: -^ ~ " w-c ( ' r^ a o- li i a ; D CD m a 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; PHYSICIAN TO THE WESTERN DISPENSARY, AND TO THE ROYAL INFIRMARY FOR CHILDREN, ETC. ETC. VOL. I. A D EA. 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. Profcsseur-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. BRESCIIET, 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 Guy's Hospital. II. DUTROCHET, M.D. Member of the Institute of France, Paris. 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 of 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 Hospital, London. JOHN MALYN, Esq. Surgeon to the Western Dispensary, and Lecturer on Anatomy at the Westminster School of 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. H. PORTER, ESQ. Lecturer on Anatomy and Surgery, and Surgeon to the Meath Hospital, Dublin. RICHARD QUA1N, Esq. Surgeon to the Norih 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, andLecturer 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, / L CONTENTS OF THE FIRST VOLUME. Abdomen Absorption Acalephae Acids, Animal Acrita Adhesion Adipocere Adipose Tissue Age Albino Albumen Amphibia Animal Kingdom .... Animal Ankle, Region of the. . Ankle, Joint of the . . Ankle-joint,Abnormal Condition of the . . Annelida Anus Aorta Arachnida Arm Arm, Muscles of the. . Artery Artery, Pathological Conditions of . . . . Articulata Articulation Asphyxia Aves Axilla Axillary Artery Azygos Back Bile . Dr. Todd Dr. Bostock . . Dr. Coldstream Page 1 20 35 W.T.Brande,Esq. 47 R. Owen, Esq. . . 47 B. Phillips, Esq. . 49 W.T.Brande,Esq. 55 Dr. Craigie. 56 Dr. Symonds .... 64 Dr. Bostock 83 W.T.Brande,Esq. 88 T. Bell, Esq 90 Dr. Grant 107 Dr. Willis 118 Dr. Brenan 147 Dr. Brenan 151 R. Adams, Esq. . . 154 Dr. Milne Edwards 164 R. Harrison, Esq. 178 Dr. Hart 1&7 Dr. Audouin .... 198 Dr. Hart 216 Dr. Hart 219 Dr. Hart 220 W.H. Porter, Esq. 226 R. Owen, Esq. . . 244 Dr.Todd 246 Dr. Alison 257 R. Owen, Esq. . . 265 Dr. Benson 358 Dr. Hart 363 Dr. Harrison .... 364 Dr. Benson 367 W.T.Brande, Esq. 374 Bladder, Normal Ana- ) D). Harrison tomy ............ Page 37G B. Phillips, Esq. . 389 Bladder, Abnormal Anatomy ........ ' Blood .............. Dr. Milne Edwards 404 Blood, Morbid Condi- ) Dft Babington .. 415 tions of the ...... * Bone, NormalAnatomy Dr. Benson ...... 420 Bone, Pathological ) WR p^^ ^ 43g Conditions of ...... * Brachial Artery .... Dr. Hart ........ 465 Bursae Mucosas ...... Dr. Brenan ...... 467 Carnivora .......... T. Bell, Esq ..... 470 Carotid Artery ...... Dr. Hart ...... 482 Cartilage ............ Dr. Benson ...... 495 Cavity .............. Dr. Todd ........ 500 Cellular Tissue ...... R.D. Grainger, Esq. 509 Cephalopoda ........ R. Owen, Esq. . . 517 Cerumen ............ W. T. Brande, Esq. 562 Cetacea ............ Mons. F. Cuvier . . 562 Cheiroptera .......... T. Bell, Esq ..... 594 Chyliferous System .. Dr. Grant ...... 600 Cicatrix ............ A. T. S.Dodd, Esq. 002 Cilia ................ Dr. Sharpey .... 606 Circulation .......... Dr. Allen Thomson 638 Cirrhopoda ......... Dr. Coldstream . . 683 Cirronosis .......... Dr.Todd ........ 694 Conchifera .......... M. Deshayes .... 694 Contractility . . ...... Dr. Alison ...... 710 Cranium ............ J. Malyn, Esq. .. 724 Cranium, Regions and \ Df ToM Muscles of the. ... * Crustacea .......... Dr. Milne Edwards 750 Cyst ................ B. Phillips, Esq. . 787 Death .............. Dr. Symonds ---- 791 Analytical Index. , .................... 809 THE CYCLOPEDIA OF ANATOMY AND PHYSIOLOGY. ABDOMEN, (in anatomy,) with which the terms venter and alvus are sometimes used synonymously. Gr. yaarr?^. Germ, bunch, un- terleib, kinterleib. Ital. venire, panda, ubdo- mine : the French anatomists use the word abdomen as we do, and also the term venire as we do belly ; also bas-ventre. It is so called, " quod abdi et tegi soleat, aut quod alimenta in eo abdantur, aut intestina ibi sint 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 Carus, of the segments of an insect, in Roget's Bridgewater Trea- tise, vol. i. p. 321. VOL. I. the thorax. (See INSECTA.) In the Arachnida there is also a similar division of the body, to which the name of abdomen has been applied, united in front with the cephalo-thorax, and separated from it by a deep groove, which leaves only a slender pedicle between them ; like that of the Insecta it contains the principal viscera. (See ARACHNIDA.) In all the divisions of the Vertebrata there is an abdomen. In fishes the abdomen is situated towards the posterior extremity of the body, and, is separated from the heart in front by a strong membrane analogous to the diaphragm ; it contains the digestive and generative organs. In reptiles the abdomen is that region which lies immediately anterior to the anus; in many classes it is not separated from the cavity con- taining the lungs, so that the lungs, heart, organs of digestion and generation are all con- tained in one great cavity ; in the crocodile, however, a layer of muscular fibres, having the appearance of a diaphragm, covers the perito- neum, where it is connected with the liver, so that the lungs do not project into the abdomen. In birds, the abdomen extends from the posterior extremity of the sternum to the anus ; it is, as in fishes, separated from the thorax by a mem- brane which, though not muscular, is analogous to the diaphragm, but is perforated so as to allow the air to pass into the abdominal cells. In Mammalia, the abdomen is placed between the pelvis and thorax, with the former of which it is continuous ; but it is separated from the latter by the diaphragm ; its principal contents consist of the digestive organs, and its size varies in reference to their respective degrees of development. ABDOMEN. ABDOMEN (in human anatomy.) In ex- amining the human skeleton, we notice that from the apex of the thorax to the inferior out- let of the pelvis, there exists one great oblong excavation. The two superior fifths of this cavity are separated from the remaining portion in the entire subject by a musculo- tendinous lamella, which, thrown into a vaulted form, constitutes the partition between the cavity of the thorax above and that of the abdomen below. This latter cavity communicates inferiorly with the space circumscribed by the ossa innominata, denominated the cavity of the pelvis; nor is there any natural line of demarcation between the two cavities. The communication between the two cavities is as free in the recent subject as it is in the skeleton, and under various con- ditions the contents of those cavities pass from the one to the other. A plane extended hori- zontally from the linea iliopectinea on one side to the corresponding line on the other would constitute an artificial floor to the cavity of the abdomen, properly so called, and a limit be- tween it and the pelvis; and this artificial divi- sion of a cavity, naturally single, may be useful in describing the positions of viscera, but to understand the functions of the abdomen, it will be expedient to consider that cavity and the pelvis as one. Some anatomists ob- ject to the use of the term cavity as applied to the abdomen, because no cavity can be said to exist, except in the skeleton or in the evisce- rated subject; neither can there properly be said to be a cavity of the thorax or of the cra- nium, inasmuch as that cavity is obliterated so long as the viscera are in a 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. Hence, then, we derive a natural subdivision, in treating the subject of this article, into two heads: 1. the anatomy of the walls of the abdomen ; and, 2. the anatomy of the cavity of the abdomen. J. Of the walls of the abdomen. — One of the most striking differences between the abdomen and the other great visceral cavities consists in the small proportion of bone that exists in its walls. The osseous boundaries of the abdomen may be thus enumerated : superiorly, towards the posterior and outer part, the false ribs ; posteriorly, the lumbar region of the spine, which by its transverse processes affords strong- points for the attachment of muscles, and by the bodies projects into the cavity, forming an imperfect septum, slightly convex on its anterior surface, and dividing the cavity into two symmetrical portions. Inferiorly, the alae of the ilia afford lateral expansions, which support some of the contents of the abdo- men, and the pelvic brim completed behind by the promontory of the sacrum, forms the opening by which the cavity of the true pelvis communicates with that of the abdomen. Between the inferior margin of the thorax and the superior margin of the false pelvis are stretched muscular lamellffi 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 fat subjects, or where the intestines or peritoneal cavity are much distended from any cause, this surface is in a variable degree collapsed, and more or less concave, but especially so in very thin and emaciated subjects. There is a con- stant adaptation in the condition of this surface to that of the abdominal viscera, so that the practitioner can in general argue pretty accu- rately, from the state of the abdominal surface, respecting that of the abdominal viscera, ex- cept in cases where every thing is masked by a superabundant deposition of adipose substance. So close is the apposition of the abdominal wall to the surfaces of the subjacent viscera, that in some cases of extreme emaciation the peristaltic movement of the intestinal canal is manifested by the successive elevation and depression of small portions of the walls corresponding to the dilated and contracted portions of intestine. This surface is divided into two equal and symmetrical portions by a groove which exists along the middle line, and which is chiefly ap- parent in the two superior thirds. This groove commences below the ensiform cartilage, where there is a slight depression, denominated the scrobiculus cordis, (creux de 1'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 Pig-.l Eg-. 2. with hair ; in the female it is much more pro- minent than in the male, and is called the mons Veneris. In subjects where the muscular sys- tem is well developed, there exists on each side of this median groove an oblong convexity, ex- tending from the anterior surface of the lower part of the chest to the pubis ; these convexities indicate the situation of the'mYi 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 fig. 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 contrac- * Gerdy, Anatomie des Formes Exterieures, p. 189. The above engraving is reduced from the folio plates which accompany this work. 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 * Anatomic Topographique, p. 423. t The division of the surface of the abdomen into regions is as old as Aristotle. } 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 : (s7ri,upon, over ; yaa-Tr^, the stomach.) The epi- gastrium is bounded superiorly and laterally by the margin of the thorax, and its inferior limit is indicated by the transverse line. The verti- cal lines subdivide it into two lateral regions, each of which is bounded immediately above by the lower margin of the thorax, beneath which these regions extend in a direction up- wards and backwards : they are hence called hypochondria (Wo, under, p^ov^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 hypogastrium, (vnro, beneath, yac-T»£, 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 zone to the primary regions included between the horizontal lines. — Anat. Chirurg. t. ii. ABDOMEN. *3 In and between these several structures ramify the various arteries, veins, lymphatics, and nerves, which constitute the vascular and ner- vous supply to the abdominal parietes. 1 . The skin on the anterior and lateral parts of the abdomen is thin and smooth, and in some parts covered with hairs, as along the middle line, especially below the umbilicus and over the pubic region. Along the median line the cutaneous follicles are largely developed, and during pregnancy an increased secretion of pigmentum is said to take place, producing a brownish colour of the skin in these regions. In women who have borne children, the skin becomes wrinkled to a considerable de- gree, and the epidermis exhibits, as Winslow has remarked, a great number of lozenge- shaped spaces disposed in a reticular manner.* In the epigastric region the skin is much more sensitive during life than in the other parts of the abdomen, and with some persons sympathizes with the stomach in a remarkable degree, so that pressure on it even in the healthy state produces a degree of pain or un- easiness in that organ, or even a tendency to nausea. In the umbilical region we observe a depression, the floor of which is more or less elevated in the centre. This depression is de- nominated the navel or umbilicus, (the dimi- nutive of umbo, a nob or button.) It is produced by the firm adhesion of the skin to the subjacent structures, its true nature being that of a cicatrix, occupying the site of a former perforation through which the umbilical arteries and veins and the urachus passed in maintaining the circulation between the foetus and placenta. In very fat persons, the depth of the depression is often very much increased by reason of the great thickness of the abdomi- nal parietes, and in some instances its form assumes that of a slit, and sometimes, instead of a depression, there is a greater or Jess pro- minence of the integument. In the lumbar region the skin is thicker and firmer than in the others; and we generally find it in a state of congestion after death, in consequence of the position of the body. 2. The subcutaneous cellular tissue on the anterior surface of the abdomen has obtained especial attention from anatomists, particularly that portion of it which is found in the hypo- gastric regions. It is denominated the superficial fascia^ and is merely an expanse of cellular tissue possessing the same general characters * Winslow's Anatomy, by Douglas, v. ii. p. 160. t The application of the term fascia to the sub- cutaneous cellular investment in various parts of the body has occasioned no small degree of confusion among anatomists. A singular degree of confusion exists in Velpeau's description of this fascia : he observes in one place that the deep layers of the subcutaneous cellular tissue constitute the super- ficial fascia, and in the next page states that " the superficial fascia is nothing else than the cellular tissue condensed, whose laminae strongly applied one against the other, are ultimately reduced to somewhat of the aponeurotic form." I shall adhere to this latter definition, and consider superficial fascia as synonymous with subcutaneous cellular tissue. — Velpeau Anat. Chirurg. vol. ii. p. 4 and 5. as that which is found in all other parts of the body ; it is continued upwards over the thorax, laterally into the region of the back, inferiorly along the thighs, and into the scrotum. It varies in thickness according to the quantity of fat which is deposited in its cells ;* in some in- stances it has been known to possess a thick- ness of three inches. Thin but muscular subjects afford the best examples from which to study the superfical fascia of the abdomen : in such subjects we find it in general of a much denser character than in others, very strong and elastic and easily divisible into laminae, produced, no doubt, by the pressure which it experiences from the weight of the abdominal viscera, and the constant attrition occasioned by the action of the abdominal muscles. In the iliac region, immediately above Poupart's ligament, the density of this fascia is most conspicuous. Here some have regarded it as a 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 (ballons ou pouches) are closed over the axis of the body. When this superficial fascia is dissected off, a very thin layer of cellular membrane, perfectly diaphanous, is found to adhere to the subjacent aponeurotic expansion. This will be found particularly adherent over Poupart's ligament, and is that which is referred to by some ana- tomists (as Manec, Cloquet, &c.,) as a deep process of the superficial fascia which adheres to Poupart's ligament, and so forms a super- ficial septum between the abdomen and thigh. To see this layer the superficial lamina should be raised by commencing the dissection of it * Cloquet says it is, as it were, decomposed by the deposition of fat. — Recherches Anat. sur les Hernies de 1'Abdomen, p. 11. t Diet, de Medecine, art. abdomen. $ Vid. Blandin, Anat, Topng. B 2 ABDOMEN, below and carrying it upwards ; the expansion will then appear to arise from Poupart's liga- ment, and spread over the subjacent aponeuro- sis. In some subjects it is so thin as to appear to be little more than the proper cellular cover- ing of the muscle and its aponeurosis, but in others it assumes a considerable degree of density. It may be called the deep layer of the superficial fascia; it deserves attention from the fact that the femoral hernia, in its ascent on the abdomen, lies between it and the super- ficial layer. It is to this fascia that Scarpa must allude under the name of " aponeurotic web of the muscle of the fascia lata," and hence some have called it Scarpa's fascia.* The whole of the superficial fascia has been called Camper's fascia, because it was first fully described by that writer.f On the posterior wall of the abdomen, in the lumbar regions, the cellular tissue is more abundant and more lax ; here we frequently find it infiltrated with serous fluid, in conse- quence of the usual supine posture of the body after death. It is continuous above with the subcutaneous tissue in the dorsal region, and below with that in the glutseal 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- minal.) When the superficial fascia covering the an- terior and lateral surfaces of the abdomen has been dissected away, this muscle is brought into view. It consists of a flat muscular portion, situated superiorly and posteriorly, and of a tendinous or aponeurotic lamella anteriorly and inferiorly, but which is largest and strongest in the latter situation. The muscular portion of the external oblique is attached by separate fasciculi to the external surfaces of the eight inferior ribs, from the fifth to the twelfth inclusive. These fasciculi indigitate at their attachment with similar ones, of the serratus magnus, from the fifth to the ninth inclusive, and of the latissimus dorsi from the tenth to the twelfth. From these points of attachment, described by most English anatomists as the origin of the muscle, the fibres pass obliquely downwards and forwards, with different degrees of ob- liquity, the middle fibres being the most ob- * Vid. Scarpa on Hernia, by Wishart, p. 22 ; also Todd on Hernia, Dub. Hosp. Reports, vol. i. p. 246 ; and Flood's plates of Inguinal and Femoral Hernia. t Camper, Icones Herniarum, p. 11. lique, the superior taking a direction nearly horizontally inwards, and the posterior ones passing nearly vertically downwards. The an- terior and middle fibres are inserted into the outer convex border of the aponeurotic lamella of the muscle, but the posterior are inserted into the outer lip of the two anterior thirds of the crista of the ilium by short tendinous fibres. The fibres of this muscle vary considerably in length, those which are highest up being the shortest, the middle ones the longest, and next in length the posterior fibres. The aponeurotic lamella of the external oblique muscle is found on the anterior part of the abdomen, both su- periorly and inferiorly. In the former situa- tion the aponeurosis is extremely thin and weak ; it is transparent, so that the upper extremity of the rectus muscle which it covers is visible through it. This, too, is the narrow- est portion of the aponeurosis, which increases in breadth, strength, and thickness as it de- scends. The aponeurosis, like the muscular portion, consists of a series of fibres, for the most part inclined obliquely downwards and inwards, excepting the superior ones, whose direction is horizontal. At several places these fibres are separated from each other so as to allow the subjacent muscle to be seen through the interval. At various parts the tendon is perforated by vascular apertures, which are oc- casionally so enlarged as to admit little peri- toneal prolongations to pass through them. Along the middle line, from the ensiform car- tilage to the symphysis pubis, the aponeurosis forms an interlacement with its fellow of the opposite side, and this interlacement with that of the subjacent aponeuroses constitutes the tendinous line called linea alba, which, as Velpeau observes, may be regarded as the centre in which all the fibrous elements of the abdomen terminate. Just above the symphysis pubis, the decussating fibres are not inter- mixed in the same manner as in other parts of the linea alba : there the bundle of one side crosses anteriorly or posteriorly to that of the other, without any union of fibres, to be in- serted into the pubis of the side opposite to that from which it came. A little above and external to the pubis, a separation of the fibres of the tendon of the obliquus externus takes place, leaving an opening which is denominated the external abdominal ring, through which the rounded bundle composed of the spermatic vessels and duct (the spermatic cord) passes in the male, and the round ligament of the uterus in the female. The aponeurotic fibres which form the immediate boundaries of this opening are termed the pillars of the ring, of which one is superior, internal, and anterior, the other is in- ferior, external, and posterior, and passes behind the cord. External and inferior to this opening, we observe that the aponeurosis of the external oblique muscle is extended from the pubis to the anterior superior spine of the ilium. On the pubic side, the fibres, which are the same that form the inferior pillar of the ring, are in- serted into the spine of the pubis, and being ABDOMEN. reflected backwards, outwards, and a little upwards, they are likewise inserted into the linea ilio-pectinea, which commences at the spine of the pubis. The lower margin of the tendon is thus folded back a little as it arches over the excavation between the pubis and ilium, so as to present towards the abdomen a slight channel-like excavation, which affords origin to the muscular fibres of the internal oblique as well as to those of the transver- salis, whilst it has the appearance of a rounded ligamentous cord towards the thigh. In this manner is formed Poupart's ligament, which, contrary to what its usual name denotes, is not a distinct ligamentous cord, but the in- ferior margin of the external oblique stretched from pubis to ilium, and folded a little upon itself. By its superior margin it is continuous with the fibres of the tendon of the external oblique, which fall obliquely upon it ; by its in- ferior margin it is intimately connected with the fascia lata of the thigh ; externally it is inserted into the anterior superior spine of the ilium ; and by its pubic extremity it has three attachments, 1. to the body of the pubis; 2. to the spine of the same; and 3. to the linea ilio-pectinea, constituting what has been called Gimbernufs ligament, which has a sharp slightly crescentic margin directed backwards and outwards to- wards the femoral vessels.* (See GROIN, REGION OF THE.) The external abdominal ring is a triangular opening, situated obliquely ; the superior angle being directed upwards and outwards, and its base, represented by a line uniting the pubic insertions of the two pillars, resting upon the pubis. The superior angle is formed evidently by the separation of the fibres of the aponeu- rosis, the primitive direction of which is the same as that of a perpendicular from the apex to the base of the triangle, viz. downwards and in- wards, (sacrad and pubad.) This separation, however, is strengthened, and the angle round- ed by some tendinous fibres which inter- sect the oblique ones nearly at a right angle, arising as a cord of variable thickness from Poupart's ligament, and passing upwards and inwards over the apex of the ring, gradually separating into several tendinous fibres. These fibres are sometimes very strong, at other times very feeble and scarcely perceptible ; but it rarely, if ever, happens that they are completely absent ; they have been termed intercolumnal bands. I have seen them so strong that they could be distinctly dissected off the external oblique aponeurosis, like a separate tendinous expansion; but most fre- quently they are so united to the aponeurosis as to render it impossible to remove them without injury to it. These fibres are evi- dently intended, as Scarpa expresses it, " to fix the limits of the inguinal ring, and to oppose the further divergence of the tendi- nous pillars towards the side." They are * The terms crural arch, and ligament of Fallophis, are also used synonymously with Poupart's liga- ment. Velpeau calls it bandelette ilio-piibienne 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 hernise, I have not found them particularly developed; nor is it con- sistent with the general result of pressure from within on tendinous fibres to believe that such pressure would produce an increase of deve- lopment in them. The size of the external abdominal ring is greatest in the male subject, but here it varies considerably, sometimes closely embracing the cord as it passes through it, and at others appearing much too large for it. In the male the parts which pass through it are the sper- matic cord, enveloped in its proper tunic, and in one of condensed cellular membrane pro- longed from the fascia transversalis, a branch of the genito-crural nerve, the cremaster mus- cle, the cremasteric artery, and the spermaticus superficialis nerve. In the female, we find the round ligament of the uterus, covered and accompanied by similar parts, excepting the cremaster. From the margin of the external abdominal ring, a cellular expansion or fascia is carried over the cord or round ligament, and has been denominated fascia spermatica. This fascia consequently forms a covering of any hernia that may be protruded through the external ring; and, accordingly, in old 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 : interiorly the fascia lata of the thigh is related to the margin of the external oblique muscle, both as it covers the glutaei, and as it lies in front of the thigh. Along the middle line the aponeuroses of opposite sides meet at the linea alba, and superiorly the mus- cular fibres are related to and sometimes con- nected by a fleshy slip with those of the pecto- ralis major, and the aponeurosis is continuous with that of the same muscle.* When the ex- * " By its position, the direction of its fibres, and the short distance to which its fleshy portion extends forwards, the external oblique corresponds so much to the external intercostals, that one is led to say that it represents them in the abdomen." — Merk<-l. 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 interims (obliquus ascendens, ilio-abdominal, ilio-lumbo-costi-abdominal ) is smaller than the preceding muscle, which it resembles in shape and general characters. The direction of its fibres, however, is opposite, inasmuch as the fibres of the two muscles decussate with each other, thus adding con- siderably to the strength of the abdominal wall, and forming a great protection against visceral protrusions. The external attachments (or, as systematic writers call it, the origin of the mus- cle) is 1. by short fleshy fibres to the tendinous expansion covering the lumbar mass of muscles, called fascia lumborum, which is formed by the posterior lamina of the tendon of the trans- versalis abdominis : 2. to the two anterior thirds of the middle portion of the crista ilii, between the external oblique and the transver- salis as far forwards as the anterior superior spine : 3. to the groove in the upper or abdo- minal surface of Poupart's ligament for about its external third. The superior fibres pass upwards and inwards, and are inserted by fleshy slips into the cartilages of the twelfth, ele- venth, and tenth ribs, in the intervals between which they are either separated from the inter- costal muscles by a fibrous intersection, or con- founded with them, and by a tendinous aponeu- rosis into the cartilages of the ninth, eighth, and seventh ribs as well as into the xiphoid cartilage. Lower down, the fibres which arise from the crista ilii, as well as those from Poupart's liga- ment, pass inwards, the superior obliquely upwards and inwards, the inferior more hori- zontally, and the lowest fibres inclining a little downwards, and are all inserted, like those of the obliquus externus into the outer convex margin of an aponeurotic expansion, which goes to be inserted along the middle line. This ten- don passes inwards for a short distance, nearly as far as the outer margin of the rectus muscle, as a single lamina. Along this margin, and as low down as the inferior fourth of the rectus muscle, the tendon divides into two laminae, of which the anterior adheres to the posterior surface of the tendon of the external oblique, and the posterior to the subjacent tendon of the transversalis, both laminae going to be inserted into the ensiform cartilage and linea alba, the one in front, the other behind, the rectus muscle. (See^/Jg. 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 laminse,the aponeurosis of the obliquus externus and that of the transversalis adhere to it more closely than they do externally to that line, and thus a thickened portion of the abdominal aponeurosis is formed, taking the course of the outer margin of the rectus muscle : this line is called the linea semilunaris, and is that in which the operation of paracentesis abdominis used formerly to be practised. The inferior margin of the obliquus internus is deserving of particular attention. The in- ferior fibres attached to the external third of Poupart's ligament in the groove formed in it pass transversely inwards and parallel to the ligament, crossing over the spermatic cord, to be inserted into the pubis. Here the muscle is confounded with the inferior fibres of the sub- jacent one, the transversalis ; so that it is not only difficult to say which muscle passes low- est down, but it is difficult, and often impossible, to separate the two muscles. Hence the lower margins of the fleshy fibres as well as of the apo- neuroses of these two muscles are constantly spoken of conjointly; however, I have several times succeeded in separating them distinctly, and I am decidedly of opinion that the apo- neurosis of the obliquus internus seldom or never descends so low down as that of the trans- versalis. The lowest of the fibres of the obliquus internus are sometimes observed to separate a little from the others, so as, instead of a directly transverse, to assume a course slightly curved with the concavity upwards and a little outwards, lying in front of the cord ; in some cases fibres of this kind are observed to lie in front of the spermatic cord, and to descend much lower down, taking of course a much more curved direction, still attached on the outside to Pou- part's ligament, and on the inside to the pubis, so that a series of curved fibres are thus found to adhere to the anterior surface of the cord and of the tunica vaginalis, exhibiting an equal num- ber of reversed arches. But this disposition is rarely seen in its most highly developed state, excepting where some tumour has been con- nected with the cord or testicle, as hernia, hydrocele, &c. This arched arrangement of muscular fibres in connection with the spermatic cord and tunica vaginalis testis constitutes the Cremas- ter muscle (x.gtpat,v, suspendo,) the great tenuity of which in the natural state of the parts has ren- dered it difficult to determine its precise attach- ments, and consequently has given rise to the great discrepancy which is observable between the descriptions of different writers. When this muscle is examined in a case of old hernia or hydrocele, it is found, as Scarpa originally described it, to consist of two bundles ; the first, external to the cord which arises from Poupart's ligament along with the internal oblique, follows the course of the spermatic cord, which it ac- companies through the external abdominal ring, sending at intervals fibres arching in front of the cord to join a similar bundle on the inner side, as may be seen in the accompanying en- graving from a plate in Sir A. Cooper's work on the testis (fig. 3). Inferiorly, this bundle, a ABDOMEN. Fig. 3. c, the internal oblique ; e, the descending fibres ; /, point of insertion into the pubis ; h, one of the re- versed arches ; d, conjoined tendons ; a, rectus muscle. good deal diminished in size, crosses over the inferior and anterior portion of the tunica vagi- nalis testis, and begins to ascend along the inner side of the testicle and cord, keeping more pos- teriorly : this constitutes the second bundle ; it gradually increases in size as it ascends by re- ceiving the transverse fibres from the bundle of the opposite side, and it is inserted, sometimes by a distinct tendon, into the pubis near its spine. In some cases I have totally failed, even after the most careful dissection, in detecting a conti- nuity by muscular fibre between these two bun- dles, insomuch as to lead me to imagine that they may be connected by a very condensed cel- lular tissue or thin 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 internus and the obliquus externus. At the infe- rior edge of the obliquus internus the spermatic cord is seen emerging from the abdomen and passing obliquely inwards and a little down- wards to the external abdominal ring. Here it lies in a groove or channel, called the inguinal canal, which extends from the point at which the spermatic cord emerges from the abdomen, (the opening in the fascia transversalis called in- ternal abdominal ring) to the external abdo- minal ring. This canal is bounded or covered anteriorly by the tendon of the obliquus externus; posteriorly by the fascia trans- versalis and some fibres of the tendon of the transversalis muscle towards the inner side ; superiorly by the margin of the obliquus in- ternus and transversalis muscles ; and inferiorly by the groove of Poupart's ligament.* (A full description of this canal will be found in the article GROIN, REGION OF THE.) 3. Transversalis (lumbo-ubdominal, lumbo- Ui-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. d * " The obliquus inter-nits 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."— Mechel. 3 ABDOMEN. ilii, the fibres arise from a tendinous lamella, which itself is trifoliate in its origin. This ten- don is found as an undivided lamella between the outer margin of the quadratuslamborum and the commencement of the fleshy fibres of the muscle, extending vertically from the last rib to the crista ilii. (Fig. 4, 1.) The three laminae of which this tendon is composed arise from different portions of the vertebrae in the lumbar region of the spine ; the posterior, which is thick and strong, and is commonly called 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 vertebrae, and covers the quadratus lumborum muscle in front (fig. 4, f). Inferiorly, the transversalis muscle at- taches itself to the inner lip of the crista ilii for its three anterior fourths, and to the ex- ternal third or half of Poupart's ligament, cor- responding to the attachments of the obliquus internus. The fleshy fibres of the muscle pass from these several points of attachment trans- versely inwards, the middle being the longest, and the superior the shortest, and are in- serted into the outer convex margin* of a tendinous aponeurosis, which extends to the linea alba. This aponeurosis is intimately connected with the posterior division of that of the obliquus internus for an extent corre- sponding to the three superior fourths of the rectus muscle, behind which both pass to be inserted into the ensiform cartilage and linea alba, (fig. 4, a,) forming the posterior wall of the sheath of the rectus. Inferiorly, as we have already remarked, these conjoined tendons go together in front of the rectus, and are inserted into the inferior fourth of the linea alba and into the pubis. At the inner extre- mity of the inguinal canal, it will be seen by carefully raising up the spermatic cord, that this union of the tendons of these two muscles ceases, and we can trace the fibres of the trans- versalis tendon passing down in a curved direc- tion, more curved as they are more external, and insinuating themselves behind the cord to be inserted into Gimbernat's and Poupart's ligament for about its external third or fourth. This mode of insertion of the transversalis ten- don was first described by Sir Astley Cooper, f and these fibres were by him called 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 Unco, semilunaris of Spigelius. f Cooper on the Testicle, p. 35. insertion of the tendon of the transversalis muscle ; but Mr. Guthrie has lately called the attention of anatomists to a variety which it is important to know, although it cannot be of frequent occurrence. In this variety the spermatic cord appears to pass through a slit in the inferior margin of the transversalis muscle, so that a bundle of muscle passes behind as well as before the cord ; the posterior one end- ing in tendinous fibres, which, like the folded fibres above described, are inserted into Pou- part's ligament.* It is very generally believed that the inferior fibres of this muscle contribute, as well as those of the obliquus internus, to form the cremaster. The two muscles are so closely connected externally by their inferior margins, that it is natural to suppose that both do send fibres to the cremaster. Sir Astley Cooper expresses the relation of the cremaster to these two muscles in the clearest way, when he says that it arises from Poupart's ligament within the inguinal canal, and there blends with some of the fibres of both these muscles.f A thin layer of cellular tissue covers the transversalis muscle, and separates it from the obliquus internus. At its superior margin it is intimately related to the diaphragm, and some of its fibres seem to be continuous with it : posteriorly, by the triple partition of its tendon, it ensheaths the lumbar muscles, and it lies upon the fascia transversalis, which, with a layer of cellular tissue, separates it from the peritoneum. | 4. Rectus abdominis ( sterno-pubien ) . After the superficial fascia has been removed so as to expose the aponeurosis of the external ob- lique, the recti muscles are seen on either side of the middle line covered by this aponeurosis, which it is necessary to slit up in order to ex- pose the muscles. The rectus owes its name to the perpendicular course of its fibres, which pass from the pubis to the thorax, nearly parallel to the middle line. It is long and narrow ; however, its breadth increases as it advances upwards, and as it increases in breadth it diminishes in thickness. At the pubis the muscle has its most fixed point of attachment, whence it is generally said to have its origin there: it arises by a short tendon from the symphysis of the pubis; this tendon is very narrow at its origin, but soon expands, and unites with the muscular fibres, which pass vertically upwards to the lower margin of the thorax, where the muscle is considerably increased in breadth, and divides into three portions; the first or internal one is inserted into the costoxiphoid ligament and cartilage of the seventh rib ; the middle, larger than the preceding, into the cartilage of the sixth rib at its inferior edge and anterior surface ; * Guthrie on Inguinal and Femoral Hernia, pp. 11, 12, 13, 4to. Lond. 1833. t Op. cit. p. 38. t " The transversalis corresponds, by the direction of its fibres, to the ' trianyularis 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 scernum and linea alba."- Meokel. 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 linea transverse. ;* they vary in number from three to five, and are always more numerous above than below the umbilicus. In general there is one on a level with the umbilicus ; the superior one being about an inch below the superior attachment of the muscle, and a third midway between these two : when a fourth and a fifth exist, they are below the umbilicus. They adhere to the an- terior wall of the sheath closely, and but very slightly or not at all to the posterior. Some- times the intersection does not go completely through the thickness of the muscle so as to appear on its posterior surface, and thus the posterior fibres are longer than the anterior ; but as Bichat remarks, it never happens that any of the muscular fibres pass from one extre- mity of the muscle to the other without uniting at least one of these intersections. Sometimes, too, the intersection does not go through the breadth of the muscle, and this is generally the case with that below the umbili- cus. The effect of these intersections is to convert the muscle into so many distinct bellies, each of which has its proper action, and is, as Beclard asserts, provided with a separate nerve.f The rectus muscle is enveloped in a fibrous sheath, the mode of formation of which the reader must have collected from the description of the oblique muscles. The anterior wall of this sheath is formed by the aponeurosis of the external oblique alone over the chest, and by the same aponeurosis and the anterior layer of that of the internal oblique, from the xiphoid cartilage to the inferior fourth of the muscle ; (both which aponeuroses over the internal half of the muscle are so adherent to each other as to form but one lamina;) and in its inferior fourth by the conjoined aponeuroses of the two obliqui and transversalis. The posterior wall of the sheath is deficient superiorly where the muscle covers the carti- lages of the ribs with which it is in contact, and inferiorly for a space corresponding to the inferior fourth of the muscle. So much of it as exists is formed by the tendon of the transver- salis and the posterior lamina of that of the internal oblique, so that the rectus appears to have passed at its inferior extremity through a transverse slit in these conjoined tendons, so as to get between them and the peritoneum. The rectus muscle covers, at its superior ex- tremity, the cartilages of the two last true ribs and a part of those of the two first false, and also the xiphoid appendix. The internal mam- mary and epigastric arteries are found behind it in the sheath. Between the recti muscles is the fibrous cord called linea alba, produced by the interlace- * Also called enervations.