiments, that contractions are more readily induced in this than in any other way. Were there no other proofs of the contractility of the arteries than those derived from the effect of chemical agents, we should not feel inclined to place much reliance on them, on account of the pos- sibility of there having been induced a perma- nent alteration of the texture from chemical action ; but the results of such experiments form an important confirmation of those which are performed with mechanical and galvanic irritation. We cannot, however, acquiesce in the opinion of Wedemeyer* and others who compare the distinct and well-marked contrac- tions of particular parts of the arterial tubes, such as those above alluded to, to the general constriction of other textures, and more parti- cularly to the shrinking of the skin which occurs from the influence of cold, passions of the mind, &c. From these considerations we are induced to adopt the opinion that the contractions which under certain circumstances occur in the ar- teries resemble muscular contractions more nearly than any other vital phenomenon. The positive evidence of direct experiment obviously proves that the contractions in general follow the application of some stimulus to the artery ; but these contractions differ from that of mus- cular parts chiefly in the length of time which elapses after the application of the stimulus before the change of size begins, in the slow- ness with which the contraction is succeeded by relaxation, and in the want of obvious cor- respondence between the force of the stimulus and the extent of contractions which follow it. Besides the more marked contractions of parts of their tubes, the arteries are subject in various circumstances to undergo a slow and gradual diminution of their diameter through- out their whole length, which is considered by many physiologists to indicate the possession by them of a property of the nature of contrac- tility different from irritability in its pheno- * Loc. cit. CIRCULATION. 667 mena and the causes which call it into action. A power of a similar kind, to which the name of Tonicity is applied, is believed to reside in the voluntary muscles.* The experiments and observations generally stated in proof of the tonic power of arteries are the following : — 1. When a ligature is placed upon an artery of a living animal, the part of the artery beyond the ligature becomes gradually smaller, and is emptied to a certain degree, if not completely, of the blood it contained. 2. When a part of an artery in a living ani- mal is isolated from other organs by means of two ligatures and punctured, the blood issues from the orifice, and the enclosed portion of artery is nearly completely emptied of its con- tents. 3. The empty condition of the arteries gene- rally found after death is believed to be, in part at least, produced by a slow contraction of the whole of the large arterial tubes ; for it has been observed, that some hours after death the arteries are much diminished in size, and this occasionally to such an extent as to be rendered impervious, as was observed in the umbilical arteries of the navel string by John Hunterj and others. 4. It has been shewn by Poiseuille| that when a portion of an artery from an animal recently dead, and one from an animal that has been dead for some days, are distended with an equal force, the portion of the artery from the recently dead animal becomes more contracted after the distending force is removed than the other one. 5. In the last place, when a large artery is divided, the cut extremities frequently become so completely constricted as wholly to prevent the issue of blood, and this kind of contrac- tion is well known to occur in a greater degree after laceration of an artery than after division by the knife : hence the less danger to be ap- prehended from hemorrhage in lacerated than in incised wounds ; and thence the possibility of producing the closure of one of the larger arteries by the mere compression or torsion of its cut end. In the three last-mentioned proofs of to- nicity the contraction of the artery followed the application of some kind of irritation ; for the exposed artery was dissected out by the scalpel, and ligatures were tightened round it, the coats of the artery were stimulated by dis- tension in Poiseuille's experiment, and in the twisting or torsion as well as in the division of an artery by laceration or cutting there is always an irritation applied to the contracting part. The tonicity or tonic contractility therefore was in some of these instances first called into ope- ration and in others increased by irritation, and ought not therefore to be distinguished from irritability as regards its cause, but only as relates to its phenomena. The evacuation of the blood from arteries * Parry, loc. citat. t On the Blood and on Inflammation. t Magendie's Journ. vol. viii. beyond the place at which they have been tied in the living body, and the contraction of ar- teries which takes place in the dead body, as well as the rigidity of muscles soon after death, or their retraction when divided in the living- body, all seem to indicate a tendency in ir- ritable parts to undergo a slow and continued contraction during the persistance of their vital powers. This tendency to contraction seems to differ from the shortening and subsequent relaxation which are the more or less imme- diate effects of stimulation in truly irritable parts, and it seems to be more dependent upon the removal of the forces by which the parts in which it occurs are kept in a state of distension than upon any other cause. It is obviously in consequence of this ten- dency to contract when not distended by a force from within, that the arteries are always nearly accommodated to the quantity of blood contained in them. But while we are con- strained to admit the existence of the peculiar slow contractile power in arteries appropri- ately denominated tonicity, we would caution the accurate physiologist against considering as the effect of this property rather than of irri- tability any of those contractions of the arterial tubes which are induced or increased by me- chanical, galvanic, or other stimuli. e. Influence of the vital powers of the arte- ries on the circulation.- — Let us now inquire in what manner the flow of the blood is influ- enced by the irritability and tonicity of the arteries. Some of those who have regarded the arteries as contributing by their active powers to propel the blood have conceived it sufficient for them to prove that there is a necessity for some additional force in the circulation besides that of the heart, in consequence of the total ex- penditure of the heart's force from the windings of the small vessels, the friction of the blood against the side, and other resistances to be overcome in the capillary system. This expen- diture of the heart's power admitted by many on insufficient grounds has been very generally overrated. Although the causes just men- tioned may diminish to a certain extent the propelling power of the heart, there are various very simple experiments which shew that the heart's action is propagated with a propelling effect through the whole vascular system, so as to act in the extreme vessels and veins. In the first place, Haller, Spallanzani, Thomson, and many others have observed in the transparent parts of animals that the im- pulse of the heart is transmitted to the very ends of the small arteries, which may be less than j^jth part of an inch in diameter, and that in some states of the circulation the impulse of the heart is continued on through the capillary vessels and into the commencements of the veins. The fact that this generally occurs when the action of the heart is weakened, and when the vessels are consequently not sufficiently distended by its impulse to react by their elasticity and convert the remitting into a uniform force, is a distinct proof that in the natural state of the circulation a greater pro- 2x2 668 CIRCULATION. portion of the force of the heart must be trans- mitted through the blood to the capillaries, and must act through them upon the column of blood returning in the veins. From the same experiments it has appeared that in general the instant any obstruction pre- vents the action of the heart from being pro- pagated onwards in the arteries, the progressive current of the blood in the small vessels be- comes slower and soon ceases, any motion which goes on afterwards being quite of a dif- ferent kind from that occurring in the natural circulation. An experiment performed by M. Magendie, and formerly referred to, also affords a very satisfactory proof that the heart's force acts in propelling the blood through the whole vascular system. M. Magendie dissected the femoral artery and vein separate from the neighbouring parts, and passing a ligature under them tight- ened it round the whole limb, excepting the two principal bloodvessels, through which the blood was allowed to flow freely. He was thus enabled to shew that the flow of blood from an orifice in the vein was immediately dependent on the force of the heart acting through the artery, as it was suddenly diminished and soon completely ceased the instant that the latter vessel was obstructed, and became more or less rapid according as it was more or less com- pressed. We would further remark that the experiments of Hales and Poiseuille, more par- ticularly the latter, have shewn that there is little if any difference in the force of the blood in arteries of very different size. On the other hand, it appears to us suffi- ciently clear that the occurrence of any general contraction of the coats of the arteries would have the effect of opposing an obstacle to rather than of assisting the progress of the blood in the arteries, just in proportion to the degree of the force of the heart, which would necessarily be expended in dilating them to the required size, in order to allow of the free transmission of the blood by them; and as, according to the commonly received opinion, the contractile powers are greater in the smaller than in the larger arteries, the operation of this contraction would be much the same as the diminution of the aperture through which blood flows from an inorganic tube, and would thus cause a still greater obstruction to the flow of blood than a general contraction. It is only on the supposition that the arteries undergo an undu- latory or vermicular contraction, proceeding from the larger to the smaller branches, that this contractile force can be believed to con- tribute to the progressive motion of the blood, because then it might be conceived to assist the elasticity of the arterial parietes in propa- gating the force of the heart along the column of contained blood, and even augment this force by an additional power. But we would remark that no such vermicular action has been ascertained to occur by any observations or experiments with which we are acquainted ; that in artificial injection of fluids into the large arteries of dead animals a force of a few pounds is found to be sufficient to propel these fluids, when not of an irritating kind, from the arteries into the veins ; and that it follows from the direct experiments of many, more particu- larly those of Hales, Poiseuille, and Magendie, that the action of the heart, transmitted by the elastic arteries, is the only cause operating in the progressive propulsion of the blood in arteries of such a size as to admit of the force of the blood being measured in them. In asserting, however, that a general con- traction of this kind, if it occurred in the vas- cular system, would upon the whole obstruct or retard rather than assist the progressive motion of the blood in the arteries, we would not be supposed to deny that the vital powers of the arteries may modify very considerably the dis- tribution of blood to different parts, for it is manifest that an increased action occurring in one part of an artery may hinder the blood from being transmitted in its usual quantity into a neighbouring part, while a dilated state of an artery or its branches, or, if we please to call it so, a diminished action or greater weak- ness of resistance of the coats of the artery considered relatively to the powers of propul- sion operating through it, may occasion the flow of a greater quantity of blood to a part, as occurs in local inflammations. Among the many indirect arguments adduced on both sides of this question may be mentioned the follow- ing. In the first place, the fact that in the lowest classes of animals, as in Vermes and Insects, which have no proper heart, the blood- vessels propel the blood by their contractile power, and that in some of the higher animals, particularly Reptiles and Fishes, parts of the vascular system, as the bulb of the aorta, a considerable portion of this vessel, parts of the veins, and so on, are distinctly contractile, and assist the powers of the heart, are adduced as proofs from analogy that the arteries in warm- blooded animals may have the same power and perform the same function. Now it may be answered to this, that the circumstance of the lowest classes of animals having no proper heart is the final cause of or an obvious reason for the greater contractility of these vessels ; and in the second place, that no rythmic con- traction is observed to occur in the arteries of warm-blooded animals of the same nature as that observed by Haller, Spallanzani, M. Hall, and others in the bulb of the aorta and other parts of the vascular system of cold-blooded Vertebrata. For similar reasons we are not inclined to attach much importance to the ar- gument in favour of the independent powers of the arteries deduced from the alleged occur- rence of circulation in acephalous foetuses, in all of which the proper muscular heart seems to be wanting; for although the distribution of the vessels in these foetuses has been suffi- ciently accurately determined, the nature of the circulation which occurs in them is a sub- ject involved in the greatest obscurity. There seems good reason to doubt that such foetuses have ever existed alone in the uterus, in which case their vessels may, as is known in many of them to have occurred, have been connected with those of a perfect foetus ; and even were CIRCULATION. 669 this not the case, the absence of the heart might be attended in these malformed productions with an unusual development of" muscular power in parts of the vascular system.* In conclusion, we may remark that the argu- ment drawn from the occurrence of circula- tion apparently little impaired through arteries which have been completely ossified for a con- siderable time, seems to be very much in favour of the view we have taken that the heart alone is the cause of the progressive flow of blood through the arterial tubes. 3. Phenomena of ' the capillary circulation. — The phenomena of the passage of the blood from the terminations of the arteries into the commencement of the veins through the capil- lary vessels, are highly interesting and impor- tant in many points of view, for the immediate respiratory change which the venous blood undergoes in the pulmonary vessels, and all those alterations of composition which accom- pany nutrition, growth, secretion, and other organic processes connected with the systemic vessels, occur in the smallest ramifications of the pulmonic and systemic circulation, and the morbid state of inflammation as well as the various pathological changes which occur as its consequences are intimately connected with an altered condition of the capillary system. a. Structure and distribution of the capillary vessels. — The name of capillary is generally given to all those minute vessels which form the means of communication between the small ramifications of the arteries and veins; but there is some difference in the opinion of anatomists and physiologists as to how much of the vascular system ought to be included under the division of the capillary vessels. Some, adhering to the strict meaning of the term, apply it to all the small vessels whatso- ever under a certain size; others hold that between the extremities of the arteries and veins there is always situated a series of minute tubes of nearly equal size in their whole length, and not ramifying like the arteries or veins, which constitute a system of vessels distinct from the others in their structure, distribution, and properties, to which the name of capillary ought to be restricted .f The last view appears to us to be founded in a partial acquaintance with the system of minute vessels, for though it may be true that in some parts of animals the capillaries have obviously the structure above described, and seem to form a system of vessels apart from the smaller arteries and veins, yet this is by no means the case in other textures ; and we think that the more extensive observation of the structure of these vessels in various parts will shew that in the greater number, as is well ascertained to exist in many, the smaller arteries pass into veins quite in a gradual manner, the ramifications of each class of vessel becoming more and * See the Researches of Elbcn, Tiederaann, Breschet, and others on Acephalous Monsters. t Dr. Marshall Hall's Essay on the Circulation of the Blood, Lond. 1831. Dr. James Black's Short Inquiry into the Capillaiy Circulation, Lond, more minute until they meet, the two kinds of vessel presenting no difference of character other than the change of direction assumed by the moving blood, which enables us to say with certainty where the artery termi- nates, and at what point the vein begins, and affording thus no reason to consider the continuous tube by which they join as different in structure from either the minute artery or vein. While we acknowledge therefore the importance of the observations which point out the existence of capillary vessels of a uni- form size in some textures, we think it necessary to retain the name of capillary as applied to all the minute vessels, both for the reason that the communicating vessels are not every where of the same kind, and that from the use already made of the term by physiological writers its meaning will thus be more easily understood. The vessels which lead from arteries to veins are of very various sizes, some admitting only one globule at once, others being so large as to allow of the passage of three, four, or even a greater number of red globules together. In tracing with the microscope the motion of the minute streams of blood as they pass through the capillary vessels, the eye is guided by the Fig. 330. Frog's foot. 670 CIRCULATION. motions of the red globules principally, for it is very rarely indeed that the current of fluid which carries the globules along can be recog- nized in the ordinary modes of observation. The capillary circulation is most easily seen in cold-blooded and in young animals, both on account of the large size of the red glo- bules and the small number of the vessels. Since the first discovery of the capillary circu- lation by Malpighi, the transparent web be- tween the toes of the hind feet of the frog has been universally adopted as the most con- venient situation for observing this beautiful spectacle with transmitted light. The fins and tail of fishes, the tail of the larva of the Frog and Newt, the external gills of the same ani- mals as well as of cartilaginous fishes, the mesentery of the Frog or of small warm- blooded animals, the wing of the Bat, the lungs and urinary bladder of Reptiles, the liver of the Frog and Newt, the membranes of the incubated egg, the yolk of the Skate's egg, are all situations favourable for the ob- servation of the capillary circulation. The capillary circulation has been viewed in only a small number of warm-blooded animals, and in very few of their textures ; but the minute injection with coloured fluids of all parts of the bodies of Quadrupeds and of Man leaves little doubt that in them also, whatever vari- eties there may be in the size, number, and distribution of the small vessels, the blood passes in every organ from the small arteries into the returning veins by minute continuous tubes of the same nature as those more easily observed in the situations above-mentioned. Some are inclined to consider the minutest or proper capillary vessels as destitute of vas- cular parietes, and consisting of mere passages through the texture of the organ in which they exist without any lining membrane. This opinion is founded on the impossibility of seeing the coats of the vessels, the rapidity with which new capillaries may be developed, and some other circumstances. The extreme degree of minuteness of the smallest capil- lary vessels must render futile any attempts to decide this question by direct observa- tion. Besides the general analogy between the larger and smaller vessels, there are several circumstances known which seem to be strongly in favour of the view that the capil- laries do not differ in this respect from other vessels. 1st, It is allowable to suppose that the active properties of the capillary vessels belong to parieties as in the larger vessels. 2d, In many transparent parts of animals in which the terminal arteries and veins do not diminish to a very small size, the coats of the vessel may be seen with the microscope, as in the external gills of the Amphibia, and in the vascular rete of the ear of birds and reptiles, in which the capillary vessels may, after having been injected, be separated from the neighbouring soft texture. 3d, The conver- sion of small into larger vessels with visible coats in those instances in which the course of blood through the vessels of a part has un- dergone an alteration, is in favour of the pre- vious existence of parietes in the smaller vessels. And 4th, The constant and regular distribution of the minutest vessels in many parts of animals appears to support the same view. The argument in favour of the non- existence of capillary parietes deduced from the alleged facility with which the blood occa- sionally passes out of the regular vessels and takes an irregular and indeterminate course through the non-vascular parenchyma of an organ, we believe to be founded, in some in- stances, in peculiarities belonging to a few parts only, and in others in inaccurate observation; for in almost all those situations in which the capillary circulation may be seen with ease and distinctness, the constancy of the minute passages which the blood permeates is un- doubted. From the more accurate means of making minute anatomical researches that have been introduced in modern times, the existence of serous, exhalent, and white vessels has become a matter of great doubt, for vessels of this description which do not admit the red glo- bules and liquor sanguinis together cannot be made obvious to the senses by the most de- licate injections or dissections ; and the ob- servation of the capillary circulation in the transparent parts of animals affords the most convincing proof that the smaller arteries have no visible terminations excepting in the capillaries and small veins. In observing attentively the web of the frog's foot and other Fig. 331. Capillaries in the web of the Frog's foot magnified. transparent parts in which the motion of the blood is easily seen, we occasionally see glo- bules of blood run into passages of the tissue which we did not perceive before ; but a suf- ficient acquaintance with the structure and dis- tribution of the smallest of the capillaries in these situations will soon convince the careful observer that the vessels into which the blood was seen to pass, apparently for the first time, existed fully formed before, that the fluid part of the blood passed in part through them, and that the stoppage of the red particles was to CIRCULATION. 671 a great measure dependent on partial or local impediments. The compression of one of the small arteries, for instance, will frequently, after causing oscillation of the globules of the blood in the smallest capillaries, be followed by the disappearance of some of them ; but in a very short time, or when the obstruction is removed, the blood regains its former velo- city and force, and flows into exactly the same passages as before. The notion that the smaller vessels are con- tinuous with the smaller lymphatics, and more especially with the excretory ducts of glands, seems to be fully disproved by the accurate researches of Malpighi, Mascagni, Panizza, Muller, and Weber, which have shewn that the lymphatic vessels originate at all parts of the body by a plexus of tubes every where closed, and that the excretory ducts of secre- tory organs begin always by shut ends. We believe it to be satisfactorily shewn that in die whitest of the textures (with the excep- tion perhaps of the cornea and crystalline lens), there is no necessity for the supposition of vessels admitting the fluid parts only of the blood, or of serous vessels, as they have been termed ; and that in all of them there exist small bloodvessels which admit very fine rows of globules in their accustomed proportion to the fluid part of the blood : for many textures which appear perfectly white or colourless, or only slightly yellow when viewed with the naked eye, are found, when examined with the microscope, to have small vessels carrying blood globules through them. Spallanzani and others shewed that very small vessels taken singly or seen in very thin layers have almost no per- ceptible colour ; and it is a well known fact that, in what are called the red textures, the colour (as of muscle for instance) is not ex- clusively dependent upon the quantity of red blood in them. It is difficult, indeed, to con- ceive how the circulation of the blood could be carried on at all, or how the red particles of the blood could ever be returned to the heart were the globules to be retained in the larger vessels, and all the white textures to admit only the fluid parts of the blood. In adopting the opinion that the arteries terminate always by direct continuity of tube in the veins, and that no other visible passages are connected with the minute vessels, we must suppose that the various interchanges of materials occurring between the blood and the organized textures or foreign matters, as in nu- trition, secretion, respiration, transpiration, &c. must take place by some process of organic transudation through invisible apertures of the minute vessels. b. Properties of the capillary vessels and in- fluence on the circulation. — From the expe- riments already referred to, it is apparent that the smaller arteries, so long as they can be distinguished from other vessels, are capable of being excited to contraction by the appli- cation of a stimulus ; but we have no means of shewing this with regard to the minutest capillary vessels, because we can scarcely apply any stimulation to them without affectin some of the smaller arteries at the same time. When it is said, for example, that the capillary ves- sels are irritable, because the application of ammonia or spirits of wine causes them to become smaller, it is difficult to determine how far this appearance of diminished size in the capillaries depends on their receiving less blood, in consequence of the contraction of the small arteries leading to them or upon the less size of these vessels themselves. In the expe- riments of Dr. Thomson and others, however, the application of salt and other stimuli ex- citing inflammation have appeared to dilate even the smallest capillary vessels, and such a dilatation can scarcely be considered as in- dicating any thing else than a less power of resistance in these vessels ; and when the ap- plication of ammonia or spirit of wine restores such ddated capillaries to their natural con- dition, we do not see that any other natural inference can be drawn from this fact than that the capillaries have been contracted by the influence of these stimuli ; for the contraction of the small arteries alone, although it might restore the lost velocity of the blood, would not diminish the capillaries to their former size. This general diminution of size ought how- ever to be carefully distinguished from the more marked and local contractions of true arteries. The velocity of the blood is quite uniform in the capillaries of the adult animal in the natural condition of the circulation. There is reason to believe the capillary vessels to be highly elastic, and to have the effect of com- pleting the change which is begun by the arteries, viz. that of equalizing the force of the heart transmitted through the blood. We do not, in observing attentively the capillary vessels, ever perceive any motions of alter- nate dilatation and contraction of their sides. The blood flows through them as through small glass tubes ; and if they act by other powers than by their elasticity alone, this action must be of so slow a kind as not to be perceptible. There can be no doubt that any action of contraction occurring in the capillary vessels, whether alternating with dilatation or not, could have no effect excepting that of ob- structing the passage of blood through them. It would act upon the contents of the arterial system much in the same way as the dimi- nution of the aperture at the end of a rigid tube would affect the flow of fluid through it, that is, either a less quantity of blood would pass through the capillary vessels in conse- quence of their less size, or a greater portion of the heart's force would be expended in di- lating these vessels to a sufficient extent. The principal reasons which we feel inclined to adduce for believing that the heart's action is continued onwards through the capillaries, and is sufficient to return the blood through the veins back as far as the heart itself, are the following: — 1. That in an animal recently killed a very small force only is requisite to cause bland fluids to follow the course of the blood, provided the injection be made before the tonic contraction has had time to constrict 672 CIRCULATION. the vessels. 2. The experiments of Hales and Wedemeyer shewing that, according to the more or less stimulating character of the fluids, their passage through the vessels was more or less easy. 3. The experiments shewing that, in an animal which has been dead for some time, steeping of the body in warm water, and the injection of warm water into the vessels, so as to clear the passage through them, puts the vessels in such a condition that a force of a few pounds is sufficient to effect the pro- pulsion of fluids through them. 4. The ob- servations of Haller, Spallanzani, Magendie, and others, that all regular progressive motion of blood in a vein, or the issue of blood from an orifice in a vein, ceases very soon after the heart's action is suspended, or when any obstacle prevents its force being communicated to the blood in the veins. 5. The observations of Spallanzani, Thomson, and others, that the impulses of the heart are visibly continued on through the small arteries and capillaries, and even into the veins in some states of the circu- lation. This phenomenon is most apparent at the time when the action of the heart is weak, and in such states of the circulation this re- mittent flow of the blood may be converted into a merely oscillatory movement without any regular progression by the gradual increase of the pressure applied to the artery which supplies the blood to the capillary vessels under observation ; a fact which shews dis- tinctly on the one hand that the force of the heart is continued on through the capillaries, and on the other that when a resistance h op- posed to the progress of the action of the heart through the arteries, no other force then operates sufficient to cause a continued and piogressive motion of the blood. But, although the small vessels do not con- tribute by their active contraction to propel the blood through them, or although they do not as a whole assist the force of the heart, it is yet very apparent that they have the power of modifying in a remarkable manner the flow of blood in particular parts. Among the circum- stances which prove this power of the small vessels to modify the circulation may be men- tioned the various instances in which there occur local determinations to particular parts, unaccompanied by any change m the action of the heart or in the general circulation. 1. The act of blushing and erection, or the reverse actions of paleness, collapse, &c. which seem to depend, in most instances at least, on some change in the terminal vessels 2. Inflam- mations or hemorrhages confined to a parti- cular part of the body. 3. The increase or decrease of secretions from glands, periodical or instantaneous. 4. The increased size of the vessels of the uterus during pregnancy, of the mammae after child-birth, &c. 5. The enlargement of bloodvessels in new growths, tumours, &c. 6. The enlargement of collateral anastomosing vessels, after the closure of the principal trunk of a limb. And, 7. The unequal growth or development of different parts of the foetus. Although we do not understand the nature of the change in the vessels which accompanies these partial distributions of blood to particular parts, yet they all suffi- ciently demonstrate that while the heart's action remains the same, the quantity of blood sent to particular parts must have been modified by some action of the vessels themselves. There are some physiologists, however, who hold the opinion that the motion of the blood is promoted in some way or other (they do not sufficiently clearly explain how) by powers acting on it during its passage through the capillary vessels; and there are a few who have gone so far as to suppose that the heart drives the blood only as far as the capil- laries, from whence it is propelled onwards into the veins by powers originating in the small vessels themselves. These opinions have been supported chiefly by arguments drawn from the facts already mentioned as illustrating the power of the small vessels to modify the circulation or to cause local variations in the distribution of the blood, as also on the fol- lowing grounds, which are ably stated in a supplement to his Outlines of Physiology,* recently published by Professor Alison, of Edinburgh, who is one of those who have more lately adopted this opinion, and by Dr. Black in an ingenious essay on the capillary circulation .f Besides the analogical argument drawn from the lower animals having a circulation of fluids without any heart, and the supposed unaided circulation in acardiac foetuses, it is stated that — 1. After the heart of the frog or such cold- blooded animals has been cut out, or a liga- ture passed round the aorta, some motion of the blood still continues to occur for a few minutes in the small vessels ; and it is farther stated, that this motion is influenced by heat, by certain applications to the web of the frog's foot, and the state of the nervous system. J 2. That while the circulation is going on with its usual freedom, the direction and velo- city of the flow of blood are subject to sud- den or rapid changes which do not admit of being accounted for simply by contractions of the vessels. 3. That the blood when out of the vessels, immediately after it has been drawn, or when extravasated in the textures, performs motions which seem to belong to itself or are spon- taneous^ 4. That the passage of the blood through the capillary vessels of the lungs is imme- diately influenced by the chemical change of the venous blood into arterial, for its velocity is diminished as soon as this change does not occur. 1 1 5. That the remoteness of the capillaries of the vena portae of the liver from the heart ren- * Outlines of Physiology, Supplement to 2d edit. Edin. 1836. t London, 1825. f Haller, Guillot, Leuret and Wilson Philip, Marshall Hall, and others. § Kielmeyer, Treviranus, Cams, Czermack, (Esterreicher, and Schultz. || Dr. Alison, loc. cit. CIRCULATION. 673 ders probable the existence in them of some power capable of propelling the blood inde- pendently of the heart's action. 6. That in the production of new vessels which occurs in adhesion or granulation, the new blood executes oscillatory motions in the rudimentary vessels while in the act of form- ing, before these parts of vessels are connected with the previously existing branches through which the heart propels the blood ; and this is said also to occur in the formation of new ves- sels in natural growth.* 7. That in the formation of the vascular area of the incubated egg the blood moves in part through the veins and small vessels before it is impelled by the action of the heart.f We would remark, regarding the oscillatory and irregular motions described by Haller and others as occurring in the small vessels of the web after removal of the heart or ligature of the aorta, that we believe some of these to be caused by the elasticity of both the arteries and veins, and others to be occasioned by the gradual or tonic contractions which take place in the arteries after death :J they occurred in all Haller's observations, but in Spallanzani's only when the apparatus of hooks constantly em- ployed by Haller was applied ; and so far as we have ourselves been able to observe them, we have always found them influenced by very slight changes. When one of the small vessels is obstructed they cease altogether, which ought not to be the case were they dependent upon powers belonging to the capillaries or the blood in them. Some varieties in the velocity and di- rection of the blood in the smaller vessels we have reason, from our own observations, to attribute to the same causes, and we think it consonant with such a supposition that heat or other agents influencing the contraction of arteries should influence these irregular mo- tions. The oscillations of blood in parts of vessels which are in the process of formation in adhesions and granulations, or in natural growth, we have not yet been able to observe so clearly as to be certain that we were not de- ceived ; but, even supposing them to have been satisfactorily proved to occur, we should be inclined to doubt the possibility of ascer- taining with accuracy that these portions of vessel are entirely shut off from all commu- nication with other vessels, so as that no im- pulse could be transmitted from the heart to them. The necessity of some change in the tissue of organs or of organizable lymph, in which new vessels are about to be formed before the propulsion of the blood into the new loop of vessel seems sufficiently obvious, * Bcellinger, Joum. des Progres, &c. vol. ix. Kaltenbrunner, loc. cit. Baumgartner, Beobacht. Viber die Nerven und das Blut. Freiburg. 1830. t [Br. Tanchose suggests as a cause for the mo- tion of the blood in the capillaries, the ceaseless removal of particles from the blood to supply ma- terials to the various secretions, &c. a constant tendency to a vacuum being thereby produced. Acad, des Sciences, Seances d'Avril, 1833. — Ed.] t See Marshall Hall's Essay, p. 95; and also Black's Inquiry, for judicious remarks upon these oscillations. but it does not appear to be as yet satisfactorily shewn that the motion of blood in the new vessels is independent of a propulsion received from the heart. Again we consider it as ascer- tained that the heart of the chick acts just as soon as any motion of fluids can be seen on the vascular area of the yolk ; and though it may be admitted that a certain change of place in the particles of the yolk is necessary in the new combinations which occur during the de- velopment of the forming parts from its substance, yet such a change or motion must be quite of an insensible kind and not in any degree ana- logous to the continued stream of circulating blood through the vessels. The stagnation of venous blood in the capil- laries of the lungs is certainly a most remark- able and inexplicable phenomenon, but if from analogy any weight is to be attached to obser- vations made upon the frog, it may be stated that the flow of blood through the lungs seems as immediately dependent on the heart's action as that through the system. The portal circu- lation is not more remarkable in respect of its isolation from the heart than the systemic cir- culation of fishes, in which animals the capil- laries of the gills intervene between the heart and the systemic aorta ; and without any dis- tinct contraction of that vessel, the circulation of the blood in the systemic capillaries as well as in the gills is very manifestly main- tained chiefly, if not solely, by the action of the heart. We do not feel inclined to attach any importance to the alleged motions of the globules of the blood out of the vessels, for we have never been able to see any such in- dicating different powers from those which produce currents in inorganic fluids, and some of the observations upon which the statement is founded have been shewn to be erroneous. We think it unnecessary to do more than merely to allude to some of the very many attempts that have been made to account for independent motion of blood in the capillaries, or what have been termed the theories of the capillary circulation. All that we know of capillary attraction mi- litates against the possibility of its being the means of causing a progressive motion of fluids, such as that which occurs in plants and ani- mals. Those who have attributed the motions of fluids in the living body to endosmosis or a principle of organic transudation, have failed in pointing out in the bloodvessels the condi- tions necessary for the occurrence of a motion proceeding from an action of this description. The electrical theory is defective in this essen- tial point, that no difference in the electrical condition of the arterial and venous blood has been shewn, and that the same cause to which the motion of the capillaries of the systemic arteries is ascribed ought to retard the passage of blood in the pulmonary capillaries, the re- lations of the two kinds of blood being there reversed. The opinion that the motion of the blood in the vessels is analogous to those cur- rents of fluids which take place in contact with the surfaces of various parts of animals, which are almost always connected with ciliary mo- 674 CIRCULATION. tions, and are described under the head of Cilia in this Cyclopaedia, isdefective in so far as neither cilia nor any power of exciting currents has yet been shewn to exist in the interior of the bloodvessels, and they have been examined in circumstances in which we conceive they would have been seen had they been present. In fine we cannot see how any power of spontaneous motion belonging to the blood itself could be a cause of progressive motion of that fluid, unless the direction of the motion were determined by the solid textures containing the blood, and in this case the same objections would apply to this explanation of the cause of motion as to the one to which allu- sion has just been made; and besides, the evi- dence of spontaneous motions of the blood ap- pears upon the whole of a very unsatisfactory kind. From these considerations we find ourselves constrained to hold the opinion that, however great the power which the capillary vessels possess of modifying the distribution of the blood, there is not reason to believe that they contribute as a whole to its progressive motion. 