— Winslow. They are, says Meckel, incontestably incomplete repetitions of the ribs in the walls of the abdomen. t Hence Meckel classes it among the polygastric muscles. ment of the aponeuroses of the opposite sides, noted in surgery as being in its inferior half the seat of the operations of paracentesis abdominis, paracentesis vesicae supra pubem, the supra- pubic lithotomy, and the Csesarean operation. This cord extends from the xiphoid cartilage to the symphysis pubis, with the anterior liga- ment of which articulation it is identified. It does not present the same breadth in its whole course, being broader in the umbilical region than elsewhere. In this region we find in the linea alba the perforation which gave passage to the umbilical vessels in the foetus and the urachus, and through which the fibrous remains of those vessels pass to be inserted into the skin, whereby is formed the cutaneous depres- sion which marks the situation of this opening. In the adult the umbilicus may be considered as a point of considerable strength ; in the esti- mation of some it is the strongest point in the abdominal parietes : in dissecting away the skin at this point, we find subjacent to it a very con- densed cellular tissue, to which and to the skin the fibrous cords into which the umbilical vessels have degenerated adhere closely ; these cords, too, adhere not only to the skin, but likewise to the margin of the fibrous ring through which they pass. " The umbilical opening, therefore," says Scarpa, " in the infant two months after birth, and still more in the adult, is not only like the other natural openings of the abdomen, strength- ened internally by the application of the peri- toneum and of the cellular substance, and on the outside by the common integuments, but it is likewise plugged up in the centre by the three umbilical ligaments and by the urachus ; these ligaments form a triangle, the apex of which is fixed in the cicatrix of the integuments of the umbilicus, the base in the liver, in the two ilio-lumbar regions, and in the fundus of the urinary bladder ; by this triangle is formed a strong and elastic bridle, capable of itself alone of opposing a powerful resistance to the viscera attempting to open a passage through the aponeurotic ring 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 t fascia Iwnbo- rum. This has extensive osseous attachments, and thus firmly binds down the subjacent mus- cles. When it is removed, the lumbar portions of the sacrolumbalis and longissimus dorsi, and a little of the spinalis dorsi, are brought into view, the two former of which are described by some as a single muscle — the sacrospinalis. The external of these muscles is the sacrolum- balis, and its outer margin may be said to con- stitute the limit of the posterior wall of the abdomen in that direction. In this situation the posterior and middle layers of the tendon of the transversal is separate from each other to ensheath these muscles, the posterior layer forming the fascia lumborum. We must refer to the article BACK for a particular description of these muscles. When the lumbar mass of muscles (as the three preceding have been called) has been re- moved, the next part brought into view is the anterior layer of their fibrous sheath formed by the middle lamina of the transversalis tendon, which is inserted into the apices of the trans- verse processes. This lamina is thin and semi- transparent, so that the fibres of the muscle * " The linea alba performs the same office in the abdomen as the sternum does in the thorax, with this only difference, that it is not formed of bone. The anterior tendons of the broad muscles are at- tached to it, in the same way that the cartilages of the ribs are articulated with the sternum, and the difference of tissue which exists between it and the sternum is attributable to the general difference of structure between the abdominal and pectoral cavi- ties, the latter being formed almost entirely of osseous parts, whilst the walls of the former are fleshy and tendinous." — Meckel. t Meckel says that this muscle rarely presents anomalies ; in this he must be mistaken, as its ab- sence is certainly not a rare occurrence. which lies immediately before it, are seen through it. This muscle is the Quadratics lumborum (ilio-costal, ilio-lumbi- costal). The term quadratus is applied to this muscle, more from its quadrilateral form than from any nearer resemblance to a square, in- asmuch as all its sides are unequal. The most fixed attachment of this muscle is its inferior, where it is inserted by tendinous fibres into the iliolumbar ligament and into the inner lip of the crista ilii for about an inch to the outer side of the insertion of that ligament. From these points the fibres proceed vertically upwards, the ex- ternal ones going to be inserted into the inferior margin of the last rib for nearly its entire length, and the internal fibres, those in parti- cular which are attached to the ligament, ter- minating by four aponeurotic tongue-like bun- dles, which are inserted into the anterior surface of the transverse processes of the four superior lumbar vertebrae near their bases. The several bundles which end in these tongue-like pro- cesses vary in length ; those which are external being the longest, as going to higher vertebrae. This muscle is covered on its anterior or abdo- minal surface by the anterior lamina of the tendon of the transversalis muscle, by which it is separated from the diaphragm as well as from the psoas magnus.* The last dorsal nerve and the first two branches of the lumbar plexus, pass between the quadratus and the aponeurotic lamina which covers it. Psoas magnus, (•vj/oa, Iambus} (prelombo, trochanterien, lumbaris.) The greatest por- tion of this muscle belongs to the abdominal region ; it lies along the side of, not only the lumbar but also of a small portion of the dorsal region of the spine, lodged in the angle between the transverse processes and bodies. It passes as high up as the twelfth dorsal vertebra, to the body of which as well as to those of the four suc- ceeding lumbar vertebrae, and to their interven- ing fibro-cartilages, the muscle is attached : it likewise is attached to the bases of the corres- ponding transverse processes, so that the inter- vals between the portions that are attached to the bodies, and those to the transverse processes, correspond to the intervertebral foramina or points of exit of the lumbar nerves, the an- terior branches of which plunge at once into the substance of the psoas muscle to form the lumbar plexus. The several bundles which thus take their origin from the vertebrae form a thick rounded muscle, which passes nearly vertically downwards, inclining a little out- wards, over the brim of the true pelvis, so as often to appear to encroach upon the circum- ference of the upper outlet of that cavity. A little way above Poupart's ligament the mus- cular fibres are inserted around a strong thick tendon. This tendon, which had commenced high up by distinct portions in the interior of the muscle, passes under Poupart's ligament over the horizontal ramus of the pubis. It descends over the capsular ligament of the hip- * SeeyJg. 4,/; see also fig. 5, where on one side the muscle has been removed from between the lamina; of the transversalis tendon. ABDOMEN. 11 joint (from which as well as from the ramus of the pubis it is separated by a bursa) over the head and along the inner side of the neck of the femur, and is inserted into the posterior part of the trochanter minor at its base, being separated by a small bursa from the surface of that process. As the tendon is passing over the ramus of the pubis, it receives by its outer margin a series of fibres from the iliacus in- ternus muscle. At its superior portion the psoas muscle is covered by a thin fibrous ex- pansion, which is attached on the one hand to the apices of the transverse processes, and on the other to the bodies of the upper lumbar vertebrae ; 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. Septi Transversi. Op. Minora, torn. 1. any influence upon the contents of the cavity. The iliac fossa affords a large surface for the attachment of one of the principal muscles connecting the thigh with the trunk. This muscle is named Iliacus internus, (iliaco-trochanterien.) This muscle fills up the iliac fossa, to the whole of whose concavity as well as to its margin, and the two anterior spinous processes of the ilium and the interval between them, its fibres are attached. From these several points of origin the fibres converge to form a thick and broad belly, which passes over the upper part of the acetabulum and horizontal ramus of the pubis, filling up the external portion of the 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. 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 Imea 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 thet/asci« 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 ihej'ascia 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 J'ascia 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'Whinuie. 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 circumttexa 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 nbro-cellular expansion lines the whole in- ternal surface of the abdominal parietes. It is so likewise with the pelvis, and also with the thorax. The cavity of the cranium, too, is lined with a fibrous membrane, although of a different nature, and doubtless performing a dif- ferent office. 5. Between the internal fibrous expan- sion of the abdomen and the peritoneum is a cellular tissue, which presents different cha- racters in each region ; it is the subperitoneal cellular tissue. Along the anterior wall it is thin and fine, except inferiorly opposite the in- ternal abdominal ring, where it becomes more abundant, as well as in the hypogastric region, immediately above the pubis. In the iliac fossa and lumbar region it is lax and abundant, especially in the latter, where there is also a considerable quantity of fat surrounding the kidney. In the iliac fossa this cellular tissue is stretched across the crural ring, and forms what Cloquet describes under the name of septum crurale. On the superior wall it is ex- tremely fine, and in very small quantity. Im- mediately behind the sternum, and in the mid- dle line, this cellular tissue communicates with that of the mediastinum through a separation of the anterior fibres of the diaphragm. This subserous cellular tissue forms the pri- mary covering of all herniae, which push a peritoneal sac before them, and as being the fascia constituting the nearest investment of the sac, it is generally called the fascia propria. * Abernethy 's Surgical Works, vol. i. p. t Colics' Surgical Anatomy, pp. 68, 69. 225. 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 herniae ; the for- mer being that by oblique descent, the latter that by direct descent. The fourth or vertical fold indicates the 14 ABDOMEN. reflection of the peritoneum from the anterior abdominal wall upon the superior fundus and posterior surface of the bladder : when that viscus is empty and contracted, this fold dis- appears totally ; it is more apparent when the bladder is partially filled, and is still more distinct in the fcetus in consequence of the greater size of the urachus at that period. Just above the pubis the peritoneum is con- nected to the abdominal wall by a very lax cellular tissue; and accordingly when the blad- der is much distended, the peritoneum is pushed upwards, and stripped off the abdo- minal wall to an extent proportioned to the degree of distension of the bladder, so that its anterior surface is then in immediate contact with the abdominal wall, and may be opened with impunity so far as the peritoneum is con- cerned. The lateral walls of the abdomen are like- wise completely lined by peritoneum, which extends backwards as far as the junction of these walls with the posterior, where it is re- flected from them so as to involve the ascending colon on the right side and the descending on the left, and here it forms on each side the folds respectively termed right and left meso- colon. From the right lateral wall the peri- toneum is continued upwards upon the dia- phragm, and contributes to form the right lateral ligament of the liver ; on the left side it is continued in a similar manner on the diaphragm, and in passing from the spleen to that muscle forms the fold called splenico- phrenic. The concave surface of the diaphragm is in greatest part lined by peritoneum : the an- terior half of the muscle is uninterruptedly covered by peritoneum, which adheres very closely to the central tendon, but is much more easily separated from the muscular portion. On the right side and in the middle, in front of the cesophageal opening, the peritoneum is re- flected from the diaphragm to the liver, forming the right lateral, coronary, and left lateral liga- ments of that organ. The posterior half of this surface is likewise covered by peritoneum, that membrane being deficient for a little way behind the opening for the vena cava and behind and on each side of the cesophageal and aortic openings : the crura of the diaphragm are covered chiefly on the outer side. The peritoneum comes into immediate con- tact with the posterior abdominal wall only in a very small portion of its extent : in tracing it on the right side we find it covering the right colon, then passing inwards over the kidney and suprarenal capsule, the duodenum and vena cava, to the 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 j below this it manifests its continuity with the layer of the opposite side by forming the left or inferior lamina of the mesentery. This lamina commences at the left side of the body of the second lumbar vertebra ; as it descends, it gradually crosses more in front of the aorta, so as to terminate at the right sacro-iliac symphysis ; the right lamina is situated quite on the right side of the spine. In the iliac fossae the peritoneum is in con- nexion with thet/«scia 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 vesicae supra pubem, and the high operation for the stone may be per- formed with impunity to the serous membrane. At the posterior wall an instrument may be passed into any part of the posterior surface of the kidney without injury to the peritoneum ; the pelvis of the kidney, or any part of the abdominal course of the ureter, may be opened too, or the vena cava; and by cutting into the bodies of the vertebrae, and the muscular por- tion of the posterior wall in the dead body, a view of all the parts which lie upon that wall may be obtained without at all injuring the peritoneum.* Further details respecting the anatomy of the peritoneum will be found in the article under that head. Vessels and nerves of the abdominal walls. — a. The arteries. — The most important arterial ramifications are found in the anterior wall. In the superficial fascia we find the superficial epigastric artery or tegumentary artery, which exists as a trunk in the iliac regions. Tin's 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 circumjie.ru 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 in any operation performed in that line, or in the internal half of the rectus muscle, and its security in such operations is increased under the altered state of parts con- * Diet, de Medecine, art. Abdomen. sequent on pregnancy, ascites, or any abdomi- nal tumour pressing similarly on the abdominal wall. In these cases the distance of the artery from the linea alba is increased by the flattening of the rectus muscle, which results from its compression. — (See GROIN, REGION OF; HERNIA; ILIAC ARTERY.) The circumftexa 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. Cramptou and Goodissen. Dub. Hosp. Reports, vol. ii. t As in the case of obliteration of the infeiior vena cava from the pressure of an aneurismal tumour observed by Reynaud. Journal Hebdom. deMed. 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 portoe. In another case, recorded by Manec, the vein originated iu the same manner by two roots, reached the umbilicus, taking a course parallel to the umbilical artery, formed an arch outside the navel, and having re-entered the abdomen, opened into the vena portae. In another instance which occurred to Cruveilhier the superficial veins in the hypogastric region were enormously enlarged, at the umbilicus they ended in a trunk as large as a finger, which communicated with the vena cava as it passed under the liver.f Berard proposes to explain, by the supposition of the existence of such anomalies as those above described, the occurrence of fatal hemorrhages from wounds inflicted at the umbilicus, which have been attributed to the persistence of the um- bilical vein.J c. The lymphatics. — Those on the anterior wall communicate above with the axillary glands, and below with those of the groin : the deep-seated lymphatics of the posterior wall communicate with the glands which lie along the lateral and anterior surfaces of the lumbar spine. d. The nerves. — The nerves of the abdo- minal parietes are derived from the inferior intercostals and from branches of the lumbar plexus. The seventh, eighth, ninth, tenth, eleventh, and twelfth intercostal nerves termi- nate in supplying the transverse and oblique muscles and the recti ; the twelfth lies in front of the quadratus lumborum muscle, and gives several filaments to that muscle. The ilio- scrotal and inguino-cutaneous nerves are the branches of the lumbar plexus which mainly supply the inferior part of the oblique and transverse muscles. One branch of 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 portse. t Velpeau, Anat. Chir. ed. 2. vol. ii. p. 32, and Manec, Dissertation inaugurale. Paris, 1826. t Diet, de Med. art. Abdomen. to the ribs, the vertebrae, and the pelvis, it becomes evident that they must likewise be destined to act upon the thoracic and pelvic cavities, as well as upon the vertebral column. In the constitution of the abdominal parietes we observe, as Berard* remarks, the most happy adaptation of structure to uses. A completely osseous covering would have greatly interfered with the functions of the abdominal organs, which are liable to experience changes both extensive and often very rapid, either by reason of the introduction of alimentary matter, whether solids or fluids, or by the disengage- ment of gases within the digestive tube, or by the progressive development of the impregnated uterus. We may moreover add that an exact repetition of the structure of the walls of the thorax would not have been well adapted to the abdomen for the same reason, namely, the too great resistance which it would afford to compression from within, thereby interfering with the distensibility of the enclosed viscera. The resistance, too, which a wall so constituted would afford to impulses from without could not have been so easily adapted to the impetus of the forces likely to act upon them as a purely muscular wall whose contractions and the intensity of them are obedient to the will. The consideration of the action and uses of the abdominal muscles naturally comes under two heads : — 1 . their action upon the abdo- minal cavity and its contents ; 2. their influ- ence on the trunk generally, or parts of it. It is the muscles that enter into the compo- sition of the anterior and lateral walls of the abdomen which act chiefly on the cavity and its contained viscera. The solidity of a con- siderable portion of the posterior wall, and the great strength of the lumbar muscles, give to that wall such a power of resistance as enables it to receive the compressed viscera without at all yielding. A reference simply to the attach- ments of the muscles of the anterior and lateral walls is sufficient to shew that these muscles when contracted must diminish the capacity of the abdomen, both in the lateral and antero- posterior directions ; and as the posterior wall is but little influenced, the viscera will be pushed partly upwards against the diaphragm, and partly downwards into the cavity of the pelvis, where their further descent is opposed by the levator ani. Hence it appears that a degree of antagonism exists between the diaphragm and the abdominal muscles, as well as also between those muscles and the levator ani. It is extremely difficult to maintain the abdominal muscles and the diaphragm at the same moment in a state of contrac- tion ; in general they alternately yield the one to the other : and when it does happen that they are simultaneously contracted, the abdominal viscera must suffer an unusual de- gree of compression ; and it is not improbable that vomiting is sometimes produced by such a cause, and defecation, no doubt, is likewise aided by it. The danger of the protrusion of some of the hollow viscera between the fibres * Loc. cit. ABDOMEN. 17 of the muscles is provided against by the variation of direction in the fibres of the several layers ; thus the fibres of the obliqui are in the directions of two intersecting diagonals, and those of the transversalis are different from both. By this arrangement a sort of network is formed, with meshes so small as to render a protrusion perfectly impossible in the healthy condition of the muscle. In the compression of the viscera the abdominal muscles are most completely congeneres, although the trans- versalis seems to be the best adapted to this action, and probably, for that reason, forms the layer which is placed nearest the peri- toneum. The recti muscles are powerful auxiliaries in affording a fixed point of attach- ment in front for the aponeuroses of the broad muscles, and the pyramidales assist in a similar manner by rendering tense the linea alba. Is this constant action of the abdominal parietes on the viscera necessary or favourable to the due performance of the functions of those organs, or to the continuance of the abdominal circulation? There certainly does not appear to be any evidence for the necessity of them for this purpose : that they are favour- able to it may be inferred from the fact that they do bear their present relation to them. We know from numerous experiments on animals, that both the transmission of the intestinal contents, and the abdominal circulation may go on when the abdominal muscles have been freely opened or removed. Hence we may answer this question with perfect justice in the words of Bichat : " The walls of the ab- domen favour these functions by their motions; but these motions are by no means essential to them." It is in consequence of the power which the abdominal muscles thus appear to exert in compressing the viscera, that some physiolo- gists have attributed the act of vomiting to their action united with that of the diaphragm; and Magendie, reviving the opinions of Bayle, Chi- rac, and Shwartz,* went so far as to deny to the muscular coat of the stomach any partici- pation in this act, and to ascribe it wholly to the influence of the abdominal muscles. But Beclard, to whom the question was referred by the Academy of Medicine of Paris, proved satisfactorily that the abdominal muscles are active in producing vomiting when the sto- mach is distended in a certain degree, and that the muscular coat of the stomach is also active in emptying the contents of that viscus. This conclusion 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 viribus atque aliquando vomitum perficere. Plerumque tamen irrita- tionem in ventriculo natam et sensum summae anxietatis, quae vomitum praecedunt, facere ut ad levandam acgrimoniam vires diaphragmatis et musculorum abdominis excitatce atque mo- lestiam de homine amoliturae, vomitum per- * Vide Haller, Elemenla Physiologiae, t. vi. sect. iv. § xiv. VOL. I. ficiant. Unde neque a sola vokmtate in pie- risque certe mortalibus vomitus cieri potest neque a sola absque voluntate natura — Quare recte conjunctas vires ventriculi et or^anorum respirationis Cl. Viri fecerunt. Et videtur dia- phragma et abdomen plus viriuin habere,quando ventriculus aut cibis repletus est, aut clausis ostiis distentus : tune enim magis ad perpen- diculum proximum ventriculum comprimui.t ct tota contingunt."* If it be admitted that the abdominal muscles are active in producing vomiting, and in defe- cation and micturition, it will follow likewise that they must assist in parturition. While* these pages were preparing for press, the fol- lowing passage presented itself to me, in an able and interesting review of M. Velpeau's Treatise on Midwifery. It so fully illustrates the part which the abdominal muscles take in promoting parturition, that I venture to tran- scribe it, " It is certain," says the reviewer, " that a woman who ' bears down ' as it is termed, with all her force, who makes the most of her pains, however feeble they may be, will thus accelerate her delivery ; and that another may more or less delay delivery by voluntarily opposing muscular action as much as she can. For example; — a woman was admitted for de- livery at M. Baudelocque's theatre ; labour went on regularly, and the pupils assembled. The dilatation of the cervix now slackened, and no progress was made during the whole night. The iltves 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, Richeiand, Physi- lo^ie par lierard, art. Digestion, § xxiv. t Medical Quarterly Review for April, 1835. p.lOO, 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 Berlin, viz., — to multi- ply the points of attachment of the obliqui muscles, and to associate them, in many ac- tions, with the recti muscles. This is explained by a reference to the action of the recti in flex- ing the pelvis: were these muscles uncon- nected with the obliqui, they would act only on the pelvis, into which they are inserted; but in consequence of the insertion of the internal oblique into the intersections of the recti, and the attachment of that muscle also to the crista ilii, the force of contraction of the recti is com- municated not only to the pubis, but also through the fibres of the obliquus internus to the rest of the pelvic margin.* The action of the pyramidales seems to be chiefly on the linea alba, which they render tense ; thus limiting the separation of the recti, and opposing the tendency to visceral protru- sion. Fallopius supposed that they acted on the bladder, especially when it was in a dis- tended state ; and Parsons conjectured that they might depress the suspensory ligament of the bladder (the urachus), and thus facilitate the contraction of that organ. The other muscles which are from situation abdominal muscles in consequence of their connexion with the posterior wall of the abdo- men, are chiefly agents in the extension of the vertebral column : in their contracted state, however, they form a tense and resisting sur- face, against which the viscera are compressed by the contraction of the anterior muscles. II. Of the Abdominal Cavity. — The annexed engraving (fig. 5.) exhibits a view of the abdo- minal cavity, the anterior and part of the lateral walls having been cut away and the viscera removed. The subject is so bent backwards as to render the bodies of the vertebras very * Berard, loc. cit., ct Berlin, sur 1'usage des enervations des muscles droits du bas-ventre, in Mem. do 1'Acad. des Sciences de Paris. 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 foetus ; 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 ABDOMEN. iy fashion of tightly compressing the lower part of the thorax has a material effect on the external characters of the female abdomen, otherwise there is no reason that the superior part of it should be proportionally less than in the male. In the foetus the abdomen is proportionally larger than at any other period of life : this is to be attributed to the imperfect development of the pelvis, and likewise to the great size which some of the abdominal viscera possess ; and as some time must elapse before the pelvis reaches its full dimensions, or the viscera lose their superfluous parts, the abdomen continues of this large size for a long period after birth. The subdivision of the abdomen into regions is especially useful in reference to the contents of the abdominal cavity, which it is highly de- sirable the student should examine, so as to be able to assign to each compartment its appro- priate contents. The abdominal viscera may be subdivided into the membranous and the parenchymatous ; the former being such as the stomach and intestinal canal, the latter, such as the liver, spleen, pancreas, &c. The viscera have likewise been distinguished in reference to their position with respect to the peritoneum, by the names' intra-peritojieal 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 venacava ascendens; the system of the vena portse ; 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 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 TNTESTINAL CANAL, KIDNEY, LIVER, PANCREAS, SPLEEN, SUPRARENAL CAPSULE. BIBLIOGRAPHY. — The several systematic writers, as Winslow, Boyer, Portal, Bichat, Meckel, Cloquet, HJarjolin, Uildebrandt, &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- veil/tier, Dictionnaire de Med. et Chirurg. ait. Abdo- men. Beclard et Berard, Diet, de Medecine. Ed. 2d. art. Abdomen. Pierer Anatomisch- Physiologisches Kealworterbuch. herausgegeben von J. F. Pierer. Leipzig, 1816. art. Abduminul- muskeln. Gerdy, Anat. des formes exterieures. Paris, 1829. p. 122 and 199. Cloquet, Recherches Anat. sur les Hernies de I'Abdomen, or the trans- lation by McWhinnie. Lond. 1835. Scarpu, on Hernia, by Wishart. Lawrence on ditto. Tudd, on ditto. Dub. Hosp. Reports, vol. i. Flood's plates of Inguinal and Femoral Hernia. Lund. 1834. Cam- per, Icones Heiniarum. Guthrie, on Inguinal and Femoral Hernia. A. Cooper, on ditto, and on the Testicle. Munec, Dissertation Inaugurale sur 1'Her- nie.1826. Colles's Surgical Anatomy. Dublin, 1811. Bardtiy on Muscular Motion, p. 337 et sqq. ( R. B. Todd.) ABSORPTION in physiology (from ub- sorbeo : Lat. absorptio, Fr. absorption, Ger. die einsaitgung, Ital. assorbimento.} The term absorption is employed in physiology to de- signate a vital organic function, the primary or immediate object of which is to furnish the system with a due supply of matter for its growth and subsistence. It is proposed, in the following article, first, to give an account of the organs by which the function is performed ; this will lead us, 2dly, to consider the question of venous absorption ; in the third place, we shall inquire into the mode in which the ab- sorbents act ; and, lastly, we shall offer some remarks upon the specific uses of the different parts of the absorbent system, and upon the re- lation which it bears to the other vital functions. §. 1. Description of the Absorbent System. — We propose, in the first instance, to restrict the term absorbent system to those organs, which are supposed to be exclusively appropriated to the function cf 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. Admiu. lib. 7, sub finem; De usu partium, lib. 4. cap. 19 ; An sanguis hi arteriis &c. cap. 5. parts of the absorbents had been seen by P^rasistratus and Ilerophilus, as well as by himself; but it appears that they were, all of them, unacquainted with the relation which these vessels bore to the other organs, and were entirely ignorant of their office and destination. These scanty observations of the ancients seem to have been entirely neglected, or even for- gotten, until the study of anatomy was revived, together with that of the other medical sciences, in the sixteenth century. In the course of the researches which were then made into the structure of the animal body, various parts of the absorbent system appear to have been brought into view, and are noticed, among other writers, by Fallopio,* who discovered the lym- phatics, connected with some of the abdominal viscera, and by Eustachio,f who detected the thoracic duct. But although their descriptions, especially that of Eustachio, are sufficiently correct to enable us to identify them, as forming a part of the absorbent vessels, yet they were unacquainted with their specific nature and office, and with their relation to the sangui- ferous system. It is generally admitted that the merit of the discovery of the lacteals is due to Aselli; this discovery he made in the year 1622. While he was examining the abdominal viscera of a dog, he observed a series of vessels attached to the mesentery, which appeared to have no direct connexion with the arteries or veins, and which, from the circumstance of their con- taining a white opake fluid, he denominated Lacteals.]: He regarded them as a distinct set of vessels, exercising a specific function, distinct from that of the sanguiferous system, and he as- certained that they took their origin from the surface of the intestines, and proceeded to- wards the more central parts of the body, but it was not until the year 1651, that their ter- mination in the thoracic duct was discovered by Pecquet. § The discovery of the other species of ab- sorbent vessels, styled, from the appearance • " Observ. de Venis," lib. 3., in Op. p. 532 ; first published in 1561. We may add the names of Fabricio, Piso, and Gassendi, who appear to have seen certain parts of the lymphatics, although they were not aware of their specific nature. See Bar- tholin, de Lact. Thor. c. 2 ; and Mascagni, Vas. Lymph. Hist. Proleg. sub init. t De Vena sine pari, Antig. 13, sub finem, in Opusc. Anat. •, first published in 1564. See Haller, Bibl. Anat., p. 224: also Douglas, Bibliog. Anat., p. 99. t Disserlatio de Lactibus ; first published in 1627. See Barlholin, 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 venat lactex, lately discovered by Aselli, which convey the chyle to the liver, and figures them in tab. 4. fi?. 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 Ilaller, and the most distinguished anatomists of the last century, that the lymphatics were detected, in the first instance, by lludbek ; that Bartholin had some intimation of the dis- covery, that he then took up the subject, and pursued it much farther than it had been done by Rudbek * There is a third individual, on whose behalf a claim of priority has been made, which pos- sesses at least considerable plausibility. We are informed by Glisson, that an English ana- tomist of the name of Jolifte distinctly re- cognized and exhibited the lymphatics of many of the abdominal viscera, previously to the alledged discovery of either Rudbek or Bar- tholin.t 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 IJewson, were among the most important in their re- sults, while we are indebted to Cruikshank, and still more to Mascagni, for their minute descriptions and accurate representations of the absorbent system, in all its parts, and with its various relations and connexions.^ * El. Phys., ii. 3. 1 ; Bibl. Anat., t. i. §. 378 and 415; and Not. 4. ad $.121. Boer. Pral. 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 Auat. 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 ; Mrascagni, Vas. Lymph. Corp. With respect to the minute anatomy of the lacteals, we are informed that they originate from certain small projecting bodies, termed villi, which are attached to the interior surface of the intestines, styled from this circumstance the villous coat. These villi are described as consisting of a number of capillary tubes, which terminate with open mouths, and that by the union of these tubes the branches of the lacteals are composed, which are suffi- ciently large to be visible to the eye. We must remark, however, that although these villi, as constituting the mouths of the lacteals, have been minutely described, and even figures given of the appearance which they exhibit in the microscope, yet that considerable doubt is still entertained of their existence, and that they are even entirely discredited by some anatomists of the first eminence.* Upon the whole we may conclude that the opinion, which has been generally adopted, respecting the capillary termination of the lacteals, is somewhat theo- retical, rather derived from the supposed ne- cessity of such a formation to carry on the functions of the vessels, than from any actual observations that have been made upon them. When the lacteals have acquired sufficient magnitude to become visible to the eye, they are seen to proceed along the mesentery, the small vessels running together to form large branches, and these again forming others that are still larger, until the whole of them unite into a few main trunks, which terminate in the receptacle at the lower extremity of the thoracic duct. During their progress, the small vessels Hist., p. 1. §. 7. art. 8. tab. 1. fig. 7; Sheldon/on the Absorb. Syst. ch. 2. pi. 3, 4, 5; Santorini, Tabulae, No. 13. fig. 3; Magendie, Physio!, t- "• p. 158 . . 0. The translation of Mascagni 's work, with copious notes by Bellini, may be advantageously consulted ; it is not accompanied by plates. For the lymphatics we may refer to Haller, ii. 3. 2 ; Meckel, Diss. Epist. de Vasis Lymphaticis ; Hew- son, Enq., ch. 3. pi. 3, 6 ; Mascagni, ps. 1. sect. 7. tab. 4 et seq. ; Cruikshank, on the Absorb., p. 148 et seq. ; Sosmmering, 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." Sammer- 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 r^9*O- ' •' ! ' '" ^ ACALEPH7E. Rhigostoma caruleu. hollow; and, when connected with the appen- dages of the digestive cavities, or when they have a vesicle at their base, very extensile. Several genera have suckers at the extremities, and along the sides, of their tentacula, by means of which the passing prey is seized. The tenta- cula which are extensile seem to be projected by the forcing of water into their internal cavity, by the contractions of the vesicles at their base. The extent to which the filamentary organ is thus lengthened, in some species, is very extra- ordinary.* It seems to be shortened again by means of the contractions of circular muscles, which force back the water into the vesicle, and of longitudinal muscles which draw it in. Peron thought that some of the pulmograda were furnished with internal air-bladders ; but Eschscholtz, on directing his attention to this point, satisfied himself that what Peron had taken for air-bladders were merely appendages of the gastric cavities, into which air had acci- dentally been introduced during the removal of the animals from their native element. Jn the cirrigrada, locomotion is effected Fig. 11. ila septentrionalis. * In the tentacula of some of the physograda, also, a similar extensibility exists. The lower sur- face of physalus, for instance, which itself seldom exceeds six inches in length, is provided with ten- tacula sixteen and even eighteen feet long. partly by the movements of the tentacules which hang down from the inferior surface; but chiefly, perhaps, by the action of the wind on the raised crest, with which most of these animals are provided. Immediately around the mouth are placed numerous small tubular suckers, similar to the feet of many echinoder- mata. Exterior to these there are longer tenta- cula, for the most part in a single row, and simple; sometimes branched. Neither of these two kinds of organs is very extensile. The disc from which the tenlacules hang, and the crest, are supported internally by a calcareous plate, which is the only organ of the kind in the whole class of acalephse. It somewhat re- sembles in structure the calcareous axis of retepora, being cellular and porous. Its nu- merous cells are filled with air, which renders the whole animal so buoyant that it floats on the surface of the water, and is wafted along by the winds. In velella (Fig. 11.) there are two plates, one placed horizontally, the other perpen- dicularly upon the upper surface of the former. They are marked with lines of growth, enlarg- ing from within outwards, like the extravascular shells of the mollusca. The perpendicular plate in velella supports the crest, which stands upright, and exposes a large surface to the wind. Rataria (Fig. 12.) has its crest provided with strong muscular bands run- ning perpendicularly. It lies on the surface of the water, with the crest stretch- ed out, so that its whole side touches the water. When it is alarmed, the crest is suddenly contracted, and the centre of gravity is so al- . tered in consequence, that ^tana cordata. 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 Acalephae. Even Eschscholtz,* who devoted so much atten- tion to their anatomy, could not see nerves in the largest that he examined. But in Cydippe, according to Dr. Grant/f there is a structure which can be regarded only as belonging to the nervous system. It consists of a double transverse filament of a milky white colour, running round the body, near its surface, at a short distance above the mouth. The two cords of which this filament is composed unite in the middle of each of the spaces between * System, p. 19. t Trans. Zool. Soc. of Lend. i. 10. ACALEPH7E. 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 acalephae also manifest, by their con- tractions, a certain degree of sensitiveness. Several of the ciliograda alter the shape of their general mass when touched. In physalus the crest appears to be more sensitive than any other part. Many species, particularly of the pulmograda, give no signs of their feeling even the deepest and most extensive wounds of their discs. But it was observed by Spallanzani, that, by friction, and by punctures of the mus- cular membrane of the disc, the movements of contraction and dilatation could be excited in medusa?, which, having been kept in a dry place during twenty-four hours, had discon- tinued their ordinary motions, and had lost nearly two-thirds of their bulk by the running out of their contained fluids.f * Isis. Nov. 1819. t Professor Ehrenberg has very recently attempted to shew that medusa aurita is possessed of eyes, in the form of minute red points, which are seen on the surface of the eight brown-coloured masses set round the circumference of the disc. These masses, according to his observations, consist each of a yel- lowish, oval, or cylindrical little body, which is at- tached to a small and delicate pedicle. This short pedicle arises from a vesicle, in which there is placed a glandular body, unattached, presenting a yellow colour when viewed with transmitted light, a white colour under reflected light. It is upon the dorsal aspect of the yellow head, which surmounts the pedicle, that the well defined red point is seen, which Ehrenberg considers as an eye. HP. compares the eyes of medusa to those of some rotifera and entomostraca. The glandular body situated at the base of the pedicle, he regards as an optic ganglion, which, he seems to have satisfied himself, is connected with two filaments that decus- sate one another at about the middle of their course. These he describes as forming part of a nervous III. Digestion. — The structure and action of the organs concerned in the function of digestion in the acalephae are still involved in much obscurity. Even in the large and fre- quently examined physalus, it is difficult to ascertain the functions of the various parts in a satisfactory manner ; and, accordingly, there exists so much difference of opinion amongst anatomists with regard to them, that some will not even admit that it has a mouth, while others assign to it both a mouth and an anus, as well as ccecal prolongations of the stomach. Eschscholtz concluded, from his numerous ob- servations on the living animals, that, in all the physograda, the digestive organs consist merely of absorbing tubes or suckers, all of which are simple, and pendent from the inferior sur- face. He seemed to think that the action of these filamentary organs was analogous to that of the roots of plants ; — that they were en- dowed with an endosmosic power, which en- abled them to imbibe nutritious matter from the water. However this may be with regard to the simple filaments, or cirri, it appears pro- bable that the suckers are provided with orifices at their extremities, through which proper ali- mentary matter passes into the interior; for several observers agree in stating, that both the physograda, and the diphyda apply their suckers to the bodies of other animals, and re- main adherent to them for some time, during which they seem to take up some nourishing matter. Eudoxia has only one sucker. Messrs. Quoy and Gaimard have described in detail the singular filamentary organ which bears these suckers in diphyes. Generally it is seen, at first, only as a shapeless opaque mass, of a reddish colour, lying contracted within the swimming cavity. But, gradually, it is ex- tended, and then there are perceptible, along the whole of one side of a fine transparent tube, numerous suckers, of a lengthened form ; each is covered by a very delicate bell-shaped case, and has its base surrounded by groups of mi- nute vesicles, which are, probably, the ovaries. From the base there arises also a little tenta- cule or filament, susceptible of very great elongation, and which sends off many secon- dary filaments.* The digestive organs of the ciliograda are less dubious. In these we find uniformly a straight alimentary canal with two orifices, the mouth inferior, the anus superior, in the ordi- nary position of the animal. In some species there are lips formed by short and broad folds of the integument, four in number, and very sensitive. In cydippe, Dr. Grant found these lips capable of rapid extension and retraction. circle placed, throughout the greater part of its course, immediately along the bases of the row of tentacules that surround the disc, so as to form, as it were, the outer wall of the circular vessel, or ap- pendage of the intestinal cavity, which runs round the margin of the disc. The same observer de- scribes another nervous circle, composed of four ganglion-like masses, disposed around the mouth, each being in connexion with a corresponding group of tentacules. (Ehrenberg, in Miiller's Archiv fiir Anat. Physiol., &c. 1834. p. 562.) * Ann. des Se. Nat. x. 8. 42 ACALEPHvE. The mouth is large, the oesophagus straight and wide; the stomach is, for the most part, of an ovate form, the intestine passes in a straight line, and with a uniform diameter, to its ex- tremity. The anus has a prominent circular margin in cydippe. No absorbent vessels can be seen arising from the gastric cavity. In many species, the alimentary canal is so large as to occupy the greater part of the interior of the body. \\ hen 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, salpse, &c., have been found in the stomachs of cihograda. 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 rhizostonm. By injecting milk into its gastric cavity, the canals in its arms, and their oscules can be rendered visible ; and it is then discovered that from the minute oscules, which are situ- ated in indentations along the margins of the arms, small vessels proceed inwards, and, uniting in twos and threes together, open into one large canal which runs through the middle of each arm. These arms are large, fleshy, foliated organs, eight in number; each of which has a triangular shape. The eight canals above mentioned unite two and two, so as to form four great trunks, which open into a large central cavity, — the only one in the body. This cavity is situated at the base of the central process pendent from the lower surface of the disc. The base, in rising upwards, enlarges into four fleshy columns, which lose them- selves in the disc. It is between these four fleshy columns that the cavity of the stomach is placed. The intervals between the columns would form so many openings into this cavity were they not closed by a fine and plaited membrane, which bulges outwards when the stomach is filled. From the circumference of the stomach, at equal distances, sixteen vessels arise, and run directly towards the margin of the disc. These vessels may be regarded as arteries, and will be hereafter described along with other structures more nearly resembling the parts of a circulating system. But Cuvier* was disposed to consider them as cceca ; although he ad- mitted that he could discover no other vessels fitted to discharge the functions of arteries. He remarked that if we regard them as arteries, we must look upon the little vessels which lead from the appendages or arms to the central cavity, as veins, or as lymphatics; and then we might say that the sea is as a stomach to the rhizostoinu, 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 proved \ 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. la others it is surrounded by a ring of conside- rable density, in which muscular fibres can be distinctly seen. In medusa aurlta, 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. des Sc. Nat. xxviii. 24!(. ACALEPIl^E. 43 stance of fishes being found in them.* From each sac, four vessels arise, which run out- wards to the circumference of the animal. Other species (e. g. medusa capillutit) have the four gastric sacs in free communication with one another ; and, frequently, (e. g. in petagia, chrysaoni., and a'gina,) 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 tiinu ; and of branched vessels in medusa and sthenonla. 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 Cari/bdca war- supiulis, (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 tubi'S.J In Aitrelia phosphorea, (Lam.) ( Pelagia, Esch.) which formed the principal subject of Spallanzani's observations on the acalephae, there are four groups of membranous tubes, convoluted, and resembling in structure the intestines of vertebrate animals. Although he did not trace their connexions, Spallanzani appears to have regarded them as truly parts of the alimentary canal. He observed that they exhibit a peristaltic motion, both in the water and in air, which can be increased by the application of stimuli.§ The food of the pulmograda consists of various marine animals — -small fishes, mollusks, * Gaede, Beytriige zur Anat. iind Phys. der Medusen. t Ann. des Sciences Nat. xxviii. 251. | Eschscholtz, op. cit. Travels loltz, op. < , 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 acalephae. But perhaps the peculiar apparatus of radiating vessels connected with the gastric cavities in the pulmograda, and the aquiferous canals of the ciliograda, which seem to per- form nearly the same functions as the vascular system of higher animals, may be conveniently and properly considered under this head. In the physograda, Eschscholtz saw what he considered as the rudiments of a circulation ; namely, distinct vessels arising from the roots of the tentacula, and ramifying on the in- ternal surface of the air-bladders ; but it does not appear that he traced these further, or that he saw the movements of a fluid within them. The vessels in the ciliograda, within which a fluid is seen to move, are situated chiefly beneath the cilia-bearing arches. This fluid is supposed by most modern anatomists to be merely water ; but by some it is regarded as a peculiar fluid, the product of the animal's digestive powers. If it be water only, the canals in which it moves must be considered as being analogous to those of the aquiferous system of other classes of invertebrate animals, which has been so fully illustrated by the re- searches of Delle Chiaje,* and which is pre- sumed to be subservient to the respiratory function. The vessels in question arise in Beroe 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 Vcrtebre, 4to. Napoli, 1823-25. 44 ACALEPHJE. the other. They then terminate in another annular vessel, which surrounds the mouth. In their course they give off numerous branches. From the oral circle of vascular structure arise two large vessels, which run along the walls of the gastric cavity, and ap- pear to unite with the other circle at the anal extremity. These last Eschscholtz regarded as veins, and the eight external vessels as arteries. He supposed that the veins, passing along the walls of the stomach, absorbed the nutri- ment, and then carried the circulating fluid to the cilia for aeration. In the course of his observations on the Beroe 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 cesium naiadis, Eschscholtz thought that he saw the system of vessels more dis- tinctly than in any other of the acalephae. He thus described it: " From the base of each of the two tentacules, a vessel takes its rise, and goes towards the bottom of the stomach. Here the two vessels unite, and form a little vascular circle around the water-canal (intestine). From the upper margin of this circle, four straight vessels arise, which go towards the two rows of cilia-bearing organs placed on the dorsal sur- face. Under these they run, two in one di- rection, and two in the other. At either extremity of the body, these unite with certain vessels running superficially along the sides, and which complete the circulation by entering the first set of vessels just before they begin to run beneath the ciliated organs. All these vessels are simple canals, of the same diameter throughout, without any visible branches. They contain a colourless watery fluid, in which mi- nute yellowish globules are seen to move. In the vessels which arise from the bases of the tentacules, the globules mount upwards ; they assume a rotatory motion in the vascular circle; and, in the four dorsal vessels, they seem to move, some in one direction, others in the other. It is probable that what appears to the eye as one vessel, is, in reality, composed of two vessels, running parallel and close together."f Seeing that the radiating vessels which arise from the gastric cavities of the pulmograda seem to carry out the nourishing material to all parts of the body, and that they are, in some species at least, connected with other vessels which form a complete circle, we are disposed to class them under this head along with the vascular structures already described. The exact analogies of their functions, however, have not yet, we conceive, been distinctly made out. From the stomach of rhizostoma, formerly described, sixteen vessels arise, and pursue a straight course outwards to the margin of the disc, near which they all enter, at equal dis- * Mem. Wern. Soc. iii. 401. t Op. cit. p. 14. tances, a circular vessel, which passes com- pletely round the circumference of the animal. Four of the radiating vessels correspond with the four fleshy pillars of the process supporting the arms, and there exists on the internal sur- face of each of these pillars, a groove, which establishes a direct communication between the corresponding vessel, and one of the large vessels of the central process. The other twelve are distributed by threes in the intervals between the first four, and arise from those parts of the stomach which are closed by the plaited membranes. The space intervening between the circular vessel and the margin of the disc is occupied by an innumerable multi- tude of little vessels which form a net-work like the finest lace.* In medusa aurita, there are also sixteen radiating vessels, four of which arise from each of the four sacs, into which the gastric cavity in this species is divided. Two of the four vessels in each group are simple, the other two are several times bifurcated ; both the simple main trunks and all the 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 .f Carus remarks with regard to the circular vessel, that " it may be considered as an extremely simple rudiment of the great cir- culation of superior animals, in case we view the radiating as chyliferous vessels."}; V. Respiration. — It is probable that the air- bladders of the physograda, the swimming organs of the diphyda, and the cilia of the ciliograda are all subservient, in a greater or less degree, to the respiratory function, as well as to locomotion. The vessels in the last men- tioned class, which have been described above as appertaining to the circulating system, are regarded by some as respiratory organs ; and by Lamarck were compared to the tracheae of insects. They have been called aquiferous trachea;. Those who consider them in this light believe that they are open at two points, so as to admit the circumambient fluid to pass freely through them. The most recent and accurate observations, however, leave it doubt- ful whether this really takes place in the ciliograde acalephae. With regard to the pulmograda, several parts and organs have been pointed out by different observers as being, in all probability, the seats of the respiratory function. Cuvier thought that the delicate plaited membranes which exist between the fleshy pillars of the central process in rhizostoma, and which form in part the walls of the stomach, might be re- garded as the organs of respirarion. Eisenhardt supposed that he saw them in certain tentacu- lated processes attached to the membranous partitions which divide the gastric sacs of some species from one another ; while Gaede looked upon the four small sacs which overlie the * Cuvier, Jonrn. de Phys. xlix. 4U8. t Garde, Anat. der Medusen. t Carus, Couip. Anat. (by Gore,) ii. 266. ACALEPH7E. 45 gastric cavities in medusa aurltu as subser- vient to the same function. These sacs com- municate directly with the gastric cavities by means of openings in the membranous par- titions whicli 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 acalephse 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 acalephse. But, for the most part, a slight touch of any part of their surface, and chiefly of the pendent tentacula, is followed within a few minutes, at most, by a burning pain, redness, swelling, and some- times even a vesication, of all that portion of the skin which touched the animal. Sloane said of the physalus, (" what the seamen call caravels, or Portuguese men-of-war,") " They burn violently — they do suck themselves so close to the skin that they raise blisters, and cause sometimes St. Antony's fire."* Even on our own coasts, severe cases of inflammation of the skin are occasionally seen, which have been produced by the irritation received during bathing from some of the larger pulmograda. In physalus, the stinging property seems to reside chiefly in the fluid with which the ten- tacula are filled. It continues to act power- fully even after the organs containing it have been detached from the body. And not only so, but it is said by some observers that its peculiar properties are so permanent, that vessels in which the animals have been placed must be washed several times in water, and carefully scoured before they can be used without inconvenience. On one occasion it was found that linen, which 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 acalephae 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 medusae 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 tin's fluid being mixed with other fluids, as with fresh and salt water, and especially cow's milk, imparts its lumi- nousness to them ; that when spread over solid bodies it continues to shine for several minutes; and that in it there generally exists that irri- tating substance which produces the stinging effect. Spallanzani applied some of this fluid on two occasions to the tip of his tongue. It excited a burning sensation, which lasted more than a day. A similar feeling, but much more painful, followed the accidental application of a singledrop of the same fluid to the conjunctiva.f In most of the acalephae, the external cover- ing is very fine, smooth, and delicate ; but sometimes it is granular, or even warty. It does not appear that these differences in its structure have been observed by any naturalist to be connected with corresponding differences in the power of emitting light. (See LUMI- NOUSNESS, ANIMAL.) VII. Generation. — The organs of this func- tion cannot always be satisfactorily ascertained. This may, in a great measure, be owing to their minuteness and transparency when not in action. Ovaria and oviducts, however, are dis- tinctly seen in several species; but no other organs connected with the generative function have hitherto been discovered. According to Eschscholtz, the ovaria in the physograda con- sist of several groups of vesicles and filaments, * Journ. Roy. Inst. 1831, p. 205. t Travels in the two Sicilies, iv. 250. 46 ACALEPH/E. Fig. 13. 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. Qnoy 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.* 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- A portion of the tremity) many minute ovigerous filament hexagonal corpuscules ; of Diphyes much magnified. 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 capiltata, and M. aurita, and by Eschscholtz in some species of ci/anca, st/ie- 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.^ 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, arid have locomotive powers, like the ova of the purifera and polypi feru.^ The colours of the acalephae 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 acalephae. 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 cyane. 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 tin's 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 membramform appearance, and is characterized by an aug- mentation of thickness and of density : the third period is characterised by still greater density and the presence of vessels. Stoll believed that these membranes might become organised in twelve, nine, or even eight days after the inva- sion of the disease. Home believed that vessels might appear in twenty-four hours. In the fourth period, the membrane loses some of its thickness, and every day assumes more and more of the appearance of cellular tissue ; and when perfected, there is not only identity of appearance between cellular tissue and these membranes, but also, according to Laennec,* identity of use, and even of disease, except that this tissue very rarely contains adi- pose matter, f Nothing in our subject is more curious or more important than the organisation of these membranes ; their vessels are thin, delicate, and similar to those of the pia mater ; their form and their direction are extremely simple ; they are not tortuous, and they proceed, usually, in fasciculi, almost like the lymphatics of the extremities. We may easily convince ourselves that their formation is sometimes very prompt, by the perusal of the following case. A por- tion of strangulated intestine, which, after the incision of the herniary sac, did not present many bloodvessels, was examined after the death of the individual, which occurred in twenty-nine hours after the operation, by Sir Everard Home : he found the portion of in- * De 1' Auscultation Mediate, tom.ii. p. 293. t Laennec states that he has " quelquefois " seen fat developed in these cellular laminae. Loc. cit. — ED. testine which had been strangulated profoundly inliamed, 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. [Jowever small be the canal, it is these fibrous fasciculi which should, by thinning, form the tunics of the bloodvessels." These delicate observations have not, so far as I know, been confirmed by other observers : those authors who have spoken of newly deve- loped vessels, among whom we may name Hunter, Monro, Soemmering, do not speak of this mode of development. Hunter and Home explain it differently; they say there is at first a formation of small ampullae, containing only a colourless fluid : second, a union of these ampullae, and production of a vascular net- work, not yet supplied with blood : third, an inosculation between the newly developed vessels, and those of the inflamed membrane, and next the ingress of blood. Beclard was of the same opinion.f Gendrin thinks that the new vessels are developed by the action of the primitive vessels ; he says, " that the blood is excreted by the adjoining capillaries, opening into the soft and fibrinous tissue deposited in the inflamed part; this blood becomes concrete, and the vascular impulsion, a tergo, being con- tinued, new blood is pushed into it and hollows it. Thus the little vascular rudiment is pro- longed into an irregular, flexuous, and unequal stria, which meets another and unites with it, continuing in this way to prolong itself into the least resistent portion of the fibrinous de- position. "\ To some extent the opinions of Laennec and * Loc. cit. t Anat. Generate, p. 195. | Hist. Anat. des Infhun. torn. ii. 6 1 >')3 and 1571. E 2 ADHESION. Gendrin are alike ; they believe that the forma- tion of the new vessel consisted in this, that the little clot was perforated, and that it was pene- trated by liquid blood. The experiments of Brande* would, however, lead to a different conclusion ; he shewed that the air contained in the blood had much in- fluence in the formation of bloodvessels. This air is carbonic acid gas, and its quantity appears to be nearly equal in the two kinds of blood ; being estimated at a cubic inch for every ounce of blood. This gas maybe separated from the blood by the air-pump, and it escapes with a kind of bubbling or effervescence, causing the ascent of the mercury in a barometer attached to the apparatus. It has been remarked that during the coagu- lation of the blood, a large quantity of carbonic acid gas escapes; this coagulation, observed under the microscope, has shewn that the gas, by escaping in all directions, forms a net-work of canals, the branches of which anastomose with each other ; and that this net-work pre- serves its form after desiccation. It has also been established that it is this gas which forms those canals in coagulated blood ; because, if by means of the air-pump we deprive the blood of it, before it is coagulated, they do not occur. Sir E. Home has even injected the vessels which were developed in the coagulum soon after the blood was taken from a vein. If the formation of new vessels occur even in a coa- gulum of blood removed from the living body, but preserving still a certain quantity of its heat, and of its vitality, with more reason might we expect that a similar phenomenon should obtain during life : and this fact has been de- monstrated by experiments performed on a rabbit, in which had been produced a hemor- rhage from a small branch of the mesenteric artery : after twenty-four hours, the coagulum which was formed was injected. The formation of vessels in coagulated blood, by means of the carbonic acid gas which tra- verses it in all directions, is in perfect accord- ance with the observations which have been made by M. Bauer upon germinating wheat, which were instituted for the purpose of shewing the influence of the globule of air. These globules are manifested below a bud of mucilaginous substance; they push it forward, elongate it, and thus form a filament. I do not, however, believe that either of these theories correctly explains the pheno- menon. It was for a long time believed that false membranes were never organised ; that nature had given to the parts of our economy an almost unlimited power of development, but not the faculty of communicating life to the products of the circulation; that false mem- branes appeared to be organised only because they constituted a kind of frame-work through which vessels from the inflamed tissue might be prolonged: ulterior observations, however, have shewn that these media are really or- ganised. We have no general rules as to the time when such organisation shall commence. It seems to be dependent upon inexplicable individual dispositions. It may, however, be remarked, that the greatest analogy exists be- tween the mode of development of vessels in these media of adhesion and their mode of production in the membrane of the yolk in the chick, saving always this remarkable circum- stance, namely, the inconstancy, the irregu- larity of the work of organisation in the former, and, on the contrary, the constancy and the regularity of the occurrence in the latter case. These media are in fact secreted by a tissue, the vitality of which is exalted to a certain extent, and it appears to impress upon the pro- duct of its secretion a commencement of vitality, as in generation. All these circumstances ap- pear to me to demonstrate that these vessels are the product of a spontaneous generation — a true epigenesis ; so indeed, to a certain extent, thought Hunter. 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.* He carefully observed the changes which occurred in an ulcer of the leg. By using a lens which enlarged objects eight times, he saw that granulations were formed in the fol- lowing manner : 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 organisable matter by which it is surrounded ; and at a later period we may discover vascular filaments attaching the ad- herent portion of the new tissue to that upon which it has been developed. These filaments are as much more evident as the adhesion is more immediate : of this we may very easily assure ourselves by cutting transversely two portions of digestive tube which have become to a certain extent adherent by their external tunic. The adhesion may be already very solid at the points where contact is so imme- diate that we can scarcely distinguish the in- terposed matter. Very delicate red capillaries creep through this matter, whilst perhaps at the distance of some lines, and even at the centre of an already organised point, the contact having been less immediate, a plastic layer of one, two, or more lines in thickness, may be seen uniting the surfaces, but not presenting either the solidity or the organisation of the exces- sively thin layer which adjoins it. When these adhesions have existed for a cer- tain time, the serous structure completely dis- appears. This destruction of serous membranes at the adherent point is very evident around ADHESION. hernia 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 hernise thus circumstanced have been described as having no hernial sac. This sac has, however, originally existed, but has disappeared by the adhesions which have been formed between it and the displaced organs, adhesions by which the cellular tissue which replaces the serous membrane has been deve- loped. If we consider these adhesions in relation to their frequency in the serous cavities, we see that they exist most frequently in the pleura, existing in nearly half the adult bodies ex- amined. After the pleura comes the perito- neum, then the pericardium ; those of the tunica vaginalis are less common, but the arachnoid is, of all serous membranes, especially relative to its extent, that where these adhesions are most unfrequent. The absence of mobility appears singularly to favour this phenomenon : thus in the pleura they most frequently occupy the superior parts, and in the peritoneum most frequently occur between the viscera forming a hernia, and be- tween the convex surface of the liver and the diaphragm. The membranes between which such adhe- sions occur, must usually, of course, be in intimate relation, the one with the other during the time when the process is in progress of accomplishment, though now and then the distance is considerable ; but they may after- wards become separated to great distances : those cellular bands which are so commonly seen in the thorax are evidences of this fact. Some circumstances tend to demonstrate that these bands in serous structure may at a certain period of their existence be absorbed and disappear, and the secreting surface be reproduced. M. Ribes states that occasi- onally we do not find any trace of such bands, nor any adhesion in the peritoneum of persons who have had penetrating wounds of the ab- domen. Beclard examined an insane person who had several times stabbed himself in the abdomen. At the points where the more recent of these wounds had been inflicted considerable adhesions were found; beneath the older cicatrices no vestige of adhesion was found. A case of artificial anus occurred in the practice of M. Dupuytren, by which faecal matter passed during twelve days. The pa- tient died at the end of seven months. At the examination after death, it was found that the portion of intestine in which the accidental opening had existed, was distant from the ab- dominal cicatrix between four and five inches. A very attenuated cellular band extended from the cicatrix to the portion of intestine. Doubt- less a short time would have sufficed for the absorption of this band, when the intestine would have been set at liberty and the serous surface restored. In the course of lectures which Bichat de- livered only a few months before his death, he maintained that adhesion was never pro- duced between mucous surfaces, and that con- sequently the cavities lined by this tissue were never obliterated. Few statements have given rise to more extensive discussion than this ; few discussions have up to the present moment been attended by less satisfactory results. In his first dictum I believe he was clearly right, in the second as clearly wrong. Mr. Hunter's opinion was in accordance with that of Bichat : he says, " that in all the outlets of the body called mucous membranes, the order of inflammation differs from that which occurs in cellular membrane, or in cir- cumscribed cavities. In these latter adhesive inflammation is immediately admitted to ex- clude, if possible, suppuration." In internal canals, where adhesions would in most cases prove hurtful, the parts run immediately into the suppurative inflammation, the adhesive in- flammation being in common excluded.* Mucous membranes, when unchanged by disease, are not capable of becoming adherent the one to the other, and the reason of this is simple. 1 have already stated that no per- manent adhesion can occur in the living body without the intervention of a new tissue, which at a certain indefinite or undetermined period of its existence becomes organized. A pseudo-membrane of considerable extent may be thrown out upon an inflamed mucous surface; but this membrane, 1 apprehend, never becomes organised, and union between mucous surfaces cannot therefore be permanent unless some other agency be called into action. But, as soon as inflammation has destroyed the characters from which these membranes derive their name ; when the mucus, which like an inorganic layer appears to oppose itself so successfully against immediate contact, thereby preventing the organization of the effused mat- ter, no longer exists ; when the cellular element which forms the basis of this membrane is developed, then adhesion by means of the union of granular surfaces is effected with the greatest facility ; of this we have evidence in most of the mucous canals. It is not rare, for instance, to meet with complete obliteration of the vagina, of the cystic duct, and so on. It is stated very generally that the opinion of Bichat is entirely unfounded ; that inflam- mation of the vagina is followed by complete occlusion, without destruction or transforma- tion of the mucous membrane, and that similar effects may occur in the Fallopian tubes, the uterus, and other mucous canals. That these are produced is perfectly true, but never until the disorganization to which I have alluded has occurred. It is maintained triumphantly as a con- firmation of the opinion that no transformation occurs, that when these adhesions are sepa- rated, we have the healthy mucous membrane performing its functions as before. This, how- ever, is not the case ; the membrane is essen- tially different, and it is not without difficulty that we can overcome its tendency to enter into adhesion again. That a membrane is pro- duced, which performs functions analogous to * Loc. cit. p. 305. ADIPOCERE. the primitive membrane, is true. If we ex- amine a fistulous canal which has existed for a certain time, we find it invested by a mem- brane similar in appearance, and performing1 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. Sb'emmering, 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 (In Conroiirs sur le Croup. t Diet, flcs Sc. Med. toin. 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 penchondrium, 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 AUTERY, 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. Besoet, De inodo quo natura soliitum redintegrat. 4to. Lugd. Batav. 1763. (Rec. i i Sandifort Thes. Diss. vol. iii. p. 147.) Spallanxani, Prodrome, &c. sopra la reproduzione animali, 4to. Modena, 1768. Ejus, Upuscoli de fisica, &c. 2 vo'. 8vo. Modena. 1776. Et/ting, De consolidatione vulnerum. 4to. Argent. 1770. Moore, On the process of nature ia the filling up of cavities, healing wounds, &c. 4to. Lond. 1789. Nannoni, De Smiilium partium corp. hum. constit. regeneratione. (In Roemeri Delect. Opusc. Ital. vol. i.) Arnemann, Versuclie ueber die Regeneration an lebenden Thieren. 8vo. Gottinj;. 1782. Murrai/, 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 Mcdendi, pars v. & vii.Svo. Vienna, 1768. Hunter on the Blood, Inflammation, &c. Bichat, Anatomic Gen. Beclard, ditto. Breschet, Diet, de Med. art. Adherence. Cruveilhier, Diet, de Med. et Chir. Prat. art. Adhesions. Laennec, De ['Auscultation Mediate, torn. ii. pp. Ill, et seq. Brande, in Phil. Trans. 1818. Gendiin, Hist. Anat. des Infl. passim. 2 torn. Paris, 1826. Andral's Pathological Ana- tomy. Home on Ulcers. 8vo. Lond. 1801. ( Benjamin Phillips.} ADIPOCERE, fromadeps and ecru: 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 con verted 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 oft'al 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 Jess of a similar change ; and Dr. Gibbes (Phil. Trans. 1794) found that lean beef, se- cured in a running stream, underwent a change into fat in the course of three weeks. Fat, and the adipose parts of animals, also undergo a change in appearance and composition under similar circumstances : tallow becomes brittle and pulverulent, and may be rubbed between the fingers into a white soapy powder.* Gay Lussac, Chevreul, and some other emi- nent chemists, conceive that muscular fibre, skin, &,c. is not convertible into adipocere, but that this compound results entirely from the fat originally present in the substance, and that the fibrin is completely destroyed by putrefaction. There are cases, however, in which the conversion of muscle and of fibrin into fat can scarcely be doubted, (Annals of Philosophy, xii. -51,) 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. Tiie 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 coois; 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. — Fourcrny,Acad.Rle.des Sciences de Paris, 1787. Gibbes, Conversion of animal muscle into a substance resembling spermaceti. Phil. Trans. 1794. Conversion of animal sub- stances into fatty matter. Phil. Trans. 1795. Vide also Annalcs de Chimie, t. v. 154 ; t. viii. 17 — 72 ; Crell's chemische Annalen for 179'2 and 1794 ; and John's Tabellen. 1. B. p. 35. ( W. T. Brande.) * If a portion of the- fatty degeneration of tlio liver be immersed tor 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 substince. — R. B. T. ADIPOSE TISSUE.— (Lat. Telaadipota Fr. tissu adipeux, tissu graisseujc, Germ, das Fttt, Ital. adipe. Many of the old anatomists, as Mondini, Berenger, Vesalius, and Spigelius, represent the fat (udeps vel pinguedo) of the animal body as entirely distinct from the membra na curnosu, or cellular membrane. The separate existence of a proper adipose membrane, however, si- tuate between the skin and the filamentous tissue, or membrana curnosa, was first taught by Malpighi, then distinctly maintained by De Bergen and Mor_ragni, 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 sacculi, and by Morgagni under that of sacculi pingnedi- nost. 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- * Osteologiu Nova, Lond. 1691, and Obs. Nov. ile Ossibus, Auist. 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 stated in the following manner. First, the vesicles of the adipose membrane are closed all round, and, unlike the cellular tissue, they cannot be generally penetrated by fluids which are made to enter them. If the temperature of a portion of adipose membrane be raised by means of warm water to the liquefying point of the contents, they will remain un- moved so long as the structure of the vesicles is not injured by the heat. If again an adi- pose packet be exposed to a solar heat of 104° Fahrenheit, though the fat be completely lique- fied, not a drop will escape until the vesicles are divided or otherwise opened, when it ap- pears in abundance. The adipose matter, therefore, though fluid or semifluid in the living body, does not, like dropsical infiltra- tion, obey the impulse of gravity. Secondly, the adipose vesicles do not form, like cellular tissue, a continuous whole, but are simply in mutual contiguity. This arrangement is de- monstrated by actual inspection, but becomes more conspicuous in the case of dropsical effu- sions, when the filamentous tissue interposed between the adipose molecules is completely infiltrated while the latter are entirely unaf- fected. Thirdly, the anatomical situation of the adipose tissue is different from that of the filamentous tissue. The former is found, 1st, in a considerable layer extended immediately beneath the skin ; 2dly, in the trunk and ex- tremities round the large vessels and nerves ; 3dly, between the serous and muscular tissues of the heart ; 4thly, between the peritoneal folds which form the omen turn and mesentery ; 5thly, round each kidney; and, 6thly, in cer- tain folds of the synovial membranes without the articular capsules. In each of these situations it varies in quan- tity and physical properties. In the least cor- pulent persons a portion of fat is deposited in the adipose membrane of the cheeks, orbits, palms of the hands, soles of the feet, pulp of the fingers and toes, flexures of the joints, round the kidney, beneath the cardiac serous membrane, and between the layers of the me- sentery and amentum. 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- giudo, and the latter by that of sebum. The subcutaneous adipose membrane is, when viewed as a whole, more elastic, softer, and less granular than the omental fat, and evi- dently presents the arrangement of vesicular bags much more distinctly than the omental. It is in the subcutaneous adipose membrane indeed, almost exclusively, that the vesicular arrangement can be recognized. The subcu- taneous cellular fat also contains a greater quantity of oil than the omental, which abounds chiefly in firm, brittle, granular fat. The situation where the vesicular structure of the adipose membrane is most easily de- monstrated is in the hips between the skin and the gluteal muscles, and at the flexures of the joints generally. In the former situation especially, the constituent fibres of the vesi- cular bags are tough, firm, and ligamentous, and the bags themselves are large and distinct. It is a remarkable anatomical character of the sebaceous or tallow-like fat that its distri- bution is confined chiefly to the external or commutual surfaces of several of the serous membranes ; and this arrangement presents a series of interesting anatomical analogies. Thus sebaceous fat is found on the external surface of the pleura costalis, between it and the inter- costal muscles, and between the layers at the posterior and anterior mediastinum. It is also found between the cardiac pericardium and the muscular substance of the heart, especially around the vessels of the organ. In some of the large mammalia even this circumstance is connected with peculiar anatomical appear- ances. Thus, in the heart of the dolphin (del- phinus tursio) we find the cardiac pericardium formed into broad prominent fringes, consisting- each of two folds of the membrane, between which is interposed a considerable quantity of sebaceous fat. In the same manner the several amenta, or peritoneal duplicatures in the abdo- men, may be recognized as analogous fringes containing more or less sebaceous fat ; and the omental appendages (appendices e.pipluic 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 membrane-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 vuteriu Indicci, a forest-tree of the camphor family, indigenous in the Indian Archipelago. In a species of croton indigenous in China, namely, the crotou seliiferum of Linnaeus, the stillhigia 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 a>eurites trilobn, a native of the Sandwich Islands, of the same natural family with the croton, are the candle- nuts of the inhabitants of these remote regions. It is chiefly in the subcutaneous layer that the organization of the adipose membrane has been investigated. The constituent vesicles or bags consist of firm, tenacious, ligamentous, gray, or whitish-gray coloured substance, mu- tually united by means of delicate filamentous tissue. These vesicles or sacs receive arterial and venous branches, the arrangement of which has been described by various authors, from Malpighi, who gave the first accurate account, to Mascagni, to whom we are indebted for the most recent. According to Malpighi,* the bloodvessels divide into minute ramifications, to the extremities of which are attached the membranous sacs, containing the globules of fat so as to bear some resemblance to the leaves attached to the footstalks of trees. These ve- sicular or saccular arteries are afterwards di- vided into more minute vessels, which then form upon the vesicular sacs a delicate vascular network. According to Mascagni, who repre- sents these vessels in accurate delineations, the furrow or space between each packet con- tains an artery and vein, which, being subdi- vided, penetrates between minute grains or adi- pose particles, of which the packet is composed, and furnishes each component granule with a small artery and vein. The effect of this ar- rangement is that each individual grain or adipose particle is supported by its artery and vein as by a footstalk or peduncle, and those of the same packet are kept together not only by contact, but by the community of ramifications from the same vessel. These grains are so closely attached that Mascagni, who examined them with a good lens, compares them to a cluster of fish-spawn. Grutzmacher found much the same arrangement in the grains and vesicles of the marrow of bones.* It has been supposed that the adipose tissue receives nervous filaments; and Mascagni con- ceives he has demonstrated its lymphatics. Both points, however, are so problematical, that of neither of these tissues is the distribution known. The substance contained in these vesicles is entirely inorganic. Always solid in the dead body, it has been represented as being fluid during life, byWinslovv, 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 transl licence. 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. Kaspail, 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 potdsstc, either of which has the effect of consolidating the inclosed or central portion * De Omento, Pingucdine, ct Adiposis Ductibus, p. 41. * 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 Itas- 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 (crTect.%, sebum, sapo,j and eluine, (thuwv, oleum.) The former is a solid substance, colourless, tasteless, and almost inodorous, soluble in alcohol, and pre- serving its solidity at a temperature of 176° Fahrenheit. Elaine, on the contrary, though colourless, or at most of a yellow tint, and lighter than water, is fluid at a temperature of from 63o to 65° Fahrenheit, and is greatly more soluble in alcohol. To the presence of stearine in a large proportion, the intra-serous sebaceous fat owes its solidity and firmness; whereas the elasticity and softness of the sub- cutaneous adipose tissue, and the marrow, depend upon the predominance of elaine. It is farther important to attend to the ele- mentary composition of fat. Each variety of fat consists of carbon, hydrogen, and oxygen ; and a few, as hog's lard, blubber, nut oil, and almond oil, contain a small trace of azote. The proportion of the carbon is greatest and varies in general from 7-10ths to 4-5ths of the whole. The proportion of hydrogen varies from l-10th to l-5th. That of oxygen varies from four or five parts in the hundred to 12 and 13. It appears, therefore, that fat and each of its constituent principles are a highly carbonaceous animal substance. Little doubt can be entertained that animal fat is the result of a process of secretion. But it is no easy matter to determine the mode in which this is effected . Previous to the time of Malpighi it was a very general opinion that the blood exuding from the vessels was con- verted into adipose matter. This fancy was refuted by Malpighi, who, departing, however, from strict observation, imagined a set of ducts, (duct us 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 Buysch 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, Iluysch, 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 tlie adipose vesicles; and hence it has been inferred that the arterial blood contains no adipose or olea- ginous matter. It may be doubted, however, whether facts of this kind are adequate to prove whether adipose or oily matter does not naturally exist in the blood, and both from the experiments of Chevreul, and those of Lecanu and Boudet it appears that small quantities of adipose or puriloid matter may be obtained from this fluid. M. Chevreul, for example, shows that fatty matter may be obtained from the fibrine of arterial blood ; and from a series of elabo- rate and accurate experiments, estimates the quantity of fatty matter in fibrine at from four to five per cent.