4. Phenomena of the venous circulation. — In the natural state of the circulation the flow of the blood is nearly quite uniform in the veins, as may be seen when a vein is opened in the common operation of venesection. In those rare instances in which the flow from a vein is accelerated after each beat of the heart, in the same way as the arterial jet, it may be supposed either that the intermitting impulses of the heart are, from some circumstance or other, transmitted more freely and to a greater dis- tance than usual through the capillary vessels, as is known occasionally to happen, or, what is more probable, that the larger branch of the vein receives the successive impulses directly from neighbouring large arteries, which are more than usually dilatable. As the size of the veins is generally greater than that of the corresponding arteries at the same distance from the heart, and as they are also more numerous, the velocity of blood is less in these parts of the veins than of the arte- ries ; and as the whole venous system contains considerably more blood than the arterial, the velocity of the blood taken as a whole must be less in the veins than in the arteries. The same quantity of blood must be brought by the venae cava to the right auricle as issues from the left ventricle, (making allowance for the expendi- ture by secretions, &c.) and consequently the velocity of the blood entering and of that issuing from the heart must be equal. Again, the ve- locity of the blood must be gradually on the increase in its progress from the small to the larger veins, because the capacity of the vessels into which it flows is gradually becoming less. In the systemic veins, excepting the venae portae, the direction of the flow of blood is de- termined by the structure of the valves, which permit of the return of blood from the extremi- ties of the veins towards the heart, but oppose, by the filling of their pouches and the apposi- tion of their free edges, a complete obstacle to the reflux of the blood in another direction. The principal cause of the progressive flow of the blood in the veins is unquestionably the force of impulsion of the heart continued through the arteries and small vessels, as ap- pears from the flow from the remote part of an opened vein and the simple experiments of Hales, Magendie, and Poiseuille already re- ferred to. Hales ascertained, by introducing tubes into the larger veins of the horse, that the pressure on the blood from behind, or vis a tergo, is sufficient to raise the blood in the tube to a considerable height above the level of the heart, and is consequently more than sufficient to re- turn the blood to the auricle of the heart. The blood did not, in Hales' experiments, in ge- neral at first rise in the tube connected with a vein more than six inches, but this he shewed to proceed from the easy escape of the blood by lateral communicating vessels, for when the other large veins were tied, or when they became fully distended with blood, that fluid sometimes rose in the tube connected with a large vein to a height of three or four feet. M. Poiseuille* demonstrated, in a still more satisfactory manner, the action of the pressure of the heart on the blood in the veins by means of the bent tube with which he mea- sured the pressure of the arterial blood : and this fact is proved in an equally convincing manner by Magendie's experiment of isolating the principal artery and vein from the other parts of the limb of an animal, in which it was found that the flow of blood from the vein is immediately stopped by pressure or ligature of the artery. It is scarcely necessary, in order to obtain a proof of this fact, to have recourse to the vivisection of animals, for in common bleeding from the arm, the flow of blood from the vein will be found to be immediately influ- enced by the state of the artery, and even with- out the division of a vein, it is easy to observe the action of this force of impulsion which drives the blood onwards towards the heart in any of the superficial veins of the arm by the application of external pressure, a mode of illustration successfully adopted by Harvey in his explanation of the course of the blood. These very simple experiments are looked upon by some as quite sufficient to demonstrate the proposition that the blood is moved in the veins by an impulsion from behind, and that that impulsion is derived from the action of the heart; while others, not satisfied with this ex- planation, have endeavoured to point out addi- tional forces as contributing to the progressive motion of the blood in the veins. The larger veins are, like the arteries, highly elastic, and they are generally regarded as stronger proportionally to the thickness of their coats than the arteries. This elasticity belongs chiefly to the external cellular coat, for a mid- dle fibrous coat is not apparent in most of the larger healthy veins, and in those rarer in- stances in which it is apparent, it is very much thinner than in the arteries. The smaller or capillary veins appear also to be possessed of some degree of irritability, for they have been * Magendie's Journ. vol. x. CIRCULATION. 675 seen to contract on the application of a stimu- lus in the web of the frog's foot by Drs. Thom- son and Hastings. This, however, occurs much more rarely than the contraction of the small arteries. It has been remarked that in some animals muscular fibres are prolonged from the auricle upon the adjoining part of the vena cava; and Spallanzani, M.Ilall,Flourens,* and others have recorded the fact of the rythmic contraction of parts of the great veins adjoining the auricles. But, excepting in these situations and in the caudal heart, observed by M. Hall in the Eel, muscularity of the veins cannot be considered as having any effect in promoting the flow of the blood in these vessels. The progressive motion of the venous blood takes place with li'.tle force, and is therefore subject to considerable variations from external pressure. Thus the flow of the blood may be much accelerated by raising a limb, or retarded by keeping it in the depending posture from the mere effect of gravitation, and the common practice of making a person who is bled in the arm call the muscles of the arm into action during the operation, is a sufficient proof that the pressure of the muscles may be the means of accelerating in a considerable degree the venous circulation, — an effect obviously depen- dent on the disposition of the valves. Gravita- tion or muscular action are, however, only occa- sional causes of the acceleration of the flow of blood in the veins, and both, but particularly gravitation, may in some instances offer an ob- stacle to its progress. There are some physiologists who believe the blood to be drawn through the veins to- wards the heart by a power of suction which operates from the side of the heart or chest. The remarks we have already made in treating of the arterial and capillary circulations render it unnecessary for us to revert in this place to the arguments employed by those who have supported the above view, merely on account of their belief in the inadequacy of the heart's force to maintain the complete circulation ; we shall only now state the direct experiments or reasonings by which it has been attempted to be proved that a vis aj'ronte or suction power draws the blood towards the centre of the cir- culation. We have already, in a former part of this article, stated our reasons for believing that the elastic power of the heart itself is not attended with any production of an appreciable force sufficient to draw the blood into its inte- rior. The facts which relate to the supposition that the chest or lungs become, during their motions in respiration, the source of a suction power which acts on the venous blood may be suitably considered under the first part of the fourth division of this article, viz. IV. The relation of the circulation to other functions. 1. Respiration. — Of the opinions of those who attribute the suction of the blood through the veins to powers within the chest, there * Annates des Sciences Natur. torn, xxviii. p. 65. are chiefly two which have of late years at- tracted attention, — those namely of Dr. Car- son of Liverpool,* and of the late Sir David Barry .f According to Dr. Carson the lungs are of a highly elastic nature, and are kept in a state of forced distension by the pressure of the atmo- sphere which enters them when the chest dilates. The lungs would collapse or fall away from the walls of the chest but for the force with which they are distended, and there is thus a tendency to the production of a vacuum within the chest or to a diminution of the pressure on the exte- rior of the heart, in consequence of which the blood is forced or drawn into the heart and chest on the same principle that fluid enters the mouth in the act of sucking. According to Sir D. Barry, at each inspira- tion of air into the chest the lungs are not suffi- ciently expanded to fill the whole of the chest, or there is, in consequence of the expansion of the walls of the chest, a less pressure within the chest than on its exterior, and the blood is pro- pelled through the veins communicating with the heart by the external atmospheric pressure. Neither Dr. Carson nor Sir D. Barry state, in a sufficiently explicit manner, how much of the force impelling the blood through the veins they conceive to be of the nature of suction : they both admit that the greatest part of this force belongs to the heart or vis a tergo, but they yet state distinctly their belief that the suction power is an important cause of the mo- tion of the blood throughout the whole venous system. The works of both these authors are replete with interesting remarks on the circula- tion in general, and more especially on the flow of blood through the veins. The direct expe- riments, however, in support of their opinions are comparatively few and inconclusive. Dr. Carson shewed that the lungs are always during life in a state of forced expansion, and estimates the pressure which the lungs of the sheep are capable of sustaining, when in the expanded condition, as equal to a column of seven inches of water. Sir D. Barry observed, in experiments made upon horses, that when one end of a tube is introduced into the ju- gular vein, and the other extremity rests in a vessel containing water, the water rose during each inspiration some length in the tube, and sank again during expiration, distinctly indi- cating the diminished pressure existing within the chest at the time of the rise of the water, and proving that the flow of the blood in some parts of the veins may be accelerated during inspiration from the same cause. Poiseuille,J by the employment of the instrument for mea- suring the pressure of the animal fluids, to which allusion has already frequently been made, has confirmed Sir D. Barry's statement, that the di- minished pressure within the chest, at the time of inspiration, is such as to affect the flow of * Inquiry into the Causes of the Motion of the Blood, &c. Liverpool, 1815. t Experimental Researches on the Influence of Atmospheric Pressure upon the Progression of the Blood in the Veins, &c. Lond. 1826. \ Loc. citat. 676 CIRCULATION. blood in the jugular vein, and to draw it in some degree towards the heart. In many persons, particularly the young and those of a thin habit of body, the jugular veins in the neck are fre- quently very distinctly seen to become full during expiration, and to be rapidly emptied and collapsed during inspiration, — a fact which shews clearly enough that the blood passing through this vein enters the chest most easily when that cavity is dilated. The position, however, of the body has a very considerable influence on this rapid evacuation of the jugular veins in such instances. Again, there are several direct experiments upon animals which are much opposed to the views at present un- der consideration. Dr. Arnott* has shewn very successfully that such a power as that supposed to aid the venous circulation could have very little effect in pro- moting the flow of fluids through soft tubes, which collapse as easily as the larger veins do, because not more than an inch of fluid at the most can be drawn through one of them by a syringe, without its sides being brought toge- ther so as to close the mouth of the syringe, and this objection is in no way removed by the circumstance that the veins are kept open by the vis a tergo of the heart, because even al- though they should be open, a force from be- fore, to adopt the incorrect expression frequently applied to a suction power, if strong enough to make any impression on the flow of the blood, would act, to a certain amount, just in the same way as if no force from behind existed ; that is, it would tend to make the sides of the vessel come together, and would thus offer an obstacle to the further progress of the blood. In repeating some of Barry's experiments, Mr. Ellerbyf found that when he introduced a tube into the jugular vein of an ass for two or three inches only, there was no suction ex- erted through it, but that the fluid in which its further extremity was immersed rose only when the tube was thrust eight or nine inches into the vein so as to reach the chest, in which case, of course, the vein was held open by the rigid tube, and the suction power was enabled to act through it to an extent which does not take place in the natural state of the jugular vein. Messrs. Ellerby and DaviesJ also found that the venous circulation was for a short time not materially impeded by opening the chest or the introduction of tubes into it through the parietes. It must be apparent to every one that the suction power or vis a fronte can exert lit- tle, if any, force of traction on the blood in the large or superficial veins of the limbs, for on making pressure upon the trunks of one of these, so as to prevent the action of the vis a tergo, we find that if the limb is at rest the motion of the blood in the part next the heart is wholly arrested. But if, while we maintain the pressure on the vein at one place we empty the vein for some way towards the heart, close the vein on the side next the heart, and then remove the pressure from the remote * Elements of Physics, vol. i. t Lancet, vol. xi. p. 326. { Lancet, vol. xi. 606. situation, the blood is at once impelled through the portion of the vein which had been emptied, by the force of the heart alone. Messrs. Ellerby and Davies have shewn that the same pheno- mena, or the absence of a vis a fronte and evi- dence of a vis a tergo, attend the flow of blood in the largest veins even, which are situated in the immediate neighbourhood of the chest ; for after the application of a ligature upon the vena cava inferior, it was found that the part of this vein between the ligature and the chest was not emptied towards the heart, and that when the part of the vena cava in the immediate vicinity of the chest was emptied, and pressure then applied at the entrance of the vena cava into the auricle, the blood rose to fill the emptied portion of the vena cava, although no suction power could in this place operate. It was also found that no fluid rose in the remote extremity of a tube introduced into the femoral vein.* These experiments shew that a suction power, whether produced in the way supposed by Dr. Carson, or in that stated by Sir D. Barry, can have very little effect in promoting the flow of blood in the veins, — a conclusion which is rendered still more certain from some other ge- neral considerations, such as the following : 1. The whole of the vessels belonging to the pulmonary circulation are placed within the chest, and consequently the flow of blood in the pulmonary veins must be independent of any suction power connected with respiration.f 2. In the fetus, as there is no pulmonary respiration, both the pulmonary and systemic venous circulations go on without any assist- ance from a suction power. And 3. In the portal circulation of the higher animals and in the venous circulation of fishes breathing by gills, as well as of those reptiles in which air is forced into the lungs by a process of deglutition, there can be no aid derived from a suction power. We have already, in our description of the varieties of form in the circulatory organs of animals, adverted to the intimate relation which very generally subsists between the structure and functions of the organs of circulation and respiration. We shall now mention a few other circumstances connected with the func- tions of circulation in the adult human body, „ which seem to depend upon this relation of the motion of the blood to the respiration. The influence of the mechanical operations of respiration is not confined to the venous cir- culation, for it has been shewn by direct expe- riment that the force of the blood in the arteries varies also from the same cause, being greater during expiration than during inspiration. This greater force of the blood in the arteries during expiration, known to Haller, Lamure, and Lorry, was proved by the experiments of Hales, Poiseuille, and MagendieJ formerly mentioned. * See also Macfadyen's Remarks, Edin. Med. and Surg. Journal, vol. xxii. p. 271 ; Cams in Meckel's Archiv. iv. p. 413 ; and Remarks in the Edin. Journ. of Med. Science, vol. ii. p. 462. t See the late Prof. Turner's Essay on the Mo- tions and Sounds of the Heart. Med. Chir. Trans, of Edin. vol. iii. t Journ. dc Physiol, vol. i. CIRCULATION. 677 It is very probably occasioned in part by the assistance which the ventricular systole receives from the collapse of the parietes of the chest at the time that the air is expelled from that ca- vity, and in part by pressure of the parietes of the chest upon its contents, and through them upon the trunks of the larger arteries. During inspiration the pressure must be, to a certain amount, removed from the larger arteries, and consequently the current of blood through them at that period will be less forcible and less rapid. The well-known fact that rupture of aneu- risms of the large arteries and effusion of blood within the cranium in apoplexy are more liable to occur during straining and other muscular efforts associated with forcible expiration, is a further illustration of the fact that the arterial pressure is greatest at the time of the collapse of the parietes of the chest. The relation of the force and frequency of the pulse to the activity of the respiration is an interesting subject connected with the facts at present under consideration.* In many per- sons, in ordinary and tranquil respiration, the force and frequency of the pulse vary percepti- bly during inspiration and expiration, and in these persons, when the respiration is more forcible than natural, the pulse indicates very distinctly by its changes the varying states of the chest. During an unusually long and for- cible inspiration the beats of the pulse are more rapid and weaker, and during a succeeding complete expiration, or even while the chest is kept expanded, the pulse is more full, strong, and slow. Some individuals have the power of occasioning an intermittent pulse, and some of causing the action of the heart to cease even by forcible exertion of the expiratory mus- cles. We think it probable that it may have been in this or some similar indirect manner that the action of the heart was arrested in Colonel Townsend's case, described by Dr. Cheyne in his work on the English malady, and very often referred to as a proof of the pos- session by Colonel Townsend of a voluntary power of influencing directly the heart's action. There is in general a very constant propor- tion in the ordinary state of the circulation be- tween the number of the beats of the pulse and the frequency of respiration. The average number of respirations in a healthy person may be considered as from 15 to 20 in a minute, and taking the number of the pulse in the same time at from 72 to 75, this makes one complete respiratory motion for nearly four beats of the heart. The force and frequency of the heart's action and consequent state of the pulse are well known to be considerably influenced by very slight muscular efforts, as well as by changes of position of the body even ; but it is not observed that the respiration becomes inva- riably more or less hurried in a corresponding degree with an increased or diminished fre- quency of the pulse. In very violent exercise, it is true, and more particularly in rapid mo- * See an interesting Essay by Hering in Tiede- mann's Zeitschrift, vol. v. tions which give rise to a great and immediate increase of the frequency of the heart's action, the respiration becomes hurried and forcible, or there is panting ; but, on the other hand, it does not appear that the gradual changes of the pulse, which are liable to occur from one pe- riod of the day to another, are accompanied by corresponding variations in the frequency of respiration ; and again, when by a voluntary effort we breathe very hurriedly, as for example, from 80 to 100 times in a minute, the fre- quency of the pulse is not increased by more than 8 or 10 beats in a minute.* Some physiologists hold the opinion that the motion of the blood in the capillaries of the lungs and the system is considerably influenced by the chemical changes which the blood un- dergoes in its passage through the minute pul- monary and systemic vessels. We are not ac- quainted with any facts or experiments which shew that the systemic capillary circulation is immediately dependent upon the change of the arterial into venous blood : on the contrary, such an opinion is much opposed by the facts that a free circulation of imperfectly arterialized blood takes place in the foetus before birth, as well as in many children after birth affected with malformations of the heart or greater vessels, and that a completely venous blood circulates through the system in hybemating animals when in the state of deepest torpidity. There are, however, several circumstances which appear to justify the opinion that the motion of blood through the pulmonary capillaries has a more immediate dependence on the change of arte- rialization.f In all those circumstances which cause imperfect respiration and prevent the ac- customed necessary arterialization of the blood, or in approaching asphyxia, it seems to follow from the experiments of Dr. Kay, Alison, and Reid, that there occurs from the very first com- mencement of the symptoms of impeded respi- ration, a diminution of the quantity of blood which passes through the pulmonary capillaries. There is thus produced from the first com- mencement of non-arterialization of the blood an accumulation of venous blood in the pulmo- nary capillaries and arteries, but it is equally well proved that a certain quantity of venous blood does, as Bichat shewed, gain the left side of the heart and permeate the arterial sys- tem. As the symptoms, however, of suffocation or asphyxia become more urgent, the accumu- lation of blood in the pulmonary artery on the right side of the heart and in the systemic veins gradually increases, until by the time that the involuntary motions of respiration have ceased, there appears to be a complete stagnation in the lungs, although the heart continues to beat a little longer. During the occurrence of these changes the action of the heart also is no doubt gradually becoming weaker, a circumstance which may very probably contribute to the stag- nation of the blood in the lungs, but there is good * See an account of the interesting experiments by M. Roulin on the variations of the pulse at diffe- rent heights. Magendie's Journ. Jan. 1826. t See Dr. Alison's Remarks, loc. cit. 678 CIRCULATION. reason to think that the motion of the blood is first arrested in the pulmonary capillaries. The state of our knowledge does not, it must be confessed, permit us to offer a satisfactory explanation of the cause of the above-men- tioned phenomena. We have already stated reasons against regarding the stagnation of the blood in the lungs in asphyxia as attributable to a loss of the supposed vital power of motion belonging to the blood in the capillary vessels: and we think it quite as just to regard the stag- nation as the effect of over-stimulation and constriction of the minute vessels of the lungs by the dark blood, as to attribute it, in the manner some have done, to the deficiency of that stimulation which arterial blood, without any good reason, is presumed by them to give to the small vessels. 2. Circulation within the cranium. — The limits of this essay do not permit us to do more than allude very shortly to the nature of the circulation within the cranium, — a subject, in some respects, nearly related to the facts just stated, and of great importance from the general dependence of the state of the cerebral func- tions upon the quantity and force of blood which flows through the brain. The bloodvessels within the cranium are dif- ferently situated from those in other parts of the body in this respect, that they are removed from the influence of atmospheric pressure. In consequence of the unyielding nature of the skull, and its being closed on all sides, except- ing at the places where the nerves and blood- vessels pass through the bones, the cavity of the skull must necessarily be equally full at all times ; and the spinal canal is in the same pre- dicament. The whole quantity of fluid or solid matter, then, within the cavity of the cranium and spmal canal must be always the same ; or, during the circulation just as much blood must issue as enters it, and it is physically impossible to increase or diminish the whole quantity con- tained in the brain by increased pressure, by opening of an artery or vein or any other means. It was shewn by various well devised experi- ments performed by the late Dr. Kellie,* that in animals bled to death, while the rest of the body was exsangueous, the brain retained its usual appearance so long as the vault of the cranium was entire, but that a perforation of the skull, such as to allow the atmospheric pressure to act upon the brain and bloodvessels of the head, caused the evacuation of blood from the head as from other parts of the body. While the whole bulk of the contents of the cranium, however, must necessarily remain the same, yet the relative quantity of arterial and venous blood may vary within a short space of time, the pressure exerted by the blood in the vessels may be greater or less according to cir- cumstances ; and there may occur within the skull local determinations or partial distribu- tions of the blood. When from rupture of a bloodvessel, inflammation, suppuration, or other causes, blood, serum, or pus are effused into * Edin. Med. Chirurg. Trans, vol. i. the cavity of the cranium, the circulating blood must be diminished in quantity ; when there is any obstruction to the return of the blood by the jugular veins, the pressure of the blood en- tering by the carotid artery is proportionally greater; and when the arteries which supply blood to the brain are obstructed, or the heart's action is less forcible than usual, the pressure on the brain must be diminished in a corre- sponding degree. In the natural state of the circulation the pressure exerted by the blood circulating through the cranium is subject to regular alter- nations of increase and decrease from the effect of the heart's action and the motions of respira- tion. When the brain of man or of animals is exposed by the removal of a part of the skull, it is seen to be slightly raised at the exposed part at each arterial pulsation, and more perceptibly during each expiration. The brain falls again during each succeeding inspiration, but does not sink below the level of the skull. These motions may also be perceived at the fontanelles of the infant's head, where the bony parietes of the skull are deficient. In the closed state of the skull, for the reasons previously mentioned, it is obvious that there can be no motions simi- lar to those observed in the brain when ex- posed, but nevertheless the brain must be more forcibly pressed upon by the blood at these times than at others. Haller, who had observed these motions, conceived the depression during inspiration to be caused simply by the ease with which the blood enters the chest at that time, and attributed the swelling of the brain during expiration to the obstacle then offered to the descent of the blood through the jugu- lar veins. It seems, however, probable that the greater fulness of the arteries during expiration may also contribute to raise the brain at the time when the collapse of the walls of the chest occurs : for Magendie ob- served, that when a ligature was put upon the jugular vein, the blood which issued from this vein by an aperture above the ligature, flowed with greater force during expiration, shewing that increased arterial pressure during expira- tion was continued through the capillaries into the veins. Sign. Ravina, who made a very extensive series of experiments upon these mo- tions, found that when the brain has been de- pressed during inspiration, it again swells, although no expiration succeeds, but that when raised during expiration, it does not again sink, if inspiration does not follow. 3. Influence of varieties in the distribution of arteries and veins upon the circulation. — As connected with some of the above-mentioned facts, and exerting a considerable influence in modifying- the circulation of the blood in parti- cular states of the animal economy, we may here mention a few of the more remarkable varieties in the distribution of the arteries and veins, together with the uses they have been supposed to serve in different animals. The varieties of form in the larger arteries may be considered under two heads; a, simple tor- tuosity ; and b, sudden division into many small branches. CIRCULATION. 679 a. One of the best examples of the first of these varieties, which are by no means uncommon in animals, occurs in the spermatic arteries of the bull. Two reasons have been assigned for the existence of this, viz. 1, to allow, by the greater length of the vessel, for the stretching of parts, as in the arteries of the lips ; and 2, to dimi- nish the velocity of the blood passing through the tortuous vessel, from the longer course and greater incurvation * Increased friction, which must be the consequence of greater length of the artery, will diminish the velocity of the blood through the whole vessel, and besides this, a given particle of blood passing through a tortuous vessel will arrive later at its destina- tion, in consequence of the longer course it has to run through ; but if we regard the fluid in the arteries as every where subjected to pres- sure, it is very doubtful that the increased cur- vature can be the source of any considerable retardation by diminishing the force communi- cated by the impulses of the heart.f b. The sudden division of an artery into many small branches may take place with or without tortuosity or a plexiform arrangement ; the primitive vessel disappearing or persisting, but in most cases when present, diminished in size. The most remarkable examples of this peculiarity of the arterial system are the follow- ing. 1. The intercostal and lumbar arteries of the Cetacea in the posterior part of the chest, and in the vertebral canal and the caudal artery of the same animals, which are tortuous and plexiform. 2. The brachial artery of the Por- poise, which divides at once into more than forty plexiform branches. The primitive trunks disappear, and five or more vessels emerge from the distal end of the plexus. The uterine and vesical arteries of the same animal are much divided, but not plexiform.J 3. The subdi- vided brachial and crural arteries of the Bra- dypus tiidactylus, Lemur tardigradus, L. gracilis and L. tarsius ; and the same arteries, as well as the caudal arteries of the Myrme- cophaga didactyla and M. tetradactyla. 4. The arteries of the legs of the Swan, Goose, and Turkey divide into several long branches, which anastomose with one another.§ 5. The rete mirabile of Galen on the internal carotid of many quadrupeds, and the rete mirabile on the common carotid of the Frog. 6. The rete mirabile of Hovius on the ophthalmic artery of some animals, the Seal for instance. 7. The mesenteric arteries of the Sow at their com- mencement. 8. The subcutaneous arteries of the Hedgehog. The uses of these very various forms of arte- ries it must be confessed is very little known. Some of them may, like other peculiarities in animal structure, and more especially those be- longing to the vascular system, be remains of the foetal condition of the arteries in which * J. Hunter. t M tiller's Physiol, vol. i. p. 198. \ See the accounts of these varieties by J. Hun- ter in the Phil. Trans. Sharpey, Meeting of British Scient. Assoc. in Edin. Sept. Iy34. Breschet, Armal. des Scien. Natur. 1834. Baer, Nov. Act. Nat. cur. 1835. § Cuvier, Lecons d'Anat. Comp. vol. iv. they exist.* The most common opinion enter- tained as to their effect on the circulation is that they retard the velocity of the blood, and render its flow more uniform, thus preventing the parts supplied by them from being affected by sudden changes .f Other secondary conse- quences of the diminished velocity occasioned by these peculiar structures have been imagined, as for example, 1, diminished rapidity and greater durability of muscular contraction, as in the Sloths;! 2, security against obstruction of the circulation from pressure, as in climbing animals wh ich cling long and forcibly to branches of trees ; § 3, or these plexuses have been regard- ed as intended to increase the capacity of the arterial system, and to serve as reservoirs for blood, as may be the case in the Cetacea.|| In some of the above-mentioned animals the tor- tuosity or multiplied divisions of the arteries are accompanied by a similar condition of the veins, as in the Porpoise. The most remarkable variety in the form of the venous system, and the one to which a use may be most easily assigned, is the large dila- tation of the vena cava inferior in the neigh- bourhood of the liver, which occurs in those animals which from their mode of life are in the habit of remaining long under water, such as the Seal, Otter, and Diving Birds. The pur- pose of the venous sinuses in these situations is manifestly to allow of the accumulation of venous blood in the vena cava without an un- usual distension of the right side of the heart and bloodvessels leading into it and from it, which is the effect of long submersion or im- peded respiration in animals unprovided with this peculiarity of structure. The venous and arterial plexuses of the Cetacea very probably serve the same purpose. The muscularity of these sinuses alleged by some must have the effect of emptying them more easily than would be accomplished by the vis a tergo. 4. Influence of the nervous system upon the circulation. — It is a very general opi- nion among physiologists that a considerable influence is exerted by various parts of the nervous system upon the function of circu- lation as a whole, and through it upon the different processes of the economy concerned with nutrition, as digestion, secretion, growth, animal heat, &c. There is some difficulty, however, in ascertaining the exact relation which subsists between particular parts of the nervous and circulatory systems. It is mani- fest that in many instances the circulation in the bloodvessels is modified by a nervous in- fluence which operates on the heart alone, while in others it is affected by an alteration of the vital powers of the bloodvessels themselves. We refer the reader to the articles Contrac- tility and Heart for an account of the modifications to which the circulation is liable from the operation of nervous influence on * Baer, loc. cit. f Barclay on the Arteries, p. 36. t Carlisle, Phil. Trans. 1800. Roget, Bridge- water Treatise. § Vrolik. fj J. Hunter, loc. cit. 680 CIRCULATION. the heart alone. We shall only remark in this place that although the heart may be excited to contraction by the direct stimu- lation of its muscular substance, and although the effect upon the heart's action of bodily exertion, of emotions of the mind, and of severe injuries of the brain and spinal mar- row, all of which can be supposed to act upon the heart through the nerves only, are un- doubted; yet it is well ascertained that the heart cannot in general be excited to con- traction by the direct stimulation of its nerves, and that its action may be regarded as auto- matic to a certain degree, and little dependent upon the immediate transmission to it of any nervous influence from the cerebro-spinal or ganglionic nervous systems, since the rythmic contraction of the heart continues to go on for a time in some animals after the division of its nerves, and in others even after its complete separation from the body. It has also been frequently found that after the complete de- struction of the brain and spinal marrow of an animal the circulation of the blood can be maintained for some time by means of artificial respiration, — an experiment which proves that the motion of the blood in the vessels is not immediately dependent upon nervous influ- ence.* Many circumstances, however, seem to shew that the state of the vessels, and in consequence of this the velocity and force of the blood, are susceptible of very considerable modification from local affections of the nerves belonging to the part in which they may have been observed to occur, or from general alterations of the nervous powers of the system. It is probable that nervous influence operates much more powerfully in modifying the circulation through the small than through the large vessels, indeed we know of no direct satisfactory experiments which demonstrate the effect of nervous in- fluence upon the larger arteries exclusively. The experiments which seem to prove most satisfactorily the influence of the nervous system on the circulation in the small vessels are those performed on cold-blooded animals by Legal- lois^ W. PhilipJ Flourens, and particularly those of Marshall Hall,§ the general result of which may be stated as the following: that after the destruction, whether sudden or gradual, of the brain or spinal marrow, the flow of blood in the remote parts becomes more languid and is gradually more and more circumscribed, while the action of the heart continues, and its power seems not to be diminished in a propor- tional degree. But in such experiments as those just mentioned, performed in general in cold- blooded animals, it must be at all times ex- ceedingly difficult to find an accurate mode of measuring the force of the heart, and conse- * We refer here to the experiments of Haller, Whytt, Fontana, Spallanzani, Legallois, W. Philip, Clift, Flourens, and Muller ; Humboldt, Fowler, Brachet, Treviranus, Weinhold, &c. t Exper. sur le Principe de la Vie. $ Exper. Inquiry into the Laws of the Vital Func- tions. § Loc. citat. p. 99. quently they cannot be regarded as affording sufficient evidence that there did not occur along with the languid state of the circulation a certain diminution in the heart's power. They do not at least entitle us to conclude that the decreased velocity and stagnation of the blood in the remote parts is caused mainly by the loss of the vital powers of the capillary vessels, for these changes of the circulation may in a great measure be the effect of other causes, as the loss of power of the heart, and that more permanent alteration of the textures which very probably accompany the severe injury done to the body. On the other hand it may be remarked that the coldness and im- paired nourishment common in palsied limbs, the known increase or diminution of the various secretions from mental emotions, and direct or sympathetic affections of the nerves belong- ing to the glands or other secreting organs, the phenomena of blushing, erection, inflam- mation, and the like are all very direct and satisfactory proofs that the small vessels and the capillary circulation may be influenced by affections of the nerves. As a further confirma- tion of this may be mentioned, 1, the inflamma- tion and other consequences of the division of the fifth pair of nerves which occur in the eye; 2, the statement of some, as Treviranus, that the division of the nerves of the leg of a frog impedes the circulation: 3, the assertion by others, as Baumgartner, that after the division of the nerves or the destruction of the spinal marrow, the peculiar oscillations which he, along with Doellinger and Kaltenbrunner, has observed to precede the formation of new blood- vessels do not occur ; and 4, the observations of Nasse, which are stated to shew that the reunion of wounds is retarded or put a stop to by the division of the nerves belonging to the wounded part. Krimer,* whose experiments on this subject are numerous and remark- able, states that the circulation was always much impaired by the abstraction of nervous influ- ence from the division or ligature of the nerves; that the jet from the femoral artery of a qua- druped was much less strong after the division of the crural nerve ; that the capillary circula- tion of the frog's web ceased soon after the nerves were cut or tied ; that the arterial blood passed through the systemic capillaries without undergoing its proper change into venous ; and that salt did not produce the accustomed effect of dilating the capillaries when the nerves of the part were injured, but that these effects were induced when galvanic irritation was applied to the divided nerve. In reference to these experiments it may be remarked that most of them are at variance with experiments of a similar nature performed by others, more especially those of Haller, Spallanzani, Whytt, Fontana, Legallois, W. Philip, Flourens, and M. Hall, none of whom remarked so immediate and complete a stoppage of the circulation from removal of the nervous influence. Again, in palsied :■- j u.c circu- lation is frequently little or not all disturbed, * Physiologische Untersuchungen. Leipzig, 1820. CIRCULATION. 681 and sometimes the secretions, natural growth of parts, and reunion of wounds have been found to be little impaired by injuries of the nerves. We may therefore form the conclu- sion, that although the circulation in the small vessels is obviously liable to be modified by the state of the nerves in their neighbourhood, or perhaps by affections of the nervous system in general, there is no reason to consider the capillary circulation as more immediately de- pendent on nervous influence than the action of the heart. Bibliography.— We have deemed it advisable to reserve our historical sketch of the discovery of the circulation and the knowledge of that impor- tant portion of physiology to this part of the article, thereby consulting brevity in uniting it with the literature of the subject. The Chinese have been conceived to have enter- tained correct notions of the circulation before they had any intercourse with Europe, — a supposition, the erroneousness of which is sufficiently demon- strated by their description of the commencement of the circulation of the radical humours and vital heat at three o'clock in the morning, their passage through the lungs in the course of the day, and termination in the liver at the end of twenty-four hours, as well as by the different manipulations practised by them in the operation of venesection. In the time of Hippocrates and Aristotle, al- though the principal bloodvessels were described— apparently from dissection of animals, — the course of the blood appears to have been wholly un- known. Towards the end of the second century Galen describes accurately the distribution of many of the bloodvessels in the lower animals. He ap- pears also to have known the anastomoses of the arteries and veins, and the structure and uses of the foramen ovale in the foetus, but his works afford no evidence of his having known the course of the blood in either the pulmonic or the systemic circulations. He described the arteries as arising from the heart, the veins from the liver ; and some of those passages of his works in which it is alleged that the circulation of the blood is pointed out, are either inconsistent with one another, or are believed to have been introduced at a later time than Galen's. Galen believed that the blood passed through the septum of the ventricles ; he knew that the arteries contained blood, but he believed its motion to be of an oscillatory kind. (De usu pa i t i urn ,. 