* Lecanu and Boudet have also recently shown that crystals of pearly- coloured matter having the characters of an adipose substance exist in, and may be ob- tained in small proportion from the serum of the blood .f These inferences apply, according to the authors, to blood in its healthy state. In certain states of the system the blood drawn from the veins has presented serum of an opaque or milky appearance, and which has been proved to depend on the presence of adipose or oleaginous matter. Thus, indepen- dent of opaque or milky serum noticed by * Journal de Physiol. torn. iv. p. 119. t Journal de Pharmacie, 1830-33. 00 ADIPOSE TISSUE. Schenko, Tulpius, Morgagni, and others, Ilewson and several cotemporaiy 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 Ilewson, that in persons in whom the serum was opaque or milky, this depends on the presence of fat which is undergoing ab- sorption, or resumption into the system. This representation, however, was entirely conjec- tural ; and no direct proof of the fact that oil does exist in certain states in the venous blood was given till Dr. Traill, in 1821 and 1823, furnished accurate chemical evidence on the point. The inferences of Dr. Traill have been since confirmed by the experiments of Dr. Christison, who found that milky serum con- tains oleaginous or adipose matter, consisting of the two adipose principles 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- nutrition 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, ar.d 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 * E'lin. Mud. 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 fecu/a are prepared by the vegetable tissues for the nutritious stores of the vegetable during the process of development, he ob- serves that, in like manner, fat is deposited whenever the nutritious function is in excess in the animal organs. It was a singular fancy of Fourcroy that the deposition of fat in animal bodies was in- tended as a sort of vent for the superfluous and unnecessary proportion of hydrogen, since the idea is at variance with chemical facts ; and it is not less singular that such a hypothesis should receive any countenance from Blumen- bach. Carbon is the principle which predo- minates most largely in fat: and if any atten- tion is to be given to such views, the adipose tissue ought to be regarded as the outlet for superfluous carbonaceous matter, or at least carbonaceous matter in a much larger pro- portion than hydrogen and oxygen. The pro- per physiological view, however, of this ques- tion appears to be, — that as the tissues of the animal body consist chiefly of carbon, hy- drogen, oxygen, and azote united in variable proportions, and as most of these tissues either contain or seem to require azote, the adipose appears to be destined to receive whatever carbon, hydrogen, and oxygen, are not re- quired to be united with the azote, in the forma- tion of the albuminous, the gelatinous, or the albumino-gelatinous tissues. On the mechanism of the deposition of fat we possess no exact information. But various facts may tend to throw some light on the cir- cumstances under which it takes place, arid 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 Pneumatischen Phytochemip, 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 fetus 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 cancelli, adipose or oleaginous matter is deposited in the intra-osseous tissue within the cancelli, and as the vessels of the medullary membrane gradually mould the medullary canal, this oleaginous matter is most abun- dantly deposited in the interior of the cylin- drical bones. The marrow, however, is much less oleaginous, and more like a pulpy paste than it is in the adult. During the periods of boyhood and youth fat continues very sparing in the adipose tissue, and especially in the male sex. After puberty, however, it becomes more abundant, especially in females. After this period the deposition of fat depends more or less on the habits of the individual, as to eating and drinking and corporeal exertion. In general the deposition of fat becomes more copious and general after the age of forty or forty-two than previously. From these several facts it appears to result that fat is to be regarded as a secretion by the capillary vessels of the adipose tissue from the blood, and that the tissue and its vessels are to be distinguished from the fat or the matter secreted in the relation of vital agents and organic products. Upon the whole the idea of Haller as modified by Mascagni regarding the origin of the fat appears to be the most probable, viz. that, while the arteries secrete an imperfectly formed oily fluid, the thinner parts are absorbed either by lymphatics or by veins, and the residue is left in a more con- sistent and solid form. I think, in conclusion, that, taking all the circumstances already stated into consideration, it may be inferred that adipose matter, or its constituent elements exist in the blood, chieHy 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 been denominated diffuse inflammation of the cellular membrane, I 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. «. 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 die same manner, and affects, almost exclusively, the adipose tissue around the anus and rectum, and along the gluttfi 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 thesame 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 lush-coloured, and at length suppressed ; and the patient, after muttering delirium and typhomania on the second day of the attack, with subsultus teiuli- niini, 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 1 60 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. !H. 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, &c. mucous discharges, especially from the pulmo- nary and intestinal membranes, as in chronic catarrh, inflammation of the intestines, and dysentery ; 8th, long and intense heat, whether natural, as during hot summers, or artificial, as in furnaces, hot-houses, &c. ; 9th, running, riding, and every species of fatiguing exercise long-continued, as is exemplied in the case of grooms at Newmarket, Doncaster, &c. ; 10th, states of long disease, not organic; llth, night- watching and want of sleep in general ; 12th, immoderate use of spirituous liquors; 13th, habit of eating bitter and spiced or acid aliments. Yet even in these states the fat of the animal body is seldom entirely wasted. In several organic diseases, in which great emaciation takes place, a considerable quantity of fat is always found in the orbits behind the eyeball, round the substance of the heart, around the kidneys, in the colon, and in the mesentery and omentum. Thus one or both lungs may be extensively occupied by tubercles and indu- rated portions giving rise to the usual symptoms of pulmonary consumption terminating fatally, yet without removing the fat from the subcuta- neous layer of the chest and belly; and in various organic affections of the brain espe- cially, a considerable quantity of fat is found, not only in the subcutaneous layer, but at the outer surface of the serous membranes. ADIPOSE TISSUE. According to the observations of William Hunter, anasarcous dropsy is the only disease in which the fat of the adipose membrane is entirely consumed. " This disorder, when in- veterate, has that effect in such a degree, that we find the heart or mesentery in such subjects as free from fat as in the youngest children." This, however, is in some degree denied by Bichat, who contends that it is not uncommon to find much subcutaneous fat in subjects greatly infiltrated.* It is obvious that much will depend on the stage of the disease. It cannot be expected that the moment serous infiltration appears in the filamentous tissue, all the fat should be at once removed from the adipose. The process of absorption is gradual as is that of deposition ; and the infe- rence of Hunter may be regarded as nearly exact in reference to long-continued, or what he terms inveterate dropsy. It is certain, that while it is very difficult to deprive the bones of ordinary subjects of oil, those of dropsical sub- jects are the only ones which it is possible to obtain free from this substance. In certain diseases, especially those the ter- mination of which is attended with serous effusion into the cavities of the serous mem- brane, the fat is partly absorbed or may be converted into a sort of sero-gelatinous fluid. In chronic dysentery, for example, the subcu- taneous fat and that of the heart and omentum, in a great measure disappear, while in their place we find effused an orange-yellow coloured sero-albuminous fluid, of a jelly-like aspect, which coagulates on the application of heat orthe 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. Steatojna. — 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. Lipoiiia. — 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 I have seen in other regions of the body, though the contents are firmly connected together, and some filamentous threads may be seen here and there, or the tumour may even be separa- ble into masses, I have not been able to trace the distinct arrangement of cells, mentioned by Morgagni and Boyer. VVeidmann 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, (aS^w^a, pulticula, aii «9a^«, pultis genus,} and mtliceris (jUsAtxyjgK, 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. Mclanosis. — 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. (Breschet.) It is also to be noticed that it is never deposited exactly in the site of orga- nic fibres, but always between them, and very generally in the precise situation of the adipose particles. These several circumstances show that the melanose disease consists not in a de- generation or conversion into another substance, but in the deposition of a new form of matter in the manner of a secretion. In what form the melanose substance is first deposited we have few accurate facts to enable us to form a judgment. Laennec is of opinion that it is first deposited in a solid form, and afterwards becomes fluid. The former he con- siders the stage of crudity, the latter that of softening (ramollisement.) Several facts, how- ever, would lead to the conclusion, that when first deposited it was fluid, and afterwards ac- quired consistence. Thus in several dissec- tions performed by Drs. Cullen and Carswell,* the matter of the small tumours, which are supposed to be of short duration, were found to be softest, and sometimes as fluid as cream. In like manner, in a case recorded by M. Chomel, in which the disease was found in the liver in the shape of large cysts, the melanose matter was more fluid in the centre than in the circumference of the cysts. Upon the whole, if the melanose deposite be, as is supposed, an inorganic secretion, the idea of its bring poured forth from the vessels at first in a fluid or semi- fluid state is most probable, and most consis- tent with the usual phenomena and laws of animal processes. BIBLIOGUATHY. — Mnlpiyhi, de omento, pingue- dine, ct ailiposis ducttLms. Op. Omn. fol. Loud. lb'86. C. A. De Bcryen, Programing de Mem- braua CVlhilosa in Haller Disp. Anat. Select. torn. iii. Haller, Elernenta Physiologiae, lib. i. sect. 4. W. Hunter, On Cellular Merub. in Med. Obs. and Inquiries, v.ii. p. 26. Buchiene, Diss. de Adipe huniano, 4to. Ultraj. 1774. Janssen, Pin- gnedinis Animalis consideratio. 8vo. L. 13. 1784. Redhead, Diss. de Adipe. 8vo. Edinb. 1789. Vuyel, Diss. sur la graisse. 8vo. Paris, 1806. Alimer, Diss. In. De pinsjuedine auimali, 4to. Jen;t 1823. Heusinger, System di:r Histologie. 8vo. G-rimlz- maclier, De Medulla Ossium. (Rue. in Haller. Disp, Anat. vol. vi.) Lurry, Sin la graisse (Mem. Soc. II. de Mod. 1779. Kiihn, De pin°ues 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 egestlvc than in the ingest ive system. Of the defensive organs, or those which are exposed to surrounding agents, we may remark, in general terms, that although fully adequate to the demands of the infant under the circumstances of his existence, they acquire a development proportionate to his growing in- dependence of the care of others. The skin increases in firmness, and the epidermis in thick- ness ; the sebaceous follicles become larger and more numerous, and the hair is more abundant. There is a portion of the nervous system which we have every reason to consider more related with the functions which have been just reviewed, than with those of the animal life, and which might a priori be expected to bear a corresponding ratio of developement. We allude to the ganglions; they appear to be fully formed at birth, but what changes they undergo between that period and maturity we do not profess to know. In old age their tissue is found hardened, shrunken, and of a greyish colour. (Bichat.) The changes that we have next to take notice of are of a totally different character from the foregoing. They consist not merely in augmentations of size, correspondent ly 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 cTttppui 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 aiid 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 vertebrae 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 fasciae 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 is more 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 nbro-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 latterof the nervous substance intermediate to the external excitant, and that state of consciousness which we denominate sensation. We know AC.JK. 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- gisls 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 theirwork,De Penitiori Cere- bri Structur^,* 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-r * 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 still- stance diminishes after birth. Thus, in the full- grown foetus, the medulla oblongatais 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 cerebvi, is also grey at the commencement of extra-uterine life; but they lose this colour after a few weeks. In the thalami nptici and corpora striata there is no distinction of white and grey matter, the latter alone being visible. See Meckel, Manuel d'Analomie, t. ii. p. 717. Till the functions of these parts in mature age are belter understood than at present, it would be useless to speculate upon the physiological relations of the changes which they undergo in earlier periods. J Diet, de Med. et Chir. Pratique, art. Aliena- tion Mentale. 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 appli- 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 1-112 ; the brain at the former period weighing 9oz. 4dr., and the spinal marrow 45gr., while at the latter period the cerebral organ weighs 21oz., and the spinal l^dr. In the foetus of five months the propor- tion is 1-63, 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 in 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 papilla? 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, are 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 fingers, 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 of 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- mince;) the crystalline lens is less dense, but more convex in form. The pigrientum is in smaller quantity at birth than afterwards ; while the retina is thicker and more pulpy than in more ad- vanced periods. The yellow tint of the foramen of Soemmering does not become visible till some time after birth, but deepens with the progress of life, till the stage of decline, when it grows paler. It has been ascertained that perfect images are formed on the retina ; and yet for the first few days the child gives no indication of visual sensation, and when objects appear to attract its attention, they are only those which are vividly illuminated. The de- ficiency therefore must exist in the optic nerve, though we are ignorant of the organic condition on which this insensibility is dependent. We observe, moreover, that the eye is much more passive than in the adult, that it follows the motion of luminous bodies, or is fixed upon them with little or no apparent interference of the will. This muscular incompleteness, then, tallies with what we have noticed with respect to the other senses. The eye is known in its advance towards manhood to increase in the capability of adapting itself to different distances; but as we are ignorant of the mechanism made use of for this purpose, it is useless to look for cor- responding organic alterations. We must not omit to notice those appendages to the appara- tus of vision, called eyebrows, which become much more prominent as life advances, by the development of the frontal sinuses, and are therefore 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. Tims the eye and the ear attain a certain maturity of organization and function, long before the bones and muscles, which officiate in locomotion. The bones and muscles connected with the organs of sensation, and therefore partaking of the passive character, are also equally forward in their development. What is the probable final cause of this arrangement ? If all our voluntary motions were the immediate consequences of our sen- sations, as some of them undoubtedly are, such as those which close the dazzled eyes, or refuse the bitter food, or withdraw from pain- ful contact; — if all these followed directly on sensations, it would indeed be a strange ano- maly, if the systems that belong to each were not precisely on the same level of development. But this is not the case ; all the more impor- tant motions, important as it regards that world in which man exists, as an intelligent and social creature, though less so as it respects his individual being, are the results of a mental condition, no less distinct from sensation than from muscular motion. This state is desire, or as it is commonly called when the antecedent of action, will or volition. Probably no men- tal state is more simple than this, and it may follow any other. It is therefore the more necessary that it should be preceded by such intellectual changes as will give it a right direction; in other words, that it should come under the dominion of certain faculties. But in early life the faculties to which we allude are very imperfectly developed; those only have attained any thing like maturity which are in immediate relation with the senses ; such are perception, memory, association, and imagination ; while the reflective faculties, such as comparison, reasoning, abstraction, all in fact that constitute man a judicious expe- rienced agent, are rudimentary. The conse- quence is that the desires or volitions are pro- verbially vain and dangerous. Let us observe a child of seven years old ; his senses are suffi- ciently acute for all ordinary purposes, although they are deficient in precision and delicacy; he has seen many attractive objects, he has heard many wouderful stories, and tasted many exquisite delights; he remembers them vividly, he associates them rapidly, and often in shapes very different from those in which they were formerly combined. Desires follow which would prompt him to execute the most ridicu- lous and mischievous schemes. But happily the muscular system, by which alone he could accomplish them, is too immature and feeble for his puerile purposes. Here then is the final cause that we were in search of; the active corporeal functions of relation must not ad- vance beyond the governing faculty of the mind. But why, it might hastily be asked, should not the senses, the mental faculties, and the motive powers, all have been equally deve- loped ? The question is absurd, if we consider but a moment the manner by which the mind accomplishes its growth ; that its higher powers result from the accumulation of innumerable sensations, by which in fact the former are nourished and exercised. We shall now introduce a brief account of some researches upon the height, weight, and strength of the human body, at different ages, prosecuted by M. Quetelet, of Brussels. Not having room for the numerical tables, or the particular observations, from which his general conclusions are derived, we must content our- selves with a statement of the latter, and refer those of our readers who may be desirous of seeing the former, to the author himself. His deductions as to the growth of human stature are as follows: (1) the growth is most rapid immediately after birth ; it amounts in the first year of infancy to about two decimetres (nearly eight inches.) (2) The growth dimi- nishes as the child advances towards the fourth or fifth year; thus, during the second year his increase of height is only half what it was the first year, and during the third year it is not more than one-third. (3) After the fourth or fifth year, the stature increases pretty regularly until the age of sixteen, and the an- nual growth is about fifty-six millim, (two inch.) (4) After puberty the stature still increases, though slightly ; thus, from the sixteenth to the seventeenth year, the increase is about four centim. (If inch); and in the two following years, only two centim, and a half (one inch.) (5) The stature does not appear to be quite completed even at the age of twenty-five. — These observations refer only to absolute growth, but if the annual increase of stature be com- pared with the height which has been attained, it will be found "that the infant, after birth, increases in the first year by two fifths of his height; in the second by one-seventh; in the third by one-eleventh ; in the fourth by one-fourteenth ; in the fifth by one-fif- teenth ; in the sixth by one-eighteenth ; &c. so that the relative growth continually dimi- nishes after birth. In addition to these statements M. Quetelet has ascertained that the rules of growth are not the same in both sexes; 1st, because the female at birth is less than the male; 2dly, because her development is completed earlier; 3dly, because her annual growth falls short of that of the male. It appears likewise that the stature AGE. 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 Ibs.), that of females 2 kil. 91, (about 6^ Ibs.); 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 \\. This state- ment is deduced from the following table :f Maximum. Minimum. Medium, KIL. KIL. KIL. Male weight .... Female , 98.5 93.5 49.1 63.7 63.7 55.2 Male stature Female MET. 1.990 1.740 MET. 1.740 1.408 MET. 1.684 1.579 * Recherches sur la loi de la Croissance de 1'Homrne, par M. Quetelet. Annales d'Hygiene Publique, &c. t. vi. p. 89. t Ann. d'Hygiene, t. x. p. 27. To the above memoir M. Villerme has appended some extracts from manuscript notes found among the papers of M. Tenon, and written about the year 1783. They contain observations which correspond, in many re- spects, with those of Quetelet. The last researches of this industrious ob- server have been devoted to the muscular 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 t\\ enty-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 " Sui 1'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. xii. p. 294. 76 AGE in his career without passing those stages that prepare him for the cessation of his existence ; — what do we gain by such an explanation? Nothing ; for the term vital power which we employ is but a hypothetical cause, or if more closely examined, is scarcely even this; it is but an abstract term applicable to a number of actions that do not occur in the inorganic world. The vital power of a body is but the collective manifestation of its vital actions, and to say therefore that only a certain quantum of vital power is inherent in it, is but to express in other words the simple fact that those actions are circumscribed. Discarding this explana- tion, shall we say that the fact must be referred to some deficiency in the media of the being's existence; that, although the aliment, the air, the light and caloric are competent to the pro- duction of a certain degree of growth, they cannot extend it, and that, were their conditions different, the animal development would be more perfect. It is easy perhaps to suppose this, but we do not see how it can be proved, nor indeed that existing analogies favour it. On the surface of our globe there is every variety in the temperature, in the humidity, and in the electric conditions of the atmosphere, and every diversity in the articles of food em- ployed ; in more limited spheres there are the greatest diversities in these several respects produced artificially by the various occupations of mankind ; and although we find, both among races and individuals, great varieties of deve- lopment, which may occasionally be traced to some relation with the media in which they live, these varieties are by no means in propor- tion to the differences of the media, and in the majority of cases the former are independent of the latter. In the temperate zone, with a due proportion of animal and vegetable diet, man appears to attain his most perfect deve- lopment, and with however great skill he adapts these circumstances, he never surpasses a certain point, and from what we know of his physiology no great alteration in any one of the external stimuli of his existence could be tole- rated. A different proportion of the oxygen, nitrogen, and carbon in the atmosphere, we know full well to be noxious ; a larger or smaller quantity of aqueous vapour suspended in it will occasion many well-known maladies ; the same may be said of alterations in the ba- lance of the electricity that surrounds us. Great extremes of heat and cold may be borne for awhile, but it is obvious that they are not so well adapted to a healthy state of the system, and therefore to its growth, as intermediate de- grees ; and consequently it is not easy to con- ceive any degree either above or below these limits consistent even with existence. Fami- liar enough also are we with the effects of full and sparing, of simple and mixed dietetics, and with the fact that between certain well- known bounds lie the salutary quantities and qualities. From all which it appears suffici- ently evident, that we cannot conceive any difference 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 subject of some progressive changes. It is the stature only that is stationary, for this depends on the skeleton, which ceases to lengthen before the period we speak of. But the capability of powerful and prolonged muscular exertions increases for some years; there must consequently be a change in the muscular tissue. The intellectual faculties have not attained their maximum, although we AGE. 77 do not hesitate to consider them mature; we 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 perfect ionnement. 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 tie 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 lamina or filaments, traversing indifferent 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 lamina;. Many of these cells bear a perfect resemblance to the lung of the tortoise tribe, and they all approacli to it more or less as to a type of organisation, towards which the human being in this case seems to descend. Pathol. Anat. v. ii. p. 528, translated by Drs. Townsend and West. systems, though they are promoted by them ; they must, in fact, have assisted each other. The altered tissues could not have been easily thus changed, without a defect in the quantity or quality of the matters out of which they are formed ; nor could the latter defects have easily occurred without some alteration in the texture of the parts employed in conveying and ela- borating the nutrient fluid. It is an old saying, that the functions of the body form a circle : if this be true of their healthy condition, it is not less so of their diseases and decline. The organs and tissues subservient to the organic life having undergone vitiation and diminution, we may expect to find equal or even greater decay in the parts which are alto- gether dependent upon them, or the organs of the supplemental life. These indeed, as they are the last to be developed, are some of the first to present marks of decline, and evi- dently for the same reason, viz. because they are appended to and generated by the other parts of the system, and also are more open to our observation. The body is indeed, in this respect as in many others, not unlike a poli- tical community ; no great change can occur in its internal arrangements, such as a failure or derangement of its energies and resources, without a manifestation of this weakness or disorder in its foreign relations. Let us proceed, then, to examine the ravages which are wrought by the hand of time on the organs of locomotion and sensation, in the same order in which we have traced the deve- lopments and amplifications, once lavished by the self-same agent. And first of the bones. The process of development in these parts consisted of a certain adjustment of the animal to the earthy matter, in order to give the requisite firmness, toughness, and solidity. As life advances, the phosphate and carbonate of lime are found to exceed the proportion of the cartilage and gelatine. The general conformation of the bones is less regular ; they look shrunken and worn. When handled they feel lighter, not- withstanding the osseous substance is in excess; a fact, which results from the diminished quantity of the fluids, and one or two other circumstances to be mentioned presently. The processes and ridges, once so eminent and dis- tinct, are comparatively effaced ; this alteration accords with the wasting and diminished exer- cise of the muscles that were attached to these eminences. On looking for the lines and spaces, which are occupied in early life by cartilages or membranes, and which are visible even in manhood, we now find every trace of them vanished. Thus, the divisions between the epiphyses and shafts of the long bones, the line of union between the bones of the pelvis, and, in a still more marked degree, the sutural outlines of the bones of the head, are no longer perceptible. They are all filled up with bony deposit, and the pelvis and cranium form single bones ; even the foramina by which the nutrient arteries entered the tissue are con- tracted or obliterated. The cellular structure between the tables of the cranium is removed ; AGE. and the outer plate has approximated and indeed become identified with the inner; hence we see more depressions on the surface of an aged skull. On inspecting the internal structure of these organs, we find the cavities that contain the marrow much more extensive than formerly, and the medullary tissue reduced to a con- sistence scarcely exceeding that of oil. The cells also of the short bones and of the ex- tremities are more expanded, and the laminae which form them are very much attenuated. The deficiency of animal matter renders the bones of the aged fragile ; they are broken by the most trivial accidents. It is also the cause of their slowness to unite; for the activity of assimilative, and consequently of reparative processes, is dependent on the vascularity and fluidity of a tissue. The lightness, however, of these organs produced by the same cause is beneficial, or at all events in harmony with the state of the muscular system. If we next turn our attention to the ar- ticulations, we shall find that similar pro- cesses of disqualification for former functions have ensued. The spinal column, which once adapted itself with such ease and flexi- bility to the motions and curves of the body, has become almost as rigid as a single bone by the drying up of the intervertebral cartilages, and sometimes by the encroach- ments of ossification.* Scarcely any traces of cartilages between the ribs and the sternum.. can now be found ; one of the causes to which we alluded above, in connection with dimi- nished respiration. The same deficiency of cartilage is observable in the bones of the wrist and of the tarsus. A change, the opposite of mobility, may also be detected in the liga- ments which embrace the joints ; they are dense, dry, and inelastic. The gelatine which enters so largely into their composition has become altered in its chemical properties ; it is less easily soluble in water, and has all the characters of glue rather than of jelly. Ill-adapted as this state of the articulations is to the purposes of motion, it is, we think, not altogether difficult to discern its appropriateness to the human being at this advanced period. Were the joints supple and flexible, while the muscles have so little power, how much greater would be the risks of accidents to the aged man in the slight motions which he achieves. In order to preserve their frames from falling, those whose joints move easily upon each other are compelled to exercise those * '' Cependant il est rare que les fibro-cartilages s'ossifient chez les sujets avances en age. A la verite on voit souvent les vertebres se reunir avec les autres au moyen d'une substance osseuse, mais cette souture depend bien plus rarement de 1'ossi- fication des fibro-cartilages que de la formation de lames osseuses a la circonlerence des deux faces par lesquelles se regardent les coups des vertebres. Cependant j'ai observe quelquefois aussi 1'ossifica- tion des fibro-cartilages intervertebraux, et j'ai trouve alors, en sciant longitudinalement la colonne epiniere, que plusieurs vertebres etaient soudees ensemble, et confondues en une seule masse." — Mcckel, 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 early old age that depth of tone, which by its gravity and solemnity excites our homage. In more advanced age, however, the tone becomes hoarse, shrill, and piping ; this in all pro- bability is produced by the contraction and stiffness of the rima glottidis, but still more by the want of vigour in the muscles of the mouth and throat. The incapability of ma- naging the tone, and the tremulous articu- lation, are also results of changes in the muscles of the larynx, pharynx, and tongue, similar to those which transpire in other parts of the muscular system. Many senile impediments of speech are also produced by the loss of teeth, by the falling in of the cheeks, and by the disproportion of the lips to the space which they occupy. In our investigation of the signs of decay in the parts that are subservient to sensation and thought, we shall be met by the same difficulties which formerly opposed our way, when inquiring into the phenomena of their development. We traced the progress of the nervous substance both in the nerves and in the cerebro- spinal centre from the almost pulpy state recognized in the infant, to its firm consistence in the adult. If we now inves- tigate the anatomical quality presented by the tissue in advanced life, we shall find that it has shared the alteration of nearly all the other tissues, — that in short it has increased indensity. This fact viewed in connection with another, namely, that ramollissement and induration produce very nearly the same lesion of func- tion, will account for the failure in the sensific powers of old age. Besides this alteration in the substance of the nerves, they are found to be diminished in diameter; their neurilemmes are become, like other membranous parts, much harder and stronger. Moreover, Bichat has remarked that the nervous tissue of old ani- 80 AGE. mals is much less easily affected by reagents than that of younger ones ; so that there would appear to be an alteration in the chemical composition as well as in the mechanical con- sistence. That which has been said of the matter of the nerves is also true of the brain. The whole bulk is diminished 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 neurilemmes (for they belong to the same system) are also thicker and more resistent. The vascularity of the organ is greatly diminished ; on a di- vided surface no red dots are visible as at periods less advanced. The alterations in the mechanism of the senses must next be considered. The skin, which is the medium between the nerves of tact, and external agents, undergoes great changes in the progress of life. It becomes drier, harder, less flexible, and at the same time looser, in consequence of the absorp- tion of the adipose substance. By the latter qualities the function of the skin is more evidently impaired, in that modification of it more expressly denominated touch, or the sense of tact united with certain muscular feelings in the ringers 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. Tn 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 Rullier* 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. Age. 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 pnnctum 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. t See Abcrcromhie 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 Vitae 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 .ZEsop 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 longarviores sunt, longaevissimi pisces, quibus cor minimum, et lentissimum incrementum, et ossa nunquam indurantur.1' Primse Linece, § 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 Tucnda, and DC Marasmo. VOL. I. to the general failure of the functions of the body. It is rather a symptom of decline, or one of the phenomena in 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 AGE. once distinguished it from the dust, and that not less literally than truly it has become more and more " of the earth earthy." We have now traversed as far and as mi- nutely as our space would allow, the organs and tissues, with their various alterations. It remains for us to inquire whether any one of them may be considered to stand in the rela- tion of cause to the others. We have already dismissed the supposition, that rigidity and con- cretion are productive of the other alterations, and we also partly entertained the question, when treating of the relations between assimi- lation, the fluids, and the organs subservient to circulation and digestion. But there are one or two additional points which must be alluded to in this place. The decay of all the organs, concerned in the life of relations, has been shewn to depend on a failure in the actions which are necessary to their generation and maintenance ; these organs may, therefore, be dismissed at once from our inquiry into the causation or priority of the processes of degeneration. Yet the observation of the marked declension of the function of the nervous system throughout the body, has led to the hypothesis, that the failure in this power is the ultimate fact in the history of our decline, the fact to which all the others maybe 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. WTe do not fee! pre- pared to adopt the inference ; for if we admit this failure in the innervation of the heart, (and whether its fibres are dependent on nerves for their contractility, is still an unsettled ques- tion,) are we to pass over the condition of the blood ? Might we not say that the enfeebled contractions of the heart are referable to an alteration in the properties of its appropriate stimulus ? It is known that this vital fluid has been less affected by respiration than in former periods of our existence ; we might therefore, when searching for the earliest antecedent in decay, stop at the imperfect arterialization of the blood. But this would be, in our humble opinion, to pause too soon. The deficient oxygenationof 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 1 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 chylifkation, 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 cevebro-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 thequalityof 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 ccssc 'La gene dc " — Ciibanis. 1'influence vitulc s'accroit sans 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: (5 (3'o? |3 BIBLIOGRAPHY. — Lord Bacon, Historia vitas et mortis. Pollich, Diss. de nutrimento, incremento, statu, et decremento corp. hum. 4to. Strasb. 1763. Ploucquet, Diss. sistrns states humanas eorurnque jura, 4to. Tubing. 1778 ; (Recus in Frank Delect. Opuscul. vol. vii.) Daignan, Tableau des varietes de la vie hum. 2vol. 8vo. Par. 1786. Rush, Med. inquiries, vol. iv. Esparron, Ess. sur les ages de 1'homme, Thes. de Paris, an. xi. Ranque, Des predominances organiques des differens ages, Thos. de Par. 1803. Wesener, Spec. hist, hominis varias ejus periodos, &c. sistens, 8vo. Krasberg. 1804. Lucae, Grundriss der Entwickelungsgeschichte des menschlichen K6rpers.8vo. Marburg, 1819. Burdach, Die Physiologic als Erfahrungswissenschaft, 8vo. Leipz. 1803. Renauldin, Diet, des Sc. Med. art. ' Age.' Rullier, Diet, de Med. art. ' Ages.' Beyin, Diet, de Med. et Chir. Prat. art. 'Age.' Roget, Cyc. of Pract. Med. art. ' Age.' Copland's Diet. art. ' Age.' Also the anatomical and physiological systems of Adelon, Beclard, Bichat, Bostock, &c. &c. &c. (J. A. Symonds.) ALBINO. (Syn.Albinisnnis,Ieucopathia, leu- ctfthiopia). — 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, de Nili origine, cap. 19. p. 69 ; see also Ludolf, Hist. ./Ethiop. 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 ALBINO. form of the features and in all other respects the individuals in question exactly reserr.b!e the negro race. Another striking peculiarly 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 irom 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 sm les Americains, par. 4, sect. 1. t. ii. p. 1 et seq. ; Raynal, Hist, des Indes, t. iii. p. 288. The earliest account which we have of the South American 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 palpebiis." De Insulis nuper inventis narrat., p. 30 of " Nar. Sec. ;" see also Clayton, in Manch. Mem. v. iii. p. 261 et seq. t Buffon, t. iii. p. 399 and 415 : Wood's Trans, v.'iii. p. 328, 9 and 344. We have not been able to procure the " Voyages de Legal," which is re- ferred to by Buffon and others, as containing the original account of the Albinoes, or, as they have been termed, Chacrelos, of Java. With respect to the Bedas of Cevlon, as originally described by Riheyro, Hist, de Ceylon, ch. xxiv., and more lately by Percival, Account of Ceylon, ch. 13, and by Cordiner, Desc. of Ceylon, v. i. c. 4, it seems evident that they are not to be considered as Albi- noes. The only remark which Ribeyro makes on their physical character is, " Us sont blancs comme des Europeens, et il y a meme des roux parmi eux," p. 178. Percival, who saw some of them, states that their complexions are fairer and more inclined to a copper colour, than those of the other inhabitants ; while all that is said by these writers respecting their habits and modes of life indicates that they are a distinct race or tribe. The term Beda, or Badah, appears to be a corruption of Vaddah, or Veddah, which Knox informs us is the name of the aborigines of the island ; Account of Ceylon, p. 61 ; see also Brown, in Brewster's Encyc. art. " Ceylon," p. 704 ; Cordiner and Per- cival, ut supra. * Vossius and Ludolph, ubi supra ; Argensola, Conquist. dc las Islas Malucas, lib. ii. p. 71, speaks of Albinoes as not uncommon in these islands; De la Croix. Relation de 1'Afrique, par. iii. liv. ii. sect. ii. $. 