1. iv., vi., & vii., and his trea- tise on the question — an sanguis in arteriis natura continetur ?) The authors of a more recent date, in whose works it has been supposed that the circulation was described, are Servetus, Columbus, and Caesal- pinus. After the revival of letters, the great ana- tomist Vesalius of Brussels, in 1542, had examined more minutely than his predecessors the connec- tions of the arteries and veins : he mentions the valves of the veins, the difference between the veins and arteries, and describes the valves of the heart. He seems to have known that the blood was propelled into the arteries by the heart, and demonstrated by a more direct experiment than Galen's, that the arterial pulse depends on the systole of the heart. (De corporis humani fabrica, fol. ; and Opera Omnia, cura Boerhaave.) Servetus, the victim of religious persecution in 1553, is one of those in whose writings we find the first dawn of part of the discovery of Harvey, for he very distinctly at one place refers to the pulmo- nary circulation. The vital spirit (blood) passes by the arteries into the veins by their anastomoses. The blood cannot pass from the right into the left auricle on account of the closed nature of the sep- tum auricularum ; in the adult it must go through the lungs, where it is charged with the vital spirit obtained from the atmospheric air, and then returns to the heart. He further held that the pulmonary artery and vein from their large size must have some other use than the nourishment of the lungs merely. De Trinitatis Erroribus. Basil, 1531. Columbus, Professor at Padua and Rome, six years after the publication of the work of Servetus, published the discovery of the lesser circulation as his own. He describes it more clearly than Ser- vetus does, and held that the blood returning from the lungs is not mixed with vital spirit, but is quite pure. Libri xv. De re anatom. Venetiis, 1559. Caesalpinus of Arezzo, Professor at Pisa, gave, in 1583, a more detailed description of the pul- monary circulation than any of those who preceded him, and in two parts of his work expresses him- self in such a manner as to shew that he had some idea of the systemic and double circulation. Other passages in his works are, however, quite incon- sistent with a correct knowledge of the course of the blood, and, although we find this course more nearly indicated in the writings of Caesalpinus than in any others before the time of Harvey, he does not seem to have added much, if any thing, to the knowledge possessed by those who preceded him, but rather to have applied, and without acknowledgement, the observations of Vesalius, Fallopius, Servetus, and Columbus, to the expla- nation of the circulation. The foetal circulation seems to have been ex- amined with great attention by the anatomists of the sixteenth century. Galen had already been acquainted with the foramen ovale, and also knew, though less perfectly, the ductus arteriosus. Fal- lopius described the ductus arteriosus exactly, so also did Vesalius and Aranzii ; and after this Botallus appropriated to himself the discovery of both the foramen ovale and ductus arteriosus. Vesalius discovered the ductus venosus which was figured by Fabricius and Eustachius. Fabricius ab Aquapendente made the discovery of the valves of the veins and published it in 1603 : it is sur- prising that knowing their structure so perfectly as he did, he should have continued ignorant of their uses, and strictly attached to the older erroneous opinions regarding the circulation. Dr. William Harvey was born at Folkstone in Kent, and studied under Fabricius at Padua from 1598 to 1602. Learning from his master the structure of the valves of the veins, he engaged in experi- mental researches after returning to England, with the view of determining their uses, and in 1619, according to his own statement, taught publicly for the first time the doctrine of the double circulation of the blood, which he had demonstrated by his investigations. He did not publish any history of this discovery until after the lapse of nine years, during which he had carefully examined his doc- trines and experiments. This appeared in the Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus, first published at Frankfort in 1628. Among the contemporaries of Harvey who sup- ported his views, the following authors are re- markable. Werner Rolfink, Professor at Jena, one of the first to adopt the new view, published two years after the publication of Harvey's work. Des Cartes upon two occasions supported Harvey's views, viz. in 1637 and 1643, having been answered by Plempius. John Walaeus, Professor at Leyden, may be regarded as one of the most original of those who adopted and defended the new view. In 1640 he published two letters, addressed to Thomas Bar- tholin. Herman Conring of Hermstadt. James de Back, Amsterdam, 1649. John Trullius, 1651, Rome. VOL. I. 682 CIRCULATION. George Ent of London. Riolan was ihe only one of his opponents whose objections Harvey thought it worth while to answer. This he did in two additional Exercitationes, which are published in the Leyden edition of his works, 1737. In a journey which Harvey made to Ger- many, he endeavoured to demonstrate his views to Hoffman, but without success. In 1652 Plem- pius acceded the merit of discovery to Harvey, and adopted his views of the circulation. Harvey died at the advanced age of 79, in the year 1657, after having had the satisfaction of seeing his views generally adopted by the best-informed anatomists and physiologists, and after having enjoyed the glory due to so great and valuable a discovery. — The best edition of Harvey's treatise on the Circu- lation is that to be found in the edition of his works published by the London College of Physicians, in 4to. About this time the experiment of transfusion, proposed some time previously, sc?ms to have been first successfully performed by Dr. Timothy Clarke, Boyle, and Henshaw, as also by the celebrated Lower at Oxford, in 1660, affording additional proof of the correctness of the views oi Hatvey. Although the double course of the blood through the pulmonic and systemic circulations was fully demonstrated by these investigations, the direct passage of the blood from the smaller arteries into the veins had not yet been observed. After the introduction of the use of the mi- croscope, this additional proof was supplied by Malpighi, who discovered the capillary circulation in the vessels on the lungs and mesentery of the frog in 1661 (Epistola de pulmonibus). Malpighi observed the passage of the globules of the blood through the minute vessels, and thus satisfactorily proved that there is an actual trans- mission of the circulating blood from the arteries to the veins in both the systemic and pulmonary circulations. Leuwenhoeck, in 1673, repeated the observations of Malpighi on the capillary circulation, and extended them to different animals, at the same time adding to their value by the discovery of the nature of the colouring particles or globules of the blood (Philos. Trans. No. 102). The structure of the minute vessels in different parts of the human body was shortly after this very fully shewn by the fine injections of Ruysch, and the analogy between the structure of the minute vessels in Man and the lower animals thus fully established. For the history of the discovery of the Circula- tion, we would refer the reader to the following works. Bostock's Elementary system of physiology, vol. i. p. 343. Holler's Elementa, vol. i. p 340. Senac, Traite du cceur, Introduct. p. 68. Sabatier, Ana- tomie, ii. p. 255. Portal, Hist, de l'anatomie et de chirurgie, t. ii. p. 468. Sprengel's History of medicine, French, vol. iv. p. 85. Hecker's Gerschichte der Medezin, Hecker's Lehre vom Kreislauf von Harvey, Berlin, 1831. Barrellotti, Dialogo sulla scoperta della circolazione del sangue nel corpo umano, Pisa, 1831. When the course of the blood in the double circulation had been fully established by the above- mentioned observers, and the views of Harvey were universally adopted, the labours of anatomists and physiologists were directed to the more minute and detailed investigation of the different processes of the circulatory function. The works of Lower, Lieutaud, and Senac on the heart, and of Hales, Haller, and Spallanzani on the motion of the blood, were among the more important of those which appeared during the last century which contributed to advance the knowledge of our subject. 'Ihe second volume of Dr. Stephen Hales's Statical Essays, 1733, contains the history of the numerous experiments made by that ingenious philosopher, with a view to investigate the hy- draulic phenomena of the circulation and the first accurate measurements and calculations of the force of the current of blood in the arteries and veins, its velocity, the po«er of the heart, &c. The works of Haller on the circulation consist, 1st, of the greater part of the first and second volumes of the Elementa, containing a complete history of the structure and functions of the organs of circulation ; 2d, Deux memoires sur le mouvement du sang, &c. Lausanne, 1756 : the first memoir containing the results, the second a detailed account of the experiments. These Memoirs are also published in the Opera Minora ; also, in English, Lond. 1757. 3d, Deux mem. sur la formation du cceur dans le poulet, Laus. 1758. The work of Spallanzani, entitled Experiments upon the Circulation of the Blood, translated by Tourdes into French, Paris, An viii., and by R. Hall, M.D. into English, Lond. 1801, contains a great body of most accurate observations and experiments. The first two Memoirs are on the circulation throughout the vascular system. 'I he next two on the phenomena of the languid circulation, on the motion of the blood independent of the action of the heart, and the pulsation of the arteries. Circulation in general. — Young on the circulation, Phil. Trans. 1809. Lund's Results of modern physiological vivisections, 12mo. Copenhagen, 1825, translated in the Journal Complement, t. xxiv.-v. &c. Bourdon, ^ur le mecanisme de la circulation, 8vo. Paris, 1820. W. Philip, Phil. Trans. 1832. 31. Hull, Reply to W. Philip, Med. Gaz. x. 695. Physiol, of the circulation, Med. Chir. Review, vol. iv. 1823-4, p. 38. Flourens, Memoires de l'lnstitut. vol. x. Herbst, De san- guinis quantitate, 1822. Schwenke, Hist, sanguinis. J. Wilson. Essay on the blood and vascular system, Lond. 1819. Kerr, Observations on the Harveian doctrine of the circulation of the blood, Lond. 1819 ; (doubts the Harveian view.) Charles Bell, An essay on the forces which circulate the blood, Lond. 1819. Oesterreicher, Versuch einer Darstel- lung der Lehre vom Kreislauf des Blutes, Nurnb. 1826. Wedemeyer, Untersuch. uber den Kreislauf des Blutes insbesond. uber die Bewegung desselben in denArterien und Capillargefassen, &c. Hannover, 1828 ; also in English. Reichel, De sanguine ejusqne motu exper. Lips. 1767. Jaeckel, De motu sanguinis comment. Vratisl. 1821. Sarlan- diere, Mem. sur la circulation du sang, &c. Paris, 1822. Jos. Swan, Essay on the connection between the action of the heart and arteries and the func- tions of the nervous system, Lond. 1829. Rose, Diss, de motu sang, naturali et prasternaturali, Helmstad. 1668. Maertens, Diss, de circulatione sanguinis, Helmstadt. 1739. Araldi, Delia forza e dell' influsso del cuore sul circolo del sangue, Mem. della Soc. Ital. in Mod. 1804, vol. xi. Heart. — Barry on the circulation through the heart, &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 cceur aortique, Bresrhet'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. 8vo. p. 371. Senac, Traite du cceur, 1749. Wil- degans on the same, 1772. A. WiUon, 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. Prochasha, Opera Min. 1800, Controv. physiol. Arteries. — In addition to the works referred to CIRRHOPODA. 683 in the Bibliography of ARTF.RV, 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 contractilii y 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 synchronico, Annotat. Academ. 1835. Mich. Jager, Tract, anat. physio!, de arteriarum pulsu, Wireeb. 1820. Reinarz, Diss, de arteriarum irritahilitate propria, Bonnae, 1821. Kramp, De vi vitali arteriarum, Argentor. 1786. Veins, and 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 alter death, Med. Chir. Trans, xi. Sir D. Barn/, 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, Dames, and Serle, Lancet, xi. p. 606, &c. Poiseuille, in Ma- gendie's Journal, x. Arnott's Physics. H. Marx, Diatribe anat. phys. de structnra et vita venarum, Carlsruh. 1819. Refutation of the theories of Carson and Barry, Etlin. 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, &c. Lugenhuhlcr , 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- cipalis veines de la Grenouille, Ann. d. Sc. Nat. xxviii. 65. Nic. Oudemann, De venarum, praecipue mesaraicarum fabiica 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. — Voellinger , Munich Transactions, vol. vii. and Journal des Prosres. Do. Was is Absonderung, &c. ? Wiirtzburg, 1819. Gruithuysen, Beitrage zur Physiognosie und Eau- tognosie, &c. Miinchen, 1812. Organozoonomie, &c. 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, &c. Berlin, 1822. R. Wagner, Zur Vergleich. Phy- siologie des Blutes, Leipzig, 1833. Baumgartner, Beobacht. iiber die Nerven und das Blut, &c. Freiburg. 1833. Oesterreicher, Versuch finer Dar- stellung dor Lehre des Kreislaufs, Nurtiberg. 1830. Marshall Hall. Essay on the circulation of the blood, 8vo. Lond. 1831. J Midler, 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. Kaltenb runner, Magendie's Journ. viii. John Erelyn on the passage of blood from arteries to veins in quadrupeds, Phil. Trans, xxiii. 1702, p. 1177. Molyneux in another volume of the same. Jus. 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 vitae phaenom. et de circulatione sanguinis in pirenchy mate, Berol 1826. Kruger, Diss, de theoriae physicas tubulorum capillar, ad corp. human, applicatione, Halae Magd. 1742. Influence of the nerves on the circulation. — 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. Legallois, Exper. sur le principe de la vie, Paris, 1812. W. Philip, Laws of the vital functions. Cliff on the heart, Philos. Trans. Bracket, Expcr. sur les fonctions des nerfs sym- pathiques, Paris. Milne Edwards If 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.) CIRRHOPODA; Cirri pedia ; Cirripeds ; (xi£co; and woD;, cirrus and pes, from the curl- like form which the coiled feet or arms present. Fr. Cirripides. 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 modern 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 ; " for,'' as he remarked, " 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 antennae of the lobsters."* Bur- * An. sans Vertebres, v, 377, 2 Y 2 084 CIRRHOPODA. 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, Goldfuss, 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. Clisia. 6. Pyrgoma. 7. Acasta. 8. Coronula. 9. Tubici- 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. sur les 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- Fig. 332. 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, Jig- 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 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 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 the first series of compart- ments (a, a, fig. 333) ; the other six constitute the second series {b,b, fig. 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 which 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 wall of the compartment of the se- cond series, a, 6 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 (fig. 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. Fig. 338. i grooves are very strongly marked in some spe- cies, as in Balanus Spinbsus (Jig. 337), where the tubes are large, and Fig. 337. the walls comparatively thin. In all they inn in 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, Jig. 338). In some small species, the tubes of which are wider than those of lar-er 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 (b, Jig. 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 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." Tubkinella, 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 Anatifu, 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 elastic 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, it is by its epider- mis that tlie peduncle adheres. The peduncle pre- sents still other varieties than those just mention- ed. Pollicipes villosus hasitcovered 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 interval vular 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 arms, 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, Jig. 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- cesophageal 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 (k, 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 (/, 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 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,Jig. 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- * Burmeister'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- Fig. 342. lated internally, and embossed outwardly, are attached to the stomach. The intestine is wide, nearly without convolutions, and ta- pering towards the anus id., e, Jig. 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 terniinates 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, Jig. 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 J 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, Jig. 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 CIRRHOPODA. 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 aims 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 beneatli 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> fis- 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 3Lth 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 (?•), 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 {t, t), which may be compared to the seminal vesicle. It pursues a tortuous course towards the base of the tubular process, where (/c) it is joined by its fellow of the other side, and enters the canal * Thin description does not accord with the result of Professor Burmeister's researches. Instead of a regular series 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 (t', t'). This canal runs to the distal extremity, and opens by a minute orifice fringed with very fine hairs. In Otion Cuvieri the two 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.}: The lengthened tubular process (?, t ',fig- 344), through which 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 cany 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 whut 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 part of the soft matter which constitutes the bulk 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. t Op. cit. p. 44. X 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 tcstii lc. were of opinion that these were 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. ] 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. MuH'er, 1834, No. 5, quoted in Ann. des Sc. Nat. iv. n. s.) We are not aware what species was anatomized by Professor Wagner; 692 CIRRHOPODA. 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. Thorn p- * 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. ^^•ffcT'H 6 S pT?"**. 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. He found a considerable difference between the larva 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,f 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- peds," &c. t Ann. des Sc. Nat. n. s. iii. 31. $ Muller's Archiv, No. 5, 1834, and Beitr'age zur vergloich. phys. dps Blutes. Leipzig, 1833. $ Beitr'age zur Naturgesch. der Rankenfiisscr. Berlin, 1834. 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 antenna? 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 dorsally. 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- J'era 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 Coronulse 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 still 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 arms ; 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. ©94 CIRRONOSIS — CONCHIFERA. (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. — Leevwenhoek , Opera, iii. 472. Lister, Exercit. anat. 1696, p. 96. Cuvier, Mem. pour servir a l'histoire des Mollusques, 1817. La- march, 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 D. J. Miiller, 1834, No. v. Surmeister, Beitrage zur Naturgeschichte der Rankenfuesser, Berlin, 1834. Martin St. Anye, Memoiie sur l'organization des Cirripedes et leurs rapports naturels avcc les animaux arricules, Paris, 1835. (John Coldstream.) CIRRONOSIS. (Kiggos, fulvus ; w«t, morbus.] In a memoir published by M. Lob- stein in the first volume of the Repertoire d' Anatomie and de Physiologie* for the year 1826, this term was applied to what that author considers to be a disease affecting the fcetus 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 l'Amphitheatie d'Anatomie de Strasbourg. f 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 fcetus 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 Scikrhus. CONCHIFERA. 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 : First sub-class. BRACHIOPODA, > Or POLYMYARIA J First sub-class. ~> C 1st sub-order : valves articulated. ^. 2nd sub-order : valves free. / Order 1st. The C 1st sub-order : shell regular. & Second sub-class ' more or iess united 2nd sub-order : shell irregular. CJ ' J Older 2nd. The ( 1st sub-order : shell regular. ^ f lobes of the mantle ' U disjoined . . . C 2nd sub-order : shell irregular. mi - , , , ("1st order: afoot. Ihird sub-class, y MONOMYARIA > - , , c . {_ 2nd order : no toot. 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 (Jig. 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 f digestion, 1 circulation, with organs of < lesP™n> ° i 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 696 CONCHIFERA. Fig. 345. (a, fig. 346) placed at Fig. 346. the anterior part of the animal is deeply hid- den between the foot (6, 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 Monomyaria, (a, Jig. 348). The hps 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, Jig. 346, c,Jg. 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, Jig. 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, Jig. 347, d,Jig. 348) is a membranous pouch, commonly pear-shaped, CONl'HIFEKA. 697 sometimes globular, rarely elongated and narrow. When the oesophagus 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, fig. 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,fig. 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 conchiferous 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 (f, Jig. 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. 313 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 de- 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 7. 698 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, Jig. 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 witl out tearing them. The ventricle, ■which is regular and symmetrical in the greater number of the genera («, Jig. 349) is irregular and unsymmetrical in the Ostracean family, (a, Jig. 350). It is generally elongated and fusiform ; Figs. 349 & 350. 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 bianches 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 branchise of one side are at a consi- derable distance from those of the other side, we find, as among the Archidso, that there are then two ventricles («, a, Jig. 351,) and two auri- cles (b, b, Jig. 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, Jig. 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,Jig. 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, Poll* has given a very satisfactory account of its anatomy. It is more particularly remarkable in the Archidae, 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, Jig. 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 branchife ; here, on the * Testacea Utriusque Skilias, fol. 3 torn. OONCHIFERA. 699 Fig. 351. contrary, the auricles do not receive the blood until it lias 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 branchrae (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 lamina? (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 laminaa 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 the siphoniferous 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 Terebratulse, 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 branchial, 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 branchiae, 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, fig. 346; i, fig. Z47; 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,fig. 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, jig. 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- my aires 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 Gold fuss 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, &c. 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, jig.* 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 Cratsipeds 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 occupy, and the 702 CONCHIFERA. 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 (hji fig- 347). They are particularly conspi- cuous in the cylindrical foot of the Solens, in the flattened foot of the Tellinas, and of the Uniones, and they have a remarkable arrange- ment in that of the Cardiae. 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 Lima. Up to the present time the faculty of pro- ducing a bussus 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 Mytilacea ; and, if the horny plates of certain Archae 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 Aviculae, and leads to the belief that the horny mass of certain Archse 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 (d, fig. 353). 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 Pinna;, 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 Su- 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 strigilutus; it is cluviform when it is thicker at its extremity than at its base : it is found of this shape in certain other Solens. The 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, (a, 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 (6, fig. 359), of which the genera Cardium, Nuculti, and Trigonia present examples. Various other modifications, of less importance than those we have particularized. 704 CONCIIIFERA. 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 Mvtlusca 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, Testaceu Utriusque Sici- iia; 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 laciea 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 oesophagus, towards the base of the labial palps (1, 1, fig. 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, fig. 360) running across or over the oeso- phagus. From the edges of the ganglions many filaments arise, some of which on the sides descend into the substance of the labial palps (3, fig. 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. Nervous system of an Unto. 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, fig. 360); these descend along the body towards the base of the branchias, 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 branchias. 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 neivous 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 CONCHIl'ERA. 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 thB 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 branch is?? Among these there is one, and sometimes two, which, resting on the internal aspect of the central muscle, bend obliquely over its surface, and final y 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 espeeial 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 thern 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, Jig. 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 (r, fig. 362), and a few nervous filaments (7, 8,_/;g.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 (/, /, 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 Regne 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 Dimyana 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 united 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 to war Js 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 ia 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. (7 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. Sip/ions. — -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 subcylindrical 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 branchias. 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 papilla, (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,Jig. 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 be 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 Conchiferous 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 ot laminae 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 (a, c, c, Jig 363) ; the other, in parallel layers, secreted by the central and posterior parts 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 appearing to have undergone any great change. It is in the genera Chama, My- tilus, Pinna, Spondylus, more es- pecially that the two lamina? 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 CONCHIFERA. 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 nymphte has been given {a, 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 nymphae 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 nymphae more prominent externally than the cardinal edges, but contracting gradually under this edge in proportion as the nymphae 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 nymphae, 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 nymphee, of less depth, still show a portion of the ligament externally; finally the ligament is external when the nymphae 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, Panopus, Thrucia, Calcinella, Amphidesma, Lutraria, Mactra, Mr/a, 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, Cuculla'a ) 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, Crcnatula ), instead of having a single ligament, have a regular series of fossiculas, 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 hingx 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 concholos*tst knows the interesting genus denominated Pkolas. 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 («, Jig. 364), and advancing nearly to the middle of the valves, According to our views CONCHIFERA. 709 Fig. 36 4. Pholas. Petricola. these appendages are the first parts of the cardinal teeth. There ) 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 (ventre 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 with a duplicative 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 Pholuda 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 the 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 pholucliformis and of the Pholuda 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 hook (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, Jig. 36.5) ; 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, Jig. 365), the other posterior (d, Jig. 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 (b, b, Jig. 366). Fie. 366. A rca. 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, Jig. 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 nympfue 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 the bivalve 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 inequivalved ; 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 inequivalveand 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, Sec. 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, as certain 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 CONCIIIFERA. 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 belli/ 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. .F/g.368 A. ^ . a, anterior edge; b, inferior edge; c, posterior edge ; d, edges of the shield ; f, ligament ; f to h, nympha; h, othei extremity of the liga- ment ; i, point of the uncus or hook ; I to n, lunula; I, 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 striae, 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 Ostreao; in the latter case the edge is also said to be widely or deeply dentated. 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 Dimyana ; 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 nymphae 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 conch i- 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, Solernya), 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 fohow 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- t'e 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 pear to he 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« Mt^anpqn 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 conclii- 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. r. come free in the substance of this muscle, and there continue to increase with 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 the 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, we 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 branchia? 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 cf 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 m 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, and 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. 3 A 2 716 CONTRACTILITY. 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 Clavigellawe observe a lateral line departing, formed of the genera Fistulana, 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 Vene.rupis 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 Osteodesma, on which account it is made to depart laterally from 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 Anatinella, which we place crosswise to connect the genera just men- tioned. In the Mactracea, we pass without any very great stride from the Lutraria to the Mactra, from the Mactra to the Erycina and to the Ainphidesma. 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 Salens ( Soletellina, De Blainv.) and the Psammobite ; but we also know that the genus Psummobia 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 Solenacese. 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 Solen- ertus, Panoptea, Solen, Solemya, and Glyci- mens, 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 Lucinidce as a lateral and truncated branch of the Conchidce, divaricating from the genus Astarte. With 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 Etheria and the family of the Iiudistes 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 Placunida a famdy containing the three genera Placuna, Placunonomia, and Ano- mia, which according to our views constitute a descending and lateral line really intermediate to the Conchifera 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 coquilles, 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 dor Konchilienschaalen. Besch. der Berlin. Naturforsch. Gesell. B. i. S. 230. Mutter, Anmerk. ueber Walch, ibid, B. ii. S. 116. * * * * Cuvier, Nouvelles Rech. sur les coquilles bivalves, Societe Philomath. A. 7, p. 83. Lister, Anatomy of the Scallop, Philos. Trans. Year 1697. Ant. van der Heide, Anatome Mytuli, 12mo. Amst. 1684. Bojanus, Sendschreiben an G. Cuvier iiber d. Athmen und Kreislaut'swerkzeuge 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. t. vi. (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 Contractilit't 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 Contractilitc 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 which 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 Tonka 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 Contractilitc Organique Sensible to the contractions excited by any kind of irritation, acting on muscular fibres themselves, and the term Contractilitc 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 pait 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 Haller 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 * Sec Mayo's Outlines, 2d edit. p. 50 ct sen. 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 distant 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 Flourens, 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 Exeito-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 ;|| 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. $ Outlines of Physiology, second edit. p. 282, and Anat. and Physiol. G'omms. <5 Phil. Trans. 1833, p. 635. (I 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 the 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 Breschet, Milne Edwards, and others, to be exceptions to the general rule of involuntary muscles being inexcitable by irritation of then- 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 striae, 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.f 4. When 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 * 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 dc Phy- siologic, torn. 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 in 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 7i 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 all, very ge- nerally, such as to render their action dis- advantageous, and require 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 the 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 gLth 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 3raotn Pa,,,; °f 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 Ciliae 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- * See Hallei's Elem. Phys, torn. 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,f and the stiffening or " roideur cadaverique" of the muscles after death, — seem to be clear indica- tions of a tendency to contraction answering * SeePrater'sExpcrimental Inquiries in Chemical Physiology. t See Kichcrand'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 tire 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, or 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 power of muscles is rapidly extinguished when 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 'freatise on Asphyxia, ch. 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 pupae, 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 pupae, 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 722 CONTRACTILITY. 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 effect 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 foeius 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 ; \ and R Philosophical Transactions, 1832 t See Bracket's Recherr.hes sur le Systeme Ner- veaux, p. 36 & seq. \ 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 " Affirniantibus 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 * Loc, 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 he 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 extinguish 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 several 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 stiil 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 this 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 voluntarymuscle, 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 Remcdiis Stimulantibus. 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. xqanov; Ft. Crane; Germ, llirnschadel ; 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 Dcsmotilins 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 vertebrated 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 foetal 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 lamella?, called an inner and an outer table, which are united by an areolar ossific tissue, termed diplo'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, (/3p6^a, from (3pixu, 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, the 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, jig. 370) and ethmoid are in its front, the Fig. 370. occipital (O, jig. 372) is behind it, the two temporal (T, Jig. 370) are on its sides, and the two parietal (P, fig. 370) are above it. The sphenoid bone (from atynv, cuneus, os sphenoidale; Germ. Sphenoidal-knochen, Keil- knochen) comprehends the quadrilateral mass which forms the centre of the frame-work, the anteriorribs 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 fephip- pium, sella turcica, fossa pituitaris ) for the lodge- ment of the pituitary gland. The posterior bor- der of this depression presents a crest, the corners 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 Soemmerring 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 basilures for the lodgement of the basilar sinuses. The ala majores are those large curved pro- cesses, which, stretching outwards, forwards, and upwards, contribute to form the middle fossae 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 b>ain 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 thejbramen 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 w'ing, is the sulcus Eusta- chianus, 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 inferi- 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 pterygoidea 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. The 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 al/E 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 eaehala minor is smooth, and partly forms the anterior fossae of the skull. The processus ethmoidalis 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 vlivaris) 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 eacli side in the foramen optician 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 ala? 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. Thefrontalbone( osfrontis, coronic ; 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 puss 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, the frontal eminence (eminentia 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. t. 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 orbiturium ), 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. 373. 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 cerebii 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 ccecum. 3 B 730 CRANIUM. The orbitar 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 J'ossa (fossa lachrymalis ) 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 unticum, 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 ethmoidalis ( incisura ethmoidalis), 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 ccecum 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 bone 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 hand 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 cf 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 (jjfi^os*^?, *)9|U.o?, cribrum, osethnioideum; Germ.Ethmoidal-knochen Jcom- 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 thefbramen catcum. 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. 73 L 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 ( cellula 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 the 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 superior 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, Hinterliaupts-knoc/ien,) 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 3 b 2 CRANIUM. spine divides it into four fossae, the two supe- rior of which are the fossa cerebri for the pos- terior lobes of the cerebrum, the two inferior, the fossa 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 (the fossa jugularis ), which is bounded on the outer side by a strong rough process (the processus jugularis ), 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 condyloideum anticum for the passage of the motor linguae 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 nuchae 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- c'.eido-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 trachelo- 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 hating 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 condj/loideum posticum ) 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 Joramen 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 os basilare or os spheno- occipital. The connexions of this bone are few and simple, being, in its superior half, with the panetals ; 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 with 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 Schlufenbein.) 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 Glasserian ganglion lies ; more out- wardly and running lengthwise, is a faint sulcus (the sulcus Vidianus ), which terminates at a small opening (the hiatus Fullopii) 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 ihefossula 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 petrosus ), 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 jugularis), 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 (the Jissura Glasserij, 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 membranae 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 fossae; 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 unticum. 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 articuluris ), in which the condyle of the lower jaw is placed. This root is the eminentia articuluris, 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 two 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 ScheitelbeineoderSeitenbeine) (fig. 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 offers 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 stria, 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 surjuce 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 parictalis, 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 (fossce Pacchionii) for the granulations of the dura mater, called glandulae Pacchionii externa. 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- f36 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 sulcus 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 dura 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 parieta'.s 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 their 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 winch are situated in the calvaria, and to which the name is more suitable, are the coronal, lambdoiclul, 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. 737 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 suturcc squamosa (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 lumbdoidalis. 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 arid 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 sphenopari- 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 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 anierior 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 cre?t 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 forampn 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 digastricus between the two; and, lastly, the foramen stylo-mastoideum at the bottom of the sulcus digastricus. 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 suturae 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 coecum ; behind, by the centre of the internal crucial spine ; and, in its circumfe- CRANIUM. 73$ 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 Jbssee, 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 fosstE consist of two large fossa; 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 fossa; 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 Glasserian 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 fossa;. 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 termination of the lambdoidal suture, and the additamentum suturae squamosa; 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 internus 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 fossa; 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. no CRANIUM. 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 fossa?, five inches ; and between the extremities of the alas 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- tebra?, 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 ephippmm 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 vertebra? 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 * This was Dumeril's theory.— See Consid. gen. sur l'Analogie entre tous Ies os et les muscles du tronc des animaux. — Magasin Encyclopedique, 1808, t. iii. f Th6 celebrated Goethe was among the first to adopt this idea. He admitted the existence of three vertebrae in the cranium, (Znr Naturwis- senschaft iiberhaupt, &c. Stuttg. 1817-24.) The lurther development of it occupied the attention of O'Kcn, Spix, Meckel, Geoflroy St. Hilaire, and Car s. — bee Meckel, Anat. Desc. &c. t. i. p. 631, and Cams, Anat. Comp. par Jourdain, t. iii. Iutrod uction. — ED. CRANIUM. 741 of the sphenoid bone vertically) at once 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 angnlar 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 vertebra1, 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 foetus 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 pro- tuberances of the frontal and parietal bones {c,d,figs. 374,37 5) and radiating to- Fig. 375. wards the circum- ference of these bones, it follows that the angles will be incomplete when the rest of the bone isforraed. 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 the frontal bone being formed in two parts, is of a lozenge shape ; and it is between those two parts and the frontal an- |jl gles of the parietal bones that it occurs. These two fontanel les are conse- quently at the extremities of the sagittal suture. The inferior fontanelles are found, the anterior («, 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. Fie. 376. 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 magnu m to appear to 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 diploe 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 diploe 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 (Jigs. 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 after life ; 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 the 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, inferiorly 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 the 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 acep/ialia and anence- phulia). 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, trianguluria, 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. Bertm 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 ct ad eura doctorum virum epistohx, t. i. Hafnia;, 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 diploe 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 diploe is perfect, the augmentation being in the two tables ; in others, and indeed in the majority of specimens, the two tables and the diploe 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 aquarterofan 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 diploe 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 raem- 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, a tumour 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 spicutae 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 Osseous 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.* * 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. Occipitofrontal 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 necessaiy 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 occipito-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 l'amour ou l'art 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 Ton 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 theoccipito-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. Occipico-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 the last named muscle, as well as of the corrugator 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 ot the epicranial aponeurosis. The attachment of the muscle to the occipital bone is immediately above that of the sterno- mastoid and splenitis 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-frontalis is the corrugator supercilii muscle, it lies on 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 eyebrows, 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-lrochleator 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 prepamta, 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 ! 7. Lymphatics. — The lymphatics are very few, 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 unfrequently the seat of peri- ostitis and of nodes. II. Temporoparietal 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 tetnpora 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 Eaii.) 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. — The 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 openingthe 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. Crustaccs — 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 horny or calcareous, and form, a kind of external skeleton ; their extremities are also articulated, arranged in a double series, and constitute antennae, 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 trachea: 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. S X >>.S, ¥M$ P a . « in . ^ H 3 o» « n -.c " S. a, 2 o-g-i >. H.S rtun The Gr; notl Doi C Si .3*8 ance thai care pod Leu c o. . B — y £ s«8 O o _0< - 8.1 Ej3 S.2 J3 ° .£ § ' s 3" 2 M| 5 g-o.S Sf-o-S 2 o u V__ < w 752 CRUSTACEA. § 1. Of the skin or 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 inlegument 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 Brachyura, for in- stance, the integument consists of a corium and an epidt rmis 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 maimer 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 pigmcntum, 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 at212°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.f 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 * Chevreul and Geoffioy, Journal Complemen- taire du Diction, des Sciences Medicales, Avril 1820. Milne Edwards, Hist. Nat. dcs Crustaccs, t. i. p. 10. t Lassaignc, Journal d. Pharmacic, 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 mann er ; 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 apy 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 physiologfcal 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 the most posterior rings of the body. 754 CRUSTACEA. The Loemodipods, the Entomostraca, and the Haustellate 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. ft 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. Theoretical figure illustrating the composition of the tegumentary skeleton of Crustacea. J), Dorsal arc ; t, t, tergal pieces ; e, e, epimeral pieces ; V, ventral arc ; s, s, sternal and episternal pieces ; P, insertion of the extremities. dian line constitute the tergum (fig. 378, D ) ; the superior arc is completed on either side by two other pieces, known under the name of /lanes or epimeral pieces (fig. 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 corre- 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 * Annates des Sc. Nat. torn. i. Thorax of an A telecyclus seen from below, a, sternal pieces of the second thoracic ring ; b, episternal 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 Maja 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. 6 Talilra Saltator magnified, a , head ; b, thorax composed of seven distinct 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 lamina 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 Squilla: 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. dcs Crustaccs, 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 cm 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 * Untersuchungen ueber die Bildung des Fluss- krcbses, &c. Tr. m 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 Pandarusform 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. b 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 apodemata 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 apodemata in their interior. These septa are of two kinds ; the one, styled sternal apodemata, arise from the lines of consolidation of the thoracic sternal pieces ; the other, named epimeral apodemata, 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 lamina? 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 apodemata, 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 Fluviatilis, showing the dis- 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 balancement 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- nelidans, 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 («), which is the most Fig. 386. essential and most constant part, formed of a variable number of articulations ; the palp (6), 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 J (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 Squilla 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 the Squilla ; b, one of the small antennae. 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 (picds-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 Jig. 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 fiabelliform appendage or whip, dedicated especially to the purposes of respiration, and in the Penese 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 I 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. A bdomen o f the female ftlaja 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 7bO 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 Jiuviatilis* It 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 antennas. 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-tvventy 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. * JVTenioiies de 1'Academie 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 Cmstace*, 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 js the most favourable to precision of movement and to strength, has the 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 Jle.vion, 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 lamina;; but they vary 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 Brachyura, 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 chela 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 tegumenlary 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 * Unteisuchungen uber die Bildung des Fluss- krebses. CRUSTACEA. 763 as finally to constitute a single continuous mass only. The same thing 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 «s the three dispositions which we have mentioned from the mo- _ ment at which the nervous sys- °~~ tem appears. In this genus, in fact, we perceive on either side |gs 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 outline.* There are thirteen ,_. pairs thus constituted, corres- ponding to the thirteen seg- ments which enter into the com- IP position of the whole body. The two nuclei of each pair com- <^ municate together, in the same manner as each pair is con- 'Hftf= nected with that which succeeds, J(jl and with that which precedes it, *inp by means of medullary cords in Ar the first instance, and longitu- v i , . , ' , 3 _ or the lulitrus. dinal cords in the second. In ... i i i a, cephalic ean- all essential particulars each pair gjia . b> 5me_ 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 of SanSlia- * Vide Recherches Anatomiques snr le Systeme Kerveux des Crustaces, par M M. Audouin et Milne Edwards, Annales des Sciences Naturelles, torn. 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 antennae 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 ceti\ 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 ^{f3^ pairs, the appearance of a more immediate conjunction than ac- tually exists. To conclude, the abdominal ganglions 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. V t Treviranus.VermischteSchriften anatomischer und physiologischer inhalts, Band 2. Heft I. t Audouin et Edwards, loc. cit. 3 d 2 Nervous system oftheCymothoa. 764 CRUSTACEA. But it is more 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 Astacus Murinus, or Sj/hi/ix Ligustri. in consequence of their gliding or encroaching, as it were, upon the median line. The Lobster ( Astacus murinus ) (fig. 393) 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 (t*), 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^,fig. 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- nas (b) ; 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 antennas are composed, and the nerve ends by becoming bifurcated, in order to penetrate the two filaments in which the an- tennas 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 (rf), 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. the corresponding cord of the opposite side ; after this the two form a single nerve, which hy-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 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 then- 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 median plane; but in a species very nearly allied, namely, the River-crab ( Astacus fluviatilis), 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 oesophagus. 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 (a6), 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 CRUSTACEA. Cephah-thoracic por- 5 presented by the 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. from the Deca- _ tt M poda Macroura to the Brachyura takes place by the Homola, 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 si/stem of the Pali- nervous system nurus Vulgaris. in the Carcinus mcenas 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,t 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 geneia 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 (I), instead of the ring which it presents in the * Vide Rech. sur l'organiz. et la classific. des Crustaces Decapodes par M. Milne Edwards ; An- nales des Sciences Naturelles, t. xv. t Cuvier, Lecons d'Anatomie Comparee, t. ii. p. 314. } Audouin et Edwards, loc. cit. Fig. 395: Nervous system of the Slaja 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; /, nerves of the exterior antennae; 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 ; I, tho- racic ganglion ; in, nerves of the maxillae ; n, nerves of the first pair of legs ; o, abdominal nerve ; p, cells of the (lanes ; q, arch of the flancs. Carcinus moenas, 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 amongthe 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 by 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, pfc. 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 antenna 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 from 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. Rosenthal,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 antennte them- selves} (jig. 396, a). 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. t Reil's Archiv. und Treviranus's vermischte Schriften, 2ter Band. 2tes Heft. X Minasi, Dissertazioni di timpanetti del'udito scoperli nel Granchio paguro. Scarpa, De structura fenestra rotundas, &e. Anat. observ. 4to. Mutin. 1772; Anat. Disq. de Auditu et Olfactu, fol. Ticin. 1789. Cuvier, Le<;ons d'anatomie comparee, t. ii. filihie Edwards, Histoire naturelle des Crustacts, t. i. p. 123, 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 (Jig. 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 into vibration ;* 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. lCEA. 769 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 organs 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 colour, 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 Cyamoe, 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. MiiUcr, Zur vergleichendcn Physiologie des Gcsichtsinnes 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. Tn 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 Peneas, the Galatheae, and the Scyllari, they are square (Jig. 399), whilst the Paguri, the Phyllosoma, the Fig. 399. Squillae, the Gebiae, the Calli- anassas, and the Crabs, have them hexagonal (Jig. 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 compartmenU Fig. 402. 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 {Jig. 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 Idotea?, 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 CallianassEe, 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 (Jig. 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 Daphnia, 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 cornea?, 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, (Jig. 403,) whilst in the Decapo- da and the Stomapoda (Jig. 404) they are sup- ported upon moveable Fig. 403. 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, we 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 lip or labrum {a, fig. 405) is a median piece in the form of a simple fold, and the lower lip or languette (c) is for the most part bifid. Be- tween these two pieces and on their sides are the mandibles, (jig- 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. 406. Masticatory Organs of the Phyllosoma. a, upper lip ; b, mandibles ; c, lower lip ; d, maxilla;. 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 nameofjrtww. 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 Fig. 407. 772 CRUSTACEA. led to their ordinary denomination of maxil- lary limbs or feet (Jigs. 408, 409, 410.) Fie. 408. Fig. 409. 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 laminse, armed with teeth or serrae of various sizes, and supporting an articulated palp (/>, Jig. 408) as well as a Jtabelliform or whip - shaped appendage (c), which penetrates into the interior of the branchial cavity. The last pair of all (Jig. 410) presents Fig. 410. 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 (jig. 41 1) 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 Fig. 411. Limulus polyphemus, ( ventral aspect.) a, carapace ; b, frontal portion of the carapace; c, thorax; d, chelifera ; e, f, g, h, legs, the basilar portions of which surround the mouth and act as mandibles ; I, under-lip ; m, branchial or lamellifonn appendages ; n, mouth. itself under the shape of two thin and much expand- ed lamina 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 word 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 Fig. 413. Fig. 414. Fig.4\5 Fig. 412, Ventral aspect of the cephalu tlioracic portion of the Dichelestion. a, trunk or sucker ; b, maxillae. Fig. 413, Th; trunk or sucker magnified, a, the labrum ; b, the mandibles. Fig. 414 # 415, The maxilla:. nultimate articulation (the claws, pincers, or cheliferous extremities ). The extremity occasionally terminates in two articulations presenting no kind of unusual development, but the last of which, termi- nated by a sharp point and armed with teeth or serrae, returns upon the preceding one, so as to form a kind of hook or pincer, opening in the opposite direction, (the sub-cheliform extremities of the Squillce and Crevcttinac ). Lastly, these extremities frequently terminate in a simple acute angle of which the animal can make no use save in locomotion. In the Sucking Crustacea, which live parasi- tically on other animals and feed by sucking their blood, the structure of the oral apparatus is extremely different.* Certain pieces which must be considered as analogous to the labium and languette, are elongated, so as to form a trunk or cylindrical tube, of variable length, adapted for sucking, and in the interior of which are lodged the mandibles, now pro- longed so much that they form two slender and pointed processes the extremities of which serve as a lancet. The appendages which in the masticating Crustacea constitute the jaws, here continue rudimentary, and the three pairs of limbs which in the Decapoda complete the oral apparatus, under the name of maxillary extremities, are here transformed into organs of prehension, of different forms, by means of which the parasite attaches itself to its victim. In the whole of the Crustacea the intestinal canal presents two openings, the mouth and * See our " Recherches sur l'Organization de la Bouche des Crustaces Succurs," Ann. des Sc. Nat. t. 28 ; Burmeister's Beschreibung einiger neuen schmarotzer Krcbse, in the Acta Acad. Caes. Leop. Nat. Cur. vol. xvii. p. 1. the anus, always separated from each other by the whole length of the body. The mouth is the mere an- terior and outward expansion of the oesophagus; it is fur- nished with nothing that can properly be compared to a tongue ; the horny and la- mellar organ which writers have sometimes spoken of under this name is nothing more than the lower lip, which has already been de- scribed. The oesophagus itself is short ; it rises vertically and runs to terminate directly in the stomach. Its general structure, as well as that of the stomach and whole of the intestinal canal, bears a very close resemblance to what we observe among the superior animals. They each consist of two membranous layers separated by one of muscular fibres, always of greatest thickness in those points in which the most energetic contractions take place, and especially at the entrance into and passage out of the stomach. The stomach is of a globular form, and of very great capacity ; it fills a considerable extent of the cephalic cavity, and presents two portions very distinct from one another; the cardiac region, vertically surmounting the mouth and oesophagus, the axis of which is lost in its own ; and the pyloric region, situ- ated behind the former, and forming a right angle with it. But the most remarkable feature presented by the stomach of the Crustaceans is the very complex masticatory apparatus it contains. This consists of a considerable number of pieces, the form and disposition of which vary, and are always singularly in harmony with the kind of food taken and the general habits of these animals. The apparatus, as well from the important office it fulfils, as from its being no where else encountered in so perfect a state of development, were worthy of a description which would swell this article to too large a size ; we shall therefore be brief, and merely state generally that it consists of a great number of pieces, so connected as to constitute a kind of solid frame armed in- ternally with tubercles or sharper teeth situated around the pylorus, and capable of being- moved so as to bruise or tear in pieces the alimentary matters subjected to their action, and as they are about to pass through this opening.* The different pieces composing this appa- ratus vary considerably in the different genera, * Vide Cuvier, Lecons d'Anatomie Comparee, t. iv. p. 126, and Milne Edwards, Hist. Nat. des Crustaces, t. i. p. 67, for further details. CRUSTACEA. Fig- 416. Pig. 417. a, Cardiac portion of the stomach. 6, b, Upper portion of the frame-work of the stomach. c, Pyloric portion of the stomach. d, The small intestine. e, Termination of the biliary ducts. f, Anterior appendages of the intestine. g, Posterior appendages. h, Rectum. and even in the several species of the same genus. Still every one of them may be de- monstrated with a little care, in the whole of the Brachyura and of the Macroura. They are less numerous, and are singularly modified in proportion as we recede from these types. In the Squilla mere vestiges only of the ap- paratus are found in two semicorneous pieces covered with rounded projections ; and its functions are performed by a branch of each mandible which penetrates even to the pyloric orifice of the stomach. The intestine extends from the pylorus to the anus without curve or convolution in its course {fig.AXQ, d,k). In the superior Crustacea Liver of the Lobster. a, stomach ; b, intestine ; c, left lobe of the liver in its natural state ; d, right lobe dissected, so as to show its structure and the disposition of the biliary ducts. it may be distinguished into two portions, one of which may be named the duodenum, the other the rectum. These two portions where they occur vary extremely both in their nature and in their relative lengths. Sometimes they are separated by a valve (Lobster) corresponding internally to a circular external elevation ; but still more frequently their respective limits are not obviously marked, and among the whole of the inferior members of the family the intestinal canal is entirely cylindrical, and per- fectly identical in its constitution through its whole length. The anus is constantly seated in the last ring, and is closed by certain mus- cular fibres which perform the office of a sphincter. CRUSTACEA. 775 The biliary apparatus of the Crustacea is of very large size in the Decapoda. The liver is symmetrical (fig. 4 17), and consists of two halves generally separate one from another, and the whole organ is made up of an agglo- meration of coecums, which by one of their extremities empty themselves into excretory ducts. These by their union form larger and larger trunks, and the secreted fluid or bile is finally poured by a double channel into the pyloric portion of the stomach. The liver is found to undergo extensive modifications as it is examined in individuals lower and lower in the series; in the Edriophthalmians, finally, we discovet nothing except three pairs of bili- ary vessels analogous to those of insects. The liver is not the only secerning organ whose product is poured into the intestine. On each side of the pyloric portion of the stomach, we observe two blind tubular cavi- ties narrow and much elongated in their form, which pour out a whitish fluid (fig. 4\6, f, f); and at the point of conjunction of the two por- tions of which the intestine frequently consists, as has been said, there is a third tubular cavity or vessel in all respects similar to these two (fig. 416, g). These tubuli are all wanting in the Astacus fluviatilis, and in the Astacus ma- rinus the single posterior tubulus is the only one found. Nothing positive is known with regard to the uses of the fluid secreted in these tubuli. To conclude, there are two organs of a green colour situated on either side of the oesopha- gus, the structure of which is glandular, and which appear to bear some analogy to the sali- vary glands. B. Of the bluod and circulation. — We are altogether without positive information as to the mode in which the nutritious fluid, elabo- rated by the process of digestion, passes from the intestinal canal into the torrent of the cir- culation. Hitherto no chyliferous vessels have been detected, and we are therefore led to believe that it is by imbibition that the trans- ference takes place from the intestine to the bloodvessels in the Crustacea. The blood of the Crustacea is a colourless, or slightly bluish coloured fluid, holding an abundance of circular-shaped globules in sus- pension. It is extremely coagulable. Its che- mical composition has not been investigated. This nutritious fluid is put into motion by a heart, and circulates through a vascular system of great complexness. Willis,* Swammer- dam,f Cuvier,| Desmarest,§ and several others have given a description of this system ; but there are still innumerable points upon which opinions remain different. The following are the conclusions to which M. Audouin and I have come from a careful study as well of the anatomical disposition of the circulatory apparatus of the Crustacea, as of the progress of the blood through its interior. || The circulation of the blood in these ani- mals is accomplished in a manner very similar to what takes place in the Mollusca. The blood pushed forward by the heart is distri- buted to every part of the body, from whence it is returned into large sinuses situated at no great distance from the base of the branchite ; from these sinuses it is sent on to the respi- ratory apparatus which it traverses, and from which it then finds its way to the heart, to recommence the same circle anew. The heart is consequently aortic and single. Fig. 418. Viscera of the Cancer Pagurvs. f, heart; a, ophthalmic artery; o, abdominal artery ; c, stomach; e, skin g, branchiae, inverted to show the efferent vessels; h, vault of the flancs : n, bianchia; in their natural position ; m, flabellum ; I, liver; h, testicles. * De anima brutornm, caput tertium, p. 16. t Collect, academique, partie ctrangere, t. v. p. 126. \ Lecons d'Anatomie Comparce, t. iv. p. 407, et Regne Animal, Ire ed. t. ii. p. 512, et t. iii. p. 5. § Considerations sur les Crustaces, p. 57. || Recherches anatomiques et physioloiiques sur la Circulation dans les Crustaces. Ann. des Sc. Nat. t. 11. 776 CRUSTACEA. The heart is always found in the median line of the body, and lying over the alimen- tary canal near the dorsal aspect. Its form is various ; in the Decapods it is nearly square, and lies in the middle and superior part of the thorax, being separated from the carapace by tegumentary membranes only, and may be seen in the space included between the two vaults of the flancs. In structure it appears to be composed by the interlacement of nu- merous muscular fibres, fixed by their extremi- ties to neighbouring parts and passing to some distance over the aggregate at either end, so that the whole organ brings to mind such a figure as would be formed by the super- position of a number of stars the rays of which do not correspond. In the other orders this general form of the heart varies conside- rably, from the figure of an oblong square of rather inconsiderable size, as it occurs in the Decapoda (fig. 418, /|), to that of a long cylin- drical vessel extending through the whole length of the body as it appears in the Stoma- poda (fig. 419), and the Edriophthalmians. In the former of these it gives origin to six vascular trunks, three of which issue from the anterior edge, and three from the posterior surface ; each of the six openings is closed by a valvular apparatus which prevents the regur- gitation of the blood. The first of the three anterior vessels is situated in the median line and is distributed to the eyes, in consequence of which we have entitled it the ophthalmic artery (a, fig. 418). Lodged within the substance of the general te- gumentary membrane, it continues its course without undergoing any subdivision along the median line through the whole length of the thorax, until, arrived opposite the eyes, it sub- divides and terminates in two branches which penetrate the ocular peduncles. On the two sides are the two antennary arteries. They run obliquely towards the an- tennas, sending off numerous branches to the tegumentary membrane in which they are at first lodged; they then plunge more deeply, sending branches to the stomach and its mus- cles and to the organs of generation, between which they insinuate themselves by following the folds of the same membrane which parts them. Lastly, each of these vessels subdivides into two branches, one of which proceeds to the internal and the other to the external antenna. Two hepatic arteries arise from the fore part of the inferior surface of the heart, and pene- trate the liver, there to be ramified ; but they are only found double and distinct from one another so long as the liver is met with divided into two lobes, as it is in the River-crab and Lobster. From the posterior part of the same surface of the heart there proceeds a large trunk, which, from its importance, might be compared with the aorta. This is unquestionably the vessel which many authors have spoken of as a great vena cava : we have entitled it the sternal artery. It bends forwards, giving origin to two abdo- minal arteries (o,fig. 418), dips into the sternal canal, distributing branches to the different thoracic rings, as also to the five first cephalic rings, which it passes over in its course. Meet- ing with the oesophagus it bifurcates, but still sends branches to the mandibles and the whole of the anterior and inferior parts of the head. The bulb presented by the sternal artery at its origin, in the Macroura, is the part which Willis characterized as the auricle of the heart. As concerns the two abdominal arteries, which may be distinguished into superior and inferior, and which arise from the kind of cross which it forms almost immediately after its exit, they are in precise relationship in point of size with the magnitude and importance of the abdo- men itself. In the Brachyura they are mere slender twigs ; in the Macroura, on the con- trary, they are capacious stems, and the inferior of the two sends branches to the two posterior pairs of thoracic extremities. The disposition of the three first vessels is the same in the Stomapoda as in the preceding species ; but the great vessel which represents the heart being extended through the whole length of the body, supplies immediately other arterial branches in pairs, and in number equal to those of the rings. Fig. 419. Arterial system of the Sqtdlla, b, heart ; a, anterior artery. Fig. 420. Venous system of the Maja. a, venous sinuses ; b, branchiae ; c, vault of the Bancs partly taken away ; d, legs. CRUSTACEA. 777 The blood returns from the different parts of the body by canals, or rather vacuities among the tissues, (for they have no very evident appropriate parietes,) which terminate in the venous sinuses, situated close to the branchiae. In the short-tailed Uecapoda we find no more than a double series of these sinuses, included within the cells of the flancs above the articulations of the extremities. They com- municate with one another, and they appear to have no parietes other than laminae of cellular membrane of extreme tenuity which cover the neighbouring parts. Each of them, neverthe- less, receives several venous conduits, and gives origin at its superior and external part to a vessel which, traversing the walls of the flancs at the base of the branchiae, conducts the blood to the latter organs. This is the external or afferent vessel of the branchiae. We find the same lateral venous sinuses in the Macroura; but instead of communicating with one another athwart the thoracic septa, as is the case in the Brachyura, they all empty themselves into a great median vessel, which is itself a venous sinus, and occupies the sternal canal. In the Squilla this sinus is al- most the only vessel which serves as a reservoir to the venous blood. The blood, after having been arterialized in its passage through the capillaries of the branchiae, is poured into the efferent vessel, which, as we shall immediately have occasion to see when treating of the respiratory process, runs along the internal surface of each bran- chia. It enters the thoracic cells in the same manner as the afferent vessel passed out from them, bends upwardly under the vault of the flancs, and thus takes its course towards the heart. It is to this portion of the canal that we have given the name of branchio-cardiac vessel. The mode in which the blood enters the heart is still a subject under discussion. Our in- quiries lead us to believe that this fluid, poured by the branchio-cardiac canals into a sinus situated on each side of the heart, penetrates this organ by means of certain openings situated in those parts of its substance which are directly opposite to the canals mentioned. But Messrs. Lund and Strauss imagine that the blood is effused as it were into the peri- cardium (which is named auricle by the latter anatomist) to penetrate from thence by open- ings situated on the superior surface of the heart.* These openings, however, we conceive to be closed in the natural state by means of a membrane, and it is also worthy of remark that the writers just cited were unacquainted with the lateral openings which establish a much more direct communication with the interior of the organ. We must also add that the celebrated John Hunter, whose labours upon this subject have hitherto remained un- known to the world, but which have, very re- cently been given to the public by Mr. Owen, * Lund, Doutes sur l'existence du systeme circu- latoire dans les crustaces, Isis 1825. Strauss, Anat. comp. des Animaux atticuies. VOL. I. had long ago ascertained the existence of the venous sinuses and of the lateral openings of the heart, although he seems to have thought that the circulation was not complete in the manner we have described it.