13, " Albinos, hommes blancs, ou We meet with a few scattered remarks in the writings of the ancients, which render it evident that t'lis peculiar state of the human body had fallen under their notice. We have the follow- ing passage in Pliny : " Idem " (Isigonus JNicreensis) " in Albania gigni quosdam glauca ocu'.orum acie, e pueritia statim canos, qui nrctu plus quam interdiu cernant."* The same circumstance is referred to by Aulus Gellius : " . . . . in ultima quadam terra, quae Albania dicitur, gigni homines, qui in pueritia canescunt, et plus cernunt oculis per noctem, quam inter diem;"f and by Solinus : he says that the Albanians " albo crine nascuntur ;" " glauco oculis inest pupula, ideo nocte plus quam die cernunt."J P''ny> m speaking of the inhabi- tants of a certain district in the interior of Africa, names them Leucaethiopes ;§ and, as it has been supposed that in this passage he referred to the Albinoes, the term has been applied to them by some eminent modern naturalists; || but it appears more probable that the Leucaethiopes were a tribe of negroes whose complexion was rather less dark than that Mores blancs," informs us that they compose a considerable body of attendants at the court of the king of Loango ; the same statement is made by Ludolf, ubi supra, and by the author of the Hist. Gen. des 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 maybe remarked, must have belonged to the Malayan variety. See also Winterbottom, Account of Sierre Leone, v. ii. p. 166 et seq. ; Stevenson, in Brewster's Encyclopaedia, art. " Complexion," p. 41, 2; Bory St. Vincent, L'Homme, t. ii. §. " Hommes Monstreux," p. 143-7 ; also in Diet. Class. d'Hist. Nat. art. " Homme,*' p. 166 et seq.; Renauldin, in Diet, des Scien. Med. art. " Albino ;" Lawrence's Lect. p. 287 ; Is. St. Hi- laire, Anom. de 1'Ovganization, 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, Monje, Journ. Phys. 1782, p. 401 et seq. Suppl. We have no very distinct account of Albinoes among the Chinese and Monpiols, but they appear to be as frequent among the Malays and native Americans as among the j^Ethiopians. * Hist. Nat. lib. 7. cap. 2. See the note of Cuvier, in his edition of 7th . . llth books of Pliny, t. i. p. 18. t Noct. Attic, lib. 9. cap. 4. - t Polyhistor, cap. 15. p. 25. See the remarks of Saumaise, Excrc. 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. || 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 variety. ALBINO. 85 of the Africans generally.* It has been like- wise supposed that Celsus alluded to the Al- bino, when he speaks of a peculiar condition of the skin under the name of Leuce ;f but this appears to be a morbid cutaneous affection, and to have no reference to the subject now under consideration. From the number of Albinoes which were supposed to exist in certain countries, as well as from the marked peculiarity in their ap- pearance, an opinion was long entertained that they formed a distinct race or variety of the human species,! originating in some unknown cause, and bearing the same relation to the other inhabitants of the countries in which they are found that the acknowledged varieties of the human species bear to each other. But this opinion, although sanctioned by high authority, may be considered as decisively disproved by the well-ascertained fact, that Albinoes are born of parents who do not possess this characteristic peculiarity of the skin, hair, and eyes.§ Although Albinoes are of comparatively rare occurrence in Europe, yet we have had a suffi- cient number of examples to render us per- fectly familiar with the appearance which they present, and with the precise nature of the * See the note of Hardouin in loco, Valpy's ed. p. 1285, Le Mairc'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 ,met with any Indians that were less black than ordinary, v/ere accustomed to call them white ; Pers. Nar. by Williams, v. iii. p. 287 et seq. See Prichard, in Medical Cyclop. Art. " Tem- perament," p. 163. t De Medicina, lib. 5. cap. 28. § 19. :f This appears to have been the case even with Haller, El. Phys. xvi. 4. 13. p. 492. Voltaire main- tains this hypothesis, Essai sur les moeurs, CEuvr. t. xiii. Introd. and p. 7, 8. Buffon inclines to it; but his opinion on this point is not decided or uniform, t. iii. p. 501. See Is. St. Hilaire, p. 295. § In addition to the authors already referred to, we have a case of this kind by Helvetius, Hist. Acad. Sc. 1734, p. 15 . . 7. The Albiness described by Buffon was born of black parents : see also Castillon, in Berlin Mem. 1762, p. 99 . . 105 ; Dic- quemarc, Journ. Phys. 1777, p. 357 . . 0, and 1788, p. 301 et seq. ; Hist. Acad. Scien. 1744, p. 12, 3; and Maupertuis, Ven. Phys. p. 135 et seq. : 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. C03. 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. CEcon. 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 evei> 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 BIu- menbach, p. 278 . . 0, in Lawrence, p. 281 . . 9, and in Is. St. Hilaire, ut supra and §. 5. One of the earliest of what may be considered as the correct descriptions is that of Buffon, Supp. t. iv. p. 559 et seq. The descriptions of Blumenbach, $. 78, and of Saussure, Voy. $. 1037 . . . 1043, are par- ticularly correct and characteristic : to this we may add the more recent account of Is. St. Hilaire, t. i. par. 2, liv. 3. ch. 1, $. 2 and 5. We are informed by Ludolf, ubi supra, that the first modern writer who distinctly mentions the Albino is Tellez. f Blumenbach particularly characterizes the •whiteness of the hair of the Albino as being " gilva, colori cremoris lactis quodammodo comparanda," p. 275. $ See Vossius, Ludolf, De la Croix, Cook's First Voyage, and Winterbottom, ut supra ; Blumen- bach, p. 274; Buffon, in Hist. Acad. Scien. 1760, p. 17 ; St. Hilaire, p. 304, 5 : Wafer, in his de- scription of the white inhabitants of Darien, p. 134, et seq., says that there is a white down on their skin. § Wafer, p. 134-8 ; Buffon, t. iii. p. 503 ; Wood's Trans, vol. iii. p. 420 ; Voltaire, t. xv. p. 269,70; Pauw, t. ii. p.9, 10; Raynal, t. iii. p. 288; Du- bois on the People of India, ch. xv. p. 199 et seq. ; Firmin, t. i.p. 153. . 5; Dalin, in 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 Peau, t. ii. p. 193 . . 203 ; Blandin, Diet. Med. Chir. Prac. "Al- binie ;" Breschet, Diet, de Med. " Albino;" Sonini, in his edition of Buffon, t. xx. p. 355-6, note. So far as regards the state of the intellect, the charge is repelled by M. Sachs, who gives a minute account of the peculiarity in his own person and that of his sister ; Hist. Nat. duor. Leuc;cthio- pum. Jefferson informs us, that the Albinesses, of whioh he gives an account, were " uncommonly shrewd, quick in their appchension and reply,'1 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.]; In the majority of cases the peculi- arities which constitute the Albino are connate, and continue during life without any change. There are, however, some instances, where the whiteness of the skin does not exist at birth, but makes its appearance at a subsequent pe- riod, generally by slow degrees, until the com- plete Albino character is induced.§ When * Vossius, p. 68, informs us that they are avoided by the other negroes, as supposed to be diseased. De la Croix says the negroes regard them as mon- sters, and do not permit them to multiply, ut supra. Dubois, p. 199 et seq. observes that they are named lepers by birth, and that when they die their bodies are not buried or burnt, but cast on dunghills. See also Firmin, ubi supra. t Blumenbach, p. 277 ; Lawrence, p. 287 ; St. Hilaire, p. 296. J Phil. Trans, vol. xix. p. 781, and Lowthorpe's Abridg. vol. in. p. 8 •, Buffon, t. iv. p. 565. tab. 2, et p. 571, tab. 3; Arthaud,inJourn. Phys. 1789.|pt. 2. p. 277,8 ; Rush, in Amer. Trans, vol. ii. p. 392 et seq. ; Camilla, El Oron. Ilus. t. i. p. 109 et seq. ; Ditto, Hist. del'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. Ixx. p. 248 ct seq. ; Le Cat, sur le Pcau, 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. Ililaire, §. 4. p. 312 ct seq. once formed it does not seem that it ever dis- appears, or is even in any degree diminished, nor have we any authentic accounts of its being removed by any constitutional change, either natural or morbid, or by external applications. Although, as has been stated above, this peculiarity occurs in individuals, who did not derive it from their parents, yet, like all those deviations from the ordinary structure of the body, which have been styled accidental varie- ties, when once produced, it is disposed to propagate itself by hereditary descent. There are also certain individuals, who have a ten- dency to produce it; so that even among the few European Albinos, of which we have a minute account, we have cases of its occurrence in two or more members of the same family, either as connected by parental descent, or by collateral relationship.* We have no instance on record of the offspring of a male and female Albino. The whiteness of the skin and hair, both general and partial, is not confined to the hu- man race ; it is found in most, if not in all the species of the mammalia, and in some of these, as in the dog, the horse, and the rabbit, is the subject of daily observation ;f in most of them, however, the peculiar state of the eye does not exist. These white varieties, like other analogous cases among the lower animals, when once produced, are strictly hereditary, in which re- spect they differ somewhat from the human Albino. Various opinions have been entertained by physiologists respecting the nature of this pecu- liarity, whether it should be considered as a morbid affection,]; depending upon a diseased state of the constitution, and also respecting its immediate or efficient cause. The first of these points may be regarded as a verbal con- troversy, depending altogether upon our defi- nition of morbid action ; but we conceive, that according to the ordinary definition of the term, we should not consider it as a disease, but as a connate deviation from the perfect structure of the animal frame, not produced by an external cause, and not removable by a remedial agent. For a correct knowledge of its physical cause, we are indebted, in the first instance, to an in- genious conjecture of Blumenbach 's, who ac- counted for the red colour of the eye, and its extreme sensibility to light, by the absence of the pigmentum nigrum.§ * See particularly Saussure's account of the two boys of Chamouni and Sachs's Narrative ; also Blu- menbach, p. 276 and 279, note ; Firmin and Jeffer- son ut supra ; Pauw, t. ii. p. 25 ; Bory St. Vincent, L'Hommc, 'p. 144, mentions an Albino of the third generation; Is. St. Hilaire, passim. t 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 Leucaetbiopum, et De Gen. Hum. var. $. 78. ALBINO. 87 This conjecture was shortly after verified by Buzzi of Milan, who took advantage of an opportunity which presented itself, of dissecting the eye of an Albino, in which the pigmentum nigrum could not be detected.* He also ex- amined the structure of the skin, which appeared to be deprived of the rete mucosum, that part of it in which its specific colour is supposed to reside ; the hair was also found to be deficient in its central coloured part.f Whether, in these cases, the pigmentum nigrum of the eye and the rete mucosum of the skin are absolutely deficient, or are only deprived of their colouring matter, so as not to be detected by the eye, is a point on which different opinions have been formed by anatomists ; J perhaps, upon the whole, we may be induced to consider the lat- ter opinion as the most probable. What are the circumstances in the consti- tution of the parents which should lead to this peculiarity in their offspring is entirely un- known, nor have any conjectures been formed on the subject which can be considered as even plausible.§ The hypothesis of Buffbn, 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." t Sachs gives us a minute account of the analysis of the hair of the Albino, compared with Vauquclin'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 foetus, by an impression made upon the mother ; it is characterized as a " cessation totale, momentanee d'action cerebrale ; " Journ. Compl. t. xv. p. 250 et seq. Is. St. Hilaire essentially adopts this hypo- thesis, ascribing the peculiar state of the skin to an " arret de developpement," in consequence of which the colouring matter is not formed at the requisite period, p. 319,0. The idea, that it depends upon something peculiar in the seminal matter of the parent, which was maintained by Herodotus, Thalia, §. 101, and was controverted by Aristotle, Hist. Animal, lib. 3. cap. 22, has been revived by Mau- pcrtuis, Diss. 2, and by Pauw, t. i. p. 179, and t. ii. p. 21. Le Cat refers the colour of the negro to a pecu- liar substance, which he names " /Ethiopc 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 et seq. and because the production of the Albino is complete in the first instance, and not brought about by any gradual or progressive alteration. It appears that we must come to the con- clusion, that although the anatomical or phy- sical cause of the peculiarity is ascertained, yet that we are entirely ignorant of its remote cause, or of that train of circumstances which leads to its production.* * " The following cases have not been referred to in the body of the article ; De la Nux, 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, Anirn. CEcon. p. 250, 1 ; Trail!, in Nich. Journ. v. xix, with an Add. by the editor ; Mansfeldt, Journ. Compl. t. xv ; Ansicux, in Journ. Med. de Corvisart, t. xiv, p. 263, 4. For the following epitaph, which appears to have been written on an Albino child, we are indebted to a literary friend, the Rev. Jos. Hunter. " Upon Thomas, son of Ric. Elmhurst by Mar- garet his wife, daughter to Ric. Micklelhwaite : 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 Jonrn. Med. de Corvisart, t. xiv. Araensola, Conquist. de las Islas Malucas. Lond. 1609. Aristoteles, Opera iiDuVal. 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 Leucasth. Gott. 1786. Bory St. Vincent, in Diet. Class. d'Hist. Nat., " Homme ;" Ditto, 1'Homme. Par. 1827. Bostock, in Brewster's Encyc. " Albino." Bowdlch, 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. Bujfon, 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. Conk's first voyage, by Hawkesworth. 'Lond. 1773. Ditto, second ditto. Lond. 1777. Ditto, third ditto. Lond. 1784. Gardiner's Description of Ceylon. Lond. 1807. Cortesius, De Insulis nuper invent. Narrat. Colon. 1532. Dalin, Amoen. Acad. t. vi. De la Croijc, Relation de 1'Afrique. Lyon. 1688. De la Nux, in Hist. Acad. Scien. pour 1744. Dique- marc, in Journ. Phys. pour 1777 and 1788. Dubois, on the people of India, (trans.) Lond, 1817. Dud- dell, on the eye, and Suppl. Lond. 1729. Firmin, Dcsrrip. de Surinam. Amst. 1767. Fisher, in Manch. Mem. v. v. Gellius, Noctcs Attica:. Basil, 1565. Goldsmith's Animated Nature. Lond. 1822. Gaultier, in Journ. Phys. t. Ixx. Gumilla, El. Oro- noco ilust. Madrid. 1745. Ditto, Hist, dc 1'Oro- noquc (trad.) Avignon. 1758. Haller, Elem. Physiol. Laus. 1757. Helvetia, 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 Guinec. Par. 179,3. Jefferson's Notes on Virginia. Phil. 1794. Knvx's 38 ALBUMEN. Account of Ceylon. Lond. 1681. Labillardiere, Voyage. Par. 8. Lawrence's Lectures. Lond. 1819. Le Cat, Traite de la Pcau. Arnst. 1765. Lowthorpe's Abridg. of Phil. Trans. (2d. ed.) Lond. 1716. Lu- ciarats a Gnevio. 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. Plinivs, 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." PtolemcEus, Geographia, a Bertio. Amst. 1618. Rayer, Traite des maladies de la Peau. Par. 1826. Raynal, Hist, des Indes. Neuch. 1785. Renuuldin, in Diet, des Sc. Med., " Albino." Ribeyro, Hist, ^de Ceylon. Trev. 1701. Rush, in Amer. Trans., v. ii. and iv. Sachs, Hist. Nat. duor. LeucEethiopum. 1812. St. Hilaire, ( Isid. ), Anomalies de 1'Organization. Par. 1832. ; Ditto, in Diet. Class. d'Hist. Nat., " Mam- miferes." Saitssure, Voyages dans les Alpes. Ge- nev. 1787. Soliiitis, Polyhistor, cum Salmatii, Exerc. Plinian. Traj. ad Khen. 1689. Stevenson, in Brewster's Encyc. " Complexion" Traill, in Nicholson's Journ. v. six. Vultaire, CEuvres. Par. 1819. Vossius, de Nili Origine. Hag. Com. 1666. Voyages, Hist. Gen. des, Haye, 1747. Wafer's New Voyage. Lond. 1699. Winterbottom's Account of Sierra Leone. Lond. 1803. (J. Bostock.) ALBUMEN, (Fr.Allumine, Germ. Eyweis- sslojf,) 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. EIIUVS. Theory. Carbon.. 8 48 51.61 Hydrogen 7 7 7.53 Nitrogen 1 14 15.05 Oxygen 3 24 25.81 G. Lussac. Prout. 52.883 50.00 7.540 7.78 15.705 15.55 23.872 26.67 1 93 100.00 100.000 100.00 White of egg, when heated to about 150°, coagulates, that is, it becomes a white, translu- cent, and somewhat elastic substance, which, when cautiously dried, shrinks up and assumes the appearance of horn, becoming tough, yel- lowish, and insoluble in water. Two parts of white of egg and one of water entirely co- agulate when duly heated ; equal parts remain, under the same circumstances, semi-fluid ; a mixture of one part of white of egg and ten of water becomes opaque, but is not coagulated ; and a milkiness is perceptible when the al- bumen only forms a thousandth part of the solution.* Fresh-laid eggs, and those which have been oiled upon the surface do not per- fectly coagulate when put into boiling water, in consequence, probably, of the dilute state of the albumen. One hundred parts of the fresh albumen of the egg, when carefully evaporated in vacuo, leave a residue = fifteen parts. One hundred parts of the coagulated white of a duck's egg (dried in vacuo with sulphuric acid) leave 13.65 parts, which, steeped in water, acquires its original appearance, but in four days only took up 68 of water, though it had Iost86.35.f When albumen is made part of the voltaic circuit, it presents appearances dependent upon the power used, which, when considerable, excites so much heat as to coagulate it; but with a feeble power and the poles sufficiently distant, coagulation ensues most plentifully at the negative platinum wire ; a coagulum also forms at the positive wire, where acid is also sparingly evolved. These phenomena are much interfered with by the evolution of gaseous matters at the respective poles, which occasion a froth, and the appearance of more extensive coagulation than actually occurs. When coagulated white of egg is boiled for several hours, it shrinks up and becomes har- dened, communicating traces of animal matter to the water. Heated by high pressure steam in a copper digester to 400°, it blackens the interior of the vessel, and dissolves, leaving a small residue of unaltered albumen. The solution is brown, and has the odour of boiled meat (from osmazome ?). This action deserves further investigation.! White of egg soon runs into putrefaction, and evolves sulphuretted hydrogen. The se- rum of blood kept for two years in a well- stopped phial, blackened its interior, and be- came a stinking, pale, yellow liquid, still co- agulable by heat, and containing hydro-sul- phate, carbonate, and acetate of ammonia, and a fetid volatile matter : a portion of yellowish white purulent-looking matter, containing un- decomposed albumen, remained at the bottom of the phial. Coagulated white of egg, even under water, long resists putrefaction. * Bostock, Nicholson's Journal, vol. xiv. and Medico-Chirurgical Transactions, vol. i. and ii. t Chcvrcul, |Mem. du Museum vii. 180. Ann. de Ch. ct Ph. xix. 46. t Gmclin, Handbuch der Thcorctischcn Chcmic, ii. 1053. 3rd rd. Frankfort, 1827. ALBUMEN. 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 daik 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.)lj 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. Wb'hler's Translation. Dresden, 1831. t 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 Thier. Chemic. 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 axcess 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 FIBRINE, 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 albximen 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. t Prevost et Dumas, Ann. de Chimie et Physique xxiii. 52. and acids ; when it is too dilute for such detection, it may be subjected to voltaic elec- tricity, or tested by corrosive sublimate, or by ferrocyanate of potassa; the alcali should, in the latter case, be previously neutralized by acetic acid. It would appear, from Orfila's experiments, that white of egg is an antidote to the effects of corrosive sublimate when taken into the stomach, and that, if administered in sufficient quantity immediately after the recep- tion of the poison, it prevents the progress of the symptoms. The white of one egg appeared sufficient to render four grains of the poison ineffective. The readiness with which some metallic oxides are received into the system may per- haps be ascribed to their affinity for albumen, with which some of them form compounds not easily decomposable, and in which the metallic oxide cannot be detected by the usual tests, till they have been subjected to heat sufficient to decompose the organic matter. Mercury and silver are thus, in certain cases, detected in the secretions and excretions. ( W. T. Brands.) AMPHIBIA.— (A/AfpKj utrinque, #10?, vita. Fr. Amphibies. Germ. Amphibien. Ital. Amphibie.) A class of vertebrated animals, hitherto almost universally considered as an order of REPTILIA, constituting the Batrachia of the later erpetologists. To the retention of the latter appellation, as derived from the Greek name of a single form of the group, and as bearing no reference to any character either of structure or of habit, there is an obvious objection. The term Amphibia is therefore here adopted, as designating one of the most striking peculiarities of the class ; namely, the change which takes place at an epoch of their life, more or less advanced, from an aquatic respiration by branchiae to an atmospheric respiration by true lungs, and an equivalent and consequent alteration in their general structure and mode of life. The Amphibia may be characterized as " vertebrated animals, with cold blood, naked skin, oviparous reproduction, and most of them undergoing a metamorphosis or change of con- dition, having relation to a transition from an aquatic to an atmospheric medium of respi- ration." These characters, by many of which the am- phibia are distinguished from the reptilia, are sufficiently determinate and important to justify our considering them as a distinct class, ac- cording to the generally received principles of zoological arrangement ; notwithstanding most even of the modern writers on the subject have retained them as merely an order of reptilia. But it will also be seen that if in the adult state they approach the reptilia in many points of their general structure, their organization, during the early and imperfect condition of the tad- pole, partakes no less of that of fishes. As an osculant or intermediate form, connecting two others of higher typical importance, it may be, certainly of greater extent, and consisting AMPHIBIA. 91 of groups having more striking distinctive cha- racters, there is not, perhaps, a more interesting and satisfactory instance in the whole range of the animal creation than is afforded us in the class of amphibia : a circumstance which can only be fully appreciated by following out the structure of each system of organs, first as it exists temporarily in the tadpole, and ultimately in its permanentcondition 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 branchisB. 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. — AMPHIPNEURTA. Body elongate, formed for swimming. Feet either four, or two anterior only. Tail com- pressed, persistent. Respiration aquatic by means of branchiae, throughout life, co-existing with rudimentary lungs. Branchiae external, persistent. Eyes with palpebrae. Genera, Proteus, Siredon, Menobranchus, Siren, Pseudobranchus. Order 2. — ANOURA. Body short and broad. Feet during the tad- pole state wanting ; afterwards four, the hinder ones long and formed for leaping. Tail before the metamorphosis, long, compressed ; after- wards totally wanting. Ribs wanting. Ver- tebrae few and anchylosed. Tympanum open. Respiration at first aquatic by branchia? ; after- wards atmospheric by lungs. Branchiae at first external, but withdrawn within the chest before the metamorphosis. Impregnation effected ex- ternally during the passage of the ova. Genera, Rana, Hyla, Ceratophrys, Bufo, Rliinella, Otilopha, Ductylcthra, Bombinator, Breviceps. Order 3. — URODELA. Body long, slender. Feet always four. Tail long, persistent. Ribs very short. Respi- ration at first aquatic by external branchiae, afterwards atmospheric by cellular lungs. Ver- tebrae numerous and moveable. Tympanum concealed. Impregnation internal. Genera, Salamundrina, Salamandra, Molge. Order 4. — ABRANCHIA. Body long, formed for swimming. Feet four. Cranium solid. Tail compressed. Respi- ration by means of lungs only: branchice none. No metamorphosis known. Genera, Menopoma, Amphiuma. Order 5. — APODA. Body elongate, slender, anguiform. Feet none. Tail very short, almost wanting. Lungs one larger than the other. (The existence of branchiae at any period of life unknown.) Ribs very short. Sternum wanting. Ears concealed. Impregnation unknown, probably internal. Genus, CtKciliu. 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 witli these habits, we find these animals absolutely tail- 92 AMPHIBIA. less, the body contracted longitudinally into as short a space as possible, the vertebrae very few, and anchylosed or soldered together into a single immoveable piece, and wholly devoid of ribs. On comparing with this formation, on the other hand, the extensive developement of the tail, the long flexible body, and gracile form of the newts or aquatic salamanders, and reflecting upon the obvious object of this structure in facilitating their motions in the water, we should hardly be prepared to find that the extraordinary extension of the hinder extremities in the frogs, the primary object of which is to afford the great powers of leaping just alluded to, is made subservient also to their aquatic life, by enabling them to swim with great facility, aided by a web of skin extending between the toes of the hinder feet. Now as we shall hereafter see, when treating on the respiration of these animals, that the occasional presence of water, and its applica- tion to the surface of the skin, is equally essential to the well-being of both these forms, it is very interesting to observe how admirably this peculiarity in the general re- quirements is provided for by the very different, and even opposite, construction of their form and limbs, which their individual habits of life demand. But to return to the detailed anatomy of the skeleton. On examining the general texture of the bones in this class, there is an obvious advance towards the firm calcareous substance of those of the higher forms of vertebrated animals when compared with the bones of fishes, they being more compact, and less tran- sparent and flexible than in the latter animals. The cranial bones, though they retain to a certain extent the character of those of fishes, in the permanent disunion of the different centres of ossification, at least in many in- stances, yet they do not overlap each other, as in that class, but, on the contrary, remain with their margins at least in contact, and in many cases actually united, though not by true sutures. The elements of which the cranium is essentially composed, and which in a higher grade of organization are found consolidated, are here still exhibited as distinct pieces ; a state of things which is strikingly imitated in the progress of the development of these parts in the highest classes during their growth. It is also to be observed that the bones of the face are more closely united to those of the cranium and to each other in the higher than in the lower forms of the class, exhibiting distinct and obvious links in the development of these parts, which we see so beautifully and gradually perfected in the as- cending series from fishes up to man. The following enumeration of the separate cranial bones of the amphibia, as existing in the menopoma alleganiensis, the gigantic sala- mander of America, will illustrate the general relations of the distinct centres of ossification, here remaining permanently detached. Fig. 14. In figs. 14 and 15 the different elements are thus designated : — a. the frontal ; b. the exterior frontal ; c. the parietal ; d. the nasal ; e. the occipital ; f. the pterygoid ; g. the tympanic; h. the jugal ; i. the superior maxillary; k. the intermaxillary ; /. tbevomer; m. the sphenoid ; n. corresponding to the or- bitary processes or alre 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 as hyoides that the principal interest attaches in the present class, as it is that bone which undergoes the most remarkable changes in its form and relations during their transforma- tion, passing from the office of supporting the branchial organs into a true os hyoides, and thus offering, as Cuvier has beautifully shewn, an elucidation of the true nature of this ap- paratus in fishes. As this bone, however, has a direct relation with the respiratory functions, I shall explain these changes while treating on that part of the subject. The spinal column varies exceedingly in the different forms of the amphibia. In the highest form the vertebrae are fewer than are found in any other animals. In the common frog Fig. 16. there are but nine, and in the pipa only eight. Of the nine vertebrae in the frog, the first, the atlas, «, 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 vertebrae of the adult frog have long transverse processes (Jig- 16, i), 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) 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 vertebras 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 vertebra1, commencing with the second, bear ribs, which are extremely small, and in fact merely rudimentary. In the tail the trans- 94 AMPHIBIA. verse processes are only found on a few of the most anterior vertebra. The spine of the proteus is not sufficiently different from that of the siren to require any particular description. The construction of the members, both an- terior and posterior, especially the latter, will be found to be arranged on very different plans, according to the habits and requirements of the different groups, and particularly their mode of progression. In the apoda, as the cacilia, 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 (jig. 16, f. Jig. 17.) consists of the scapula, the clavicle, and the coracoid bone, which all combine to form the glenoid cavity for the head of the humerus. The scapula is composed of two very distinct portions. The upper, (Jig. 17, a,) which is Fig. 17. permanently cartilaginous, at least at its mar- gin, is articulated moveably to the inferior and more solidly ossified piece, (Jig. 17, b,) at the inferior and posterior part of which is the arti- cular surface forming its portion of the glenoid cavity, immediately anterior to which it is at- tached to the clavicle. (Jig- 17, c.) This bone is slender and straight, and is connected beneath with its fellow in the median line. The coracoid bone (fig. 17, d) is considerably larger than the clavicle, and is also connected with its fellow by its broad median margin. The sternum consists of several pieces, ex- tending from before the clavicles to some dis- tance behind the coracoid bones; the latter terminates in a broad xiphoid cartilage. These parts differ considerably in their relative pro- portions in different genera. The arm is developed in a very inferior de- gree compared with the hinder extremity. The humerus (Jig. 17, g) is short and thick, having a rounded head, received into the glenoid ca- vity of the shoulder-joint. The opposite extre- mity forms an almost globular surface for its articulation with the bone of the fore-arm, which is still shorter, and consists of the radius and ulna united, (fig. 17, li,) having only a slight groove to show their line of union. The carpal bones (jig- 16, i) are six in number, supporting the four metacarpal bones, (Jig. 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, (jig. 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, (jig- 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 us culcis and the astragalus. Between these elongated bones and the metatarsal are four small tarsal bones. The metatarsal bones (Jig- 16, p) are much elongated, as are also the phalanges, (fig. 16, q,) for the purpose of forming strong oars or paddles with the intervention of a broad web of integument. The inner toe is consi- derably developed, and the whole structure of the foot and leg thus combines to furnish a pow- erful and efficient organ of progression. The elongated forms of the aquatic sala- mander, the proteus, the siren, &c., in which the vertebrae are developed to so great an extent, present the opposite extreme in the structure of their limbs. These are small, feeble, and ap- pear as it were abortions. In the genus triton and in the salamandra, which possess both an- terior and posterior extremities, they differ but little in their general form and development. The bones of the fore-arm as well as of the leg, instead of being respectively anchylosed into a single piece, as in the frogs, are permanently separate, consisting of a distinct ulna and radius in the former, and an equally distinct tibia and fibula in the latter. The toes are four, both before and behind ; they are short, slender, and of slight construction. This imperfect development of the extremi- ties is, however, as we have seen, admirably compensated by the extraordinary extent of the spine both in the body and the tail ; and while the limbs afford but very imperfect means of progression on land, the structure of the spine AMPHIBIA. 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 suclden 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. Thesalamanderhas about sixty above and below. In the tadpole state of the frog the mouth is very small, and, instead of teeth, is occu- pied only by minute horny plates of just sufficient consistence to abrade the soft mixed food which it finds on the surface of animal or vegetable substances in the water. Its sto- mach and intestinal canal are of very different form from that which they afterwards assume. The intestine is of nearly equal size throughout its whole length. It is very long, being not less than ten times the length of the actual space from the mouth to the anus, and is coiled up in a circular form, occupying the greater part of the abdominal cavity. The canal, as we shall presently see, changes its character materially during the metamorphosis of the animal, becoming gradually shorter until it is not a quarter of the length, in proportion to the size of the animal, which it exhibited in its earlier condition. In the adult amphibia the whole alimentary canal is of a very simple character. The esophagus 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, Sec. 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 Jlall 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 Midler'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 sangui ferous 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 (lei 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 artcriosus, 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 aorta, and at its base gives off the pulmonary artery. The two veins which return the blood from the rudimentary air-sacs gradually enlarge as these cavities become more important, and assume the character of lungs ; and at length they receive the name, as they perform the function, of pulmonary veins. These by de- grees become, as it were, distended at their point of union with the heart, and ultimately form the second auricle. This general description will be better un- derstood by a reference to the subjoined figures taken from the tabular views of M. St. Ange, of which an English edition has been published by Mr. Jones.* The following detailed description of those figures is necessary to the correct understanding of this intricate but interesting arrangement. Fig. 18. The first period, previous to any change having- taken place in the branchiae, is given in fig. 18. Four pairs of trunks (1, 2, 3, 4) go off from the heart. The first branch on each side (1) gives off a small anastomotic branch (5) ; after which it becomes divided into numerous branchial filaments (6); these, by their ulti- mate subdivision, terminate in a capillary tissue or network (7), from which arise other minute returning vessels, forming, by their junction, a single large vessel (9), which brings back blood into the general circulation after it has been aerated in its course through the branchiae. The second branch (2) also gives off a small one (14) previously to its subdivision in the second branchial leaflet, which branch enters the returning vessel ; thus producing a com- munication between the two vessels 2 and 9, as in the former case. The returning vessel then terminates in the arch of the aorta, in which the two vessels 13 and 15 also terminate. The third principal vessel (3) is similarly distributed on the third branchial leaflet, and the corresponding returning vessel (16) termi- nates in the aorta, as in the other case. The arch of the aorta, thus formed, gives off a branch (21), which, after receiving the fourth branch from the heart (4), goes into the lungs (19). The second period, shewn in Jig. 19, occurs Fig. 19. * Tabular view of the circulation in vertebrated animals. VOL. I. when the branchiae begin to contract. The anastomotic branch (5), shewn in the former figure, is not much enlarged, and assumes the character of a continuous trunk with 1. The branches (11 and 12) have increased in size, but the original continuation of 1 going to the bran- chiae, has decreased in the same proportion. The anastomotic branch (14) has acquired the size of the arch of the aorta, whilst the continuation of 2 is diminished, and the branchial leaflet is contracted in a corresponding degree. The branch 3 has become exceedingly small; and 4, which was before the smallest, is now the largest of all. By these changes in the relative di- mensions of the different vessels, especially in the enlargement of the anastomotic branches, the whole system of the circulation is gradu- ally being altered, until, in the third period, (Jig. 20,) it has assumed the character of that in the reptile, by the total obliteration of the branchiae and their vessels, and the enlarge- ment of those branches, which, at first only anastomotic, have now become principal. In the adult condition of the animal, there- H 98 AMPHIBIA. 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 vena; cavae. The blood from the two auricles is sent together into the single ventricle where it becomes mixed, and this mingled arterial and venous blood, thus but half purified, is propelled by the same impulse, partly into the pulmonary arteries to be more perfectly purified, and the remainder through the aorta and the whole circulating system to the different organs of the body. The aeration of the blood, therefore, is but imperfect; a condition which is met with equally in the whole of the reptilia. VI. Respiration. — The preceding observa- tions on the circulation have in some measure necessarily anticipated the account which we have to offer of the correlative function of re- spiration, and the character of those changes * Zool. Journal, vol. ii. t Beitrage von dem Herzen der Batrachier, 8vo. 1832. f Part iii. p. 213. to which its organs are subjected in the transit of the amphibia from the pisciform to the reptile state. Breathing water, in the first instance, exclusively, these animals are fur- nished in the tadpole condition with branchiae or gills, of a leaf-like form, considerably sub- divided, though far less so than in the fishes. These branchiae are, in the first instance, in all cases external ; but in the higher forms of the class they remain so situated only for a brief space, becoming, as in the frogs and toads, internal at a very early period of their ex- istence. They are supported by cartilaginous or osseous arches, connected with the os hy- oides, and the changes which they undergo are accompanied by alterations in the form of that bone, to which allusion has already been made, and an account of which will now be given. At that period of the tadpole's existence, at which its branchiae are in full action, and the lungs still restricted to the state of a black- ish, rudimentary tissue, we find the tympanic bones, (Jigs. 21, 22, e,} developed to a great Fig. 22. extent, and forming the basis to which the branchial apparatus is suspended, by means of a rather thick angular portion, (Jigs.21, 22, a.) This has been shewn by Cuvier to represent what in the fishes is composed of three bones, and is the medium by which in them the whole branchial apparatus is suspended to the temporal, and which bears also the branchi- ostegous rays. Between these two lateral branches is a single piece, (Jigs. 21, 22, 6,) which, according to the same authority, cor- responds to the chain of bones placed in most fishes between the two first branchial arches. To the posterior point of this bone are attached two rhomboidal portions, (c, c,) to the external margins of which are suspended the arches on which the branchiae are supported, and which represent the chain of bones in fishes, bearing the two last branchial arches. As the age of the tadpole increases, and its metamorphosis is proceeding unseen, (Jigs. 23, 24,) we find the branches which support Fig. 23. Fig. 24. d the branchial apparatus (a) gradually lengthen- ing, and becoming more and more slender, and at length exhibiting the two long cartila- ginous pieces, by which the os hyoides is AMPHIBIA. 