* In the most inferior groups of the class of Crustaceans the apparatus of the circulation becomes much less perfect, and even seems to disappear entirely in the last of the Haustel- late tribes. In the Argula, for instance, there still exists a heart, but the arteries as well as the veins appear to be nothing more than simple lacunae, formed in the interstices between the different organs ; and in the Nicothoa, &c. no distinct trace of any portion of a circulatory system has yet been discovered. C. Of the respiration. — The Crustacea, like all the other tribes especially formed for living under water, respire by means of certain parts of their external covering modified in its struc- ture in order to fit it for this function, and known under the name of branchia. This character is even so completely inherent in the organic type proper to this class, that it is still preserved in certain species which live on the land and not in the water. Nothing, however, can be conceived more various than the form and disposition of the organs of the branchial respiration among these animals : in some the function is per- formed by an extremely complex apparatus, consisting in great part of organs created ex- pressly for this end ; in others it is delegated to certain appendages which do not exist for the office exclusively, but are rather turned from their more ordinary and obvious uses to subserve this important function. In others still, we neither discover special organs of respiration nor other parts whose structure fits them evidently to supply the place of branchiae; in these cases we can only suppose that the oxygen held in solution by the water acts upon the nutritious fluid of the aaimal by the inter- medium of the entire tegumentary covering. Let us first review the respiratory apparatus in its state of greatest complexity, but com- mencing with it in the embryo and following it in its progressive development, in order that we may be the better prepared to compare it with those forms which will be presented to us among species less elevated in the series of the Crustaceans. In the earliest periods of embryotic life of the common Astacus fluviatilis, we discover no trace of branchiae ; but at a somewhat more advanced stage of the incubation, though still before the formation of the heart, these organs begin to appear. They are at first small lamellar appen- dices of extreme simplicity, attached above the three pairs of maxillary extremities, and repre- senting the flabelliform portions of these limbs. Soon these lamellar appendages elongate and divide into two halves, one internal, lamel- lar and triangular, the other external, small and cylindrical; lastly, upon the surface of * Catalogue of the Physiological Series of Com- parative Anatomy, contained in the Museum of the Royal College of Surgeons, vol. ii. 3 E 778 CRUSTACEA. this, stria? are observed to appear, which are the rudiments of the branchial filaments. During this interval the thoracic extremities have become developed, and above their bases other branchiae have made their appearance, presenting in the beginning the form of tuber- cles, and subsequently that of stilets ; smooth and rounded on their surface, but by-and-by becoming covered with a multitude of small tuberculations, which by their elongation are gradually converted into branchial filaments similar to the preceding. During this period of the development of the branchiae these organs are applied like the extremities to the inferior surface of the embryo ; but they sub- sequently rise against the lateral parts of the thorax, become lodged within a cavity situated under the carapace, and thus are no longer visible externally. The cavity destined to protect in this manner the branchial apparatus, is neither more nor less than an internal fold of the common tegu- mentary membrane. It shows itself first under the guise of a narrow groove or furrow, which runs along the lateral parts of the thorax below the edge of the lateral piece of the carapace. This longitudinal furrow is not long of expand- ing, and becomes consolidated by its superior edge with the internal surface of the carapace, which, by being prolonged inferiorly, consti- tutes the external wall of a cavity, the opening of which, situated above the base of the extremities, becomes more and more contracted, and ends by being almost entirely closed. The space in this way circumscribed encloses the branchiae, and constitutes what is called the respiratory cavity of the Decapod Crustaceans. From what has just been said, it would ap- pear that the embryo of the Astacus fluviatilis presents four principal periods with reference to the state of the respiratory apparatus; lstly, that which precedes the appearance of this ap- paratus; 2dly, that during which the branchiae are not distinguishable from the flabelliform ap- pendages of the extremities, or in which it consists of simple lamellar or stiliform pro- cesses, which appear as mere processes of other organs especially dedicated to locomotion or to mastication; 3dly, that characterized by the transformation of these extremely simple appendages into organs of a complex structure, entirely distinct from the extremities, but still entirely external ; 4thly and lastly, that during which the branchiee sink inwards and become lodged in a cavity especially adapted for their reception, and provided with a particular apparatus destined to renew the water neces- sary to the maintenance of respiration. If we now turn to the examination of the apparatus of respiration in the different groups in which it exhibits important modifications, we shall, in the series of Crustaceans, encounter permanent states analogous to the various phases through which we have just seen the apparatus passing in the most elevated animals of the class. And, in fact, the first period which we have particularized above in the embryonic life of the Decapod is exhibited in the permanent condi- tion of some inferior Crustaceans, in which not only is there no special organs for respiration, but in which none of the appendices occur with such modifications of structure as would fit them to become substitutes for the branchiae, in which, consequently, the process of respira- tion, that is the aeration of the blood, appears to take place over the surface of the body at large. The greater number of the Haustellate Crustacea, of the Entomostraca properly so called, of the Copepoda, and even of the Phyllosomata, appear to belong to this type of organization. A state analogous to that which characterizes the second period in the development of the embryo of the Decapod, is presented to us in a large number of other Crustaceans, the orga- nization of which is more perfect than that of the animals of which mention has just been made, we mean the Branchiopoda and Edri- ophthalmia, in which, although we do not yet find branchiae properly so called, that is to say, organs peculiarly devoted to respiration, we discover certain appendages of the extre- mities which serve for this function. In the Branchiopoda (Jig. 421) the whole of the tho- racic extremities present a lamellar conformation, and the two external portions of the appen- dages corresponding to the palp and flabellum (J'ouet ), form membra- nous vesicles of a flat- tened form, soft to the touch, and highly vas- cular, the structure of which appears eminently calculated to facilitate the action of the air upon the nutritious fluid. (b, c,fig. 421). In the Amphipoda another step appears to be taken in the elaboration of the respiratory apparatus. Not only does the function of respiration tend to become centred in certain appendages, whose structure is modified for this end, but this localization, if the term may be allowed, becomes more complete ; for the two appendicular portions of the thoracic extremities no longer concur indistinctly and Fig. 422. Fig. 421. vicariously in the performance of the function ; the palp (b,Jig. 422) has other uses apportioned to it, and the flabellum (c) alone plays the part of the branchiae. These appendages, in other re- spects, do not present any thing peculiar in their CRUSTACEA. 779 conformation ; they appear like a vesicular or foliaceous expansion, of an extremely soft tex- ture, which is attached to the inner edge of the base of the thoracic extremities; their dimensions generally increase from before back- wards, and the last pair of thoracic extremities is not furnished with any : their total number varies from eight to twelve. These organs, suspended under the thorax, float in the ambient fluid, and the water in contact with their surface is incessantly renovated by means of the motions performed by the abdominal extremities of the animal, motions which occa- sion a rapid current from behind forwards along the ventral aspect of the body. In the Loemodipoda, the parts which perform the office of branchiae are vesicular bodies formed by the flabelliform appendage of a certain number of the pairs of thoracic extre- mities. In the Isopoda, finally, the locomotory extremities no longer serve for respiration, the function being committed to the five first pairs of abdominal extremities which are entirely devoted to it and cease to have any other uses. These extremities, which are designated under the name of false branchial limbs, consist of a cylindrical articulation, supporting two folia- ceous, soft membranous laminae, vascular in a greater or less degree ; frequently, too, we perceive on their inner side a small appendage, which may be regarded as analogous to the femur or stem of the other extremities, whilst the two laminae, of which mention has just been made, appear to represent the palp and the flabellum. In the greater number of Iso- poda these organs are completely exterior, but in several (such as the Idotea) the last ring Fig. 423. Fig. 424. Respiratory apparatus of the Idotea. of the abdomen supplies them with a cavity, the entrance to which is closed by valves which constitute the two appendages of the same ring. The Stomapoda which have already supplied us with an instance of the absence of deter- minate organs of respiration, also exhibit something analogous to the transition state of this apparatus during the second period of the embryonic life of the Decapod. In the genus Cynthia the branchiae are represented by a small membranous cylinder, attached by its middle to a peduncle, itself implanted upon the extremity of the basilar articulation of the five first pairs of abdominal extremities. The third type of the respiratory apparatus specified above, is presented to us by other Stomapods, known under the names of Squillae and Thysanopodoe. In these creatures, in fret, we discover branchiae properly so called, the structure of which is greatly complicated, more so even than in the Crustaceans at the very head of the series; still the respiratory apparatus as a whole is much less complete, for they are not included in a cavity, and float freely in the water which bathes the entire sur- face of the body of the animal. In the Squill;? (Jig. 425) the branchiae are attached to the basilar joint of the first five pairs of abdominal extremi- Fig. 425. V .'' 1 Vs One of the brunchice ! ft.}-. '|f • of the Squilla. a, a / \ i§! I branchia fixed to the 8 i ] - abdominal extremity ties, and each consists of a long cylindrical tube, upon one of the sides of which proceeds a series of small tubes disposed parallel to one another like the pipes of an organ and support- ing in their turn a series of long cylindrical and very numerous tubes.* In the Thysanopoda the branchiae also resemble plumes, but in- stead of being situated on the abdomen, they are attached to the thoracic extremities.f Finally, the last or highest term of develop- ment which we have mentioned in the River- crab, is also presented to us by the entire order of Decapod Crustaceans. Not only is the func- tion of respiration thrown upon particular organs, created expressly for this purpose, in the whole of these animals, but further, the organs themselves are lodged and protected within especial cavities, and the renewal of the water necessary to their functions is secured by the action of distinct appendages belonging more particularly to the masticatory and loco- motory apparatuses. Let us now take a survey of the branchial cavity. It occupies (fig. 426 ) the lateral part of the thorax, and extends between the vault of the flancs and the lateral portion of the cara- pace, from the base of the extremities all the way towards the dorsal aspect of the animal. As we have already said, it is formed by an in- ternal fold of the common tegumentary mem- brane, which, after having formed the vault of the flancs, re-descends towards the base of the extremities to become continuous with the carapace. The internal and inferior wall of this cavity is consequently formed by the vault of the flancs itself, and its external and superior wall by a membranous septum, which in the greater part of its extent is for the most part connected with the corresponding portion of * Cuvier Lemons d'Anat. comp. t. iv. t Mem. sur une disposition particuliere de l'ap- pareil branchial chez quelques crustaces, par Milne Edwards, Ann. des Sciences Nat. torn. xix. 3 E 2 780 CRUSTACEA. Fig. 426. Branchial cavity of the Maja Squinado laid open. a, branchiae ; b, vault of the flancs ; c, carapace ; d, efferent duct ; e, valve. the carapace. This last part of the walls of the branchial cavity presents an epidermic layer of extreme thinness, but covering a thick and shaggy membrane, the texture of which is found to vary, as we shall see by-and-by. The cavity thus formed communicates ex- ternally by two passages, the one destined for the entrance, the other for the exit of the water necessary to respiration. The disposition of the efferent opening varies but little ; that of the afferent orifice, on the contrary, presents great varieties in the different groups of which the class of Decapods is composed. The efferent orifice always occupies the ante- rior extremity of the branchial cavity, and is continuous with a canal (d, fig. 426 And f, Jig. 428) the parietes of which are formed su- periorly by the epimeral pieces of the last ce- phalic rings, and inferiorly by the pterygo- stomian portions of the carapace (b, fig. 427j. Fig. 427. Head of the Maja Squinado. a, afferent opening of the branchial cavity ; h, carapace ; c, anterior extremities ; d, posterior maxillipedes. This canal runs forwards, passes to the out- side of the oral apparatus, and terminates in front of the mouth (g,fig- 428). In its interior there is a large valve, which is falling and rising continually, as if it moved upon a pivot, and w'^ich in this way occasions a rapid current Fig. 428. The same parts, the posterior maxillipedes and a por- tion of the carapace having been removed. a, afferent opening ; d, portion of the posterior maxillipedes ; e, commencement of the efferent canal (f) g, the termination of the efferent canal ; h, the valve. from behind forwards in the water with which the cavity is filled. This valvular apparatus is neither more nor less than the flabelliform appendage of the second pair of maxillipedes which acquire dimensions in relation with the importance of the new function they have here to perform (/;, fig. 428). In the long-tailed Decapoda, and in the greater number of Anomoura of the same family, the respiratory cavity is open along the whole extent of its inferior edge ; the carapace is not applied accurately to the lower margin of the vault of the rlanc, and it is by the empty space thus left above the base of all the extremities that the water makes its way to the branchiae. In the Brachyura the afferent orifice of the branchial cavity is more circumscribed, but varies in a still greater degree. In nearly all the Crustacea it exists almost immediately in front of the base of the first pair of ambulatory extremities, and con- sists of a kind of eleft, of considerable breadth, which in this place occurs between the edge of the carapace and the thorax (a, fig. 427), and which is occupied by a prolongation of the ba- silar joint of the external maxillary limb (d), disposed in such a manner as to close it com- pletely or to open it at the desire of the ani- mal. In the genus Dorippus a slight variety in the disposition of this opening is ob- served ; here at first view it appears to be pierced directly in the pterygostomian portion of the carapace ; but it is in reality formed by an empty space left between the edge of the dorsal shield and the base of the external maxillary limb ; only here, this space, in- stead of presenting itself immediately in front of the base of the anterior extremities, is se- parated from this by a prolongation of the carapace. In the genus Ranina the carapace is joined to the thorax above the whole of these limbs, so as to leave no opening in this situation for the passage of the water, and it is at the origin of the abdomen that the afferent opening of the branchial cavity occurs. Lastly, in the Leucosia, this cavity is in like manner completely closed above the base of the extre- mities, and it is by a conduit parallel to the efferent canal, and opening outwardly likewise CRUSTACEA. 781 in front of the mouth, that the water reaches the interior of the branchial cavity. Fig. 429. Mouth of the Leucosia. Fig. 430. The same, without the external or posterior max- illipedes. The branchiae contained in the two cavities, one on either side, whose conformation we have now described, are disposed along the vaults of the flancs. They are shaped like a quadran- gular pyramid, the base being fixed by means of a peduncle to the inferior part of this vault or to the membrane which extends from its in- ferior edge to the basilar articulation of the corresponding limb; some of them are even inserted into this articulation. Each of these organs consists of two large longitudinal vessels situated on the opposite edges of a transverse septum, which extends from the base to the apex of the branchia, and presents on each side a great number of lamel- lar or cylindrical pro- longations. Of these two principal vessels the external is the affe- rent one, of which men- tion has already been made in treating of the circulation and its organs ; the internal again is the efferent vessel ; the capillaries by which these two communicate run in the substance of the branchial lamellae, situated on either side of the median septum. In the whole of the Decapoda brachyura and anomoura,and in the greater number oflhema- croura, the folds of the tegumentary membrane which constitutes each branchia, are in the form of very thin lamella, directed perpendi- cularly to the axis of the pyramid, and lying one over another like the leaves of a book. But in Crawfish, the Lobster, the Nethrops, the Palinuri, the Scyllari, and the Gebiae, these lamella are replaced by a multitude of small cylinders, attached by their base, and closely packed side by side, like the bristles of a brush. The number of branchial pyramids varies greatly, especially in the Macroura ; at the most it is twenty-two, as is the case in the astacus and the most nearly allied species; in other macroura the number is eighteen, as in the Palinuri, Scyllari, Penes ; fifteen, as in the Gebiae ; twelve, as in the Pandalus ; ten, as in the Calianassae ; eight, as in the Palemons ; and even seven only, as in the Crangons, Ilip- politi, Sergestes, &c. In the Anomoura the number also varies very much. In the Bra- chyura we can almost always reckon nine branchiae on each side of the body; two of this number, however, being merely rudiment- ary ; sometimes two or one of these last is entirely wanting; and there are even species in which the branchia, which usually occu- pies the antipenultimate ring of the thorax, is missing. The mode in which these organs are placed varies in a like degree : in the Brachyura {fig. 426) the whole, with the exception of two rudi- mentary branchiae, are arranged along one and the same line, and rest parallel to one another upon the vault of the flancs ; the two last rings of the thorax never support any, and of the two rings which correspond to the second and third pairs of extremities, each presents a single py- ramid attached to a hole pierced in the epimeral piece nearto its inferioredge (/?g\384). The five branchiae, situated in front of these, are attached above the edge of the vault of the flancs, and with the exception of the first are connected two and two upon com- mon peduncles. Lastly, the two rudimentary branchiae which complete the seriss anteriorly, Fig. 431. are arranged under the base of the preceding, and attached to the basilar articulation of the second and third pairs of maxillary extremi- ties. In the Anomoura and the Macroura, the branchise are often found arranged in several ranks, and generally occur on the two last thoracic segments, as well as upon those that precede these (Jig- 431). In the greater number of the Decapoda the flabelliform appendages of the maxillary or of the ambulatory extremities penetrate into the respiratory cavity, and by their motions sweep, as it were, or stroke the surface of the branchiae. Some anatomists have even imagined that it was by their action that the water necessary to respi- ration was renewed in theinteriorof the branchial cavities;* but this is a mistake; these appen- * Cuvier, Lemons, t. iv. p. 432. 782 CRUSTACEA. dages have little or no influence upon the cur- rent which is continually traversing the respi- ratory antrum, and which is produced by the motions of the great valvular lamina, already described as belonging to the second pair of the maxillipedes, and situated in the efferent respiratory canal. The very secondary part which the flabelli- form appendages of the thoracic extremities play in the interior of the respiratory cavities, is of itself a sure indication of the indetermi- nateness of their numbers and relations to the branchial pyramids. Thus whilst in the Lobster and the nearly allied genera, these ap- pendages, to the number of five on either side, belong to the four first pairs of ambulatory ex- tremities and to the third of the maxillary pairs, and run from below upwards between the branchial fasciculi, we only find three pairs in the Brachyura, belonging exclusively to the maxillary extremities, and penetrating into the branchial cavities horizontally, two on the outer surface of the branchiae and one between the inner surface of these organs and the flancs. We said in beginning this article that the Crustacea, by their general conformation, were evidently adapted to a purely aquatic life ; this proposition must only be understood as gene- rally applicable to the class, because there are genera which form exceptions to it, in regard to which we have still a few words to add. The Telphusiee and some other families of Crustaceans have the power of emerging from the water, and of entering it again after a longer or shorter stay upon dry land. But this fact is to be explained by the smallness of the two openings by which each of the branchial cavities communicates with the exterior, by which means a very small amount of evaporation only takes place from them. The whole of the Crab tribe have, in a greater or less degree, the faculty of the par- ticular species mentioned, provided the air by which they are surrounded is saturated with moisture; because if they die asphyxiated when brought into the air under ordinary cir- cumstances, it is principally because their bran- chiae having become dry are thereby unfitted to accomplish their functions. But there are other species which are re- markable for the faculty they possess not only of living habitually out of water, but be- cause they are infallibly drowned by being kept long immersed in that fluid — these are the Gecarcini or land-crabs. Many hypotheses were broached to afford an explanation of this phenomenon, when a careful study of the diffe- rent forms under which the organs of respira- tion present themselves in these different genera, led us to discover in the membrane which lines the walls of the respiratory cavities, modifica- tions analogous to those which are observed among fishes of the family of the Acanlhopterygia pharyngeal labyrinthiformes, &c. Sometimes we found folds and lacuna? capable of serving as reservoirs of a certain quantity of water; sometimes, as in the Birgus, a spongy mem- brane equally well calculated to store up the fluid necessary to keep the organs of respira- tion in the state of humidity essentially neces- sary to enable them to perform their functions. It is well known, too, that the Land-crabs of which we are now speaking, never remove far from damp situations. Some naturalists are of opinion that the tegumentary membrane with which the branchial cavity is invested, is also the seat of active respiration; M. Geoffroy St. Ililaire even goes so far as to regard the growths with which the surface of this membrane is covered in the Birgus, as constituting a true lung. - It would appear, consequently, that it is owing to the activity of the function of aerial respiration in the Gecarcini, that these ani- mals are drowned when plunged under water, although they be provided with branchias ; and it is owing to these organs being kept in a suitable state of humidity that these creatures owe, at least in part, their faculty of breathing air. We have said above that the principal cause of the death of our ordinary Crustaceans exposed to the air is the drying up of their branchiae ; but this is not the sole cause of the asphyxia they suffer; it would seem that the collapse of the branchial lamella? which takes place when these organs are not supported by the water, and the greatly diminished extent of surface thereby exposed to the oxygenated fluid, con- tributes mainly to prevent aerial respiration from proving adequate to maintain life among the common aquatic Crustacea. With regard to the modifications presented by the respiratory organs of the Onisci, which like the Gecarcini live far from water, nothing certain is yet known. The opinion that the abdominal false limbs, which serve as respi- ratory organs among the Isopoda in general, are here vesicular, and perform the office of lungs internally, whilst their external surface acts in the manner of gills, still requires to be confirmed. § 6. Of Generation. Sexual organs are readily demonstrated in the whole class of Crustaceans, but those of the two sexes never exist in the same indivi- dual. The doubt which at one time pre- vailed in regard to this fact, and which mainly arose from no other than females of certain species having ever been taken, is at once put an end to by the circumstance of the con- siderable dissimilarity in their external form, which occurs between the males and females of tliese species; this dissimilarity indeed is, in some instances, so great that naturalists were led into the error of regarding the male and female of the same creature not only as be- longing to different species, but even to diffe- rent genera. Oviparous reproduction is also a constant character of the class. Generally speaking, the reproductive appa- ratus, whether in the male or in the female, is perfectly distinct, especially at the period when the organs composing it are in a state of acti- vity ; and one of the most remarkable facts which the careful study of this part of the structure of the class has afforded, is their com- CRUSTACEA. 783 plele state of doubleness ; on either side of the body we find an organ perfectly distinct, and often wholly independent of its fellow ; to such an extent, indeed, is this carried, that among the facts with which modern science has been enriched in regard to the structure of the Crus- tacea, one by no means the least interesting is that in which an animal of this class was actu- ally found presenting in either half of its body a different sex, each apparatus complete in every one of its conditions, and even with the whole of its modifications.* Another fact, not less striking, is that of the analogy which exists, at least among the more perfect Crustaceans, between the male and the female reproductive organ This similarity is so great that the simple inspection of the organ is not alone sufficient to inform us always of its true nature, which in some instances can only be ascertained by the most careful examination. The male apparatus consists essentially of an organ the secreting instrument of the fecunda- ting fluid, and of an excretory canal variously modified. These two parts are contained within the thorax along with nearly the whole mass of other viscera, and never extend lower down than the last ring of this region of the body. They are not always very distinct from one another, and it frequently happens that the testis and the excretory canal are confounded inextricably under the form of a single tube, nearly identical in its structure from beginning to end. The length of this canal is occasionally very great and variously convoluted and con- torted, so that its relations with the other tho- racic viscera become excessively multiplied. This peculiarity we observe very well in the Maja and the Cancer pagurus (see fig. 418). The canal, which throughout is single, is capillary at its commencement, but increases gradually in its dimensions to its termina- tion. In the Astacus fluviatilis, on the contrary, the two portions of the male reproductive apparatus are perfectly distinct, and severally completely developed. The testis {a, fig- 432) consists of capillary secerning vessels, which are readily demonstrable, and presents three lobes, two of which lie forwards upon the sides of the stomach, and one backwards underneath the heart. From these three lobes two excretory canals (b) take their origin. In the Edriophthalmia the male organ is com- posed of two or three elongated vesicles, which terminate in a common excretory canal. It is in the Cancer pagurus perhaps that the male organ of generation is most highly de- veloped. It occupies of itself a large por- tion of the thorax {fig- 418). The testis pre- sents the appearance of a kind of grape cluster, formed of four principal lobes, which, studied minutely, are found to be made up of an infinity of extremely delicate ver- micular canals, contorted so as to form great numbers of pellets. This first portion of * An account of an Hermaphrodite Lobster, by Dr. Nichols, Philos. Trans. 1730, p. 290. Fig. 432. the organ is situated in front of the thorax, and terminates in a primary large convoluted vessel lying on the side of the stomach ; be- hind and in connexion with this we perceive the vas deferens, properly so called ; it is a canal of considerable size, much convoluted, and of a milky white colour; it traverses the thorax, still twisting about, penetrates the cell of the last pair of ambulatory extremities, and opens outwardly on their basilar piece. This indeed is the situation in which the copulatory organs of the Crustacea generally appear. Still, in many Brachyura of the Catometopa family, the Ocypoda and Grapsus, for ex- ample, the external opening of the male gene- rative organ is found on the sternal part of the last thoracic ring; and there are even several of these animals in which the efferent canal, after having attained the external surface in the basilar articulation of the last pair of ambu- latory extremities, returns inwards, and pene- trates by a small groove, which conceals it until it has attained to that portion of the sternum which is hidden by the abdomen ; an example of this occurs in the Gonoplax ; In the ordinary state the excretory canal termi- nates on the edges of the opening, but at the instant of sexual intercourse the extremity of the canal undergoes a kind of erection, and by becoming folded upon itself like the finger of a glove, projects externally, so as to form a kind of penis adequate to the intromission of the fecundating fluid. This later circumstance was long unknown to naturalists, who were 7m CRUSTACEA. accustomed to look upon the members of the first and second abdominal rings as the ex- ternal male instruments. These two pairs of extremities, in fact, (fig. 433), are distinguished Fig. 433. Blembers of the first and second abdominal rings of tlie Male Muja. from the rest by their shape, which is styli- form, and their structure, which is tubular, being composed of two horny laminae convo- luted one upon another, the first including }he second. But direct observation has de- prived them of all claim to be considered as fulfilling any office of so much consequence in the economy of the Crustacea as that of con- veying the fecundating fluid from the body of male into that of the female. At the most, they can only be regarded as organs of excita- tion, and which the animal may perhaps em- ploy at the same time to guide the male into the female organ. The female reproductive apparatus of the Crustacea, in its highest state of complication, consists of an ovary, an oviduct, and copulatory pouches. Fig. 434. Female organs of the Maja Squinado. The ovaries in theDecapoda brachyura resem- ble four cylindrical tubes (a, b,fig. 434) placed longitudinally in the thorax, and divided into two symmetrical pairs, each opening into a distinct oviduct, yet communicating with one another by a transverse canal («'), and by the intimate union of the two posterior tubes in a portion of their length {b'). The ovi- ducts, as well as the ovaries, are of a whitish colour; they are short, and become united in their course to a kind of sac (c), the neck of which extends to the exterior of. the ani- mal's body (d); there is one of these on each side, and they are known by the name of the copulatory pouches. It is into these reser- voirs that the male pours the fecundating fluid, which is here stored up and applied to the ova as they pass in succession along and out of the oviducts. These, after a course which is never long, terminate at the vulvas, openings formed in the sternal pieces of the segment which supports the third pair of ambulatory extremities. The Anomoura and Macroura have no copa- latory pouches, and their vulvae are situated on the basilar joint of the ambulatory ex- tremities of the third pair. The mode in which fecundation is accomplished in these genera is consequently much less apparent than in the Brachyura. Many writers are of opinion that this operation takes place ir» the interior of the ovaries, a process that appears by no means feasible on account of the inequality of development of the ova, which is such, that the last of them are not in being even long after the first have been ex- pelled. It would perhaps be more correct to suppose that fecundation does not take place till after the ova are laid, which we know to be the case among the Batrachia and the greater number of fishes. The female Crustacean does not abandon her eggs after their extrusion. Those of the Deca- pods preserve them under their abdomen by means of the abdominal extremities modified in their structure (Jig. 390 and 435) ; the Edriophthalmia, again, keep them under their thorax by means of the fla- belliform appendages of the extremities belonging to this region {fig. 436); whilst the inferior genera, such as the Entomostraca, &c. have sus- pended to the external orifices either horny tubes or a Fig. 436. Ventral aspect of the female Cymothoa. p, legs ; f, flabelliform ap- pendages which unite so as to form a cavity des- tined to contain the ova. CRUSTACEA. 785 pair of membranous sacs which contain and transport them from place to place. These varieties in the accessory organs of gene- ration, are in many cases sufficient to distin- guish the sexes : thus, among the Decapoda brachyura, the females are known at a glance by their wider abdomen, which is sometimes of such dimensions as to cover almost the whole sternum. Sometimes these sexual diffe- rences extend to the antennae and to various other organs; sometimes it even influences the size, and occasionally, as we have said, the general external conformation is modified to such a degree, that the male and the female of one and the same species have been taken as types of two distinct genera. There are some species jof which the females only are as yet known to naturalists. The ovum appears to be formed in the walls of the ovary, from whence it is detached when it has attained a certain size, and falls into the cavity of the organ. We have already stated in what manner it is expelled, and in what mode fecundation is accomplished in its pas- sage through the oviducts, or after its extru- sion. The distinguished German naturalist, Rathke, has given particular attention to the divers phases of the evolution of the egg of the Astacus fluviatilis, as well before as after its escape from the ovary and oviduct ; and we believe we cannot conclude this article more satisfactorily than by presenting our readers with a simple and brief analysis of his work* The first and earliest form under which the ovum meets the eye in the ovary is that of a transparent vesicle, its walls of extreme te- nuity, and filled with a watery fluid. This is the vesicle of Purkinje. By-and-by there is another membranous and very thin envelope formed all round this vesicle, and in the minute interval that separates the two coverings there is a second fluid deposited, transparent like the other at first, but soon becoming opaque, whitish, and viscid; this is the vitellus or yolk. As this increases in size, the vesicle of Purkinje, which still preserves its first dimen- sions, quits the centre, and goes to be attached to the circumference, which, at last, it almost touches at one point. During this time the vitellus or yolk is continually declining in transparency, on account of the formation of an infinity of globules, which, at length, transform it into a viscid mass of a deep brown colour. During the last stage of its continuance in tlie ovary the vesicle of Purkinje disappears, and the first rudiments of the germ are disco- vered. This series of changes might induce the belief that the germ is neither more nor less than the liquid of the vesicle shed upon the surface of the vitellus. Its form at first resembles that of a slight whitish cloud, which, by slow degrees, changes into an opaque white spot, well defined, and covering nearly the sixth part of the entire surface. The egg is in the above state at the time it * Untersuchungen uebcr die Bildunp; und Ent- wickt'lung des Flusskrcbses, fol. Lcipz. 1829. is received into the oviducts. These canals secrete an albuminous fluid, which surrounds the vitellus and its envelope, and which itself becomes covered with a membranous involu- crum, called the chorion or dermoid envelope of the ovum. Another membrane still is thrown around the last, to serve as the means of attaching the ovum to the false abdominal extremities of the mother. When the process of incubation begins, the surface of the yolk is first seen to be- come covered with star-like or serrated spots, whitish in the fust instance, and then white, which by-and-bye disappear entirely. The germ at the same time is extended uniformly over the whole surface of the yolk ; but again it seems to collect towards a point under the form of a white spot, which is the blastoderma. This spot, after undergoing certain variations in its form and dimensions, ends by becom- ing elliptical with a slight furrow in its mid- dle, shaped like a horse-shoe. This furrow soon extends ; its extremities meet, and its centre becomes depressed, so as to assume the appearance of a sacculus of some depth. The blastoderma enlarges at the same time, and presents the appearance of a cordiform spot. It is at the bottom of the sacculus but just mentioned, and in the nearest point of the blastoderma, that the first rudiments of organs make their appearance. It is now that the orifice of the sacculus begins to enlarge ; the edges separate ; its bottom rises, so as at length to become pro- minent, and a small nipple-like elevation ap- pears upon it, hidden in some measure by the edge of the sac, which turns out to be the rudiments of the posterior portion of the body. At the same epoch there are formed anteriorly, on either side of the median line, two pairs of small strap-like bodies, which are by-and-bye discovered to have been the rudiments of the antennas, and another pair, which are the ear- liest vestiges of mandibles. Between the two anterior antennas an azygous point presents itself, which is the rudiment of the labrum, and which, by the progressive development of the neighbouring parts, shifts by slow degrees to its final position between the second pair of antennae. By slow degrees the blastoderma, the pe- ripheral portion of which is much thinner and more transparent than the middle portion, is seen to extend on the surface of the vitellus, and at length to envelope it completely. Du- ring this time the three pairs of spots which represent the antenna? and the mandibles are growing larger, their edges becoming distinctly defined, and their extremities are receding from the surface of the blastoderma, under the form of a little cylinder, the end of which before long divides into two. After the an- tennas have been seen, the peduncles of the eyes make their appearance, and detach themselves by degrees from the blastoderma, as the pre- ceding appendages had done. The nipple-like projection which we have seen formed at the bottom of the small blastodermic sac enlarges at the same time, and assumes the form of an 786 CRUSTACEA. elongated lamina, the free end of which is turned forwards, and before long advances nearly to the labium. In the space included between the mandibles and the fold formed by the abdominal lamina of the embryo, of which we have just spoken, we now perceive the rudiments of two pairs of jaws and of the first pair of maxillary extremi- ties, then of the second pair of these latter or- gans, and soon afterwards of the third pair. These appendages appear in the same man- ner as the antennse, and in proportion as they are evolved, the fold that marks the origin of the caudal lamina of the embryo recedes from the anterior part of the body; by little and little the basilar portion of the lamina becomes straightened, so as to gain the same plane as the remainder of the blastoderma, whilst its terminal portion continues bent underneath against the former. The five pairs of ambula- tory extremities make their appearance succes- sively in the same manner as the antennae and the oral appendages ; the same may be said with regard to the abdominal extremi- ties; and whilst this formation is going on, the annular divisions of the abdominal portion of the body are observed to be evolved. The carapace at length begins to be formed in the manner already indicated, and the ex- tremities, as they sprout, alter their shapes, and become more and more unlike one another, as they approach the term of their embryotic development. The alimentary canal begins to be formed by its two opposite extremities. The earliest traces of the oral aperture are perceived nearly at the same time as the labrum, under the form of a small cavity, which becomes continually deeper and deeper. Some short time after- wards, and before the appearance of the jaws, we distinguish towards the summit of the ab- dominal tubercle, a slight depression which grows rapidly deeper in order to form the anus. About the same period a very delicate and gelatinous-looking membrane begins to be formed between the inner aspect of the middle portion of the blastoderma and the vitellus ; this increases rapidly, and sends prolongations towards the mouth and anus, which soon be- come hollowed out into a cavity, and are fi- nally converted into two small perpendicular canals. The one of these canals terminating at the mouth is the commencement of the oesophagus and stomach ; the other,with which the anus is soon found to be in connexion, is the rudiment of the intestine. The rest of the membrane in question is observed to extend rapidly and at length completely to envelope the vitellus. At this epoch of the develop- ment of the embryo, the sac thus formed covers the blastoderma, incloses the yolk, and towards its lower part presents two funnel-like portions by which it is made to communicate with the gastric and intestinal portions of the digestive canal, the formation of which we have just had occasion to speak of. These two portions of the digestive canal as they increase in size approach one another ; the rest of the sac folds inwards upon itself, and diminishes more and more in size until it disappears entirely, and the stomach and in- testine form one perfectly continuous tube. At the point where the intestine is connected with the sac inclosing the yolk, two small thickenings are seen, which by-and-by acquire the form of appendages and become covered with little warty-looking enlargements; this is the liver beginning to be formed. The enlarge- ments of which we have spoken constitute its lobuli, and these slowly divide into a mul- titude of long slender vessels. The heart begins to be developed about the same time as the intestinal canal. It makes its appearance towards the dorsal part of the body, a short way above the commencement of the abdomen, and shows itself at first under the guise of a small pyriform cavity hollowed out of a membrane supplied by an inner la- mina of the blastoderma. The arteries begin to show themselves towards the same period in the substance of this same blastodermic lamina, and in the beginning present neither ramifications nor any communication with the heart. We have already spoken of the develop- ment of the apparatus of respiration and of that of the nervous system at such length as to render it unnecessary to enter farther upon these parts of the subject here. The greater number of the Crustacea do not escape from the membranes of the egg until they have attained such a perfect state of develop- ment, that they possess the whole of the organs they will ever exhibit, and have attained a form which differs but little from that which is to distinguish them when arrived at matuiityor become adult. The case, however, is different as regards some of these animals ; these are born in some sort prematurely, and only attain their distinctive formation after their exit from the egg. The changes which they undergo between the term of their birth and that of their perfect growth are sometimes so great that they are every way deserving of the name of metamorphoses. These changes, whatever their amount, may depend on the following circumstances: — 1. the continuation of the normal work of development, which has not been completed in the ovum ; 2. the unequal growth of different parts of the body; and, 3. the atrophy and complete ulti- mate disappearance of certain parts. It is among the lower Crustaceans that tliis kind of premature birth takes place most fre- quently : thus the sugient Crustaceans and the Entomostraca quit the membranes of the ovum at a stage of development which corresponds with one of the earlier of those under which the Decapoda present themselves to our notice; they are all of an oval figure, and only appear provided with a very limited number of styli- fbrm extremities. The common Cyclops, for instance, does not show the posterior part of the body at the time of its exclusion from the ovum, although this subsequently forms an elongated tail ; it is nearly spherical at first, and is provided with no more than two antennas and four extremely short feet. It continues CYST. f87 in this state till the fourteenth day, when a small projection makes its appearance from the hinder part of the body ; on the twenty-second day it acquires a third pair of extremities, and on the twenty-eighth day it changes the tegu- mentary covering of its body.