99 attached to the cranium ; (jig. 25, a,) the single piece (/>,) and the two rhomboidal pieces (r, r,) in the meantime become united and extended, (Jigs. 25, 26,) and gradually lose by absorption Fig. 25. Fig. 26. d the branchial arches, and ultimately form a broad disc, the body of the os hyoides, the anterior margin of which on each side is di- lated into a scutiform process, and the posterior margin bears two bony appendages, which are, in fact, the posterior cornua of that bone. Such are the changes which this bone un- dergoes during the gradual passage of the amphibious animal from the tadpole state, in which it represents the class of fishes, to its perfect or reptile condition; and it affords a most interesting instance of the manner in which the true nature of an organ, existing under ambiguous circumstances in one class of animals, is often clearly illustrated by its cha- racters, or, as in the present instance, by its transformations, in another. The minute filiform branchiae, which are appended to the tadpole of the frog im- mediately behind the head, have essentially the same structure as is observed in the gills of the perennibranchiate family, as the siren and the proteus, though in a different form. In the proteus each branchia consists of three principal divisions or branches, from each of which proceed seven or eight leaves, again sub- divided into numerous regular leaflets form- ing the ultimate divisions of the branchiae, on which the extreme capillary branches of the vessels ramify, and in which the blood under- goes its necessary change. A minute rami- fication of the branchial artery, conveying the impure blood from the heart, enters each leaf- let at its base, (Jig. 27, a.) and passes, along Fig. 27. its shorter or inner margin, giving off capillary branches in its course, which, after meandering over the surface of the leaflet, and commu- nicating with each other in various directions, pass over to the opposite margin of the leaflet, and reunite in a corresponding ramification of the branchial vein (6), which passes out at the base to combine with the corresponding branches from the other leaflets, and convey the aerated blood back to the heart. This is the general structure, modified however in the different genera, by which this important func- tion is effected in all the amphibia, as long as they are confined to their aquatic life ; and whilst the higher groups lose these organs as they advance, and acquire the necessary organs for atmospheric respiration, those of the lower forms retain them throughout life, coexistent with rudimentary lungs; and thus probably exhibit the remarkable phenomenon of a two- fold mode of respiration at one and the same time in the same individual. Such, then, is the general structure of the organs of aquatic respiration, whether in the early and transitory form in which it is seen in the frog and the salamander, or in the perma- nent character which belongs to it in the peren- nibranchiate group of the siren, the axolotl, the menobranchus, and the proteus. But as the former of these groups acquires gradually a per- fect and unmixed atmospheric respiration, and as the pulmonary cavity serving this office is only slowly developed, so we find in the pe- rennibranchiate forms that the lungs also exist, though in little more than a rudimentary state. The early condition of the lungs in the cadu- cibranchiate genera, in which they ultimately exhibit a somewhat advanced structure, is that of a mere rudimentary sac, without internal cells or any appearance of even the commence- ment of that more perfect structure which they afterwards acquire. Gradually, however, the inner surface is furnished with small processes, forming little sacs or cells, on which the capil- lary branches of the pulmonary vessels ramify, and through the infinitely attenuated surfaces of which the impure blood undergoes its essen- tial process of depuration. In the lower forms of the class, as in ihe pro- teus anguinus for instance, the air-bags, for they scarcely deserve the name of lungs in this state, never arrive at this advanced stage of develop- ment, but remain permanently in the condition of simple membranous sacs. Every part of the apparatus belonging to that organ is equally rudimentary. The glottis consists of nothing more than a small slit in the lower part of the fauces, placed between the branchial apertures of each side. The margin of this little opening, which has no cartilaginous ring to support it, is furnished with a small soft pair of muscles, by which it is opened. The tube leading from this opening speedily bifurcates, and one passes to each air-bag. In this rudiment of a trachea and of bronchi, there is no appearance of car- tilaginous rings ; it is a mere membranous canal, each branch of which opens without any other apparatus into its air-cell. From the perfect condition of the branchiae, and the very H 2 100 AMPHIBIA. simple structure of these pulmonary sacs, it will readily be seen that the function of respiration could be only very ineffectively aided by the latter organs, even were there no other diffi- culty arising from the imperfect structure of the apparatus which in the air-breathing amphibia serves the office of conveying the air into the lungs. A short description of the means by which the act of inspiration is effected in the frog will enable us to judge how far it may be possible that the rudimentary lungs in the pro- tens and siren are to be considered as performing any such function. In the adult frog, toad, salamander, and all others of the higher orders of amphibia, the reception of air into the lungs is effected not by the primary expansion of the pulmonic cavity and the consequent rush of air into it, but by the act of forcing air into the lungs, or in fact by a simple act of swallowing. This is effected in the following manner. The os hyoides and tongue are brought downwards to a considerable extent, and the cavity of the mouth being thus much enlarged, the air enters by the nostrils. The pharynx is then shut at the posterior part, so as to prevent the passage of air into the oeso- phagus, and the cavity being suddenly con- tracted by means of the muscles acting on the os hyoides, the air is necessarily forced through the glottis and trachea into the lungs, as the posterior nares are closed either by their mar- gins acting as a valve, or by the pressure of the tongue against them. This view of the mode of inspiration explains the cause of the well- known fact, that if the mouth of frogs be held open they perish from actual suffocation ; for the motions of the os hyoides being thus im- peded, and an external passage being also afforded for the air, respiration by the injection of air into the lungs is obviously impossible. Any other mode of inspiration, connected with the primary expansion of the thoraco-abdo- minal cavity is obviously impossible in the frog and its congeners, from the total absence of ribs. It may not be out of place to explain here the mode in which the peculiar noise uttered by the male frog, called croaking, is produced.* Ac- cording to the observations of P. Camper, the inspired air is forced against the inferior surface of the tongue, the protuberance of which di- vides it as it were into two currents, which pass into the membranous sacs adhering to the lower jaw and existing exclusively in the males. From these sacs it is directed over the tongue, and by its vibration the peculiar sound in ques- tion is produced. It is an interesting question whether in the perennibranchiate amphibia, the organs which have just been described as rudimentary lungs, do ever serve the purposes of respiration in even the smallest degree ; and it is one of no small difficulty. The superficial structure of the nares in the siren and the proteus, in which they almost exactly resemble those of fishes, and which would preclude the mode of inspi- ration practised by the frogs, together with the slight and attenuated character of the mem- * Comment. Soc. Reg. Scient. Gbtting. v. ix. branous tube and sacs, would almost lead to the conclusion, assumed by Rusconi,that in the proteus at least these organs do not exercise any function appertaining to respiration. If these animals be confined for a considerable time in the same water, the branchiae become purple instead of having the florid red colour which characterizes them in a healthy state, and they die asphyxiated. On the other hand, the very excitement of the two sacs, accom- panied by tubes of such length, and opening to the pharynx by a sort of simple glottis, go- verned by a distinct muscular apparatus, would seem to warrant the opinion that a nearer affi- nity to true lungs is to be traced in these organs than in the air-bag of fishes, though recent observations have shewn the latter organ to be analogous to the lowest rudimentary state of lungs in the higher animals. The chain of affinities, therefore, is here perfect, as far as re- gards the pulmonary cavities. VII. The nervous system. — The centre of the nervous system offers a not less striking in- stance of the progressive development of the am- phibia in their passage from the pisciform to the reptile state than those which we have already shewn in the organs of the other functions of the body. The condition of the brain in the early state of the frog tadpole, the genus in which the changes are most strongly marked, is almost ex- actly that which it possesses in the fishes. The linear arrangement of the different lobes, the broad and lobed form of the medulla oblongata, the small cerebellum, the large size of the op- tic thalami, with the distinct ventricles which they contain, and the very diminutive extent of the hemispheres, all evince a low degree of development, and one not yet emerged from that which we find in the brain of fishes. The same imperfect character is also observed in the spinal marrow, which even in the frog is con- tinued into numerous coccygeal vertebrae, and as the extremities are not yet in existence, is devoid of those enlargements which afterwards take place where the nerves of the anterior and posterior members are given off. The brain becomes developed, however, in a very short period ; the changes which take place being very rapid, though at last not very considerable; the hemispheres become enlarged, expanding laterally and in some measure upwards, con- stituting the first step towards that superiority in position, as well as in size, over the other lobes, which is so conspicuous a character of these important portions of the brain in the higher animals. Fig. 28. represents the brain Fig. 38. 1, pneumogastric nerve; 2, ninth pair; 3, sixth pair ; 4, acoustic ; 5, fa- cial ; 6, the eye : 7, optic nerve and its tubercle ; 8 and 9, base of the hemi- spheres ; 10, anterior por- tion of ditto; 11, pedicle of olfactory lobe. in the common frog after Serres. As the limbs begin to make their appearance, the enlarge- AMPHIBIA. 101 ments of the spinal cord are observed to take place, and the contraction of the coccygeal ver- tebrae into a single linear bone, is accompanied by a corresponding diminution in the length of that part of the spinal marrow, which at length only extends, in the form of a small filament, into the anterior third of that bone. The inferior condition of the brain which has been described as existing in the tadpole of the higher species, is permanent in the proteus and other perennibranchiate genera ; so that the brain of the animal just named bears a very obvious resemblance to that of the larva of the aquatic salamander or triton. VIII. The organ of vision. — The eye differs considerably in its form and magnitude in dif- ferent genera of the amphibia, and without any very apparent relation to either their habits or their circumstances. In the frogs and some others they are remarkably large and prominent ; in the salamanders they are comparatively small, though from their at least equally aquatic habits, this difference might perhaps have scarcely been anticipated, and in the coecilia, as the name imports, the eyes are scarcely if at all visible. In the latter animal the same object has doubtless been intended by this absence of vision, as in the mole and many other ani- mals, whose common subterranean mode of life would render the possession of acute sight not only generally useless, but an extreme inconvenience on their occasional appearance above the surface. In some points of their structure the eyes of the amphibia are not remotely related to tho.se of the fishes ; as, for instance, in the flattened anterior surface of most of them, arising from the small supply of the aqueous humour, and in the depth of the crystalline. In some of the lower forms, there can scarcely be said to be a true orbit, the eyes being fixed as it were in the integuments, and surrounded by a mass of minute veins, intermixed with extremely small branches of nerves. Rusconi states that in the proteus he was not able to discover muscles, nor even the optic nerve ; though on carefully and gently raising the hemispheres of the brain a minute nervous filament was seen going to- wards the foramen which serves for the passage of the ophthalmic artery ; but whether this was the optic nerve or not, appears a matter of entire doubt. In fact, the structure of the eye in this animal, on the whole, is very imperfect. In the frog, on the contrary, the eye is fully developed, and all the essential parts of its structure sufficiently conspicuous. The globe of the eye is large and projecting ; the scle- rotic is considerably solid and tough, and semi- transparent ; the cornea is large, and though somewhat flattened, is much less so than in fishes, or in the lower forms of the elass. The inner surface of the choroid is extremely black, and the external of a silvery whiteness. The ciliary processes have not with certainty been discovered in these animals, unless, as Altena suggests, a little tubercular mass, occupying nearly their situation, and closely connected with the edge of the choroid and with the cap- sule of the crystalline, may be a modification of this structure. The iris is covered on its posterior surface with pigmentum nigrum ; the anterior having a shining metallic lustre, pre- cisely similar to that which we see in fishes. The contractility of the pupil asserted by Carus is denied by Altena and others. The retina is thick, and covers the whole internal surface to the capsule of the crystalline. The vitreous humour is, in proportion, abundant, and the lens is large and of a spheroidal shape, consisting of numerous concentric laminae, en- closing a nucleus of extreme density, exhibiting a close relation to the state of this part in fishes. There are in the frog three palpebrse ; or perhaps, with greater strictness of analogy, it might be said that there are two palpebrae, and a sort of expansion of the inferior, serving as a membrana nictitans. The superior pal- pebra is small, and is not possessed of any degree of mobility; the inferior is broad, ex- panded, and semitransparent. It has an in- ternal membranous expansion, which has just been alluded to, and which is capable of cover- ing the whole eyeball. IX. The organ of hearing.— The function of hearing exists in very different degrees in the different groups of amphibia. The aquatic habits to which the lower forms are confined by their branchial respiration, would render an acute perception of sonorous impulses as unne- cessary as it would be incompatible with the dense medium in which they live ; and we find in this sense, as in every other function of the body, the most perfect concord existing be- tween the habits of the animal and its structural arrangements. The pisciform aquatic genera of this class, therefore, are found to possess as near an affinity to the fishes in the structure of the organ in question as in most others ; and in this they are also imitated by the tadpole state of the higher reptiliform groups, the adult condition of which exhibits a much more ad- vanced development of the acoustic organ. In the proteus and the allied genera, there is neither a tympanic cavity, nor membrana tym- pani ; it consists of a large cavity hollowed as it were out of the temporal bone, at the bottom of which cavity is the sacculus with its creta- ceous body ; the fenestra oval is is closed by a bony lamina, the representative of the stapes. Behind the sacculus are the membranous semi- circular canals. The whole organ is covered externally by the integuments, without any pos- sible communication with the atmosphere. In the frog, on the other hand, the whole structure is more complicated. The sacculus, which is membranaceous, is filled with the cretaceous matter, which is here semifluid, having the appearance of cream. The semi- circular canals are contained within the sub- stance of the temporal bone. The ossicula auditus are three, united, and contained within the tympanum, which they traverse, and are attached to the membrana tympani, a broad round membrane, perfectly superficial, and very distinct from the surrounding integument. The cavity of the tympanum is not capacious. It 102 AMPHIBIA. communicates with the external air by means of an Eustachian tube passing from it to the fauces. In all the essential parts of this struc- ture, there is but little variation from that which exists in the true reptilia. X. The organ of smell. — The nares in the perennibranchiate amphibia are, like those of fishes, confined to little more than a slight cavity on the anterior part of the head, and having no continued canal by which they can communicate with the cavity of the mouth. In the proteus the similarity of this organ to that of fishes is so complete, that even the pli- cated radiations of the lining pituitary mem- brane are almost exactly imitated. It is of considerable size, and is contained in a length- ened canal or cavity, the parietes of which are in no part osseous. The nostrils terminate im- mediately under the upper lip. The olfactory nerves are rather large, and no sooner emerge from the cavity of the cranium than they divide into numerous branches of various lengths, which enter every part of the soft pituitary membrane. In the more highly developed genera the organ of smell has the more advanced structure which is observed in the reptilia. The nostrils are partly cartilaginous, partly osseous, and extend into the cavity of the mouth, though the posterior openings are placed much more for- ward than in the higher classes of vertebrata. The olfactory nerves enter the nostrils through two openings in the ethmoid bone. The ab- sence of the convoluted and extensive surfaces of the turbinated bones, the entire simplicity of the canal of the nostrils, and the small extent of its surface, must restrict these animals to a very circumscribed enjoyment of this function; and it is probable that the sensibility to odours is much more acute in the aquatic forms, in which the organs of sight and of hearing are so im- perfectly developed, than in the frogs, in which the organs of these senses are much more elaborately formed. XI. Of the organ of taste. — The sense of taste, in all the amphibia, as well as in fishes, is probably very obtuse. The tongue in the urodela is small, and attached closely at every part. In the anourn, on the contrary, it is developed to an extraordinary degree; it is very long, bifid, and the anterior half is not only free, but, in its quiescent state, doubled back upon the posterior fixed part, and capa- ble of being thrown forwards and again re- tracted with the rapidity of lightning, serving as a most efficient means of arresting the quickest movements of insects, which it con- veys into the back part of the mouth to be swallowed. The application of the tongue as an assistant in respiration, by closing the posterior nares, in all higher groups of the class, has been before alluded to. XII. The dermal or tegumentary system. — The absence of all hard scaly adventitious covering to the skin of the amphibia is one of the most common, or perhaps it may be said, the only universal peculiarity by which they are, as a class, distinguished from all reptilia. The amphibious nature of their progressive development, or the existence at the earliest period of even rudimentary branchiae, can scarcely be said to be without exceptions, as several genera have already been mentioned as not having yet been observed in this condition. But the naked skin is a character belonging equally to all, from the serpentiform coecilia to the typically amphibious frog, and the pisciform axoloth and proteus. The skin of the aquatic genera is soft, smooth, and furnished with a secreting surface, by means of which it is kept constantly moist, and in a state suitable for that cutaneous respira- tion which strikingly characterises these ani- mals. Many of those which are generally inhabitants of the land, as the terrestrial sala- manders, the toads, and others, are provided with numerous cutaneous glands, which secrete a tenacious milky fluid, which is somewhat acrid, and may perhaps be deleterious if swal- lowed in any quantity ; though the old opinion of the poisonous nature of these animals is altogether without foundation. The fluid which is poured out from these cutaneous follicles in the common salamander is copious, of a milky colour, and consists of mucus, with the addi- tion of some acrid matter, the nature of which is not yet known. From the quan- tity which is suddenly secreted when the ani- mal is injured or any part of the surface irritated, it is not improbable that even the effect of fire may for a few moments be arrested by it ; and thus may have originated the fable of the salamander having the power of remaining unconsumed and unhurt when thrown upon burning coals. The acrid nature of the cuta- neous secretion of the toad was confirmed by the observations of Dr. Davy a few years since. The cuticle of these animals is frequently shed ; that of the aquatic species comes off in shreds, and is washed away from the skin. In the toads a very curious process takes place for its removal. When the cuticle has become dry and unyielding, and a new and softer surface is required, the deciduous layer splits down the median line of the back and of the abdo- men at the same time. The whole cuticle is thus divided into two parts. By numerous con- vulsive twitchings and contortions of the body and legs, this separation becomes more and more considerable, and the cuticle is gradually brought off the back and belly in folds towards the sides. It is then loosened from the hinder legs by similar movements of those limbs, and finally removed from them by the animal bring- ing first one and then the other forwards under the arm, and by then withdrawing the hinder leg its cuticle is left under the fore leg. The two portions are now pushed forwards to the mouth, by the help of which the anterior ex- tremities are also divested of it. The whole mass is now pushed by the hands into the mouth, and swallowed at a single gulp. The new cuticle is bright, soft, and covered with a colourless mucus ; the old skin was harsh, dry, dirty, and opaque. This curious AMPHIBIA. 103 process I have repeatedly watched. I have observed shreds of cuticle hanging about the terrestrial salamander, which would lead to the opinion that this animal does not disengage itself from its deciduous skin in the same manner as the toad ; but as the individuals under notice were not in health, the observa- tion is inconclusive. But the most interesting circumstance con- nected with the functions of the integuments of these animals, or indeed with any part of their economy, is their cutaneous respiration, or the power which the dermal surface possesses of effecting those changes in the blood, which are essential to life, and which are usually per- formed by particular organs set apart for that express object, and modified according to the aquatic or atmospheric medium in which the depurating agent is applied to them. Although the experiments of Spallanzani had long ago demonstrated that carbonic acid was produced by the contact of the atmosphere with the skin of frogs, the subject had never been examined with the care and attention which its importance demands, until the in- vestigations of Dr. Edwards of Paris, given in his work " On the Influence of Physical Agents on Life," set the question at rest, and esta- blished the proposition by a series of interesting experiments, so admirably arranged, so satis- factorily conducted, and so logically reasoned upon, as to leave no vacuity in the regular line of induction, nor doubt of the strict correct- ness of his conclusions. The existence of a cutaneous respiration in frogs was proved by the simple experiment of tying a piece of bladder over the head so tightly as to produce complete strangulation, and then placing them under water. On examining the air contained in the vessel after an hour or two, a sensible quantity of carbonic acid was de- tected. On placing frogs in vessels filled respec- tively with river water and with water which had been deprived of its air by boiling, and inverted over the apertures perforated in the shelf of a pneumatic trough, containing ninety- eight and a half pints, those in the latter lived on the average little more than half as long as those in the aerated water. On trying the effect of stagnant water renewed at intervals, they were found to live two months and a half, and then died from accidental neglect of renew- ing the water. Similar results followed ex- periments made under running water. The effects of temperature in these experiments were very striking, and prove that the duration of life under water is in an inverse proportion to the elevation of the temperature from 32° to about 107, at which point the animals die almost instantly. But these effects of tempera- ture were found to be modified by an increase of respiration, whether by their rising to the surface and breathing the atmosphere, or by the quantity of aerated water being increased. Such is a rapid glance at some of the results observed by this distinguished physiologist, on the cutaneous respiration of aerated water ; those which are connected with atmospheric respiration by the same surface are no less interesting. In order to render the experiments as rigorously satisfactory as possible, pulmo- nary respiration was prevented by actual stran- gulation, rather than by keeping the mouth open, a method which appears liable to some degree of uncertainty. A ligature was passed round the neck of six frogs, using the most rigid compression, so as completely to exclude any possible passage of air. One of them lived twenty days ; those placed in five ounces and a half of water had died in from one to three days. As the severity of the operation of strangulation might probably have hastened death, another mode was tried, namely, the total excision of the lungs, — an operation which appeared to produce but little suffering; the animals were then placed on moist sand. Of three frogs thus treated, two died on the thirty- third day, and the remaining one on the fortieth. Other experiments were instituted to resolve the converse of the former proposition, whether life can be prolonged by pulmonary respiration alone, unaided by that of the skin ? The re- sult of the experiments made upon tree frogs and upon the bitfu obstetricans, was that pul- monary respiration is not sufficient to support life, without being accompanied by the influ- ence of the skin. The results of these experiments are not only highly interesting as regards the habits of the particular tribe of animals which were the subject of them, but still more so with refer- ence to some important questions in general physiology ; but as their bearing on these points can only be shown by viewing them in relation with all the other subjects treated of in the admirable work from which they are taken, it would be out of place to consider them here. It is impossible, however, not to be struck with the evidence they afford, that the respi- ratory organ, that surface through the medium of which the blood undergoes its necessary change by the action of oxygen, whether pul- monary, branchial, or cutaneous, and whether the medium of its access be water or the at- mosphere, is in all cases similar, being a modification of the cutaneous surface. And as we see in the instance before us, the same surface capable of performing either atmos- pheric or aquatic respiration, the inference is obvious, that pulmonary and branchial organs may, and probably do, possess an identity of structure.When it is considered too that moisture is absolutely essential to atmospheric respira- tion, whether pulmonary or cutaneous, the identity of the two processes becomes still more unequivocal. This view of the subject receives considerable confirmation from the fact that branchiae are in many animals capable of exercising the office of atmospheric respiration through the medium of a very small quantity of water ; as the land crabs of torrid regions are enabled to traverse immense districts under a burning sun, by means of those little reservoirs of 104 AMPHIBIA. water, described by Dr. Milne Edwards, formed by duplicatures of the lining mem- brane of the branchial cavity. The eel too, as is well known, will live for a long time out of water, from its branchial cavity being capable of retaining a sufficient quantity of water to bathe the branchiae for a considerable time, thus preserving those organs in a respirable state. XIII. Of transpiration and of secretion. — The particular condition of the skin already described, naked and consisting of a moist mucous surface, would render it probable that cutaneous transpiration should be exceedingly extensive and rapid in these animals ; this is in fact the case to such an extent, that when exposed to too great a degree of heat, the eva- poration of transpired fluid is sufficient to pro- duce a very rapid decrease in the weight of the animal ; which, if exposed for a sufficiently long period to its influence, becomes almost dried up and dies. One object, and that not an unimportant one, of the sensible transpiration of fluid in these animals, the frogs especially, is un- doubtedly to preserve the skin in a condition fit for the performance of that cutaneous respi- ration which has been described. But its still more obvious purpose is to afford a quantity of fluid for evaporation from the surface, in order to reduce and equalize the temperature of the body when exposed to a degree of heat, sufficient to incommode or injure it. This will appear very reasonable when we reflect that these ani- mals will die in a few minutes, if placed in water of 107 degrees of Fahr., though respiring freely with the head above the water, whilst, on the contrary, they will support for hours the action of damp air of the same temperature. The water which is thus transpired is not the result of the absorption of fluids taken in by the mouth, for these animals do not appear to drink. It is received by absorption on the surface of the skin, to which part it is after- wards restored when necessary. But in order to be ready whenever circumstances call for its use, the fluid thus absorbed is conveyed into a membranous cavity, formed generally of two lobes, opening into the cloaca, where it is re- tained, to be again absorbed, and again con- veyed to the surface for the purposes just men- tioned. When a frog is suddenly alarmed, or seized, it ejects from its cloaca a quantity of pure, limpid water, for the purpose of lighten- ing itself, that it may leap with greater facility. This fluid is expelled from the sac in question, and is often mistaken for urine, and the sac for a urinary bladder. Hence, if a frog be kept in a moist situation, without having access to water in any form but in vapour, the skin is always kept moist, and the water-bag always filled. Such is the function attributed in the first place by Townson to the sac in question, and after him by Dumeril, Altena, and others ; but Cuvier, Dr. Grant, and many other anato- mists consider that it is the true urinary blad- der. That Townson's opinion is correct ap- pears, says Altena, " from the circumstance that the ureters do not terminate in the bladder, but in the rectum itself." Dr. Grant states, that on the contrary, "the bladder receives the ureters." The kidneys are of a lengthened form, in the aquatic genera, but are shorter in the frogs and other unoura. XIV. On the restoration of lost parts. — The fact that parts lost by accident, or re- moved for the purpose of experiment, become reproduced in many of the lower animals, has been known for ages. The actual multipli- cation of the species in many, perhaps all the polygastric animalcula, by spontaneous sepa- ration,— that of the hydra by artificial division, — the restoration of lost arms in the different species of asterias, of the anterior or posterior extremity of the body in the earthworm, of the claws of the lobster, and other Crustacea, and of portions of the head in the pulmo- niferous mollusca, are, all of them, phenomena which have attracted the attention, and occu- pied the experiments of physiologists, at va- rious periods. The experiments of Plateretti, Spallanzani, Murray, Bonnet, and others, have shewn that it is not in the invertebrate forms alone that we are to look for this phenomenon, but that the amphibia, and even some reptilia, will reproduce either the limbs or the tail, when removed. This restoration of the tail in the saurian reptiles is indeed a common occurrence, and it often happens that the new tail is double through the whole of the restored length. Of all the observers of this curious phe- nomenon in the amphibia, Bonnet* stands pre- eminent for the laborious and patient zeal with which all his experiments were conducted, no, less than for the conscientious strictness with which they are recorded. In many experi- ments he cut off the anterior or posterior limbs of the common water salamander or triton, which he found to be invariably restored, and even the toes were reproduced, and acquired some degree of motion. The tails were also amputated at various distances from the base, and were always renewed. The same limb was in some cases removed and restored four times consecutively. In all cases it was ob- served that warmth encouraged and that cold retarded the regeneration of the part. The restored portions were not generally well- formed, but in some instances varied by excess, in others by defect. One of the most extra- ordinary results was that which followed the extirpation of an eye from one of these ani- mals. In the course of a year this organ was completely restored, and its organization was found to be perfect. Dumeril records a remarkable experiment of this nature, in his latest work on the rep- tilia. The subject was the triton mar- moratus. Three-fourths of the head were cut off, and the animal was deposited at the bot- tom of a large vessel having half an inch depth of water, which was constantly renewed. It continued to live, and to move slowly. The * CEuvres, in 4to. Ncufchatel, 1769. AMPHIBIA. 105 nostrils, the tongue, the eyes, and the ears were gone; the animal could therefore enjoy no relation to external objects but by the sense of touch. It nevertheless evinced conscious- ness, creeping cautiously and slowly about, occasionally raising the neck to the surface as if attempting to breathe. The process of cica- trization at length completely closed the aper- tures of respiration and of deglutition. It lived three months after the operation, and then died from accidental neglect. After all, this expe- riment proves only the respiratory function of the skin, a fact already sufficiently established by the observations of Dr. Edwards before detailed, and its cruelty does not appear to be compensated for by its results. XV. Of reproduction, — The impregnation of the ova in the amphibia, is effected without actual coitus ; that is to say, it either takes place out of the body, as in the anoura, or the impregnating fluid is received by the mere contact of the external opening of the cloaca in the two sexes, as in the tailed forms. The only exception to this statement is in the land salamander, the male of which has a small intromittent organ. The act itself of impreg- nation therefore differs materially in these two divisions of the class. The generative organs of both sexes are double, and are placed sym- metrically in the abdomen. The testes in the higher forms of the class, the frogs and toads, are small globular oval bodies, having exter- nally a bright white appearance, from the tunica albuginea, and internally a somewhat loose texture, and a yellowish colour. They are placed behind the liver, attached to the vertebral column ; the vasa deferentia are numerous, disposed in pairs; they form a small epididymis, and passing on the outer side of the kidneys back towards the cloaca, dilate into vesiculae seminales, just before they terminate in that cavity. These organs, as in many other animals, become much enlarged at the breeding season. The ovaria are situated in the anterior and upper part of the abdomen, and are internally divided into numerous sacs, by duplicatures of the peritoneum, by which also they are bound to each side of the spine. These sacs are torn at the period of depositing the eggs, whether by the pressure of the arms of the male, as asserted by Prevost and Dumas, or otherwise, appears uncertain. The oviducts are small at their commencement, and become large towards their termination in a sort of dilated sac, which Altena terms the uterus; they are of a pulpy substance, having an in- ternal secreting surface; and the eggs during their passage through them become enveloped in a gelatinous mass. They dilate into a sort of uterine cavity just mentioned, which opens into the cloaca. The mode by which the eggs of the frog pass from the ovaries into the oviducts appears yet to be doubtful. The observations of Pre- vost and Dumas on this subject are generally received as correct, but their statements are denied in some particulars by Altena, and doubted in others. They state that the ova, detaching themselves from the ovaries, are seized by the opening of the tube, but they do not state the mode by which this act is effected. It is a question which was long since examined with great care by Swammerdam, and which brought him into a controversy ; and he con- fesses at last his ignorance of the mode in which it actually takes place. The ovaries enlarge greatly at the breeding season, and the ova at the time of their depo- sition fill the body almost to bursting. At the time of impregnation the male placing himself on the back of the female, embraces the body with astonishing force with the anterior legs, which are pressed under the axillae, and the tuber- cular thumbs, which are at this period con- siderably enlarged to enable him to retain his hold, are so essential to this object, that if they be cut off, he can no longer clasp the female with the requisite force. The instinct which instigates the male frog to this act at the season of breeding is astonishingly powerful, and sometimes no less remarkably blind. Thus, it is recorded by Walter, and has been often observed by others since his time, though the object of this curious fact has been un- accountably overlooked, that frogs are occa- sionally found in the spring adhering with great force to different parts of the skin of pike ; and a near relative of the writer of this article has seen an instance of the same kind, where several frogs were so closely fixed to a large pike as to require some force to remove them. This instinct of adhesion is, in fact, sometimes fatal to its legitimate object. I have before now taken from the water a large con- glomeration of male frogs, amounting to per- haps twelve or more, with one solitary female in the middle of the mass, dead and putrid, and even some of the males, towards the in- terior, pressed into an almost lifeless and shape- less lump. While the male is thus closely embracing the female, an operation which sometimes lasts for more than a month, the eggs, to the num- ber of several hundreds, are gradually ejected from the cloaca, either in masses as in the frog, or in double chaplets as in the toad, an I impregnated by the sprinkling of the semen, as they pass out under the male. In some species, as the bufo obstetricans, the female is assisted in the act of expulsion by the hinder legs of the male. When the eggs are thus deposited in the water, the jelly-like substance in which each is enveloped absorbs a large quantity of it, and the whole mass speedily enlarges to many times the size of the animal from which it was expelled. The male of the bufo obstetricans just men- tioned, when, by his assistance, the eggs are excluded, attaches them to his thighs by glu- tinous threads, and carries them about with him until the young are ready to leave them, when he seeks a pool of water in which he deposits them, and the young shortly afterwards come forth. The impregnation of the tailed aquatic 106 AMPHIBIA. genera, as the tritons, is effected by a totally different mode. During the spring, the males acquire a considerable dorsal membrane, which runs the whole length of the back and tail, and is sometimes curiously indented or fringed at its edye. This membrane is gradually lost after the breeding season, and its use appears to be to assist in the act of impregnation. The male, instead of adhering to the female like the frog, swims by her side pursuing her in all her rapid and changing courses through the water, till at length both remaining for a moment quite still, he suddenly turns up, by the assistance doubtless of the dorsal mem- brane, and places for an instant the edges of the cloacal aperture in contact with hers. It is at this instant that the semen is ejected and received. The eggs are afterwards deposited slowly, and comparatively few in number, upon some part of an aquatic plant, on which the female supports herself by holding by her hinder legs. When the embryo has gradually acquired its larva development, and is ready for its aquatic life, it bursts the thin membrane which encloses it, and emerges in the fish-like form which has been so often alluded to in this paper. XVI. Metamorphosis. — The changes which take place in the different organs during the progress of this extraordinary phenomenon, have been already detailed. It remains to trace the general form of the animal from the egg through its larva condition till it receives its permanent form, and to point out some remarkable peculiarities observed in different genera. In the frog, the toad, and probably all the anoura, the respiratory organs undergo a double change, the branchiae being first external for a very brief period, and afterwards internal during the remainder of its larva existence. In all the other forms in which branchiae have been detected, they remain external till they are lost. The tadpole, whether of the anoura or of the wodela, possesses, at first, as we have seen, the same means of progression as belong to the class of fishes. That of the triton retains its branchiae, co-existent with four perfect legs, until it is about a third of its ultimate length. In the frog the legs which first make their appearance are the hinder ones ; and from the great development of the tail, and the con- tinuous form of the head or abdomen, they ap- pear as if they came through immediately be- hind the head. As the terrestrial salamander, though pre- ferring moist places, does not frequent the water, the young have not the opportunity of being developed in that medium ; but as the essential character of their organisation requires that the first portion of their existence should be passed in the condition of a tadpole or larva, we find that the whole of its metamorphosis takes place whilst in the oviduct, where it is found witli small branchiae on each side of the neck, which are lost as the animal enters upon its terrestrial existence. Like the viper, there- fore, this animal is ovo-viviparous. The arrest of the metamorphosis in the lower or perennibranchiate forms is confined to the organs of locomotion in part, to those of cir- culation, and of respiration. The organs of reproduction receive their full development, though even in these there is a considerable resemblance to those of the fishes. One of the most remarkable peculiarities in the whole of this class, with regard to the sub- ject now under consideration, is the reproduc- tion and metamorphosis of the pipa or Surinam toad. It has long been known that the eggs are developed in cells on the back of the mother; but the facts connected with this curious circumstance have only of late years been ascertained. It is now established that the cells on the skin of the female are not persistent, but grow as the eggs enlarge, and are removed after the young leave them. The male impregnates the eggs as the toad, but immediately places them on the skin of the mother's back ; here they are attached by a tenacious mucus, and the skin gradually thickens in the interstices, forming at length a cell around each. In these cells the young ones not only leave the eggs, but actually undergo their metamorphosis ; and when they leave the back of the parent, they have lost all the characters of the tadpole, and have become perfect animals. It is impossible to contemplate the structure and habits of this remarkable class of animals without being struck by the many interesting points which they offer for the investigation of the physiologist. Whether we consider the evident and perfect transition which many of them present, from the form and structure of an inferior to that of a superior type or organiza- tion, the facilities which they afford us of tracing, as it were under the eye, those mys- terious changes and grades of development which in most cases are accessible only at par- ticular epochs, or are wholly concealed during their progress in the hidden recesses of the reproductive organs, or whether we view the modifications which they present of the respi- ratory and other important functions of life, it is not, perhaps, saying too much to aver that there is scarcely any class of animals which invites the study and contemplation of the lover of physi- ological science by phenomena at once so varied and so interesting as the Amphibia. BIBLIOGRAPHY. — Boddaert, Abhand. von Am- phibien, in Berl. Gesels. Naturf. Freunde B. il. S. 369. Gray, on the class of animals called by Lin- nams Amphibia. Phil. Trans. 