* Several Edrioph- thalmians are also born before they have ac- quired the whole of their extremities ; but we know of no instance of the appearance of one or more pairs of extremities after exclusion from the ovum among the superior Crustaceans. The changes of form which take place in parts already existing, and which depend on the unequal rates of increase with which the different parts" of the animal approach their final state of development, are often very con- siderable, and commonly tend to occasion peculiarities of conformation in the adult, which distinguish it from allied species, and imprint upon it the character proper to the tribe, genus, species, and even sex to which it belongs. These implicate one part in one, another in another ; here it is the thorax which grows more rapidly than the abdomen and greatly preponderates ; there it is the abdomen which, smaller at first than the thorax, increases in dimensions, and finally exceeds it in size : in other instances, again, the phenomenon of extraordinary growth is displayed in certain extremities, or even in certain articulations of these extremities, which follow differences in the proportions of the body and in the forms of its different parts. These differences contribute in general to in- crease the dissimilarity which already exists between the different segments of the body, and may therefore be regarded as a sequence in the general tendency of these animals to become more complicated in their structure in propor- tion as they rise in the series to which they belong, or in the course they have to run in order to attain their perfect state. To conclude: the modifications depending on the atrophy and the disappearance of certain parts with which the embryo is provided, tend also to individualize in a greater and greater degree the animals which experience them. As an instance of this phenomenon we may quote the disappearance of the eyes in certain llaustellate and certain Edriophthalmian Crus- taceans, and that of the greater number of the extremities in a great many of the Lernea^. The Dromise, among the Decapod anomoura, have also presented us with an instance of changes, analogous in their nature and in their consequences ; for among tjje young animals the abdomen terminates in a caudal, fan- shaped fin, as among all the Macroura and a great many of the Anomoura; but with the advance of age, the lateral laminas of this organ disappear, and the abdomen then termi- nates very nearly as it does in the Brachyura. It is among the Crustacea which are born in the most imperfect state, and which conse- quently have the greatest number of changes to undergo, that the young animals bear the greatest resemblance to one another. The anomalies of conformation encountered among * Jurinc, Histoire rtes Monocles. these Crustacea do not in general show them- selves till the latter periods of their growth. The length of this article (already, perhaps, too great) does not allow of our pausing longer on this subject, and we shall only add that the evolution of the Crustacea is one of the points in the history of these animals which appears to promise the most interesting and important series of facts to whoever will devote himself to the comparative and extended investigation of the subject.* BIBLIOGRAPHY.— Besides the references at the bottoms of the preceding columns, see Suckow, Anat. physikalisch Dntersuchung ueber Insekten and Crus- tenthiere, 4to. Hcidelb. 1818. Fortius, De cancri fiuviatilis partibus genitalibus, Miscel. Acad. Natur. Curios. Dec. 2, An l(j87, p. 48. Geseeke, De cancri astaci qnibusdam partibus, 4to. Gotting. 1817. Kohler, Obs. nonnnlas anatomicas, &c. et in systema vacorum cancri astaci, 8vo. Tubing. 1811. Herbst, Naturgeschte der Krabben und Krebse, 3 Th. 4to. Berl. 1782-1800. MuUer, En- tomostraca seu insecta testacea, &c. 4to. Kopenh. 1785. Ramdohr, Jieytrage zur Naturgescbichte einiger deutschen Monoculusarten, 8vo. Halle, 1805. Hunter, Catalogue of the Hunterian Col- lection in the Museum of the Royal College of Surgeons — Comparative Anatomy and Physiology, 4to. 1831-5. ( H. Milne Edwards. ) CYST. Kystus, (kuo-tk, bladder). Certain membranous investments, of various forms, though commonly spheroidal, being shut sacs, and developed in the midst of other tissues, have obtained the name of cysts. Up to the present moment the study of cysts is so little advanced that we can scarcely dis- cover any researches which would appear to be founded upon the observation of nature. Whilst so much attention has been devoted to the in- vestigation of many departments of patholo- gical anatomy, it is difficult to understand why this very interesting subject has been compara- tively neglected. The singularity of the cir- cumstance is not lessened by the reflection that the rules of therapeutics ought to vary with the character of these sacs, and that, consequently, the anatomical study is of first-rate importance in enabling us to proceed rationally in the treat- ment of these extraordinary products of the ani- mal economy. In describing these organs, two modes have commonly been employed ; the one, to con- sider them with reference to the product they contain ; the other, with reference to their pro- per structure. It is not our intention to adopt either of these methods of considering the sub- ject, and for the following reasons: — it is de- monstrable that cysts which are identical in texture frequently envelope totally different products, and also that the products and the cysts are susceptible of transformation to an almost indefinite extent ; and as neither method * See on this subject the observations of Rathke already quoted ; those of Thompson, " the Meta- morphoses of the Crustacea;" our own " Ke- cherches sur les changemens de forme que les Crustacea stibissent dans le jeune age." (Annalc s des Sciences Naturelles, torn. xxx. and 2ue serie, torn. iii. ) and the inquiries of Nordmanu in his Mikrographische Beitr'age, &c. 2tes Heft. 788 CYST. affords us any facility in distinguishing one kind of cyst from another, we hold them alike inadequate to lead to correct views of the sub- ject. The plan which we propose to follow may not afford any increased facility in dia- gnosis, but it is, we apprehend, founded upon a more stable basis than either of those to which allusion has been made. We mean to consider cysts with reference to the mode of their developement; and although we do not pretend that this arrangement will afford much greater facility than at present exists for the diagnosis of the species, yet it appears to us to be the most natural classification which, in the present state of our knowledge, we are enabled to offer. A considerable assistance in the dia- gnosis of these organs may be obtained from the adoption of the following principles, which, though not unerring in their application, will afford a very near approximation to the truth, in the majority of cases. Those cysts which are external, subcutaneous, and exactly glo- bular, with a thinning of the dermis, which seems to adhere to their surface, commonly contain sebaceous matter of a whitish colour, friable and semi-concrete ; those which occupy muscular interstices in the neck, the back, or the extremities, have, commonly, thin parietes, are cellulous, of irregular form, and contain either serosity or albuminous pus, in which are seen floating opaque flocculent particles ; those which surround articulations and ten- dinous sheaths — true appendices of synovial tissues — are strengthened externally by fibrous laminae, lined by a serous tissue, and contain a more or less pure synovial fluid ; those which are developed under the anterior annular liga- ment of the carpus sometimes contain small whitish bodies, in appearance not unlike a grain of boiled rice ; those which occupy in- ternal cavities, attaching particularly to the liver, usually contain hydatids, and to the ovary contain a variety of products, sometimes serous, sometimes sanguinolent, sometimes gelatinous. Until a better method of diagnosis is pre- sented, the situation of the organ will therefore facilitate to some extent the knowledge of its contents. No one, however, will rest satisfied with this means, nor underrate the necessity of pursuing the investigation of these organs, until we are in a condition to state with more cer- tainty the elements for their diagnosis. We believe that all cysts may be ranged under one of the three following categories. A cyst may be a simple enlargement, or exagge- rated developement, or other modification of an existing organ. It may be produced by the irritation excited by the presence of a foreign body, whether that body be a shot or other substance introduced from without, or a tu- bercle or other abnormal product developed within the body. It may be a new formation not before existing in the economy, and pre- existent to the matter which it may be after- wards found to contain. The last of these categories has not usually constituted an element in the consideration of the mode of formation of cysts, and the sub- ject has in this way been divested of the difficulties which it must otherwise present. Many accurate observers have expressed a belief that cysts were a consequence of the irritation occasioned by a foreign body ; in this way a large proportion of these organs must be entirely excluded from consideration, or must be treated of under the term acephalocyst. Another class of observers, admitting the exist- ence of the foregoing, have added another variety : — they have assumed that the parietes of an alveolus of cellular tissue are attacked by some "morbid affection" by which all com- munication with the adjoining cells is cut off; that the parietes of this alveolus, under the in- fluence of irritation, acquire the power of secret- ing a product entirely different from that which they furnish in their natural condition ; that the accumulation of this morbid product causes a progressive distention of this small cavity, and a thickening of the cellular laminae in the midst of which the tumour is developed : in other words, that the tumour so produced acts in the same manner as a shot or other body in- troduced from without. In the opinion that all cysts are so produced, they are fortified by the belief that, by the process of maceration, of inflammation, or of suppuration, it is possible to reduce the parietes of these organs to their " original element, cellular tissue." Such was the opinion of Morgagni, Haller, Louis. The opinion propagated by Bichat, that a certain uniformity in structure obtains in all cysts, that they are all analogous to serous mem- branes, will, it is believed, be found incorrect; there are many cysts which in structure and function are essentially different from serous tissues, for instance, some are fibrous, cartila- ginous, osseous, others are cutaneous, others covered with hair. Our fii-st class contains the greater number of those subcutaneous tumours which are so commonly seen under the integuments of the cranium, the face, and some other parts of the body, and which contain meliceric, athero- matous, steatomatous, or other matter. It has been over and over again demonstrated that those follicles which open upon the surface of the body may have their aperture obliterated : the secretion from the internal surface of the organ may still proceed, and they occasionally attain a considerable volume ; in this way "steatomatous" tumours are produced. The matter contained in these tumours has been analysed by Thenard, who obtained the fol- lowing results. One hundred parts submitted to desiccation were reduced to forty, which treated by alcohol were, in fact, dissolved : the alcohol in cooling deposited a fatty matter, which was easily melted and was similar to adipocire. The residuum, which formed sixteen parts, was of an albuminous nature; consequently there were twenty-four parts of adipocire. This adipocire did not crystallise like that of the biliary cal- culus in man ; it was deposited in flakes like those of putrid animal matter dissolved in alcohol : yet, in the matter of the cyst, it was in the form of very brilliant micaceous lamina?. These cysts frequently appear very thick, but this great thickness is a consequence of their CYST. 789 being almost constantly lined by an inorganic coat, which is sometimes susceptible of being divided into laminae ; when this coat is re- moved, there remains a veiy thin cellular mem- brane. If the lining membrane be irritated, the secretion as well as the membrane may be modified ; and the variety of these subcuta- neous tumours is thus explained. Other cysts differently formed appear to ar- range themselves most naturally in this class ; of such are those which succeed to the ob- struction of a salivary duct, ranula for instance ; those which succeed to a fistulous canal, and are produced by the obliteration of the orifices of such canal ; the mucous tissue by which the canal was previously invested becomes changed in its organization, and a serous cha- racter is acquired: — those which are occasionally produced in the lungs, by the obliteration of the canal of communication between a tuber- cular cavity and a bronchus ; in this case also a serous membrane is developed within the cavity. The second class. — Every foreign body, fluid or solid, formed within or derived from with- out the animal economy, induces in that eco- nomy an effort at expulsion. Whether the body be a shot, a bullet, or other projectile, or whether it be extravasated blood, stone in the bladder, the foetus in extra-uterine pregnancy, acephalocysts, tubercle, or other heterologous or analogous formation ; in all cases irritation or inflammation is developed, for the purpose of expelling or isolating the nocuous body. If it be in its nature irritating, it excites in- flammation, and is expelled with the pus which has been secreted around it; if it have no mechanically or chemically irritating property, it may remain in the midst of the organ, some- times passing from cell to cell, obedient al- ways to a kind of eccentric movement ; some- times nature isolates it by organising around it a cyst which is adherent by its external surface to the surrounding tissues, but which is free and smooth internally, — furnishing a fluid by which many of these bodies may be broken down, and as soon as they are removed, the walls of the cyst become reduced into cellular tissue by absorption. Frequent opportunities are afforded for ex- amining these structures in the cellular tissue. When a certain quantity of a succulent fluid is accumulated in this structure, if it cease to increase, the parietes of the cavity which con- tains it continues to be the seat of a chronic inflammation by which the formation of a cyst is determined. Until the organisation of this cyst is perfected, the surrounding cellular tissue continues red and indurated ; but as soon as the organ is completed, this redness and in- duration are commonly in progress of dis- sipation ; in some cases, however, they remain, and then it occasionally happens that the cyst participates in the morbid action, and the in- terior of the cyst may have a pseudo-membrane developed on its surface. Cysts so developed are at their commencement soft, not very con- sistent, and may be easily detached from the surrounding structure. The inflamed stratum, between the cyst and the adjacent healthy tissue, gradually acqukes a greater density and more power of resistance, at the same time that it becomes thinner, and contracts a more intimate union with the proper membrane of the cyst. When the organisation of this spe- cies of cyst is completed, the membrane is whitish, opaque, more or less thick, and as a point of comparison, denser, and thicker than a serous membrane, and it presents a surface somewhat similar to that membrane. In making a third class, it must be obvious that we incline to the opinion of Delpech, " that certain cysts do not proceed from an accidental and mechanical modification of the cellular tissue," but that they are so many new organs, so many newly developed tissues, which do not possess either the same degree or even the same kind of vitality as the surround- ing parts. In this class we range those which contain a serous or sero-mucous fluid, which are de- veloped in various parts of the body. Their parietes are sometimes transparent, at others opaque ; upon their inner surface they usually present a kind of tomentum or velvet-like tex- ture, sometimes it presents hair. Their ex- ternal surface is sometimes free on all sides except that upon which the vascular commu- nication obtains, sometimes they are com- pletely adherent. They are observed free and almost floating in the cerebral cavities, in the kidney, the liver, the lungs, and in all serous cavities. We also include in this class certain syno- vial cysts, which are observed around the articulations of the hand, of the foot, some- limes of the knee, and in the neighbourhood of the sheaths of tendons. Some persons have been disposed to refer the origin of these organs to a displacement of the synovial mem- brane which has yielded at this point; but ob- servation has demonstrated that they are cysts with dense and fibrous external, and serous internal parietes, developed in the cellular tissue surrounding the normal synovial sac. In the same class we place a species of cyst developed, so far as we yet know, under the anterior annular ligament of the carpal articu- lation,— more rarely in the vicinity of the tibio-tarsal articulation, but always around sy- novial sacs or tendons, and essentially con- stituted of small white bodies, in appearance similar to small grains of boiled rice. Of the serous cysts, we may frequently find some very small, and, as nearly as may be, empty, the membrane being puckered and plicated, and in contact with itself at points where the plicae meet. At a certain period of their existence there is scarcely a particle of fluid accumulated in them, and of course the first exaggerated exhalation which has place will be lodged without any obstacle in the cavity, the plicae will be effaced, and the pa- rietes removed to a certain distance, the one from the other. It is probable that this pro- portion between the cyst and its contents is maintained until some irritation shall acce- lerate the exhalation, much as in the serous cavities of the body. This exhalation is some- times so abundant and rapid that the parietes 790 CYST. become irritated and inflamed, and these tunics, at first characterised by so much tenuity, may, by the pure and simple effect of their rapid development, or as a consequence of their relation with very moveable organs, or by the effect of accident, to which they are exposed, become susceptible of almost unlimited trans- formation. We believe, therefore, that all the varieties composing this class owe their existence to irritation ; in the synovial the irritation is spe- cific and caused by pressure, — in the serous, we believe it to be of another kind, — in many of them it is similar to that which presides over the development of hydatids: the only difference between certain of them, those, for instance, which are so nearly isolated, having merely a vascular communication, and an hydatid, is perhaps simply, that their existence has not been sufficiently prolonged to permit with safety the rupture of this umbilical cord, if I may so term it, by which they are con- nected to the surrounding tissues ? We must now endeavour to explain the circumstances under which these cysts are developed. The experiments and observations of Cru- veilhier shew, in the most convincing manner, that humidity, abundance, and the bad or ve- getable quality of the nourishment of an animal, are unequivocal means of producing acephalocysts. If by the concurrence of these circumstances acephalocysts may be produced, it must be evident that by the agency of the same causes a modification of existing tissues, — irritation, in fact, of a specific kind, has been excited by which a state favourable to their development has been produced. Admitting then that by such means a particular kind of irritation may be set up in certain tissues, we must go further; that irritation must be suf- ficient to cause the exhalation of a particle of lymph, that lymph, as in the case of a pseudo- membrane, becomes organised, acquires step by step an individual existence, it will be the minimum of organisation and independent vitality, but still, when its separation is achieved, it will be a living being. Supposing this idea to be correct, it may follow that a variety of modifications of such products, more or less independent, may be in a similar manner pro- duced. It is certainly difficult to reconcile the mind to the idea that the process of irritation or of inflammation can, under any circumstance, excite the development of an animal possess- ing to a certain extent an independent ex- istence, but this is not more difficult than to conceive that molecules of a plastic living substance may form organic membranes, and yet this is demonstrable. This has been clearly shewn in the article Adhesion; in fact, the more we study the phenomena of organisation, the more we are impelled to admit a proper vitality in certain products of living bodies. The analogy which exists between false membranes and hydatid sacs appears to be especially calculated to elucidate this subject. But whilst the false membrane remains in vital communication with the individual, the acephalocystic false mem- brane is detached and enjoys an independent life; the false membrane acquires a vitality rivalling that of normal tissues. We believe, therefore, that a cyst may be developed, which, as far as general appearances are concerned, shall be analogous to the ace- phalocysts, wanting, however, the one great attribute, independent existence, and having a vascular communication with the tissue upon which it is developed : are not those cysts which are often seen upon the cortical sub- stance of the kidney, and upon other organs; of this class or character? Dr. Hodgkin* has inferred that those cysts which are so often found on the surface of the kidneys owe their existence to the obstruction of an excretory canal ; others have believed that this fact was demonstrated, because it was said that their contents had the odour of urine. Without denying this position, I may state that the smell of serum and that of limpid urine are not very dissimilar. If they were a consequence of the obstruction of an urinary duct, it is evident, from the size they some- times attain, that secretion has proceeded after the obstruction has been developed ; why then does it not go further ? why do they not attain considerable magnitude? In the earlier periods of their existence the organisation of these bodies is simple, but in their progress they may experience many mo- difications. Their internal and external sur- faces are essentially different. ; the internal is usually smooth and polished like serous mem- branes ; sometimes it is soft, flocculent, and easily detached : the external is in contact with cellular tissue, and partakes more or less of its character, but 'frequently it acquires a density which distinctly separates it from the surround- ing tissue. There is scarcely any form of trans- formation which may not occur in these organs. The internal surface occasionally acquires a very complicated organisation ; it may be co- vered with hair proceeding from follicles de- veloped in its parietes, and it may present other anomalies. The external surface may acquire a very considerable density, and may present something like a fibrous appearance, but upon further investigation we find that it does not possess any fibre, neither does its texture offer any linear or radiated arrange- ment. When once organised, the tunic which constitutes the cyst enjoys all the attributes of living tissues, and is susceptible of similar morbid modifications. It may become in- flamed, it may degenerate into a cartilaginous state, — may become incrusted with phosphate of lime, converted into erectile tissue, — may become scirrhous, and so on ; and the ex- halation or secretion may be so changed that cysts of similar origin may contain the most dissimilar products. Bibliography. — Cruveilhier, Essai sur l'Anat. Path. t. i. p. 202 & seq. Gendrin, Hist. Anat. des Inflam. t. ii. p. 531. Begin, Diet, de Med. et Chir. Path. art. Kyste. (B. Phillips.) * Med. Chir. Transact, vol. xv. part 2. p. 270. DEATH. 791 DEATH. — (Lat. mors; Gr. Qivarot;; Germ. Tod; Fr. mort ; Ital. morte.) This word lias acquired a variety of meanings, which it will be proper to enumerate, before explaining the sense to be adopted in the following- article. — Death sometimes expresses the time when an organic body loses the characters which distinguished it while living ; in which signification it is the opposite, not of life, but of birth, or the period when life began ; this period being dated in the animal either from the time when it left its ovum or its parent, or from the very moment of con- ception ; and in the vegetable, either from its emergence above the earth, or from the first impulse of germination. In another acceptation, Death is that altered condition of an organic body in which it is no longer the subject of certain processes which con- stituted its life. Thirdly, it may signify that series of changes which immediately precede the cessation of life; — in this meaning, death is the act or process of dying. Lastly, in the human subject, the word is employed to express the separation of the soul from the body. It will be our object not so much to follow out these several significations, which would lead into a very wide if not a vague discussion, as to consider the precise nature of that condition of the animal body to which the term Death in its physiological import is applicable, and to enquire by what signs that state may be known to be either impending, or actually present. Death in its most restricted sense may be defined to be that condition which imme- diately succeeds the abolition of all those ac- tions or properties which distinguish living from brute matter, a condition not merely negative but privative. But death is likewise applied to certain states of the organic system in the higher animals, in which the abolition of the functions is not universal. In the former sense, an animal is not dead until every vital action throughout the tissues has been extinguished ; while in the latter, dis- solution is considered to have taken place when the circulation and respiration have ceased, because the cessation of the others almost uniformly follows. We have here then an obvious distinction of Death into two kinds, which will be found to correspond with a very natural division of the vital actions into two classes; 1, those which transpire between the particles of which living bodies are composed (nutrition and contraction); and 2, those which occur between certain collec- tions of organic particles, called organs, and by virtue of which these organs constitute a whole system — (respiration, circulation, inner- vation, Ike.) The extinction of the former of these classes of functions we shall venture to designate Molecular Death ; of the latter, System ic Dea th .* * We should have been glad to have avoided a word so incorrectly formed as systemic, but its use has been sanctioned by too many and too great au- thorities for us to venture upon the substitution of The following truths respecting the mutual influence of these two kinds of death will be illustrated in the course of the present article : 1st, That molecular does not necessarily in- volve systemic death, unless the former is universal. 2dly, That when partial, as in mortification, the tendency of molecular to in- duce systemic death depends on the import- ance of the part to the whole. 3dly, That molecular death in one part can only induce the same change in another part, by means of its interference with one of the systemic func- tions. 4thly, That systemic death must neces- sarily be followed sooner or later by molecular death, — but that, 5thly, The reality of systemic death can only be proved with certainty by the occurrences pertaining to molecular death. MOLECULAR DEATH. Molecular life is constituted by two func- tions, Nutrition and Contraction, for which certain conditions are requisite. The former demands a mechanism or tissue of pores or in- finitely minute tubes, the ingress and egress of fluid, and a certain quality of this fluid ; the latter, a fibrous arrangement of particles, in most animals and in all a peculiar property called irritability or contractility. The viola- tions of these conditions are necessarily fol- lowed by molecular death. We shall consider them in detail. Destruction of the tissues. — It is all but a truism to assert that the function of a tissue must cease when its mechanism is broken up, though mere integrity of the mechanism is insufficient to maintain the function. The changes which ensue are as follows. The sub- stance is no longer capable of receiving and transmitting fluid in the same manner as for- merly ; the fluid which it contained is either confused with the disorganized solid particles, or is altogether eliminated ; the fibres are unfitted for contraction ; and the nervous filaments are paralysed. In this condition the part has ob- viously no kmc! of connection with the rest of the system, by the exchange either of fluid, or of nervous influence; it is dead both abso- lutely and relatively. If the other organs sur- vive its death, certain processes commence in its immediate vicinity, by means of which a mechanical as well as a vital separation is effected ; while the mortified part, as it is technically called, is abandoned to the play of various chemical affinities among its particles, and between these and surrounding agents. According as these changes are less or more ad- vanced, there is gangrene or sphacelus. It may happen however that the other parts of the frame may lose their vitality soon after the local injury ; but their dissolution will depend upon the violation of other conditions than that which we are at present discussing. Thus the part disorganized may be essential a newly-created one. The writer is indebted to his friend Dr. Prichard for the suggestion of somatic, which is at once correct, and sufficiently characte- ristic, but he has not had the courage to introduce it into the text, though supported by an authority no less eminent in philology than in general sci- ence. 792 DEATH. to the distribution of blood throughout the system, and the other parts may die from the want of this supply, their mechanism remain- ing entire. Or the injury, notwithstanding that the part may not be thus functionally es- sential to the circulation, may exert a no less certain operation, either indirectly by an im- pression made upon the central organs of in- nervation, and reflected upon those of circu- lation and respiration, or immediately by an impression upon the latter. (See the remarks upon Systemic Death.) The propagation of the dissolution will depend much upon the peculiar organization of the animal ; but in all cases, as we have already intimated, text- ural death in one part has no immediate in- fluence in producing the same kind of death in other parts; the latter event will be found attributable to the impediment offered by the former to some important function of the whole system. The textural lesion which we have been considering may be caused either by mechanical violence, or by chemical action, such as that of corrosive substances and of heat. It is possible that solid tissue may un- dergo spontaneous decomposition, but we are unable to ascertain the fact, because in ulti- mate structure, where fluids and solids are so intimately intermixed, we have no means of distinguishing the priority of changes. Arrest of' the fluid of nutrition. — The access of this fluid is variously provided for in the different classes of animals. The capillary cir- culation in the higher species resembles that which suffices for the whole system in the lower species, inasmuch as the blood in the capillaries of a tissue bears the same relation to that tissue, as the water in the stomach of one of the Radiata to the whole animal. The consequences of abstracting the fluid in the one case, or of cutting off the supply of blood in the other by obstructing its vessels, will be pre- cisely analogous. The polype will desiccate, lose its proper form, and decay; the medusa will shrivel and putrefy ; while in man the tissue dies, and is decomposed, as in senile gangrene, or in the sloughing of a hemorrhoid to which a ligature has been applied. Sup- pression of the action of the heart violates throughout the body the condition of vitality under discussion, and consequently all the tissues die, but the phenomena which they exhibit are not the same as in more partial obstruction of the circulation, because the chemical agencies are different, particularly that of surrounding heat. A gangrenous spot is under the influence of an atmosphere of 98° at the lowest; while the dead or dying organs of animals, which have been simultaneously deprived of their circulation, are submitted only to the temperature of the media in which they may chance to be placed. The higher this may be within certain limits, the more closely will the putrefactive changes resemble those of gangrene. It must be remembered, however, that in the latter case other chemical agents are probably presented in the fluids effused by those contiguous parts which still maintain their vitality. Dependence upon the circulation differs in different animals. The heart of a salamander may be excised, and yet the animal will live for several hours, or even a day or two after the operation ;* its possession of life being in- ferred from the exhibition, not merely of cer- tain organic actions, but even of those of rela- tion. It is plain, then, that in animals of this tribe, the brain and spinal marrow and other organs do not require so constant an inter- course with the blood as in certain other species ; and while we know with tolerable certainty that they do not need it for calorific purposes, it is not improbable that their textures are less frequently repaired than those of the warm- blooded classes. Dr. Edwards concludes that life in the above instance is maintained by the organs of innervation, whose function, as we have remarked, continues unimpaired. We should regard the integrity of their action rather as a sign than as a cause of continued vitality ; other signs being perceptible in the persistence of the capillary actions, for which the fluids still remaining in the tissues may be sufficient. Retention of fluid in the tissues. — Removal of the effete fluid is provided for in the Porifera by ejects; in the Polypifera by expulsion from the central cavity and by transpiration ; in the Acalephffi by anal apertures ; and in vascular animals by vessels especially appropriated to the purpose, by transpiration, and by various excretions. This condition of molecular life is less easily violated than those already spo- ken of, because the modes of fulfilling it are more numerous. This is equally true whether we speak of the simple animal forms, or of the tissues of the more complicated ; mortification is less frequently the result of venous than of arterial obstruction. Unquestionably turgescence and inflammation may ensue from the former, and may terminate in gangrene ; but it is far more common for the part to be relieved by the excretion of various fluids, constituting haemorrhage and dropsy, until new channels are found for the returning blood. Hence it ap- pears that a redundance of fluid is less dan- gerous to organic structures than a deficiency. Depravation of the fluid of nutrition. — It is obvious that as the structures are elaborated either from the blood in the higher animals, or from the fluids corresponding to it in the in- ferior classes, the assimilative processes must be deranged and ultimately brought to a stop, if the liquids are wanting in the proper mate- rials. Their quality may be deteriorated in various modes ; by imperfect respiration, by bad or scanty alimentation, and by insufficient or excessive excretion. Each of these causes is traced easily enough in the degenerated tex- tures of some animals, but with more difficulty in the simpler classes, because the functions just alluded to are not in the latter concen- trated within a space that admits of analysis so well as in the former. The effect of obstructed aeration of the blood however is soon mani- * Edwards, On the Influence of Physical Agents, &e. translated by Drs. Hodgkin and Fisher. DEATH. 703 fested even in the lowest grades. But we must observe, that throughout the whole range of animal existence we can more readily ascertain the changes produced in molecular action by diminished respiration, than by the entire sus- pension of this function ; because, in the first place, the arrest of the circulation so soon fol- lows that of respiration, that the subsequent events are assignable rather to the former than to the latter; and in the second place, it is impossible to cause one portion of the body to receive unaerated, while the others are sup- plied with aerated blood, since the function is in some animals too concentrated to allow of an operation calculated to act upon an isolated part, and in other animals too diffuse to enable us to interfere with it effectually in any given space. In the one case we run the risk of cutting off' the supply of blood from the whole animal ; in the other w e should find it im- possible to prevent any one part from receiving from other parts a compensation for what it loses by the obstruction of its own particular allotment of the respiratory function. Nothing however is more common than to witness the degeneration of structure produced by blood insufficiently arterialized, the imperfection of the process depending either upon disorder in the organs of respiration, or upon a vitiated condition of the atmosphere. From facts of this nature it. is legitimate to infer that were it possible for unarterialized blood to circulate, the death of the tissues must sooner or later ensue. Of the destructive tendency of blood depraved by the other causes above enu- merated we can likewise judge approxima- tively ; in other words, while there can he no question of the deterioration of structures under the operation of those causes, we are not ac- quainted with any instances in which we can attribute solely to their agency the entire cessa- tion of molecular actions. It almost always happens that other functions have previously failed, and influenced the result in question. Extinction of irritability. — Irritability might at first seem rather the result of vitality than one of its conditions ; but whether we look at the textural motions in a complex animal, or at their analogues in the entire systems of the simpler forms, we shall find irritability to be essential to the continuance of those processes in which living action consists. The alimen- tary cavity which contracts upon the nutrient fluid of the zoophyte is no less essential to the existence of the latter, than a similar action of capillary tubes in the tissues of mammalia. In each case the action is requisite, in order to bring the particles within the spheres of the textural affinities. The extinction of irritability is therefore necessarily productive of molecular death. In this instance we are compelled to speak of the privation of a property instead of defining the actual change in the part, because at present it is not ascertained what condition of the part is capable of producing contraction. Irritability is merely an expression of the fact that the substance of which it is predicated, undergoes contractions inexplicable on common physical principles. We detect nothing in the vol. r. substance, the existence of which enables us to pronounce with certainty that it may be the subject of the actions alluded to. Some have maintained that irritability ought to be ad- mitted as an ultimate fact, of which we know as much as of gravity. But we apprehend that there is this great difference in our knowledge of the two properties, viz. that although igno - rant of the cause of the attraction of gravitation, we are certain that the phenomena are co- extensive with the essential properties of mat- ter; but we are utterly unacquainted with that collection of properties to which irritability necessarily belongs. The muscle which has ceased to quiver under the galvanic wire is, for all that we can tell to the contrary, the same in composition as that which is still ca- pable of exhibiting the phenomenon. More- over the action is observed in a great variety of tissues, both in individual animals, and in the whole series ; tissues which appear to have little in common saving a fibrous arrangement of their particles. But as the action in question is stopped by causes which in no way affect the fibre as such, it is plain that this is not the only requisite. Moreover there are unequi- vocal exhibitions of contractility in animals, in which it is difficult to imagine that there can beany shortening of fibres; we allude to the Infusoria, Rotifera, Medusae, &c. Tiedemann makes a separate species of this contractility, under the designation of " eontractilite des animaux gelatineux." * There is reason to suspect that ganglionic tissue is importantly concerned in the action, partly because it is a/most universally distributed through irritable substances, and partly because contraction is prevented by causes which operate upon this tissue. As long however as there are animals which manifest contractions, but in which no such tissue can be detected, it is impossible to consider the latter an essential element in the action generally ; though it may be quite es- sential in the animals in which it is found ; just as a heart, though by no means necessary to the function of circulation in the abstract, is indispensable in the animal of whose system it forms a part. Irritability may be destroyed by substances, either applied directly to the part or acting upon the general system. Thus, the fibres of the heart may be paralysed by a solution of opium injected into its cavities, or by essential oil of tobacco given by the mouth. Light- ning annihilates the property all over the body. The motions of Infusoria may be arrested by a shock of galvanism,f by solutions of opium and camphor, and by the vapour of sulphur. Arsenical preparations have a similar effect. The contractions of capillary vessels in the higher animals may be arrested by a certain description of injuries of the brain and spinal marrow.} But it is needless Co multiply ex- amples. * Traite complet de Physiologie de 1' Homme, tra* duit de l'Allemand par A. J. L. Jourdan, D.M.P. 2de partie, p. 782. t Tiedemann, p. 617. } See Wilson Philip on the Vital Fnnctirms. 3 F 794 DEATH. Sucli tl >en are the causes of molecular death. For a history of its phenomena, when partial, we must refer to the article Mortification. Its characters when universal, that is, when the consequence of systemic death, will be con- sidered when we come to speak of the signs of the reality of death. SYSTEMIC DEATH. Systemic life is constituted by those actions which maintain the mutual dependence of the several parts of the organic whole. Such are the functions which provide new matter for the blood, (digestive secretion and absorp- tion)— that which effects a chemical change in the blood, (respiration) — that which distri- butes it through the organs and tissues, (cir- culation cardiac, arterial, capillary, and venous) ■ — that which removes from the blood effete matters, (excretive secretion) — and that which is intimately connected with all these functions, though we are ignorant of the mode of its operation, viz. the function of nervous matter or innervation. The cessation of these actions, and the consequent solution of connection between the various parts of the body, is sys- temic death. With the cessation of the re- maining functions, or those which maintain certain relations between the organic body and objects external to it, constituting the animal life of Bichat, and the relative life of others, we have nothing to do in this place. (See Sleep.) The obstruction of any one of the functions above enumerated must in a longer or shorter space of time bring the others to a termination. But, as the arrest of the circulation acts upon the other functions immediately, while the latter affect one another merely by the inter- vention of the former, we may very properly consider the causes of systemic death under the general head of Syncope. 1, Sy7tcope by asphyxia. — We shall not stop to inquire in what manner .the suppres- sion of respiration arrests the action of the heart, as the question has been very fully and satisfactorily considered in thearticle Asphyxia. For the same reason we shall waive the dis- cussion of the accidental causes of this state, viz. strangulation, submersion, &c. &c. The diseases which are said to produce death by asphyxia are those in which syncope would not supervene when it does, but for the obstruc- tion of the respiration. They are for the most part affections either of the respiratory ap- paratus itself, or of the brain and spinal mar- row ; and it is almost superfluous to add that they prevent the intercourse between the blood and pure air, either by blocking up the air- passages, or by stopping those muscular actions which are essential to a change in the contents of the pulmonary tubes and cells. Certain organic diseases of the heart itself are said to produce death by asphyxia. In these cases there is an obstruction to the motion of the blood through the left side of the heart ; and in the majority of them the asphyxial sym- ptoms are not so much the direct effects of the impediment in the heart, as of the intermediate pulmonary affections, some of the most fre- quent of which are bronchitis, oedema of the lung, and pulmonary apoplexy. When, how- ever, a person dies suddenly, with asphyxial symptoms resulting from an arrest of the circu- lation at the left side of the heart, without any intervening derangement in the organs of re- spiration, the case ought not to be considered an instance of genuine asphyxia. The ap- pearances imitative of this state (we allude more particularly to various phenomena be- longing to venous congestion) are not occa- sioned as in true asphyxia by the stagnation of blood in the extremities of the pulmonary arteries, the consequence of its not being arterialized, but by the obstacle presented to the currents in the trunks of the pul- monary veins by the lesion of the heart. In brief, the anatomical difference in the two states is, that in the one the pulmonary arte- ries only, in the other both these and the pulmonary veins are the seats of congestion ; the physiological distinction is, that in the former the obstruction is chemical, in the latter mechanical. 2. Syncope by nervous lesions.— The various parts of an animal body are bound together by a reciprocity of action, over and above that particular connection which exists between certain organs, and which results from a mu- tual subservience of function. In the latter, the association is perceptible in the normal condition of the body, as, for instance, be- tween the organs of digestion and those of secretion, or of digestion and sanguifaction, or in the sympathetic actions of the respiratory muscles ; but the other species of connection is only or chiefly observed in morbid con- ditions ; in other words, it is only when dan- ger is threatened to one organ that the others give tokens of their intimacy and of their interest in its well-being. But for our know- ledge of the existence of this community of feeling (a phrase to be taken only in a me- taphorical sense), it would be impossible to throw any light upon the fatal consequences of a great number of diseases and injuries. There can be little doubt that in all states of the system it contributes very materially to the production of that individuality which is one of the grand characteristics of organic beings, and which becomes more and more obvious as our survey rises to the higher departments of the animal kingdom. There is a manifest in- equality in this respect, even among the su- perior classes of animals. Many lesions that would be fatal to birds and Mammalia, are comparatively trivial to reptiles, not so much because the injured part is of less importance in the functional arrangements of the latter, as because other parts have less sympathy with it, There is no subject in the whole range of Physiology more beset with difficulties than the inquiry into the causation of sympathy. Vas- cular connection has been thought by some to explain the secret sufficiently, by others the contiguity or continuity of tissues. Some have seen the media of communication in the ganglionic nerves, others in the nerves called DEATH. 795 respiratory. We cannot enter into the discus- sion, and therefore refer to the article Sym- pathy. But we beg to state that we have no where seen the subject treated with more eru- dition and acuteness, than in Dr. Fletcher's Rudiments of Physiology.* But while there can be no question that all the organs are more or less related in the man- ner above indicated, it is not less evident that the connection between some is of a far more intimate nature than between others. It is almost needless to instance the brain and the stomach, the brain, spinal marrow, and the heart, the heart and every part of the system, &c. &c. By overlooking the sympathetic re- lation between the brain and the heart, Bichat fancied that when he had proved the functional independence of the latter organ, he was com- pelled to search in some third part for the link between the death of the one and that of the other.f It cannot be denied that in a large proportion of cases, the syncope which follows lesions of the cerebro-spinal system, is not a direct consequence, and that there is an in- termediate suppression of the function of the lungs, — that in other words the syncope is the effect of asphyxia.]: (see Asphyxia.) It is somewhat remarkable that the illustrious phy- siologist just mentioned should have forgotten certain pathological facts which afford con- vincing evidence that cerebral injury may pro- duce death without developing the phenomena of asphyxia; the " apoplexie foudroyante," for example, and the concussion of a blow or a fall. Nor is it less surprising that in his numerous experiments upon animals he should not have noticed what was afterwards fully demonstrated by Legallois and W. Philip, that both the heart and the capillaries may be imme- diately paralysed by violence done to the brain and spinal marrow. It must be remembered, however, that this result is much affected both by the extent and by the nature of the injury. Thus the brain may be sliced and the spinal cord divided, with no other influence upon the circulation than that which depends upon the interference with the respiratory actions ; but laceration or crushing of the cerebral matter is immediately felt by the heart and capil- laries. In these cases the circulation ceases, not because the cerebro-spinal axis takes any •part in that function, but because it is con- nected with the heart in the same manner as we have stated that all the parts of the body are more or less connected, — in bonds of alliance though not of dependence. We have reason, however, to believe that the intimacy of the alliance between the brain and the heart * Part ii. chap. vi. t Recherches snr la Vie et !a Mort, art. xii. §2. | We must not forget that even in many of these cases there is no immediate communication of injury from the part primarily affected to the organs of respiration. Thus, when a slight hemorrhage in one of the hemispheres of the brain occasions asphyxia, we are bound to believe that there is in the first place a sympathetic communication of de- rangement to the medulla oblongata, unless the hemorrhage has been so considerable as to cause compression of the whole encephalic mass. is scarcely equalled by that of any other organs in the system. The anatomical characters of syncope by nervous lesion are determined by the modus operandi of the injury. If the latter arrests the action of the heart only by obstructing the lespiratory movements, the appearances are those of asphyxia, (see Asphyxia.) But if the operation be immediately upon the heart, there will be a difference in the appear- ances, — a difference which likewise be- longs to all cases in which the circulation ceases without previous obstruction of respi- ration. The blood, instead of being accumu- lated in the right cavities of the heart, and in the pulmonary arteries, is more equally dis- tributed between these and the left cavities, and the pulmonary veins. There is generally a perceptible difference in the colour of the blood in the two sides of the heart, but some- what less than might at first be expected. The defect of arterial tint in the coagula of the left side may be fairly attributed to the drain- ing away of the serum, and consequently with it of the saline particles upon the pre- sence of which the red colour depends. Blood is found in the aorta and in many of the ar- teries. The signs produced by venous con- gestion, such as engorgement of the liver and spleen, turgescence of the cerebral veins and of those of the mucous membranes, are want- ing, as well as the tumefaction of the face, the puffing of the lips, the projection of the eyes, and the deep lividities characteristic of that condition. We must remember that the appearances are considerably modified if syn- cope has taken place gradually. In such in- stances the heart is generally found empty. The cause of this condition is obvious. In the first place, as the degree of the diastole must be proportionate to the systole, it is obvious that when the latter is enfeebled, less blood will be received into the cavities; and, secondly, as less blood is driven into the pul- monary artery and the aorta, there will be less to return' in a given space of time, and con- sequently there will be less impetus in the returning currents. It is easy to perceive that before the final and feeblest contraction, which must be succeeded by a correspondently slight dilatation, the current of blood pressing for admission must be very trifling. 3. Syncope by injuries of the heart itself— This is of too obvious a nature to require comment. 4. Syncope by injuries of other organs and tissues. — When death follows quickly upon a lesion which does not necessarily implicate tire vital organs, properly so called, we say in ge- neral terms that a shock has been given to the nervous system, in consequence of the strong- probability that some portion of this system is the agent of sympathy. If violent pain at- tends the injury, and to this succeeds loss of consciousness, and then cessation of the heart's action, it is fair to infer that the brain was first operated upon through the nerves of sensation, and that the derangement of this organ affected the circulation. But there are 3 f 2 796 DEATH. cases of injury in which syncope occurs with- out any antecedence of pam or of leipothymia, and in w:hich there is no reason for supposing any cerebral affection in the chain of events. Of this kind are extensive mechanical injuries of. the extremities, burns, rupture or over-dis- tention of the stomach, &c. Whether the nerves which convey the morbid impression belong to the ganglionic or to the respiratory class, we do not profess to decide. The im- mediately fatal efiect of a blow upon the epi- gastrium or of a draught of cold water when the body is heated, has been attributed by some to a shock given to the semilunar ganglion, and the communication of the impression to the heart; while others are of opinion that the injury is fatal by " paralysing the whole res- piratory set of nerves from the violent shock com municated to the phrenic, and thus shut- ting up as it were the fountain of all the sympathetic actions of the body."* " A blow on the pit of the stomach," says Sir Charles Bell, "doubles up the bruiser and occasions the gasping and crowing, which sufficiently indicate the course of the injury — a little more severe, and the blow is fatal. A man broken on the wheel suffers dreadful blows, and his bones are broken, but life endures — the coup- de-grace is a blow on the stomach." 5. Syncope by mental emotion. — Instances of this occurrence must be familiar to every one both by reading and by observation. In some of them the cause in question has operated either by aggravating some pre-exist- ing malady, or by calling into action some strong predisposition to disease ; as in struc- tural lesions ot the heart on the one hand, and in the apoplectic diathesis on the other. But in other instances the mere violence of a pas- sion has at once extinguished its subject with- out the intervention of moibid tendency or of actual disease. Such cases belong to the Nervous Apoplexy of some authors ; and cer- tain it is that they present a complete annihi- lation of sense and motion, but this condition is only simultaneous with, or immediately suc- ceeded by the failure of the circulation. We have no doubt that the change in the organ of the mind, corresponding to the emotion, ope- rates upon other parts of the cerebro-spmal axis, which in their turn affect the heart in the same manner as other preternatural states of that system. We are not acquainted with any example in which either high intellectual ex- citement unaccompanied by vehemence of pas- sion, or mere intensity of external sensation, has been the cause of sudden death ; nor could it be expected a priori, since in the normal condition of the economy there is by no means the same degree of connection between the action of the heart and intellectual and sen- sific conditions, as between the former and the emotions and affections. 6. Syncope by hamorrlnige. — The functions of the brain are in man so dependent upon a regular supply of blood to the organ, that a sudden diminution of it is alone sufficient to * Dr. Fletcher, op. cit. partii. chap. 6. p. 60. occasion vertigo and unconsciousness ; and this occurrence often takes place when the action of the heart itself is little or not at all affected. Every one is acquainted with the effect of a change in the relative quantity of the blood in the cerebral vessels, determined by suddenly rising from the recumbent posture. Now it has been often observed that vertigo in- duced by other causes has been followed by suspension of the circulation ; that is to say, the state of the brain, which was attended by giddiness, arrested the motions of the heart. It has therefore been inferred that loss of blood operates indirectly upon the heart through the affection of the brain. When two phenomena follow each other in such quick succession as to be all but simultaneous, it is difficult to determine which is cause and which is effect, or whether they may not be the common ef- fects of some other event. Certain facts would seem to indicate that the latter is the true interpretation of the phenomena which we are considering. Thus haemorhage some- times affects the nervous system in the manner alluded to, without presenting any check to the contractions of the heart ; not to mention that it appears more consistent with analogy to conclude that the heart must be more directly influenced by the loss of that which is its natural stimulus, than by a change in a remote organ. Again, there are cases in which haemorrhage makes a decided impres- sion upon the organs of circulation before the brain has given signs of any material derange- ment of its functions ; but in these the loss of blood is more gradual than in the former instances. " When haemorthage is very gra- dual," says Dr. Alison, " all the indications of failure of the circulation may come on — the feebleness of muscular action, — the paleness and collapse of the countenance, — the cold- ness beginning at the extremities, — the cold sweat beginning on the face, — and the pulse may become imperceptible ; without the senses or the intellect being impaired, and a slightly laborious or heaving respiration may be almost the only indication of injury of the nervous system up to the moment of death."* From facts of this description we should be willing to decide at once that it is a superfluous multiplication of causes to attribute the stop- page of the circulation in any case of haemor- rhage to the influence of cerebral changes, when the direct operation of the cause upon the heart itself is adequate to the explanation ; — were it not for the important fact that haemorrhage alone often fails to produce syncope till some circumstance has intervened, the operation of which is manifestly upon the nervous system. Thus nothing is more common in bloodletting than to find the heart unaffected by the with- drawal of a considerable quantity of its stimu- lus, so long as the posture of the body is horizontal ; but on raising the head, a change which for obvious reasons renders the brain * Outlines of Physiology and Pathology, p. 344. This work contains a most valuable chapter upon the causes of sudden death. DEATH. 797 more sensible of the loss of blood, the nervous symptoms, viz. vertigo and leipothyroia, ap- pear, and immediately afterwards the pulse falls and becomes imperceptible. In corro- boration of this fact we might at first be inclined to mention that a diminution of the quantity of the blood, so far from depressing the circulation, often appears to excite it violently, as in what has been denominated hemorrhagic reaction; but in such instances analogous effects have been also witnessed in the cerebral functions, namely, delirium and extreme sensibility, &c. On the whole we may conclude with regard to both these sys- tems that the depressing effect of haemorrhage depends rather upon the suddenness of the change, than upon the absolute diminution of the quantity of the fluid. 7. Syncope by poisons. — Some substances depress the action of the heart in the man- ner to which we had occasion to refer when speaking of syncope by mechanical injuries of the tissues generally. Of this kind are the mineral acids, oxalic acid, and the pure alkalies. They produce death, when taken in certain quantities, by means of that de- pression of the circulation which follows the destruction of the parts to which they are applied. In smaller quantities they may be more remotely fatal by exciting disease, gastro-enteritis for instance. One of the sub- stances mentioned, viz. oxalic acid, may in- duce direct depression of the circulation, un- attended by cerebral affection, even when its chemical effect upon the stomach is prevented by dilution. In this form it must be classed with a large collection of substances which in certain doses subdue the moving powers of the circulation, without any previous coma, without any alteration of the tissues, and without any gastric irritation; such are arse- nic in large quantities, tobacco, digitalis, and most of the animal poisons. To the same class belong those malarious and contagious poisons which occasionally induce fatal syn- cope before any of their ordinary effects upon the general functions ; we scarcely need to mention cholera, malignant typhus, plague, scarlatina, &c. The narcotic substances mani- festly act first upon the cerebro-spinal system ; syncope follows either with or without as- phyxia. Those which act rapidly appear to strike the circulation before asphyxia has had time to transpire ; we may instance hydro- cyanic acid, essential oil of almonds, large doses of opium and of alcohol, certain gases, particularly sulphurtted hydrogen and cyanogen, 8. Syncope by cold and lightning. — It is not clear whether these outward agents arrest the circulation through their influence upon the nervous system, or by directly paralysing the irritablity of the fibres of the heart. 9. Syncope by inanition. — In cases of this description it is probable that the failure of the heart's action is a compound result of the prostration of the nervous system, and of the diminution of the proper stimulus of the circulation. 10. Syncope by disease. — All fatal maladies must terminate in cessation of the heart'sa c- tion, but we limit the present category to those cases in which this event is unpreceded by asphyxia. The others have been hinted at under the head of syncope by asphyxia. The diseases now under consideration may, we think, be conveniently arranged as follows: — I. Those which stop the motion of the heart by obstructing its mechanism, e. g. collections of fluid in the pericardium, lesions of the val- vular apparatus ; accumulation of fat, &c. ; or by diminishing the contractility of the fibres, e.g. atrophy, or degeneration of the muscular substance ;*" or by perturbing in some unex- plained manner the nervous influence, e. g- the functional form of angina pectoris. 2. Those which are attended with hemorrhage, e. g. aneurisms, and diseases of mucous surfaces- 3. Those which induce excessive and long-con- tinued discharges. Thus fatal syncope has sud- denly terminated a fit of diarrhoea ; but it must be borne in mind that in such instances the power of the circulation had previously been greatly enfeebled either by deterioration of the blood, or by causes acting on the innervation of the heart, or by the existence of irritation in some part of the system. 4. Diseases implicating the cerebro-spinal organs. Some of these ope- rate in the same manner as those accidental injuries which produce concussion, and which have been already adverted to. Thus in that species of apoplexy which terminates instan- taneously, (apoplexie foudroyante of French authors.) the sanguineous extravasation appears to have the same effect as a mechanical shock to the whole nervous mass. The more common form of apoplexy extinguishes life by impeding the respiratory movements. We have more than once known cases of structural disease of the brain terminate by sudden syncope, but have learned nothing from the necroscopy capable of explaining why the fatal occurrence took place at the precise time when it did, rather than at any other moment in the period during which the disease had existed; though it was easy to conceive that a lesion of this description must have been competent at any time to produce such changes in the cere- bral circulation as would induce the result in question. 5. Diseases attended with what has been vaguely called irritation, either short and intense, or moderate but long-continued. This irritation consists sometimes of inflam- mation and its sequela;, and sometimes of spe- cific structural alterations. A good illustration of the former of these is afforded by peritonitis, which frequently cuts off the patient by sub- duing the action of the heart, long before this effect could transpire from derangements of the organs contiguous to the seat of disease. Still more remarkable in this point of view are the effects of acute inflammation of a synovial capsule. It is true that these affections are accompanied by violent pain, which might be said in common language to exhaust the powers of the system, or in stricter phrase, to * See Mr. Chevalier's interesting cases of sudden, death in the Med. Ch. Trans, vol. i. 793 DEATH. produce a change in the nervous system in- compatible with the continuance of the action of the heart; but mere pain will not account for the fact in question, since in other diseases it attains a more intense degree, and lasts longer, as in neuralgia, without inducing fatal consequences. The causation is probably analogous to that of syncope from mechanical injuries of tissues, to which we have already devoted some remarks. But why an inflam- matory condition of serous membranes should exert a more depressing influence upon the circulation than that of many other tissues that might be named, is a subject wrapped in deep obscurity ; yet it is scarcely darker than the question, why such changes should in the first instance excite and perturb the heart, or why a similar excitement should ensue upon the soft- ening of a cluster of tubercles, and to a degree inexplicable by the functional derangement of the part in which the tubercles exist. Dis- eases in which the powers of the system are said to be worn out, are in reality such as have gradually enfeebled the action of the heart, partly perhaps through the intervention of changes affecting the blood, the respiration and the nervous system, but probably in a great measure by as direct a relation between the diseased part and the change in the circulation, as between violent lesions of tissue and syn- cope. Under the present head are included a host of chronic maladies. 6. Diseases caused by vitiation of the blood. Such are scorbutus, certain forms of marasmus, the cachexia; revealed by dropsies, and certain fevers of a malignant character. We might also mention those depravations indicated by morbid secretions, such as tubercle, carcinoma, melanosis, &c. but that the solids are so much involved in these diseases, that it becomes difficult to determine whether the heart's action was weakened by the primary lesion of the blood, or by the secondary one of the tissues. 7. Diseases which produce vitiation of the blood. Such are that large class in which there is disorder of the cbylopoietic processes, and that smaller group in which the convey- ance of the chyle is impeded. Derangements of the secernent and excernent organs must be arranged in this division, and particularly those of the liver, the skin, and the urinary apparatus. Diabetes is a state of the system in which the blood is probably deteriorated both by defective assimilation, and by faulty excretion. Upon the whole of this class of diseases it must be remarked that we seldom or never have opportunities of witnessing their uncombined influence in depressing the organs of circulation. 11. Syncope by old age. — We have, in a for- mer article (Age) endeavoured to trace the principal events in senile decay. The death which follows this gradual decline of the func- tions, presents the strongest possible contrast to that of sudden syncope. In the latter in- stance (he assault is made upon the very citadel of life, the conquest of which secures an im- mediate surrender of the minor bulwarks and dependencies ; but in the former the fortress is reduced only after a long series of defections in the outworks, and a consequent loss of supplies, or, to quote the words of an illustrious author, " Voici done la grande difference qui dis- tingue la mort de vieillesse, d'avec celle qui est reflet d'un coup subit ; e'est que dans l'une, la vie commence a s'eteindre dans toutes les parties, et cesse ensuite dans le ccseur; la mort exerce son empire de la circonference au centre. Dans l'autre, la vie s'6teint dans le cceur, et ensuite dans toutes les parties ; e'est du centre k la circonference que la mort en- chaine ses ph6nomenes."* SIGNS OF APPROACHING DEATH. It would be tedious and altogether beyond the compass of this work to enumerate all the phenomena presented by the dying system, since they vary with the cause of death. We shall aim rather at describing and accounting for those which are common to most diseases and to natural decay; reserving to ourselves the liberty of noticing here and there some of the more striking varieties. We might rationally expect that the first indications of dissolution would appear in the relative functions ; hebetude of the senses, in- action of the muscles, vacancy of the intellect, extinction of the sentiments ; and such is, in fact, the course of events in natural death. We have known the aged man remain feeling- less, motionless, mindless, for many days be- fore the cessation of the organic functions. This kind of death is sometimes imitated by apoplexy; but in the former the destruction of the animal life does not, as in the latter, arise from a lesion of the brain ; its organs appear to undergo a gradual process of enfeeblement. In many febrile maladies there is the same priority of failure on the part of the cerebral functions, but they are generally preceded by more or less actual disease of the organ. But in the termi- nation of some disorders the functions alluded to continue to the very last, almost surviving the circulation itself. It will be found however that the seat of such disorders was remote from the encephalon,that it did not communicate with the latter by any special sympathy, and that the extinction of the cerebral functions was at- tributable to the arrest of circulation in that organ, in common with many others. The cases in which the mind is said to continue clear and vigorous amid the ruin of the body, will be found to agree in the fact that the organ is correspondently unimpaired ; they are for the most part chronic diseases of the thorax, abdomen, pelvis, and extremities. Certain affections even of the cerebro-spinal system may not interfere with the understanding and feelings until almost the last moments ; but they are such as do not involve those divisions with which thought is believed to be more immediately connected : we may instance tetanus. But although in these maladies we do occasionally observe considerable intellec- tual soundness till within a very short period of death, we have far more commonly been able to detect some degree of delirium, au * Bichatj Rech. sur la Vie ct la Mort, p. 151. DEATH. 799 exaltation of one part of the mental constitution at the expense of the others. Excitement of the imagination has, we doubt not, been fre- quently mistaken for general mental vigour. We should place such instances, however, far below those in which there remains sufficient steadiness of the understanding to direct the provisions of a will ; though by many observers such a condition of the intellect would be con- sidered a far slighter evidence of the triumphs of mind over matter, than the impassioned expressions to which the dying man sometimes gives utterance, when describing the visions of his phantasy. The delirium of the dying is often of a most interesting character, and resembles dreaming more than any other form of derangement that has fallen under our notice. The ideas are derived less from present perceptions than in insanity, and yet are more suggested by ex- ternal circumstances than in the delirum of fever and phrenitis. Thus the sight of a by- stander often suggests the image of a friend long departed, in which character the mori- bund man addresses him, and talks earnestly of persons, scenes, and events belonging to a former period of his history as if still present. The vivified conceptions are generally derived from subjects which either in his speculative pursuits, or in the business of life, have princi- pally occupied his thoughts. The last words of Dr. Armstrong were addressed to an ima- ginary patient upon whom he was impressing the necessity of attention to the state of the digestive organs. We have heard that a great legal officer not long deceased, having raised himself for a moment from his couch, said with his wonted dignity, " Gentlemen of the jury, you will find," — and then fell back on his pillow and expired. The visual conceptions reproduced in some minds often appear to have been derived from poetical reading. We re- member hearing a young man, who had been but little conversant with any but civic scenes, discourse most eloquently a short time before death, of " sylvan glen and bosky dell," pur- ling streams, and happy valleys ; " babbling of green fields," as if his spirit had been already recreating itself in the gardens of Elysium. It not unfrequently happens that the spectra owe their origin to contemplations of future existence ; and consequently that the good man's last hours are cheered with beatific visions and communion with heavenly visitors. " Saw ye not even now a blessed (roop Invite me to a banquet, whose bright faces Cast thousand beams upon me, like the sun? ' They promised me eternal bappiness, And brought me garlands, Griffith, which I feel I am not wortby yet to bear : I shall assuredly." King Henry VIII. Act iv. Sc. 2. Dreadfully contrasted with such visions are those which haunt the dying fancies of others. The previous habits and conduct of the indi- vidual have sometimes been such as to incline spectators to enquire whether in the mode of his departure frgm existence he might not already be receiving retribution; just as, in other cases, celestial dreams and colloquies have seemed fitting rewards for blameless lives and religious meditation. It would be pre- sumptuous, however, to hazard much upon the final causes of the various modes of termina- ting the career of life, not only for certain obvious general reasons, but also because we have known both the virtuous and the vicious pass away in states of unconsciousness, to all appearance precisely similar. One of the most curious instances of de- rangement that we have met with occurred in a phthisical patient. It consisted in a morbid association of ideas by mere similarity of ver- bal sound, or in other words a propensity to rhyme. Every person who came to the bed- side was sure to receive a distich in honor of his name; nor could any remark be made in his presence without his seizing one of the words uttered and finding a rhyme for it, in doing which he exhibited great ingenuity. We were unable to ascertain whether he had been addicted when in health to attempts at metre. Recitations of poetry, appearing to recur from a passive process of memory, with perfect unconsciousness of what is passing around, are frequent occurrences ; and the passages selected have often a singular coincidence with events in the life of the moribund rehearser. Sir W. Scott's touching picture of the death of Madge Wildfire has had many unfic- litious counterparts. Dementia or imbecility sometimes comes on a short time before death. It is for the most part manifested by an incapacity of concen- trating the ideas upon any one subject, and by an all but total failure of memory. The study of the degree of this condition necessary for invalidating a legal document is of great im- portance to the medical jurist. The mental weakness is in no respect so painfully exhi- bited as in the facility with which the subject of it derives pleasure from puerile amuse- ments. " Playing with flowers " is a token of approaching dissolution enumerated by a dra- matic author, one whose observation pervaded human nature in all its phases. We remember visiting a lady in the last stage of a uri- nary disorder, during the progress of which she had evinced both strength of mind and re- finement of taste: — we found her arranging with great care, and with demonstrations of delight at her success, a garland of flowers around a chamber utensil. A more humilia- ting spectacle could scarcely be witnessed. We augured that her decease was nearathaud, and she died on the following day. In the delirium under consideration, repro- ductions of visual sensations bear a considera- ble part ; but in some cases the consciousness is exclusively occupied by them; — they are mere ocular spectra. Thus with a vacant coun- tenance, half-shut eyes, and gaping mouth, and in a state of insensibility which no out- ward impression can rouse, the viotim of ty- phus is seen catching at something in the air. By the adjustment of the finger and thumb, it is evident that the imaginary objects are often minute ; and it is not unlikely that they 800 DEATH. produce a kind of annoyance like that of tnuscas volitttntes, which the hand is instinc- tively attempting to remove. Whether the production of such spectra depends upon changes in the retina, or upon changes in the cerebral extremity of the optic nerve, is not altogether certain ; but we incline to the lat- ter view, principally because other sensations are often revived though the nerves in which they originated have been paralysed or removed. x Renewals of perceptions of hearing are not uncommon. Such are imaginary voices, and sounds of tolling bells, &c. No reason has been assigned for that sym- ptom noted by the earliest observers — " pick- ing of the bed-clothes ;" or, in Dame Quickly 's phraseology, " fumbling with the sheets." But we think it may be readily accounted for as resulting from revivals of tactual sensations, which produce corresponding movements, so that the fingers grasp the bed-clothes in mis- take for the imaginary substance. Something analogous to this is witnessed in delirium tremens, a disease in which visual conceptions are particularly liable to vivifaction in the form of animals, and in which also we have witnessed the patient picking the ends of his fingers as if to remove something disagreeably adherent. Whether consciousness of bodily sensations continues till the very commencement of the death-struggle, or agony,* as it is termed, is an enquiry often put to the medical attendant either by patients themselves, or by their anx- ious relatives. The ideas entertained by per- sons unaccustomed to physiological study re- specting the pains of dying, have arisen partly from their theoretical views of the nature of the event itself, and partly from their obser- vation of its preceding or accompanying phe- nomena. When they imagined death to be a kind of forcible severing of the spirit from the body, — a separation so opposed to the incli- nation of the former that some have fancied it longing to return to the body, " iterumque ad tarda reverti Corpora, quae lucis miseris tam dira cupido : " or like the shade of Hector, "Yvx* S'ix. ptQsuv •Kta.f/.itYi "A'SiVJe /?£<3>i>££i, "Ov ttotij-oii yoouau, Ai7ro5cr' i^pornra y.ou n@nv. Iliad. XXII. 362. or when they regarded the throes of death as efforts of the confined inmate to escape from its tenement ; or when laying aside their imaginings, they witnessed a heaving respiration, cold dew on the face, and convulsive agitations of the whole frame, affections so often known to accompany in- tense bodily suffering, — it is not wonderful that the process of dying should have been considered one of distress and anguish. But the practitioner ought to be able to console * The reader will scarcely need to be reminded that this word is used in its etymological sense, cyiv, certamen. the friends of the dying by the assurance that whatever may have been the previous torture, it must be all over when once those changes begin in which death essentially consists. He must explain to them how upon the failure of the circulation, the function of the brain must cease by necessity ; that if the cessation of the former be gradual, that of the latter may and often does precede it ; that if the mortal pro- cess begins in the lungs, unconsciousness pre- cedes the arrest of the circulation ; and if in the brain, that an injury of this organ sufficient to affect the lungs and the heart fatally is sure to annihilate its own sensibility. The muscu- lar spasms, the slow, gasping, or gurgling breathing, the collapsed or distorted features, though in some cases accompanied by feeling, are altogether independent of it. Convulsion is not, as superficial observers often interpret it, the sign of pain, or the result of an in- stinctive effort of nature to get rid of the cause of pain, — it is an affection of the moti- fic not of the sensific part of the nervous sys- tem.* The pangs of the disease may last till within a short period of death, but it is a great error to attribute them to the process which brings them to an end. Such cases however are rare ;. it is far more common for the sensibility to be blunted, or for the cause of pain to subside before the phenomena of dying commence. A person poisoned by an irritant is said to die in great agony ; a very incorrect expression, since death in such cases is ushered in by coma and by convulsions un- attended with pain. Temporary syncope and asphyxia, the neatest approaches to actual death, have nothing formidable in sensation if we may judge from the reports of those who have experienced them ; so far from it indeed, that some have described feelings of extreme pleasure, connected with each of these con- ditions.f The relaxation and incapacity of the muscular system, though for the most part ex- treme, has in some cases been much less than might have been expected ; and even chronic maladies, attended during their course with great emaciation and debility, have suddenly terminated when the patients were in the act of walking, or of performing some other exertion disproportionate to the rest of the functions. The condition of certain muscles in the last stage of existence wilt be alluded to when we come to speak of the general aspect and pos- ture of the dying. The voice is generally weak and low as death approaches, but sometimes has a shriller pitch than natural; sometimes it is husky and thick, and not unfrequently it dwindles to a mere whisper. These changes are caused prin- cipally by the debility which the vocal share * Dr. W. Philip has some excellent remarks upon this subject in his treatise on Sleep and Death. t See Piincipes de Physiologie Medicate, par Isid. Bourdon, p. 319. [It was either Dr. Black or Br. Ciilleu who told his attendant friends that •' he wished he could be at the trouble to tell them how pleasant a thing it was to die." Ed.] DEATH. 