1789, p. 21. Schnei- der, Amphib. Physiol. spec. 4to. Frft. a M. 1790-92. Ditto, Hist. Amphib. nat. et literar. 8vo. Jena, 1799-1801. Laurenti, Synops. Reptil. 8vo. Vim. 1768. Meyer, Synops. Reptil. 8vo. Gotting. 1795. Latrcille, Contin. of Buffon. Hist. Nat. des Am- phib. Ditto, Hist. Nat. des Salamandres, 8vo. Paris, 1800. Brongniart, Essai d'une Classif. Nat. des Reptiles. Societe Philom. A. iii. T. 2. Oppel, Ord. Fam. u. Gattung. der Amphibien. 4to. Munich. 1811. Merrem, Tent. System. Amphib. 8vo. Marb. 1820. Roesel von Rosenhof, Hist, nat. Ranar. nostrat. fol. Norib. 1746-61. Ed. Alt. auct. germ. s. t. Naturgesch. der Froesche, &c. fol. Niirnb. 1800-15. Steinheim, Entwickelung d. Frbsche. 8vo. Hamb. 1820. Hasselt, De metamorph. ANIMAL KINGDOM. 107 Ranx temp. Groning. 1820. Kohler, Obs. Anat. in Appendices, &c. Ranar. 8vo. Tubing. 1811. Steffen, De Ranis Obs. Anat. 4to. Berl. 1815. Mertens, Anat. Batrachiorum prod. 8vo. Halle. 1820. Breyer, Fabric. Ranae Pip*. 4to. Berl. 1811. Kl'otxe, De Rana cornuta. 4to. Berl. 1816. Zenker, Batrachomyologia. 4to. Jenae 1825. Rathke, De Salamandr. corp. adip. ovariis, &c. 4to. Berl. 1818. Rtisconi, Descr. Anat. delle larve delle Sa- lamandre, £c. 4to. Pavia, 1817. Ej. Amours des Salamandres fol. Milan. 1821. Ej. Develop, du Grenouille com. 4to. Mil. 1826. Duges, Sur 1'os- teologie et la myologie des Batraciens. 4to. Paris, 1834. Funk, De Salamandrae terrest. vita, &c. fol. Berl. 1827. Cuvier, Rech. sur les Reptiles dou- teux. Par. 1807. 4to. Wagler, Descrip. et icones Ampliib. Monach. 1828. Treviranus, Protei anguin. Enceph. &c. 4to. jGotting. 1820. Rusconi e Config- liac/ii, Del Proteo Anguino, &c. 4to. Pav. 1819. Barton on the Siren. 8vo. Philad. 1808. Edwards, Influence des Agens physiques, &c. 8vo. Paris, 1824. Prevost et Dumas in Ann. des Sc. Naturelles. ( T. Bell.) ANIMAL KINGDOM, an appellation given to that great division of natural bodies to which ANIMALS belong. Like the other kingdoms of nature, the mineral and the vege- table, it is divided into numerous sub-king- doms, classes, orders, genera, and other subor- dinate groups, according to the properties and forms of the objects which it comprehends. As the primary grand divisions of the mineral kingdom are founded on the primitive forms of crystallization, and those of the vegetable king- dom on the endogenous and exogenous modes of growth, zoologists have endeavoured to find some common principle for their first divisions of the animal kingdom. The most common function in animals, and in all organized beings, is generation, and we find the animal kingdom divided into four distinct groups by the modifi- cations of this function, viz., fisslpara, genuni- para, ovipara, and vivipara. But as the fissi- parous and gemmiparous modes of generation are effected without the presence of distinct permanent organs, as the fissiparous mode occurs in isolated species belonging to classes remote from each other in the scale, and as nearly all the classes of the animal kingdom belong to the oviparous division, the modifica- tions of this system do not present the means of establishing primary divisions suitable for the purposes of zoology. Although the pro- cess of internal digestion is not so universal as the function of generation, the internal alimentary cavity is the most universal organ of animals, and its forms therefore merit a first consideration in the establishment of pri- mary groups. It is found, however, that in animals whose general structure is nearly the same, the alimentary apparatus varies so much according to the nature of the food, as to render hopeless any attempt to subdivide the animal kingdom from its modifications ; as from its having one or two apertures, from its being a simple sac or a lengthened intestine, from its having one, two, or more stomachs or glands developed in its course, or other modifications of this kind. In the circulating system we are presented with better means for such divisions than in the digestive, for the radiated classes have only vessels for their circulation, the articulated classes have a superadded ventricle, the mollus- cous classes and fishes a bilocular heart, am- phibia and reptiles a trilocular heart, and the birds and mammalia have four cavities in that organ. The respiratory organs likewise afford the means of founding primary divisions, as into ciliated, branchiated, and pulmonated classes, in ascending from the lowest to the highest forms of that system. The primary divisions of the animal kingdom adopted by Aristotle, viz., animals with red blood and animals without red blood, are ob- viously founded on a single principle of classi- fication, and correspond with the more recent divisions of vertebrata and invertebrata ; but from the number of distinct classes of animals now comprehended under eachofthesedivisions, they are quite unsuitable as primary groups in the present advanced state of the science of zoology. Considering the functions of the nervous system or the intellectual conditions of animals as a means of classification, Lamarck proposed three great divisions, the lowest of which comprehended the animals regarded by him as aput/iic or automatic, the second the sensitive, and the highest the intelligent, which, however, are too hypothetical to answer the purposes of the zoologist. Without any fixed principle for the establishment of his primary groups, Cuvier divided the animal kingdom into the radiated, the articulated, the molluscous, and the vertebrated divisions, which have been generally adopted by naturalists. From the importance of the nervous system in the living economy of animals, some have sought in its modifications a means of establishing primary or grand divisions of the animal kingdom on principles more uniform and philosophical than those commonly employed. In the radiated or lowest classes of animals, wherever the nervous system is perceptible, as in actinia, medusa, beroe, asterias, echinus, holothuria, &c. it is found in the form of filaments disposed in a circular manner around the oral extremity of the body. This lowest form of the nervous system is expressed by the term cyclo-neura, and although, like the radiated and every other character assigned to these classes, it is of partial application, it marks the uniform con- dition of that system on which the manifesta- tions of life are chiefly dependent, and which principally establishes the relations of animals to surrounding nature. A different form of the nervous system is found in the long cylindrical trunks of the helminthoid and entomoid classes, where we observe almost from the lowest ento- zoa to the highest Crustacea, a double nervous chord or column extending along the whole of the ventral surface of the body. This form of the nervous system, common to the articulated classes of animals, is expressed by the term diplo-neura, and it is found to accompany an organization generally more complex than that of the cyclo-neurose classes, and inferior to that of most of the succeeding divisions or sub- kingdoms, especially in the organs of vegetative or organic life, as the vascular, the digestive, and the glandular apparatus. The nervous 108 ANIMAL KINGDOM. system is more concentrated around the en- trance to the alimentary canal in the mollus- cous classes, where it generally forms a trans- verse series of ganglia, disposed around the oesophagus, a character which is expressed by the term cyclo-gangliata. The dorsal position of the great ganglia and nervous columns of the cephalopods, and their partial protection by an organised osseous internal skeleton, leads to the condition of the nervous system presented by the vertebrated classes of animals, where its central parts are in the form of a lengthened dorsal nervous chord developed anteriorly into a brain, and protected by a vertebral column and cra- nium. The vertebrated classes are thus de- signated spini-cerebrata, from the form of the most influential part of their organization. To the lowest sub-kingdom or cyclo-neurose division belong five classes of animals ; viz., 1. Polygastrica, microscopic, simple, transpa- Fig. rent, soft, aquatic animals, in which no nervous filament has yet been detected, generally pro- vided with eyes, with a circular exsertile dental apparatus around the mouth, and with vibratile cilia for respiration and progressive motion, and provided with numerous internal stomachs or cceca communicating with the alimentary cavity. (See POLYGASTRICA.) 2. Porifera, simple, aquatic, soft, animals, without perceptible nervous or muscular fila- ments or organs of sense, with a fibrous internal skeleton sometimes supported with silicious and sometimes with calcareous spicula, the body permeated with a soft gelatinous flesh, covered externally with minute absorbent pores, tra- versed by numerous ramified anastomosing canals, which commence from the pores and terminate in large open vents, as seen in the annexed figure of the halina papillaris, Gr. (Jig. 29), which represents the animal as alive, frf^hrffe!t~ MMffMeifF r.5KTT25^r£gGT -.v^.-'i-^AV-^.-' '-:^*zL.**'--^^i:-:-"?&^*K / '-^^^ . •-,-=rr.^-; ^h**' -' •• '(-» .fc'JJ&i. .."> -I-1" "fffy?" '- • -^---^- J-^=^--r?=jV -'- '. '-.VL . -*..'^i under water, with the usual currents passing inwards through its pores (a a), traversing its internal canals (6), and escaping by the larger vents (c, d.~) (See PORIFERA.) 3. Polypifera, aquatic animals, of a plant- like form, generally fixed, of a simple internal structure, for the most part without perceptible nerves or muscles, or organs of sense, and nou- rished by superficial polypi, which are developed from the fleshy substance of the body, as in the campanularia dickotoma, (Jig. 30), where the Fig. 30. irritable fleshy tubular portion of the animal is seen to occupy the interior of the base, the stem, and the branches, and to extend in the form of polypi from the open terminal cells. The polypi of most zoophytes are provided with tentacula around their orifice, as seen at B, (Jig. 31), and the margins of these ten- tacula are generally furnished with numerous minute processes, termed cilia, (see CILIA,) by the rapid vibration of which, currents are pro- duced in the surrounding water for the pur- Fig. 31. pose of attract- T\ s^fti/is^a ins food and rjtip ^Wtfflr of aerating the I ilk wl///R surface and Iff mrfi fluids of the l^iAliiri body,asrepre- \mllll IW J sented in fig- * W'i| jj \Iif 3' A- (See P°- liHf LYPIFERA.) 4. Aculephtz, soft aquatic free animals, of a simple structure, generally of a gelatinous and transparent texture, and emitting an acrid se- cretion which is capable of irritating and inflaming the skin like the stinging of a nettle, from which the name of the class is derived. They rarely possess a solid skeleton or a per- ceptible nervous system. They are all marine, often luminous, sometimes they possess eyes with a crystalline humour, they feed on minute floating animals, and swim by the contractions of a highly vascular and irritable mantle or by means of air-sacs, or by the rapid movement of ANIMAL KINGDOM. 109 external vibratile cilia, as in the beroe pileus represented m fig. 32. This figure represents careous spines. These animals are for the most part free, but some are fixed, as the crinoid echinoderma, the vascular system is unpro- vided with auricle or ventricle, and the diges- tive canal is seldom furnished with distinct glandular organs. There is sometimes a simple stomach with one aperture and numerous late- ral coeca, and sometimes a lengthened intestine with two terminal openings. Some marine animals without an echinodermatous covering are placed in this class from the similarity of their structure in their more essential organs, as is the case with the holothuria represented in fig. 34. The mouth (a) is here surrounded with one of the ciliograde acalephae in which the mouth (a) is directed downwards, and leads, by a narrow oesophagus, to a wide stomach (6), and from this the intestine proceeds straight through the axis of the body to the anus (c) at the opposite pole. The longitudinal nerves (g), as in holothuria, proceed from a nervous ring around the oesophagus. The ovaries (d) extend along the sides of the intestine ; the surface of the body is provided with eight longitudinal bands of pectinated broad vibratile cilia (M), and two long ciliated tentacula (ff) extend from two curved lateral sheaths. (See ACA- LEPH.E.) 5. Echinoderma, simple aquatic animals, for the most part provided with a calcified ex- terior skeleton or a coriaceous skin, the body for the most part radiated, globular, or cylin- drical, often provided with a distinct nervous, muscular, respiratory, and vascular system. These animals have received the names of echi- noderma, from the spines or tubercles which generally cover their exterior surface, as seen in the annexed figure of the echinus esculentus (Jig. 33.) The mouth (b) is here in the centre Fig. 33. Fig. 34. of the lower surface, and the intestine (b,b.) connected to the shell by a mesentery (c), on which vessels are ra- mified, passes in a convoluted manner upwards to the oppo- site axis where the anal aperture (a) is surrounded by the five openings of the ova- ries (d,d.) The mouth is surrounded with a maxillary apparatus containing five teeth, and the exterior of the complicated and solid shell is seen to be provided with moveable cal- ~o m ramose tenta- cula (c) and an osseous ap- paratus. The intestine is long, convolu- ted, vascular, supported by a mesentery, and termi- nates in a cloaca (z) at the opposite axis of the bo- dy. The rami- fied internal branchial ( ff) open from" the cloaca ; the great systemic artery receives the aerated blood from the branchiae, and the organs of generation (m) open near the anterior part of the body. The irritable coriaceous skin is supported by five broad longitudinal subcutaneous muscular bands, and five crowded series of tubular mus- cular feet extend from its surface. (See ECHI- NODERMA.) The SECOND SUB-KINGDOM Or DIPLO-NEU- ROSE DIVISION comprehends four classes of helminthoid animals and the same number of entomoid classes, viz. 6. Entozoa, parasitic, simple, internal, or fixed animals, for the most part of a lengthened cylindrical form, without distinct organs of sense or any internal skeleton, the mouth or anterior part of the body generally provided with recurved sharp spines, the body generally covered with an elastic white transparent inte- gument, the nervous system seldom distinct, the vascular system without auricle or ven- tricle, without respiratory organs, and with the sexes generally separate. (See ENTOZOA.) 7. Rotifera, minute aquatic animals with distinct nervous and muscular systems, provided with eyes, lateral maxilla?, a dorsal vessel, an intestine with two apertures, and with vibratile cilia disposed generally in a circular form 110 ANIMAL KINGDOM. around the anterior part of the body. They are termed rotifera from the appearance of revolving wheels produced by the rapid move- ment of the cilia disposed around the mouth. One of these minute wheel-animalcules, the hydatina senta, is represented highly magnified in Jig. 35, where the mouth (a) is surrounded with long vibratile cilia (b 6). The oesophagus (c) leads to a capacious stomach (). The pyloric extremity is also surrounded with strong muscular bands ((/), and beyond its pyloric valve two pancreatic simple glandular follicles (e e) open into the duodenum (g) close to the opening of the ductus communis chole- dochus (./'). In the cod (fig. 45, B) the wide oesophagus («) 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. 115 Fig. 45. cles (e 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 vertebrata. This is shown in the annexed figure of the chylopoietic viscera as I found them in the xiphias gladius (jig. 46), where the liver («) 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 cotnmunis choledochus. The pancreas (d) forms a large reniform mass com- posed of numerous straight follicles produced by the successive divisions of the great termi- nal duct (e) of this organ. This large inter- mediate organ is surrounded with a distinct muscular tunic to force its contents into the duodenum immediately beyond the pyloric valve (b). The tortuous small intestine ends by a valvular orifice (f) in a very short but distinct colon, which presents no ccecum in its course to the anus (g). The bilocular heart of fishes is entirely branchial ; it is often pre- ceded by a sinus venosus, and is always succeeded by a butbus urttriusus, which often presents numerous internal valves in its course. The venous blood is entirely sent through the gills, and the branchial veins, after giving branches to the anterior parts, unite to form the aorta which sends the arterialised blood through the rest of the system without the aid of a systemic heart. The respiration is effected by the transmission of water through the mouth or through distinct spiracula, and over the surface of the branchiae, which are internal in the adult, and are often preceded by external branchiae in the young. The lungs are always rudimentary, when present, sometimes in form of a shut single air-bag, sometimes divided or ramified, and most generally communicating by a ductus pneumatic us with the intestine or stomach, or oesophagus, but seldom employed for respiration. Fishes are oviparous and have the sexes separate ; the ovaries are continuous with the oviducts in osseous fishes, and de- tached from them in the plagiostome chon- dropterygii, and impregnation sometimes takes place internally and sometimes after the ova are separated from the body. (See PISCES.) 20. Amphibia, cold and red-blooded, verte- brated, oviparous animals, with three cavities of the heart, with a naked skin, and breathing, in the young state, by gills. These animals com- mence their career like fishes with one auricle and one ventricle, which send the whole of the blood through the branchiae, and they have at this period also double concave bodies of the vertebrae, as in fishes. Many retain the gills through life, accompanied with pulmonic cavi- ties, from which the arterialised blood is sent to a small left auricle. These animals are termed amphibia from the metamorphosis to a terres- trial from an aquatic life seen in most of the species. Their skeleton is imperfectly con- solidated, their ribs very short or wanting, their pelvic arch free or nearly so, and their atlantal and sacral extremities often very imperfectly developed or partly deficient. Their toes are destitute of claws, as their skin is of scales, and the respiration through their naked, highly sensitive, and secreting surface compensates for the imperfect development or limited use of their lungs, especially during submersion or hyber nation. Some reside constantly in the water, others occasionally, and others continue on land. The male organ of intromission is rarely developed, and impregnation of the ova is generally effected externally. The genital organs are double and symmetrically developed in both sexes. The perennibranchiate amphi- bia, especially the axolotl, have been shown by Weber to possess a double auricle like the caducibranchiate species. (See AMPHIBIA.) 21. Reptilia, cold and red-blooded, ovipa- rous, vertebrated animals, with two auricles and one ventricle, not breathing by gills in their young state, covered with scales, and with the means of internal impregnation. These animals, whether aquatic or terrestrial, breathe only by means of lungs, and their pulmonic respiration and the left auricle of the heart are i 2 116 ANIMAL KINGDOM. greater than in the amphibia. Their bones are more consolidated than in the lower vertebrata, theirpelvicarch, when developed, is more firmly attached to the vertebral column, the centres of ossification, especially of the cranial bones, generally remain detached, the extremities are for the most part more competely developed, and the toes are generally provided with claws. Their cerebellum is remarkably small, their muscular irritability languid, and they have great tenacity of life. This ventricle, which receives both the venous and arterialised blood, is more or less divided by an ascending imperfect septum. The thoracic and abdominal cavities are not separated by a muscular 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 cceca-coli, as seen in the annexed diagram (Jig. 47), showing the Fig. 47. common form of these parts in a gallinaceous bird. In these gallinaceous birds the oesopha- gus («) sends out at a right angle with its course a lar^e crop (6), with a contracted neck, and supplied with glandular follicles. Beneath this is the infundibulum or glandular stomach (c), with numerous large follicles placed between the mucous and muscular coats, and this opens into the large muscular gizzard (rf), provided externally with two strong digastric muscles (e). The cardiac and py- loric orifices of the gizzard are close to each other (/"), and towards the lower part of the small intestine a minute ccecum often indi- cates the original entrance of the yolk-bag. The two long cceca-coli (g) commence by nar- row entrances (/(), and the short colon ends in a common cloaca (Z) for the genital and urinary secretions. Inthepredaceous birds, as the eagles (JigAQ), the oesophagus («), the crop (b\ the infundibu- lum (c ), and the gizzard (de), 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 (t'j) and genital organs (/c/c) 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 pleurae 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 fema'e 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 (/») : 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 (/» /*), 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 (fig. 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. (h k h* h*) and the oviducts (f f* f* g) open towards the dorsal and lateral part. The pre- putial cavity (i) is the terminal portion in which the distinct clitoris is here lodged. The ova are impregnated internally, their chorion is calcined, and their development is effected by incubation. (See AVES.) 23. Mammalia, warm and red-blooded ver- tebrata, having four cavities of the heart, with a viviparous mode of generation, and possessing mammary glands ; with the lungs free in a distinct thoracic cavity, and generally having the body more or less covered with hair. The bodies of their vertebrae unite by rial 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 arcVi 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 suleus, 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 coscum, 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. Classis 1. Polygastrica. 2. Porifera. 3. Polypifera. 4. AcalepliJE. 5. Eehinoderma. II. Sub-regnum, Diplo-neura vel Articulate. Classis 6. Entozoa. 7. Kotifera. 8. Cirrhopoda. 9. Annelida. 10. Mynapoda. 11. Insecta. 12. Arachnida. 13. Crustacea. 118 ANIMAL. III. Sub-regnum Cyclo-gangliatavel Mollusca. Classis 14. Tunicata. 15. Conchifera. 16. Gasteropoda. 17. Pteropoda. 18. Cephalopoda. IV. Sub-regnum Spini-cerebratavelVertebrata. Classis 19. Pisces. 20. Amphibia. 21. Reptilia. 22. Aves. 23. Mammalia. For the BIBLIOGRAPHY of this article see that appended to each of the articles on the classes of animals and COMPARATIVE ANATOMY (Introduc- tion. ) (R. E. Grant.) ANIMAL (from anima, breath, the living principle. Lat. animal. Gr. Qov. Fr. animal. Germ. T/iier. Itul 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 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 attention, however, and a more careful study of tQ ttie i,jgiiest of living beings the shape is i l-»n /-ii-i<-i1i + iac* on*-] or-frirme r\f tV» d v.inrmQ nnn 1P*5 T • /* . i • _i : : J 1 ,,-,*. -.»! .r nn 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- 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 thty consist of homogeneous particles like minerals, but are made up in general of heterogeneous parts : in plants we have roots, leaves, branches, flowers, &c. ; in animals muscles, nerves, bones, and a great number of organs besides, each itself reducible to a variety of simpler parts or elements, en- titled tissues. The organic world also presents an immea- surably greater variety of forms than the in- organic : the myriads of animals and vegeta- bles that people and possess the earth differ to infinity from each other in their forms and physiognomies. Size. — Neither is there less discrepancy be- tween the inorganic and the organic world in the quality of size, which, in the first, is perfectly indeterminate, being greater or less, simply as the constituent molecules happen to be aggregated in larger or in smaller num- bers. The volume of organized bodies, on the contrary, is determinate; every animal, every vegetable, has a particular stature, a cer- tain bulk, which is that of its species also, and is within narrow limits alike in regard to all the individuals composing the kind. Composition. — Contrasted in their chemical nature, organized and unorganized bodies pre- sent numerous and striking points of dis- similarity. Modern chemistry enumerates no fewer than fifty-two elementary or simple sub- ANIMAL. 119 stances,* besides the imponderables — light, caloric, and electricity. The whole of these are met with in the mineral or inorganic world; but no more than nineteen of them have been detected in the constitution of organized bo- dies.f Six of this number, indeed, — oxygen, hydrogen, carbon, azote, phosphorus, and cal- cium, occur in such abundance as to compose almost the whole mass of organized bodies ; the remaining thirteen are met with but spa- ringly distributed, and some of them even appear to be adventitious, and by no means essential to the constitution of the bodies in which they are encountered. Speaking generally, the chemical composi- tion of inorganic objects may be stated to be the more simple, many of them consisting of a single element only, and when more com- pound generally presenting binary, and at most ternary combinations of known elements. Organized bodies, on the other hand, are never made up of single elements, they are not even binary combinations, vegetables in the aggre- gate being at least ternary, and animals at least quaternary compounds. Though the elements which compose inanimate objects, therefore, are more numerous, the combinations they enter into are less complex than those they form in the constitution of living things. Another difference in the chemical consti- tution of unorganized and of organized bodies consists in the mode or form in which the che- mical elements exist in each. In the former they present themselves immediately as it were, the chemist in his analyses coming upon them at once ; in the latter they occur under two forms, the one immediate as in minerals, the other mediate, or arranged under a variety of new and peculiar shapes, which, with reference to the bodies they mainly constitute, are con- veniently and fairly spoken of as elements, with the prefix organic, they being exclusively the products of life and organization ; these are also frequently spoken of as the immediate principles of vegetables and animals. In the inorganic world, again, the con- stituent elements of bodies are always united by virtue of, and in harmony with, the general laws of chemical affinity, whilst in the organic the compounds formed are very often even the opposites of those that would have been originated under the dominion of these laws. From this it comes that, whilst the chemist finds almost as little difficulty in recomposing * Oxygen, hydrogen, carbon, phosphorus, sul- phur, borium, silenium, iodine, fluor, chlorine, bromine, azote, silicium, zirconium, aluminium, yttrium, glucynium, magnesium, calcium, stron- tium, baryum, potassium, sodium, lithium, man- ganese, zinc, iron, tin, arsenic, molybdenum, tung- sten, columbium, chromium, antimony, ciranium, cerium, cobalt, titanium, bismuth, cadmium, cop- per, tellurium, lead, mercury, nickel, osmium, silver, gold, platinum, palladium, rhodium, and iridium. t Oxygen, hydrogen, carbon, azote, phosphorus, sulphur, iodine, bromine, chlorine, fiuor, silicium, aluminium, magnesium, potassium, 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 fluids occasionally found included within the sub- stance of minerals, are but adventitious, being in the first instance entangled among their component molecules, in the second imprisoned within accidental cavities in their substances but contributing in nowise to the existence or duration of the matter that surrounds them. Organized bodies, on the other hand, consist, uniformly of solid and of fluid parts : whilst the vegetable has its woody fibre and constituent parenchyma, it has its sap also ; and animals with their firmer bones, muscles, cellular sub- stance, &c. have likewise blood circulating through their bodies, or various fluids de- posited within their tissues, which are just as essential to their constitution and continuance as the containing parts themselves. It is even by the mutual play of the solids and fluids which enter into the composition of organized beings that they manifest themselves in action or exhibit the phenomena which are peculiar to them, and which we denominate vital. It were indifferent whether we took away the solids (were such a thing possible) or the fluids of a vegetable or an animal ; in either case it must perish. The solids and fluids of organized beings consequently are in intimate and inseparable relationship one with another. Consistence. — From this admixture of solids and fluids in the world of organization results the variety of consistence which its objects pre- sent. In the inorganic kingdom, rigidity, — rigidity, too, which is uniform, — is one of the distinguishing characteristics. In the organic, on the contrary, pliancy and softness, which vary as well in every individual as in almost * The exceptions to this position are scarcely worth noticing — one or two of the more simple organic elements, oxalic acid 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, has 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;, tremellze, &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 unimal 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 whioih infusory animals are eliminated during the decomposition of organized sub- stances, is the formation of globular corpuscles; these, by their subsequent aggregation in some cases and individual evolution in others, appear to give birth to the organized atoms that by-and-by make their appearance; and, as we have said, globules are now admitted to form the basis of the different tissues which enter into the composition of the very highest among animals. These various tissues, in fact, would seem to result from the different modes in which the elementary globules are disposed ; and it is not improbable that the difference of function they exhibit may yet be found in harmony with, and perhaps depending on, pe- culiarity of arrangement in their constituent molecules. This aggregation of the organic molecules into a variety of tissues and peculiar organs forms another essential feature of difference between the organized and the unorganized world. Minerals, indeed, as they manifest no variety of phenomena analogous to those of life, required no diversity of elementary con- stitution in their different parts ; they are con- sequently homogeneous. In minerals the com- ponent molecules are arranged in layers placed one upon another, so that their crystals can be readily cleft in a variety of directions, according to the elementary arrangement of these. In vegetables and animals, on the other hand, the constituent molecules always form tissues, the fibres of which interlace or cross one another ; in no living or organic thing do we observe aught similar to what is called the cleavage 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 ganic 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 rind, that whilst in the inorganic world the several parts may be modified without the others feeling the influence of the change in- duced, in the organic, implication of one part and modification of one action are commu- nicated to and manifested in the state and actions of all the other parts. Considered with regard to their duration, the objects composing the organic and the inorganic world differ essentially. In the former this period is determinate and definite, and, although it varies greatly, it depends in a great measure on circumstances inherent in the in- dividuals ; in the latter it is indeterminate and indefinite, and when the objects composing it cease to be, it is generally in consequence of circumstances exterior to themselves. Organized beings exist for a limited time and in oppo- sition to many of the physico-chemical laws ; unorganized beings exist indefinitely, and only in harmony with the whole of these laws. Organic beings continue to exist in conse- quence of a kind of reciprocal action with external things, and especially by virtue of an incessant change and renewal in their con- stituent elements. The very condition of ex- istence of an unorganized body is quiescence ; any new action between its molecules them- selves, or between these and others external to them, any addition to, or subtraction from, its component parts, implies the destruction of its individuality. In the organic world, new forms result from the actions of forms already existing, which have the wonderful property of producing others similar to themselves; and this in virtue of no general physico-chemical law, but of an especial power inhering in each organized being individually. There is nothing like this faculty of procreation or of generation in the in- organic world. When a crystal is produced, it is necessarily at the expense of one or of others that have already existed, or of a combination of the elements of these; destruction is here a necessary preliminary to production, and the process is simply one of re-formation, not of genesis or creation. Neither in the re-forma- tions of the inorganic world do we find that the forms are always necessarily the same as those which preceded them : the crystalline form does not depend on the nature of the integral molecules, but on their mode of aggregation and number. In the organized world, again, nothing is more certain and fixed than that the form of the new being shall resemble that which gave it birth. The last distinction we shall mention under this head of material composition and physical qualities between organic and inorganic bodies is, perhaps, less striking, though not less in- teresting on that account : it is this, — that whilst in inorganic bodies the composition is quite de- terminate, in organised beings, although con- stituting particular species, the composition may present individual differences or modifica- tions. These are designated by the titles tem- perament, constitution, $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, amklst incessant changes and renovations of the matter entering into its composition, and the continuation of the species, which is a genesis or creation, implying neither destruc- tion nor alteration in the mode of being of the individual or individuals from whom the new formation springs. Actions of unorganized and of organized objects. — But form, size, material composi- tion, duration, mode of origin, &c. are not the only particulars in the history of or- ganic and inorganic bodies which are capa- ble of being contrasted, and in which differences may be made to appear. All that exists is active; every entity performs actions, or manifests forces by which its own ex- istence is continued, and by which it participates in the various phenomena of the universe. Of these actions or forces there are two grand classes, the one general, the other special : the first are the physico-chemical laws which per- vade space and include the universe ; the second are the vital laws, which embrace within their dominion plants and animals, or things organized and having life. The most general of all the forces possessed are those of attraction and repulsion, which inhere in, and are manifested by, all existing things, organic as well as inorganic. Every object gravitates or has weight, coheres in its several parts, exhibits chemical affinities, and yields to the expansive influence of caloric. Inorganic objects exhibit these general forces alone, and are absolutely under their control. Organized bodies are also subjected to the same general forces; but they are often modified, nay, they are sometimes even abrogated and set at nought by vegetables and animals alike, in virtue of the special powers inherent in themselves. These special powers have, in fact, the singular property of subtracting, in various degrees, the beings they actuate from the in- fluence of the general laws of creation. In- 122 ANIMAL. stead of obeying the universal law of gravita- tion, vegetables, for instance, shoot upwards, and propel their juices from the roots to the leaves; animals also distribute their blood in opposition to the laws of gravitation, and by their powers of motion overcome the universal physical law that tends to fix them in one place. The force of cohesion is not a merely passive property in the organized as it is in the unorgan- ized world, and the laws of chemical affinity are especially set at nought both by plants and 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 chances 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, \\hich 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 came to an end or die. Origin. — Unorganized bodies, minerals for example, commence their existence from the instant that circumstances exterior to them- selves detach them from the mass of some other mineral, precipitate them from a state of solution in a fluid, or bring their constituent elements into a position in which they can combine together. In this, it is evident, there is nothing like generation, as the term is applied to organized bodies, which all alike, vegetables as well as animals, spring from a molecule, an atom, which has once belonged to, and which has proceeded from, a being similar to themselves. Vegetables spring from seeds, animals from eggs. Organized beings, therefore, are engendered, their existence is a consequence of that of other beings like themselves ; and in their succession they depend one upon another. Minerals, on the contrary, have no powers of reproduction ; they cease to be, if at any time they originate another mineral, and they are individually in a state of perfect independence.* In the mode in which organic and inorganic bodies continue their existence, there is also a striking dissimilarity. In the inorganic world we observe no actions tending to preserve the individual, other than those which have pre- sided over its formation : it continues to exist through the continuing agency of the affinities and of the attraction of cohesion which called it into being. Animals and vegetables, on the contrary, have special powers for their pre- servation superadded to those by the peculiar * It were long to enter here into the discussion of what has been called equivocal generation, which, if admitted, militates against several of the in- ferences just deduced. It is quite certain that infusions of any organized substance do speedily become filled with animals distinct in their kinds and lately shown to be much more complicated in their structure than was long supposed. It is almost as difficult to conceive that these infusory animals proceed from eggs contained in the fluids in which they appear, as to imagine that they proceed from the combination, per se, of their con- stituent elements. Did we incline to admit the reality of equivocal generation, it is certain that its occurrence must be referred to other than the general laws of nature, with which we have al- ready had occasion to show the laws of life to be in opposition, much rather than in harmony. It would be absurd to believe that these general physico-chemical laws, absolutely inimical to life, should at any time call it into being. Equivocal generation being acknowledged, therefore, it would seem necessary to infer a third order of laws be- sides the physico-chemical and the vital, the nature of which is altogether unknown to us. The number of creatures which were presumed to owe their being to equivocal generation, has been very much curtailed by the progress of science in modern times ; and it is not impossible that the mystery which still overhangs the genesis of the infusoria may one day be dissipated, and their pro- duction demonstrated to be in harmony with those laws which are known to preside over the origin of higher classes of vegetables and animals. ANIMAL. 