801 with all the other muscles in the system. In- terruptions of the voice are obviously often due to the state of the respiration. It must not be omitted that in some instances the voice has remained firm to the last. Of the signs of death derived from the organic functions, the first in importance are those belonging to the circulation. The mode in which the action of the heart declines is extremely various, but has for the most part some connexion with the nature of the dis- order. In maladies of considerable duration, and in which for a long time all the func- tions have suffered in a greater or less degree, the cessation of the heart's motion is nearly always gradual. The number of pulsations may, within a brief period of decease, greatly exceed the natural rate, but their energy is impaired, and the quantity of blood expelled at each systole is very small. In many acute affections the failure is evidenced some- times by increased frequency and diminished vigour of the contractions, and sometimes by their irregularity and frequency, the force being but little altered. In such cases the cause of dis- turbance is, without doubt, in some interruption of the nervous connexions of the organ. In other cases, the heart, before finally ceasing to beat, contracts with great violence, and then rapidly and suddenly comes to a stop. We have frequently noticed this kind of action in diseases of the brain, and have had reason to think that the syncope was brought on by the state of the respiration ; the latter effect, how- ever, being itself due in no slight measure to the irregular action of the heart. The increased frequency of the pulsations in a debilitated state of the heart indicates a greater susceptibility to the stimulus of the b'ood, at the same time that the resulting contractions are less efficient. The period of repose be- tween the diastole and the systole is briefer than in the normal action, besides that less time is occupied by the systole itself, in conse- quence perhaps of the very slight shortening of the fibres. In a vigorous heart the reverse of this takes place; the irritability is not such as to prevent a considerable pause after the dias- tole, and the fibres undergo a much greater degree of shortening. Why the irritability of a part should increase to a certain extent with increasing debility, is a problem yet to be solved. But we have reason to think that it is chiefly in acute diseases that the great rapidity of the heart's action is presented, and that in chronic affections there is a more gradual ex- haustion of irritability. Inequality of arte- rial action, when amounting to a great degree, is one of the most threatening symptoms that can be witnessed. We allude particularly to that extraordinary pulsation of the carotids which is sometimes observable, when the ra- dial artery can scarcely be distinguished. It is perhaps one of the "strongest presumptions that arteries possess a vital contractility, which may be disturbed in them as in other parts of the system. The state of the respiration in a moribund person is extremely various; sometimes hur- ried and panting till within a few moments of decease; sometimes ceasing gradually, in har- mony with the languishing circulation ; but sometimes slow, laborious, and stertorous, and, as Haller expresses it, " dum anxietas equidem cogit moliri, vetat debilitas."* In addition to those causes of struggling respira- tion which belong to the nervous centres and to the circulation in the lungs, the function is often dreadfully embarrassed by the accumu- lation of fluids, mucous, serous, or purulent, in the bronchia;. The quantity of these secre- tions is oftt'n increased by a state of the bron- chial membrane, analogous to what we shall notice presently in the skin, designated by Laennec " the catarrh of the dying;" but the mere accumulation of the natural quantity from defect of those muscular actions which usually remove it, whether in the fibres of lieisseisNen, or in the general respiratory appa- ratus, is amply sufficient to cause exquisite distress. Mediate or immediate auscultation detects a loud guggling throughout the chest, which is sometimes audible even at a little distance, and the vibrations of which may be felt by the hand. This sound must not be confounded with the true" death-rattle," which is produced not by struggles between air and liquid in the bronchial ramifications, but by the ejection of air from the lungs through the fluid in the trachea. It is often followed by a flow of spumous liquid through the mouth and nostrils. The loss of animal heat occurs first in the extremities, — a fact easily explicable by the smaller quantity of blood sent into them ; but it is probable that the state of the nervous system, and the cessation of the nutritive and other capillary actions, which perform so im- portant a part in calorification, may participate in the production of the result in question. The recession of heat from the limbs was no- ticed by Hippocrates, but his mode of stating the fact in one remarkable passage, his last aphorism, appears considerably affected by his theoretical views of the use of this agent in the economy.f The secretions present nothing very charac- teristic. If the disorder has been of short duration, they may have undergone no consi- derable change ; but when the declension of life has been more gradual, they are all more or less altered. The bile and the urine are often found in their proper receptacles, of a perfectly healthy character, after a short illness; while in senile dissolution they are almost always scanty and vitiated. The generation of gas in large quantities, so as to produce tym- panites, is a very common occurrence at the termination of acute diseases. % We have also noticed loud borborvgmi during the last few hours of life, occasioned by large collections of air, and by a preternatural excitement of intestinal irritability, analogous to what we have noticed in the heart and arteries. The * Elementa Physiologize, lib. xxx. § 22. t Hippocr. .Aph. § viii. 18. X Hipp. Aph. § viii. 17. 802 DEATH. secretion of saliva is almost always suppressed, and the mucus about the mouth and nasal passages is so deficient, that the lips and tongue require constant moistening when arti- culation is attempted ; not to mention the inex- tinguishable thirst which is one of the most painful forerunners of some forms of dissolu- tion. The perspirable secretions are generally rather profuse than scanty. The cutaneous surface, particularly about the face, is bedewed with a clammy exudation. It cannot be said that the weakness of the circulation is the immediate cause of this circumstance, because it frequently happens in a very opposite state of the function. It is true that the latter fact has been explained by supposing a transuda- tion of the thinner part of the blood through the coats of the capillary vessels during their disten- tion, while the former has been attributed to a spasm of the same vessels, consequent on the diminished force of the circulation, and said to have the effect of squeezing out the same serous liquid. In each case we must presume the perspired fluid to be in a state of separa- tion before the supposed agency can come into operation. The hypothesis is supported by little evidence ; but we are not sure that any other interpretation can be found much more conclusive. It seems probable, however, that the fact in question results less from so mecha- nical a process as has been hinted at, than from a chemical alteration in the fluids, in- duced perhaps by a change of innervation, in a manner analogous to those extraordinary changes which the secretions so frequently pre- sent under the influence of mental emotion. It remains for us to enumerate a few of the signs of approaching dissolution, derived from the general aspect of the body. Many of these have been described by Hippocrates wilh unrivalled accuracy. The sunken eyes, the hollow temples, the sharpened nose, the fore- head dry, tense, and harsh, the complexion sallow, livid, or black, the lips cold, flaccid, and pale, or of a leaden hue — compose the celebrated Juries Hippocratica.* All these signs admit of an easy rationale by the state of the circulation and of the muscular system. They are however in some measure due to the con- dition of the cellular tissue, which, indepen- dently of its loss of fat, is exhausted of that interstitial fluid, which in health contributes so much to the firmness and equality of the cu- taneous surface. In proof of this we may men- tion that all the appearances enumerated may be produced merely by a violent illness of a few hours ; by cholera for instance, a disease in which the serous fluid is rapidly drained from the system into one channel. Excessive fatigue and fasting will occasion appearances very similar, and therefore the Father of Medi- cine recommends us to ascertain whether such causes have been in action, before we pro- nounce the patient to be moribund. A partial closure of the eyelids and a gaping mouth * These signs are not thus grouped together in the original, but are individually mentioned in the book " npoyiwo-TDCOV," not the " rispi vot'coiv." are signs, when conjoined with the others, of fearful import. There must be an extreme depression of the nervous system when the orbicularis is unable to bring the lower lid into contact with the upper, which has drooped from relaxation of the levator palpebral, and when the masseter and temporal muscles resign the lower jaw to gravitation. A supine posi- tion with the limbs extended, and a tendency to slide down to the lower part of the bed, are indications of mortal prostration. In the pos- ture alluded to there is little or no muscular exertion ; for the extension of the legs, when the body lies upon the back, is not necessarily maintained by the action of the extensor mus- cles, since the mere support of the surface on which they rest would keep them in that posi- tion. The sliding down in the bed is owing to the inability of the glutaeal muscles to resist the gravitation of the trunk down the inclined plane, upon which this part of the body is extended when the head and shoulders are resting upon the pillow. When the prostration is less extreme, it often happens that instead of the extremities being carried forward by the impulse alluded to, the thighs are raised, the knees bent, the soles rest flat upon the bed, and the heels afford a sufficient resistance to the nates to prevent any further descent. It is evident that this position of the legs and thighs, though requiring a muscular effort for its pro- duction, needs little or none for its mainte- nance. The moribund are often impatient of any kind of covering. They throw off the bed- clothes, and lie with the chest bare, the arms abroad, and the neck as much exposed as possible. These actions we believe to be prompted by instinct, in order that neither covering? nor even contact with the rest of the body may prevent the operation of the air upon the skin. There are actions and re-ac- tions between the air and the blood in the skin, similar to those which occur in the lungs, and hence in asphyxial disorders the symptoms alluded to are very marked ; but the mere influence of the air upon the cuta- neous nerves has been proved by Dr. Edwards to be beneficial to the vital powers. Certain it is that these symptoms are sometimes prominent in cases where the respiration is very little in- volved in the mortal struggle. Orfila, in one of his cases of poisoning by sulphuric acid, mentions that the subject of it made con- stant efforts to remove even the lightest kind of covering. The appearance of the face is by no means such as we have described it above, in all cases. The kind of death must always have a great influence on the expression. On fields of battle the corpses of those who died of stabs are easily distinguished by the countenance, from those who fell by gun-shot. In the for- mer an extremely painful impression must have been transmitted to the brain, which pro- duced the usual change in the nerves and muscles of expression; in the latter a con- cussion was given to the whole system, para- lysing without any intermediate sensation, so DEATH. 803 that no expression remained more than that of the repose of the muscles. The nature of the disease also modifies the facial expression of the dying. In some we observe the impress of the previous suffering, as in peritonitis and in cases of poisoning by irritants ; in others the character is derived from a peculiar affec- tion of some part of the respiratory apparatus, as of the diaphragm in pericarditis ; or from an affection of the facial muscles themselves, as in tetanus and paralysis. But the condition of the mind is perhaps more often concerned in the expression than even the physical cir- cumstances of the body. For, as some kind of intelligence is frequently retained, and strong emotions are experienced till within a few moments of dissolution, the features may be sealed by the hand of death in the last look of rapture or of misery— of benignity or of anger. Every poetical reader knows the pic- ture of the traits of death (no less true than beautiful) drawn by the author of the "Giaour." But such observations are not confined to poets. Haller could trace in the dying coun- tenance the smile which had been lighted by the hope of a happier existence : " AdfuU gentis J'ugienti anima spei non rarb in mori- bundis signa vidi, qui serenissimo vultu, non sine blando subrisu, de vita excesserunt." * Watchers of the dead have often affirmed, and we can ourselves testify to the fact, that a smile has appeared upon the countenance some hours after death, though no such expression had been witnessed at the time of the event ; which is not difficult of interpretation if we consider that an extremely slight muscular action is sufficient to give any kind of expres- sion, particularly that of complacency, — that mortal rigidity is produced by a species of contraction in muscular fibres, (to be discussed more fully hereafter), and that this change seldom takes place till several hours after death. SIGNS OF ACTUAL DEATH. The discrimination of true from apparent death is not a matter of mere physiological interest. It is of great importance that the medical practitioner should be able to decide in doubtful cases whether the resources of art may be dispensed with, or the rites of sepul- ture be permitted, as well as to give evidence, in certain medico-legal inquiries, of the pre- cise period at which an individual expired. We have not space to record the numerous cases that may be met with in various authors, proving that even the most sagacious and ex- perienced observers have been at times de- ceived as to the reality of death. In the works of the ancients there are frequent allusions to premature interments. Pliny has a chapter, " De his qui elali revixerunt ;" and among other cases mentions that of a young man of rank, who was revived by the heat of his funeral pyre, but who perished before he could be rescued from the flames. " Hsec est con- ditio mortalium," is the reflection of the phi- losopher, " ad hasce ejusmodi occasiones for- * Elcm. Phys. lib. x\x. § 23. tunte gignimur, lit de homine ne morti quidem debeat credi." Celsus asks, " si certa futura; mortis indicia sunt, quomodo interdum de- serti a medicis convalescant, quosdamque fama prodiderit in ipsis funeribus revixisse ? " " Complura fuerunt exempla," says Lord Bacon, " hominum, tanquam mortuorum aut expositorum a lecto, aut delatorum ad funus, quinetiam nonnullorum in terrfi conditorum, qui nihilominus revixerunt."* In the writings of Winslowf and Bruhier J will be found an ample collection of melan- choly instances of premature interment, besides those which are scattered through various sys- tematic works upon forensic medicine. Un- intentional vivisection, moreover, has befallen other instances than the celebrated subject of Vesalius. Few of our readers have not shuddered at the tale of the dismal fate of the Abbe Prevost, who, having been struck with apoplexy in the forest of Chantilly, was taken home for dead, but recovered his con- sciousness under the scalpel, and died im- mediately afterwards. We must not recount the marvellous recoveries recorded by French authors, of Madame Mervache, the wife of a jeweller at Poitiers, who was restored to life in her grave, by the attempts of a robber to despoil her of the rings with which she had been buried ; and of Francois Civille, a Nor- man gentleman, whose custom it was to add to the signature of his name, " trois fois mort, trois fois enterre, et trois fois par la grace de Dieu ressuscite." The English reader will find an interesting selection of cases in the Appendix to Dr. Smith's Principles of Fo- rensic Medicine, and in the article Premature Interments in the Encyclopaedia Britannica. We shall only add that Bruhier collected fifty- two cases of persons buried alive, four of per- sons dissected prematurely, fifty-three of per- sons who recovered without assistance after they were laid in their coffins, and seventy-two falsely reported dead.§ We shall arrange the indications of death under three heads : — 1st. Signs of the extinction of vital functions and properties. 2dly. Changes in the tissues. 3dly. Changes in the external appearance of the body. 1. The arrest of the circulation and respi- ration would at first appear to afford decisive evidence that a person is no longer alive. But this sign is liable to the two-fold objection that we cannot distinguish with absolute certainty the minimum of the functions mentioned, from their complete annihilation, and that re- coveries have taken place after their real or * Hist. Vita; et Mortis, § x. t Dissert, an mortis incerta sint indicia. t Dissert, sur l'Incertitude des signes de la mort. § Louis in his Lettres sur la Certitude des signes de la mort, insinuates that some of Bruhier's cases are apocryphal. A more recent and perhaps a more authentic collection of cases will be found in M. Julia de Fontenelle's " Recherches medico- legales sur 1'incertitude des signes de la mort," &c, 1834. 804 DEATH. apparent cessation. The case of Colonel Townshend, related by Cheyne,* is too well known to need recital here. Perhaps the most unequivocal examples of their suspension are certain cases on record of restoration after sub- mersion for several minutes. In some of these there is good reason to believe that there was no genuine asphyxia, but that syncope took place immediately, and consequently that there was no stagnation of blood in the extremities of the pulmonary arteries. As to the alleged cases of persons who have been, said to lie many hours and even days without pulse or breathing, we do not hesitate to express a belief that the observers were deceived, and that in reality both these functions were per- formed, but in so low a degree as to escape detection, just as hybernating animals were supposed to be, during their torpor, in the pre- dicament alluded to, until the researches of Dr. M. Hall proved that these animals do actually respire and maintain their circulation, though in a much less degree than when awake. It will be the duty of the practitioner to adopt every method within his reach of ascertaining the actual condition of these func- tions; but he must remember that they are often inefficient and even fallacious. Thus, with regard to the common modes of trying the respiration by a mirror, or by light downy bodies placed near the mouth and nostrils, it is obvious that the former may retain its clearness, because the halitus is not in suf- ficient quantity to stain it, or may be dimmed by exhalations from the air-passages which are not the products of respiration ; and that the downy substances may be stirred by currents of air, or remain unmoved by the trivial ex- change which takes place between the external atmosphere and the air in the chest of the person examined. Winslow's test of a vessel full of water placed on the lowest part of the thorax is of little utility, since we know that the diaphragm may be the only muscle em- ployed in expanding the chest. As to the circulation, it may continue though no pul- sation can be felt over the arteries or the car- diac region, and no sound be perceptible by auscultation mediate or immediate. Few prac- titioners would be willing to apply M. Fou- bert's test, to wit, that of making an incision in one of the intercostal spaces, and feeling the heart with the ringer! The loss of irritability in the muscular fibres is of far greater consequence than either of the foregoing signs. It may be present when re- covery is out of the question, but its absence is quite conclusive. Galvanism affords a cer- tain and ready method of detecting this pro- perty. According to the researches of Nystenf irritability is first extinguished in the left ven- tricle ; after forty-five minutes it has left the intestines and stomach ; a little later the blad- der; after an hour the right ventricle ; after an hour and a half the cesophagus; after an hour * English Malady, page 307. t Recherches de Physiologic ct de Chimio Pa- thologiquc. and three quarters the iris. It next takes leave of the muscles of the trunk, then the lower and upper extremities, and lastly the right auricle. The duration of contractility is short- ened by a warm and humid state of the at- mosphere, by ammoniacal gas, carbonic acid, and sulphuretted hydrogen. It is unaffected by carburetted hydrogen, chlorine, and sulphur- ous acid ; nor is it found diminished in cases of asphyxia by strangulation and immersion. The annihilation of that particular kind of contractility of tissue, which is equally dis- tinct from muscular contractility, irritability, and elasticity, is one of the surest signs of death. We see it wanting in the collapsed edges of a wound which has been inflicted on the skin of a dead body, as contrasted with the gaping appearance of a similar lesion made during life. The loss of animal heat, though an invariable occurrence at some period after death, is not unfrequently noticed in disease. Every prac- titioner must have met with it in hysterical cases ; and it is a matter of notorious obser- vation in cholera. On the other hand we have known the heat of the body not only continue but even return at a considerable period after death has unequivocally taken place ; a fact attributable either to chemical actions of a cadaveric description, or to the continuance of the processes which developed caloric during life. The mean time requisite for the com- plete cooling of the body is fifteen or twenty hours ; but the process is modified by a great variety of circumstances. It is slower after acute than chronic maladies, but is very con- siderably retarded in asphyxial cases, except those occasioned by submersion. Calorification is not the only function that may survive what is commonly called death ; thus the rectum and bladder have been known very frequently to discharge their contents after death ; and, which is still more remark- able, parturition has taken place under such circumstances. The continuance of secretion, absorption, and nutrition has been argued from the exhalation of serous fluids in some parts, their disappearance in others, and the alleged growth of hair. Some of these facts are more rationally explained on such physical principles as are involved in transudation, endosmose, penetration, &c. &c. ; as to the growth of hair, there is great reason to doubt the accuracy of the testimonies to the fact. Ilaller very justly observes that shrinking of the skin would produce an apparent elongation of the beard, which is the part upon which the observation alluded to has been most fre- quently made. 2. The first alterations in the physical pro- perties of the solids after death are softness and flexibility, to which succeed sooner or later the opposite conditions of firmness and rigi- dity. The softness or want of elasticity may be owing partly to differences in the distri- bution of the fluids in the tissues^ and partly to changes in the tissue itself. The flattening of those parts upon which the weight of the body rests, the effect of deficient elasticity, DEATH. 305 is considered by Blumenbach a valuable cri- terion of the reality of death. The flexibility of the joints obviously depends upon the re- laxation of the muscles. Rigidity is a change which has attracted great attention from its importance as an evi- dence of death. Its period of accession de- pends principally upon the nature of the ma- lady. After long and exhausting illnesses, its appearance is early, but the duration is brief, and the intensity trifling. The same remark applies to the modifying influence of old age. When the individual has been cut off by sud- den accidental causes or by acute diseases, it comes on for the most part much later,* lasts longer, and is more intense than in the former instances. It may appear within half an hour after death or may be delayed twenty or thirty hours, according to the circumstances just mentioned. The mean duration is from twenty-four to thirty-six hours ; but it may last six or seven days according to Nysten, whose researches upon this subject are very valuable. We remember observing it once on the eighth day after death in the body of a criminal who had been executed by hanging, but are not aware at what time it had com- menced. The parts which first present this change are the neck and trunk ; it then appears in the lower extremities, and lastly in the upper. Its departure observes the same order. it is yet to be proved that rigidity is not an invariable consequence of death. Nysten at- tributes Bichat's assertion of its non-appear- ance in some cases of asphyxia, to the lateness of its developement. If it could be wanting in any case, it would probably be so in sub- jects attenuated and ol flabby fibre. Louis in hisLetterson the Certainty of the Signs of Death declares that he never found it absent even in the infirm and age-worn patients of Salpetriere, and Fodere gives a similar testimony to its universality .f The seat of rigidity is the muscular sub- stance. Of this we may be assured by the following facts. (1). It is observed in all those animals (including many of the invertebrata) which have a distinct muscular tissue (2). Its intensity is in a direct ratio with the develope- ment of this tissue. (3). it is destroyed by division of the muscles, a fact first noticed by Nysten.J (4). It remains when the cellular membrane, skin, aponeurosis, and ligaments are removed. § (5). When very strone, it ren- ders the muscles prominent as in voluntary contraction, or in that spasm which is induced by rammolhssement of the brain and spinal marrow. Ch. Louis makes a remark of this kind in his admirable memoir upon some cases of sudden death. || In hemiplegiac subjects rigidity is observed * We very recently however observed the phe- nomenon only an hour and a half after the death of a boy by acute peritonitis. f Med. Leg. t. ii. p. 361. % Rech. de Physiol, et Pathol. Chim. \ Devergie, Diet, de Med. et Chir. Prat. Art. Mort. || Rech. Anat. Path. p. 500. to be no less stiong in the paralysed limbs than in those which were unaffected by the disease. The temperature of the body has been said to influence it. Beclard* speaks of cooling as being always antecedent to rigidity, and Nysten has made a similar statement. But we have had many opportunities of disproving this observation. Ch. Louis noticed the pheno- menon in some of the cases just adverted to, while the bodies were quite warm. Its occur- rence in cold-blooded animals is, we think, a sufficient refutation of the idea that it bears any necessary relation with the loss of heat. Moreover Devergie has very properly pointed out the inconsistency of this notion with the fact that rigidity appears first upon the trunk, the region which is the last to be deserted by calor.c. The cause of rigidity is referred by most authors to a sort of lingering vital contraction. It is often spoken of as the last effort of life: "11 semble que la vie," says Nysten, " se rel'ugie en dernier lieu dans ces organes, et y determine le spasme qui constilue !e roi- deur.'' f This author not only refers it to con- traction, but endeavours to explain how a very low degree of the ordinary kind of contraction may be sufficient to stiffen the muscles though not to move the part with which they are con- nected. Supposing that a muscular effort equal to 20 would completely bend the elbow, one equal to 10 would semiflex it; one equal to 5 would bend it a quarter of the distance ; while a force equal to l-20th only, would perhaps produce no motion at all, nothing but rigidity ! Beclard alleges three causes; the last contrac- tion of muscular fibres, the general cooling of the body, and the coagulation of the fluids. The second of these we have already disposed of. Notwithstanding the high authorities in favour of the opinion that rigidity is caused by a vital contraction, we confess that to us it appears a very untenable position. All mus- cular contraction in its normal condition alter- nates with relaxation ; and although rigidity might be supposed to bear some analogy to the tonic spasm of tetanus, it differs widely from the latter in one important respect, that when overcome by violence it does not return. When we consider that the continuance of the phenomenon in question is long after the cessation of any vital action ; that the usual time of its accession is precisely that which we have every reason to consider the most unfavourable for the occurrence of any vital action, viz. when all animal heat is ex- tinct, and when sanguineous congestions in the depending parts of the body prove the capil- laries to have lost their contractility ; it is diffi- cult to regard the process as of a vital cha- racter. The mere fact that the rigidity comes on and remains long after the muscles have ceased to respond to the stimulus of galvanism, reduces the hypothesis to the last degree of improbability. Moreover we should scarcely expect the last act of life to be performed in * Anatomie Generale, p. 127. t Op. cit. § v. art. 3. 806 DEATH. the extremities ; we should naturally look for it about the trunk, in conformity with the order of disappearance observed by all other vital actions; but as we have stated above, this phe- nomenon both appears and declines first upon the trunk ; in other words, according to the hypothesis, the muscles in this part expire while those of the extremities are still alive. Devergie is puzzled to reconcile the long continuance and intensity of rigidity in cases of asphyxia from carbonic acid, with the fact that this agent is destructive to contrac- tility. We are somewhat surprised that he was not brought, by the mutual opposition of these facts, to consider that rigidity and vital contraction have nothing in common but the tissue in which they are manifested. The third cause enumerated by Beclard is the coagulation of the blood. This is probably nearer the truth than are the other explanations of the phenomenon ; but it would be more correct to say that rigidity and coagulation of the blood are effects of the same causes, viz. coagulation of fibrin. They occur about the same time, and are impeded by the same agents. It has been proved that the muscles are the subjects of the rigidity, that they are contracted, and that their contraction is not of a vital nature. As this change must there- fore be either mechanical or chemical, what more probable cause (in the absence of actual demonstration) can be imagined than the coa- gulation of fibrin in the muscles? The rigidity occasioned by certain diseases may be mistaken by an unpractised observer for mortal stiffness. This error is most likely to be committed in cases of hysteria, for this affection, not content with imitating almost every other malady, has been often successful in mimicking death itself. Tetanus is in- stanced by some authors as a disease likely to occasion mistakes of the kind alluded to. This may be true of hysteric tetanus, but not of the idiopathic or of the traumatic species, which have characters too striking to be overlooked by even the most inexperienced. Besides, if the rigidity of any given case, supposed by one to be cadaveric, were by another proved to be tetanic, we are of opinion that the condition of the subject would be not a whit less hopeless, since the case implies that the respiration and circulation are apparently extinct ; and when this is the case in tetanus, we may feel quite certain that if the patient is not actually dead, he is quite irrecoverable. Nysten de- clares that the rigid spasm of disease may be always distinguished from that of death by the circumstance that it precedes the loss of heat in the former case, while in the latter the order of the events is just the reverse. This test holds good in a very large proportion of cases, but must not be implicitly relied upon, because, as we have before observed, corpses not unfrequently retain their caloric for some time after rigidity has commenced. A better criterion is that of overcoming the rigidity by force ; if it be cadaveric, the contraction is completely annihilated ; if morbid, it will return when the force is withdrawn. A species of rigidity more likely to be con- founded with the cadaveric is that which is sometimes found in the dead body, but which is the product of disease. Of this description is the spasmodic contraction which often con- tinues after death by apoplexy and other cere- bral and spinal diseases ; and the observation of which is as old as the time of Hippocrates. M. Marc relates the case of a gentleman who went to a theatre apparently in good health, and after the representation was over, was found by his friends sitting in the front of the box, with his head resting upon his hands, and his elbows on the ledge. He had died of apo- plexy, and been retained in that position by the tonic spasm of his muscles.* This con- traction is unquestionably vital, but it ceases after a few hours, and the flexibility is then succeeded by true cadaveric rigidity. In medico-legal cases it is of the utmost moment to bear this distinction in mind, but it is one that has received much too little attention. Many of the standard works upon forensic medicine are altogether silent upon the subject. Its importance was proved by a case which occurred in France some years ago. The body of a man named Courbon was found in a ditch, with the trunk and limbs in such a relative position as could only have been maintained by the stiffness of the articulations. This stiffness, moreover, must have come on at the very time when the body took the said position, unless it could be imagined that the body had been supported by the alleged mur- derers until the joints were locked by cada- veric stiffness, a supposition infinitely too im- probable to be entertained for an instant. But by regarding the rigidity as of a spasmodic nature (resulting from apoplexy, of which there were sufficient proofs in the necroscopy), the difficulties of the case were altogether removed. A full report of the case, and of the medico- legal consultation upon it, will be found in the seventh volume of the Annales d' Hygiene. In death by asphyxia there is often a spasmodic contraction which may continue for some time after decease. Orfilaf is of opinion that this may be readily distinguished by the continu- ance of animal heat, which he agrees with Nysten in judging to be incompatible with rigidity. While denying the universality of this principle, we think it sufficiently extensive to admit of a very useful application in a great number of instances. From what has been said, it can scarcely be doubted that rigidity is a certain evidence of death. Prior to this there is no indication derivable from changes in the tissues which can be depended upon; but the flexibility that follows it affords, if possible, still stronger proof of the condition of the body. There is no state with which it can be confounded if we except the interval between spasmodic and true post-mortem stiffness; but very little cau- tion is requisite for avoiding a fallacy of this description. * Annales d' Hygiene, &c. t.vii. p. 604. t Lefons dc Med. Leg. t, ii. p. 195. DEATH. 807 The next remarkable change which takes place in the tissues is putrefaction, a process in which the ultimate elements of the body, operated upon by external causes, enter into combinations incompatible with the existence of those proximate principles of which the tex- tural molecules are compounded. Some phy- siologists conceive that even putrefaction is not a necessary sign of death. Winslow, however, pronounces it " unicum signum;" and Bruhier expresses a similar opinion. Hal- ler* says that it may commence in a living person, but that death must be very near at hand. He relates of one Vandenhoeck, his bookseller, that when lying in the last stage of a malignant fever, he prophesied his approach- ing end, and that he grounded his prediction upon his sense of smell. Orfila, one of the greatest authorities upon this subject, considers the commencement of putrefaction a less un- equivocal sign than true rigidity ; his opinion rests upon the fact that he has known persons completely recovered, notwithtsanding the skin was covered with violet spots, which exhaled an infectious odour.f It is remarkable that so acute an observer should have overlooked what seems a very obvious consideration, viz. that these violet spots being caused by extra- vasated blood, perhaps in a state of decom- position, afford no indication that putrefaction has begun in the solids. Sphacelus, though consisting in decomposition, need not be con- founded with putrefaction. The latter change begins always, according to the observation of M. Devergie, either ujion the abdomen or the thorax, and has the appearance of a large diffused patch of a green colour, which after- wards becomes brown. The brown portion is surrounded by a green areola indicating the extension of the process. Into the history of putrefaction we cannot enter, but must refer to the valuable " Exhumations Juridiques " of MM. Orfila and Lesueur, and to some papers by M. Devergie in the second volume of the Ann. d'llygiene on the changes in the bodies of persons drowned, and also to a controversy upon the latter subject between this author and M. Orfila, in the fifth and sixth volumes of the same work .J After the decomposition has advanced to a certain stage, but sometimes without any putre- faction at all, the tissues, instead of being dissi- pated by conversion into liquid and gaseous substances, which is the essential part of the putrefactive process, may be converted into solid matters widely differing from the original molecules. (See Adipocere and Mummi- FACTION.) 3. We have lastly to notice a few signs of the reality of death gathered from the external aspect of the body. The appearance of the face has been already described among the signs of the moribund state. We have only to mention in addition, that instead of the t*J * Op. et loc. citat. t Op. cit. t. ii. p. 231. X Devergie's papers are embodied together with more recent observations in the first volume of his "Medecine Legale," published a few months ago. paleness or lividity that were present at the time of death, a rosy hue may appear upon the cheeks, which has not unfrequently occa- sioned a deceitful hope that life was not yet extinct. The cause was very rationally as- cribed by Mr. Chevalier to the action of at- mospheric air upon the blood accumulated in the capillaries. This phenomenon is more likely to occur when syncope has followed asphyxia. We remember it once very dis- tinctly in a person who had died of acute hepatitis, but in whose last hours there had been considerable pulmonary congestion ; it made its appearance on the third day after death. The state of the eyes has been much insisted upon by some ; particularly their dul- ness, the shrinking of the cornea* from the diminution of the aqueous humour, and the viscid mucous secretion which forms what is called the film of death ; but these appearances may be absent in real death, and present be- fore life has terminated. Thus the eye is often prominent and glittering after death by carbonic acid, and by hydrocyanic acid. The iris is generally represented to be in a state of dilatation. Winslowf paid conside- rable attention to it, and states that he gene- rally found the pupil of a moderate size, often much contracted but never much dilated. WhyttJ makes the same observation. The fact appears to differ with different animals. Thus in the cat and pigeon the pupil dilates after death, while in the rabbit it contracts. § Our own observations upon the human sub- ject incline us to report the pupil a few hours afier death as in a state midway between con- traction and dilatation. It is difficult to speak with precision upon the point, because that which would be relative contraction in the pupil of one person would be dilatation in another, and vice versa. We have known ob- servers confound immobility with dilatation, and to this circumstance we attribute the common statement that the pupil is dilated at and after death. It is evident that if we admit that the contraction and dilatation de- pend upon predominant action of the lon- gitudinal or of the circular fibres, we ought to expect in the death of the part neither the one condition nor the other ; but as the con- tractility of this as of other muscular parts may survive the cessation of the central func- tions, either set of fibres may prevail for a time. It must be remembered however that con- traction of the iris may depend upon a cause altogether different from contraction of its fibres, viz. congestion of blood in its tissue, which is said to have some analogy to the erectile. M. Renard states that in some ex- periments upon dead bodies instituted for the purpose of ascertaining the effects of com- piession of the diaphragm upwards by the development of gas in the abdomen, found * Louis fancied that this sign was invariable, t Op. cit. % On the Vital and other Involuntary Motions of Animals, p. 129. (J Mayo's Outlines of Physiology, p. 292, 3d edit. 803 DEATH. that it occasioned " refoulement vers la tete de la portion fluide du sang qui est contenu dans l'oreillette droite, et par suite, repletion, tumefaction des vemes du cou, de la face, de l'encepbale, suintement, exsudation sereuse ou sanguinolente par les porosites, les extre- mites des reseaux capillaires ; quelquefois aussi, par suite de ce reflux dans les reseaux capillaires, fesserrement de la pupille, reple- tion, distension, saillie des yeux, qui etaient d' abord ternes et relaches, &c. &c."* M. Villermef has described an appearance of the hand which he considers characteristic of death. He says that when dissolution has taken place the fingers are brought together and slightly bent, but that the thumb is