123 agency of which they have been created. Inorganic bodies exist through the absence of all change in their interior; organized beings exist by force of change : there are two pro- cesses, one of renewal, the other of decom- position, perpetually going on within them ; they are continually appropriating from bodies exterior to themselves a quantity of matter which they have the singular faculty of ela- borating into their proper substance, and they have at the same time the power of withdraw- ing portions of the matter which already forms them, and rejecting these from their interior as no longer fitted for their preservation. Vege- tables, by means of their roots and their leaves, draw from the earth and from the air materials which they elaborate into juices fitted for their nourishment, at the same time that they throw off, especially by means of their leaves, a por- tion of the matter which had been absorbed, either as superfluous or as improper to enter into their composition. In the same manner ani- mals appropriate to themselves various amounts of matter in the shape of atmospheric air and food, from which they prepare a fluid proper for their maintenance, at the same time that they, by virtue of peculiar processes, with- draw from their bodies such portions of mat- ter as have already fulfilled their destination, and cast them out under the form of excre- tions. Organized bodies, consequently, are preserved as individuals by a process of nu- trition, a process which implies dependence on other bodies, and alternate appropriation and rejection of the particles of these ; the ex- istence of an organized being, in fact, only con- curs with the presence and appropriation of substances external to itself, with a perpetual accession of matter on the one hand, and of its rejection on the other, whilst unorganized bodies are more certainly continued, as their state of isolation or abstraction from all ex- ternal influences is more complete. Organized beings, in a word, continue to exist by virtue of certain inherent especial powers ; un- organized simply by virtue of the general powers that pervade the universe in harmony with which they were originally framed. The modifications undergone by organized and unorganized bodies are peculiar and cha- racteristic in each class. In the first place modification or change is no necessary con- dition to the existence of an unorganized body, as it is of one that is organized. A mineral in a state of complete isolation might remain eternally unchanged ; a plant or an animal, on the contrary, cannot be conceived as existing for a moment abstracted from the universe around it, and without undergoing change. A mineral, in the instant of its formation, acquires all the properties that distinguish it at any after-stage of its existence ; in plants and animals, on the other hand, as we witness an origin, so we observe a series of modifications denominated nge.t, — 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 intus-susception. Organized bodies, conse- quently, as they alone are generated, as they alone possess powers of self-preservation and of reproduction, so do they alone grow, advancing necessarily from infancy to maturity and old age, or exhibit what are called ages. (See AGE ) Organized bodies further meet our obser- vation in two different states, — those, namely, of health and of disease, nothing correspond- ing to which is encountered in the inorganic world. Whatever has a beginning has also an end. But the mode in which organized and un- organized bodies cease to be, and the influences that determine their periods of being, are ex- tremely different. A mineral ends when the affinities that combined it, and the attraction of cohesion that held its particles together, are overcome. This language implies that its destruction is effected by agencies external to itself — by the action of other bodies, and of circumstances over which it has no controul. The destruction of a mineral is, therefore, in nowise necessr-ru, neither is it spontaneous: abstract a mineral, as we have said, from all external agency, and its endurance is inde- finite. Very different is the case with regard to animals and vegetables ; as their continuance depends on the process of nutrition, their end hangs upon the cessation of this act; and as the tenure by which they enjoy existence is temporary, the machine of organization being calculated to endure but for a season, their death or destruction is both spontaneous and necessary. Organized bodies which alone owe their being to generation, which alone continue their existence, reproduce their kinds, grow, attain maturity, and become aged by virtue of powers inherent within themselves, so do they alone die. The period of endurance of unorganized bodies may often be calculated approximatively according to their masses, their densities, the aptitudes of their elements to enter into new combinations, &c. ; that of organized bodies cannot be inferred from these or any other merely mechanical principles. Indeed, data from which the duration of organized bodies may be estimated are altogether wanting. We only know that every species has within nar- row limits a period which it cannot pass; but why this period should, in particular instances, 124 ANIMAL. be confined to a few weeks, 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 tlie 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. \Ve 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 intus-sus- 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, camp/tor, extractive matter, $ r. 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 between every part of individual organized beings. The cellu- lar tissue consists of filaments and laminae, 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. Physiologic, Ister 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 sixtli 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-cartiiuginous 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 si/stems, 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 manifestation*, 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 die 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 brain and medulla oblongata in the higher animals, the nervous ganglia in the lower, and these same parts are the instruments or elabo- ratories of the internal sensations. Both of these kinds or modes of perception were alike necessary to the beings endowed with them. The external sensations are the watchmen of the system, admonishing animals of the pre- sence of the objects they require for their pre- servation ; the internal feelings, in like manner, are centinels which admonish them of their wants and lead to the employment of the organs by which these may be supplied. By the faculty of locomotion, again, an animal accomplishes all the promptings of his inward nature ; he places himself in relation with the beings and the things which he is ad- monished by his instincts or internal faculties are necessary to him for his preservation as individual and continuance as species. Made aware of his wants by perception, by the faculty of locomotion he is enabled to minis- ter to them. These two powers, let us ob- serve, always exist together; the one, indeed, necessarily supposes the other. Sensibility or perception is the monitor, locomotion the agent. Without perception locomotion could have sub- served no end ; without some capacity of loco- motion perception would have been a vain in- heritance. Vegetables evidently possess no power of locomotion analogous to that inherent among the higher animals, — where the seed falls there the plant springs, there it attains maturity, and there it dies. Neither do they manifest any thing like sensibility in outward act that can be ascribed to volition or consciousness : their nature, in fact, made perception unnecessary to them; and having no power of locomotion, it would have been useless in the two great acts by which organized beings minister to their pre- servation as individuals and to their existence as species. Still it is impossible to deny every thing like capacity of outward motion to vege- tables. Although they have no power of trans- porting themselves over the surface of the earth or through its waters like animals, many of them exhibit motions in their leaves and flowers in relation with the state of the atmosphere, and the diurnal revolution of the earth ; the sexual organs in several species move the one towards the other; and about the foot-stalks and petioles of the mimosa pudicu and other plants we observe particular organs that con- ANIMAL. 1-29 tract when stimulated, very much in the same way as the muscular fibre among the higher animals. Moreover, the motions by which the radicle constantly seeks the ground or tends downwards and the plumula shoots into the air, that by which some of the higher phano- gamous plants twist in spirals around objects near them, and by which all preserve one side of their leaves towards the light, cannot be held as accidental or merely mechanical acts. Seve- ral genera of the confervae and tremellae even exhibit such remarkable oscillatory movements • as have induced different naturalists and phy- siologists to reckon them among the number of the animals. With all this, however, locomotion among vegetables is a very limited power contrasted with the faculty among animals. These exhibit all the automatical motions of vegetables, and have in addition a particular system, the mus- cular, superadded to their organization, by which many of the most important offices of the eco- nomy are performed : not only instrumental in procuring the food by which they are main- tained, but in putting into play the digestive and respiratory apparatus by which the nutri- tive juices are prepared and assimilated, and finally distributed among the higher tribes to every part of the body. The existence of this system is in fact one of the grand characteristics of the more perfect animals. By its means they react upon the external world and modify it according to their wants ; by its means they guide their senses and enlarge the sphere of their acquaintance with things beyond them- selves ; by its means they impress the air with the tones and articulate sounds, or execute the signs by which they make known the various states of their affective or moral and intellectual being to one another ; finally, by its means the sexes approximate, and those acts take place which lead to the engenderment of new indivi- duals and the continuance of species. The best informed among physiologists, how- ever, do not confine the motions of all animals to the act of the particular tissue we denominate muscular. The polypes and many even of the massy acalephs, to say nothing of the smaller infusories, rotifers, &c. though they move freely, cannot be shown to possess muscular fibres in their constitution; neither indeed can any nervous system, upon which muscular contractions and voluntary motion have always been held dependent, be demonstrated in these creatures. It is consequently probable that the means by which spontaneous motion takes place in these lower animals are peculiar, as indeed we must acknowledge the evident mo- tions which occur under many other circum- stances in the world of organization to be. But let us now turn to the special manifesta- tions of vitality of the two great classes of organized beings we are engaged in examining. These we shall consider in the following order, which is also that we have adopted in contrast- ing the manifestations of activity of unorganized and oiganized 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 female, furnishing a germ, which sub- sequently to its impregnation by the male organ undergoes a series of evolutions that end in the issue of an individual resembling the parents, and fitted by its own acts to preserve itself and to continue its kind. Both of these modes of reproduction are common to vegetables and animals. Confervae 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 a.ndj'e»tale, — is also exhibited by vegetables and anima'.i 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 a^ain, or any destruction of the organs them- selves, but simply because the term of existence of the organism of which they formed a part is complete, — they perish with the system to which they belonged. Another grand though not an invariable dis- tinction between vegetables and animals is the mode in which the sexes, or sexual organs — for these may be taken as synonymous terms — are distributed among the individuals of each class. Speaking generally, it may be said that the sexual organs are as commonly divided be- tween two individuals among animals by whom K 130 ANIMAL. the species is represented, as they are confided to one among vegetables, which is, therefore, singly the type of its kind. In both classes, indeed, there are exceptions to this general law : the flowers of all vegetables do not contain stamina and pistilla, or male and female organs, neither are the opposite sexes invariably repre- sented by two different individuals among animals. In many plants the male organs are known to exist in one flower, the female in another, but both developed on the same branch ; in many others, again, they exist on dif- ferent stems, and are often evolved widely apart from one another. In the same manner, many of the lower tribes of animals include within their individual organisms male and female organs; this is the case with several tribes of the genus mollusca, gasteropoda, the helix, limax, and lepas, for instance, with the whole of the extensive classes of the annelida, en- tozoa, echinodermata, &c. But though there be resemblance to this extent among vegetables and animals in regard to organs, in the act by which fecundation is accomplished there is a wide and essential difference ; for whilst vegetables impregnate themselves, or, rather, whilst the impregnation of vegetables is a purely passive process, with- out perception of or concurrence in its accom- plishment on their parts, — the pollen of the anthers of those flowers that have male and female organs being simply shed upon the pistilla, the impregnation of animals, so far as our knowledge goes, appears to be almost as generally a consequence of a connexion be- tween two different individuals, and of volition with consciousness on their several parts. Although many animals have both male and female parts included within the same organism, it would seem that comparatively few have the power of impregnating themselves : two in- dividuals of the like species meet, and give and take reciprocally ; so that there is, in tact, much less difference between the highest and the lowest tribes of the animal kingdom in the essentials by which races are continued, than at first sight appears, much less certainly than there is between the vegetables and animals that are most nearly allied. The modes in which fecundation takes place in vegetab'es at large, and in an imals probably without exception, are inherently and essentially distinct : an her- maphrodite animal is still a very different thing from an hermaphrodite flower. Another difference between vegetables and animals, less important, indeed, but still in- teresting, lies in the number of the organs pos- sessed by each destined for the continuation of the species. In many vegetables the organs are single, one flower being taken as a repre- sentative of the sexes ; in a much larger pro- portion of plants, however, the organs are mul- titudinous. Among animals, on the contrary, with a few exceptions in the very lowest tribes, the asterias, &c. where they are multidinous, the essential male and female organs, the testes and ovaria, exist singly or in pairs only. A third diversity, and one that is striking and almost universal, between those species of plants and animals in which the sexes are represented by two individuals, lies in the difference of conformation, size, and general character of the individuals in the one class, and their perfect similarity in the other. There are very few dioecious plants the males of which are distinguishable from the females ; there are very few 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 dasses 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 le- 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. Mere 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. The food of animals, however, may be stated generally to be both more various and also more complex in its chemical com- position than that of vegetables, and whilst vegetables take all their food in a liquid shape, animals much more commonly live on a mix- ture of solids and fluids. The assumption of food by vegetables and animals takes place under very different cir- cumstances. In vegetables it is necessary and independent of the individual; it is also in- cessant ; and, farther, it takes place from the external surface, inasmuch as it is with this that the materials which supply the nutriment are in contact. Animals, however, have not generally their food prepared for their use brought into con- tact with their bodies, neither are they passive in its assumption ; they have mostly to search for it abroad, and are provided with special organs for this purpose. The act by which 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 capil'ary 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, acalephse, 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-mle 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 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 among the lowest tribes of animals which takes place in all vegetables : the substances fitted for their nourishment penetrate or are absorbed into their systems, and are there assimilated without the intermedium of any special apparatus. We mount but a very short way in the scale of the animal creation, however, before we meet with a peculiar pouch, destined for the reception of the aliment, and accomplishment of the first steps in the processes by which, in the more perfect animals, it is finally assimi- lated. This pouch is the stomach, and with the rest of the digestive apparatus with which it is connected, is in intimate and uniform re- lationship with the kind of food upon which animals are led by their instincts to live. All the accessaries of the assimilating cavity or stomach which we find in animals, from the organs of sense that guide them in their choice of aliment, to the lips that seize it, the teeth or jaws that bruise it or destroy its vitality, the muscular actions by which it is swallowed, and the chemico-vital processes by which it is dissolved, and the purely vital sen- sibilities by which such parts as are proper for nourishment are retained, and such as are im- proper for this purpose are expelled, — all of these are wanting among vegetables. There are yet other processes which form an essential item in the acts by which organized beings universally continue their existence, which it is necessary we should include in this summary of the common, particular, and dis- tinguishing attributes of vegetables and ani- mals. One of the most important of these is Respiration. — The leaves in the more per- fect vegetables are the instruments of respi- ration ; their place is supplied by the general surface in those plants that are aphyllous. Vege- tables that live in air act immediately by means of their respiratory organs upon the ambient medium ; those that live in water, upon the air held in solution by the fluid around them. Vegetables are well known to exhale abun- dantly from the surface of their leaves, or stems, in case they have no leaves. The mat- ter exhaled is principally water. They have also the farther property of decomposing one of the elements of atmospheric air, namely, carbonic acid gas. In the sunshine the leaves of vegetables fix the carbon which enters into the composition of this gas, and set the oxy- gen at liberty ; in the dark, however, a very different process goes forward ; they then actually absorb oxygen and exhale carbonic acid gas ; the balance, however, in the aggre- gate is not equal between these opposite pro- cesses, a much larger quantity of carbon being fixed by the decomposition of carbonic acid gas and oxygen set at liberty, than there is of oxygen absorbed and carbonic acid gas set free. These acts are essential to the life and health of vegetables ; their end and object appear to be the preparation of their proper nutritive fluids or cambium : the sap which reached the leaves, colourless, not coagulable, without glo- bules, mere water holding carbonic acid, acetic acid, a muco-saccharine matter, and various salts in solution, is in them converted into a greenish fluid, partly coagulable, and full of globules, which special vessels then distribute for the growth and maintenance of the different parts. The respiratory act is necessary, and goes on without the aid or concurrence of the indi- vidual among vegetables. Animals are no less dependent than vege- tables on communication with the air of the atmosphere, either immediately or mediately, for a continuance of their existence, or the manifestation of those acts whose sum con- stitutes their lives. In the very lowest tribes the communication between them and the air of the atmosphere takes place over the surface of the body generally, without the intermede of any particular organ or organs for the pur- pose. The fluids absorbed into their 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 may ap- ANIMAL. 133 pear, slender as the means of accomplishing it may seem to be, it is nevertheless essential : interrupted for any length of time, the animal inevitably perishes. A process of such im- portance, as may be imagined, is not long left without its appropriate and special apparatus. This varies extremely in its structure, in the different tribes of animals, and according to the circumstances surrounded by which they live. Some have lungs, 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 involuntariness of the act in the one, and its voluntariness in the other, its occurrence with unconsciousness in the one, and with con- sciousness in the other. The nutrient juices thus prepared have 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 pump or transmit the sap from the roots to the leaves, for instance, as we have already had occasion to state, run within the woody parts of plants ; those that receive the modified juices of the leaves, again, take their course downwards within the bark. These two sets of vessels anastomose within the substance of the leaves, but no where else ; the second set can alone be said to have a distribution throughout the vegetable, for every part appears to depend on them for its supply of nourish- ment, even the extreme points of the roots, which were themselves the first instruments in collecting the aliment still unfit for the purposes of nutrition. The best informed vegetable physiologists are of opinion that the nutritive fluid once sent off from the leaves never finds its way back to these organs again ; it is ab- sorbed or fixed by the different parts or struc- tures to which it is distributed, ministering to their increment generally, and enabling each to manifest its specific function in the vegetable economy. In this motion of the fluids of vegetables it is evident that there is little analogous to what we find within the bodies of animals somewhat elevated in the scale. But let us first cast a hasty glance at what does take place within this other division of the organic kingdom be- fore instituting a comparison between the func- tions of circulation in the two. All animals, from the mammalia downwards to the entozoa, — birds, reptiles, fishes, the mollusca, Crustacea, arachnida, insecta, and, among the radiata, the holothuriae, echini, and asteriae, include within their organisms particular canals or vessels for containing and distributing their nutrient juices, and within which, moreover, these are in motion in a circle. In the aca'.ephoe 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 oft' 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, Sec. Secretion is, therefore, a much more extensive function among animals than among vegetables ; the products are still more various, and the apparatus by which they are eliminated is, generally speaking, far more complicated among the former than among the latter. Certainly, in the very lowest tribes of animals, secretion is an exceedingly simple process contrasted with what it becomes in the higher, whose organization is more complex. Among the polypi, medusae, and entozoa, the whole of this function seems to consist in a kind of transudation, or exhalation from the surface of their homogeneous bodies, without the intermedium of any special organ. Among animals higher in the scale we find secretion performed in two modes, — by vessels, when the act is entitled exhalation, and by means of certain special organs named glands, an arrangement which we also find among vege- tables. The skin and pulmonary surface are the great implements of exhalation among animals, as the leaves are among vegetables ; almost all the rest of the secretions take place by the instrumentality of glands. In vegetables secretion seems to be limited to the preparation of the nutrient fluid by the elimination of certain matters, and, so far as our knowledge extends of the end to be an- swered by any act, for the formation of the generative fluids; we do not, in fact, find among vegetables any apparatus set apart for the excretion of matters derived from a change in the constituent particles of the organs once formed. Among animals, again, the apparatus by which this depuration of the system is ac- complished is one of the most important of all to the preservation of the individual. Secretion among vegetables is a function much more under the influence of external circumstances than it is among animals ; it is also more sub- ject to periodical changes among the former than among the latter, and whilst the function is mostly called into activity by the stimulus of light, heat, &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 beines 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 cctusex, under the title of life, vital principle, sou/, &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- fervae, 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 format ions, 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 ? \Ve 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?, tremellae, and simplest vegetables are also peculiar to them, they differ from those manifested by the simplest animals in being entirely under the influence of external influences, and showing nothing like spon- taneity. The tissues of all animals, even the most complicated, show traces of a vital ten- sion or contractility, different from simple elasticity and not depending on muscularity; the cellular membrane, skin, fibrous tissues generally, excretory ducts, and vessels of all descriptions tend to contract upon the parts ANIMAL. 139 and fluids they surround and include. This tonicity or peculiar contractility disappears in great part with the cessation of life : a wound made in a dead body never gapes as it does in a living one. Something of the same kind exists in vegetables ; the sap as- cends with greatly increased velocity in the young shoots under the influence of stimuli of different kinds, and its flow is checked by nar- cotics and altogether arrested by poisons ; it is probable, therefore, that it takes place in con- sequence of a vital tonicity or contractility in the sides of the sap-vessels which contain it. From this general review of the physical construction and vital phenomena of the two grand classes of organized beings, vegetables and animals, it is impossible not to remark the strong features of resemblar.ee, and yet the numerous points of difference they exhibit. Both have a beginning, which happens very much in the same way in each ; bolh live as individuals by the susception of aliment and its prepration by a variety of processes, which, in their essence, differ but little from one an- other ; both continue themselves as kinds in a surprisingly similar manner ; both exhibit the changes denominated age; both have a merely temporary existence, consequently both exhibit the phenomenon entitled death, and both are decompounded after the cessation of life, their constituent elements assuming new shapes, in obedience to the general laws of chemical affinity, which had been set at nought during the existence of the individuals in either class. Notwithstanding these striking points of re- semblance between vegetables and animals in all that is essential or general, it is impossible, as we have seen, to condescend upon par- ticulars without immediately detecting differ- ences that distinguish in the most marked manner the individuals of the one class from tliose of the other. It is always in their lowest or most simple species that we remark the most striking similarity between vegetables and animals, and it is among these that we constantly find ourselves most at a loss for characters distinctive of each. We observe no evidence of anything like a connected chain of being from the lowest or most simple, to the highest or most complicated vegetable, and from this through the most inferior animal upwards to man ; it is, on the contrary, in the extremes or lowest grades of each that the greatest similarity prevails; here vegetables and animals approximate very closely, here they literally inosculate, but from this common point they begin to form two distinct series, which diverge ever more and more widely from one another as they ascend. Without attention to particulars, it would seem impos- sible to adduce as ultimate terms of distinction between vegetables and animals, other faculties than those of voluntary motion and sensation as peculiar to the latter, in virtue of the one of which powers they are rendered in a great mea- sure masters of their own existence, whilst by the other they are endowed with consciousness of many of the various acts that take place within, and of the phenomena that occur without them. Even this distinction, how- ever, is only applicable as regards species con- siderably raised above the lowest; would we indicate the differences between the most in- ferior members of either series we must con descend upon particulars, and, in some in- stances, even call in analogy and inference to our aid in laying down the chart of their re- semblances and dissimilarities. COMPARISON OF ANIMALS WITH ONE ANOTHER. This head is also comprised within that of our entiie Cyclopaedia. The glance we shall cast over the field it embraces will, therefore, be very cursory, and the views taken of the objects it presents extremely general. Physical qualities and material constitution of animals — In point of size, animals differ most widely from one another. The existence of some is only made known by the aid of a powerful microscope, the length of others ex- ceeds a hundred feet, and their weight amounts to many tons. These extremes include animals of every intermediate bulk. Theyb/vrt 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 aie established. Some animals present themselves in the likeness of a globule, others of a Jilument, and others of a small flattened membrane (the cyclides). Various animals, again, from exhibiting no uniform or regular shape, have been entitled amorphous or heteramorphous. Animals which exhibit a determinate form naturally arrange themselves into two classes ; their bodies are either disposed around a centre, or they consist of two similar halves cohering along a middle plane or axis; the first are the radiata, the second the binaria or symmetrica of naturalists. The radiata are not a very extensive class of animals, neither is their organization extremely complicated. The symmetrical is a much more numerous class than the radiated, and includes within its limits creatures of such simple structure as the en- tozoa, and of such complicated fabric as quad- rupeds and man. Of the symmetrical animals, some consist of a mere trunk without appen- dices or limbs ; those that are provided with limbs, again, have them in the shape of feet, fins, wings, or hands, according to the media in which they live. In some the body forms as it were a single piece, in others it is divided into portions, such as head, trunk, and tail. Sometimes it is naked ; at others it is covered with shells, scales, spines, hair, &c. Some- times the general integument is continuous, unpierced by any opening that leads to the interior, at others it is reflected inwards, and lines extensive cavities there contained. 140 ANIMAL. With regard to structure, as may be imagined, the amorphous tribes, at the bottom of the scale, are the most simple of all. The bodies of some of these are without any internal cavity, and without any division of parts; they are homogeneous masses, generally gela- tinous in appearance, and simply cellular in structure, without arrangement into tissues or particular organs. The external surface of these animals imbibes the matters which are fitted to subserve the purposes of nutrition, and we may presume that it throws off by transpiration such particles as are worn out or have accomplished this end. The external surface is also the organ of respiration in these animals. They procreate by the evolution of gemmi from their surface, and if they possess sensibility the element to which it is attached must be generally diffused throughout their sub- stance. The organization of the radiata becomes con- siderably more complicated. Fluids are no longer absorbed from the external surface of the body ; we meet with an internal cavity, the rudiment of a digestive apparatus, having a single opening in some of the species, which serves consequently for both mouth and anus, but in others presenting two openings, a mouth properly so called on one side of the body, and an anus on the other. Through the walls of this cavity the nutritive fluids make their way, and infiltrate the general mass of the animal's body. In this class we also discover the rudiments of a nervous and of a muscular sys- tem. The nervous system consists of rounded masses of a soft whitish substance, equal in number to that of the radii composing the animal, connected together by slender white cords, and sending off filaments of the same description to all parts of the body, but espe- cially to the outer integument, and to the inter- nal digestive apparatus. The muscular system consists of reddish and whitish fasciculated fibres disposed in the line of the motions. The external surface of these animals is still the only organ of respiration they possess. The three systems now enumerated — the digestive, the nervous, and the muscular — are readily demonstrated in the majority of the symmetrical animals, and are even very soon found to have acquired complication, and to have sundry other parts and organs superadded to them. The digestive apparatus consists of .a mouth for the susception of aliment, of a stomach for its elaboration, of an intestinal canal from which the nutrient juices are ab- sorbed, and of an anus from which the un- digested residue is expelled. Whilst in the radiata the nutritious fluids passed through the parietes of the digestive cavity to impregnate the body of the animal, and be assimilated with its substance ; in the binaria we find vessels, the mdiments 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, WHY* 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 exteinal respiratory surface we by-and- by find an especial system dedicated to the aeration of the juices prepared for nutrition ; this is the respirator'/ 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 1o make use of this elastic fluid suspended or dissolved in water. The existence of this separate respiratory apparatus presupposes that of another system, namely, the circulatory. The fluids prepared by the organs of digestion are not yet fitted to minister to the growth and nutrition of the organization; to be made apt for this purpose they require exposure to the air in the lungs or gills wherever these organs exist, and these be- ing distinct, or contained in a particular region of the body, a series of conduits were re- quired, first to carry the fluids thither, and to transmit them subsequently to every part of the organization for its support. Like all the other systems of animals, the circulatory exists of various degrees of complexness; when first encountered it consists of a series of simple canals or vessels, which diverge on every hand ; by-and-by it has several, and finally one, forc- ing piece, or heart superadded to it, which impels the fluids by its contractions to every the most remote part of the organization. Among animals, however, nutrition is not a process simply of addition or composition ; it is also, perhaps universally, one of subtrac- tion or of decomposition. We have seen the composition provided for by special systems in animals occupying very low grades in the scale of creation ; we mount but a short way before we encounter an apparatus which pre- sides over the decomposition also in the shape of another system of vessels, the veins and especially the lymphatics ; these collect the superfluous and worn-out particles from every part, pour them into the general current of the circulation, wherein being exposed in the vital elaboratory of the lungs they are either assi- milated anew and made fit once more to form an integral part of the organization, or, being subjected to the action of certain glands, they are singled out, abstracted, and finally ejected from the system entirely. In the most com- plicated animals therefore a peculiar appa- ratus for the depuration of the system is su- peradded as complementary to the absorbents. This we find in the glandular bodies familiarly known as the kidneys ; the vehicle in which the decayed particles are withdrawn is the urine. \\ hen we examine the instruments of sensa- tion, we find them becoming gradually more ANIMAL. 141 and more numerous, and the nervous system generally more and more complicated as we rise in the scale of animal creation. The ner- vous system is before long found to consist of other parts than a series of similar ganglions supplying at once the organs of sensation and those of digestion ; it has a central part super- added, from which issue immediately the nerves that supply the organs of the senses, — sight, hearing, taste, and smell, which at the same time make their appearance with their especial capacities. This central superadded portion is the brain, with its prolongation in the vertebrata entitled spinal marrow. Nor in the more perfect classes of the animal king- dom is the nervous system even thus simple ; among them it consists essentially of two grand divisions, the one including the brain and spinal cord and the nerves thence pro- ceeding, the other constituted by the system of the great sympathetic, or that series of ganglions which, situated on either side of the vertebral column, from the head to the pelvis, are con- nected with one another, and with the cerebro- spinal system, by branches of communication, and furnish the digestive apparatus with almost the whole of the numerous nerves it receives. The nervous system in its relative degree of development and complexity becomes the ultimate standard by which the perfection of animals is estimated, and their place in the scale of creation assigned to them : if man stand alone and unattended, as he undoubtedly does, upon the summit of the pyramid, it is only because he possesses in his brain the organs of certain moral and intellectual facul- ties which occur in no other living thing; these confer on him his humanity; these are the ma- terial parts to which the soul is wedded during his existence. In intimate connection with the functions of phrenic or animal life, and developed nearly in the same ratio, is the muscular system, the most universal agent of locomotion. Exceed- ingly simple at first, and operating at great disadvantage through a want of levers and points of support, we trace it becoming gra- dually more complicated as we ascend, and, finally, provided with a complementary skeleton or frame-work by means of which it acts to the best advantage. The skeleton among animals is of two kinds, — external and horny, internal and osseous. In the first case the muscular system is inclosed within the resisting pieces which it has to move ; in the second it is without these, and is arranged around them. The bones and muscles together compose the numerous and variously fashioned instruments with which animals accomplish the promptings of their inward appetites and instincts. They form feet, fins, hands, the prehensile tail, &c. The muscular system, and a modification of the osseous, the cartilaginous, moreover, com- pose the most universal instrument by which animals communicate their vicinity, their states, their dispositions or affections, &c. to one ano- ther— tins is the larynx. The means by which species are continued, are extremely varied. The very lowest tribes of animals we have seen shooting forth buds exactly like vegetables, and these being in due season detached from the body of the parent, find themselves fitted to commence an inde- pendent existence. At the next step we take in ascent, however, we meet with particular organs of reproduction ; and, singular enough, the moment these exist they are not of one, but of two kinds, denominated male and fe- male. Sometimes these organs are possessed by single individuals, far more commonly, however, they are divided between two, whence the so uniform division of the beings com- posing the animal kingdom into sexes. The simplest form of the male organ of generation is a gland secreting a fecundating fluid (the testis) and an excretory duct : the simplest form of the female apparatus of generation is a gland or body producing germs (the ovary) and an excretory duct. In a greater state of complication or development these essential parts in the male have an instrument super- added to them by which the fecundating fluid is carried directly into the body of the female, and in the female the ovary has a dilatable cavity superadded in which the germ remains for a season, and until its included embryo attains such a state of development as is com- patible with its more independent existence surrounded by the circumstances amid which it is afterwards to live. In the higher classes, the connection between the parent and offspring does not cease immediately on the birth of the latter, and in the highest of all we find the female furnished with a complementary apparatus (the mammae), from which she fur- nishes her young with food during the first period of its existence. Actions of animals. — The foregoing rapid sketch of the grand features of distinction among animals with reference to their struc- ture naturally leads to the inference of di- versity of function in harmony with the pecu- liar organization possessed by each. In the lowest grades of animal existence we have seen to how simple a process the act of nutrition — this act so complicated among the more elevated tribes, — is reduced. It consists merely of imbibition or absorption by and of exha- lation from the general surface of the body. The matters absorbed appear to be assimilated incontinently, or to be made a part of, and to receive the form proper to, the animal in the instant of their assumption : applied imme- diately to the homogeneous organism, the nutriment is forthwith made a portion of its substance. The vital decomposition of the bodies of these lower animals is accomplished with the same simplicity and directness : the surface that absorbs is also that which exhales the worn-out particles of the system. The first step by which nutrition becomes more complex, as we rise in the scale of cre- ation, is the institution of a process of solution (digestion), by which the matters appropriated as aliment are prepared for reception into the body. This process of solution is accom- plished by powers inherent in the animal itself, within a cavity destined for the purpose. In 142 ANIMAL. our survey of the structure we have already seen to how great an extent the organization became complicated as a consequence of this centralization of the office of digestion, and with what variety of superadded function this complication was attended, namely, external absorption, sanguification or the formation of a fluid, the pabulum of nutrition, confined within vessels, respiration, circulation, and, finally, assimilation, in regard to the compo- sition ; whilst with reference to the vital de- compositions we have discovered another spe- cies of interstitial or internal absorption, and depuration of the system by one principal apparatus, the kidney, to which the cutaneous and pulmonary exhalations may be added as supplementary. But every one of these functions, and its organic apparatus, are themselves modified, according to internal aptitude, and in con- formity with the circumstances surrounded by which animals commence and continue their existence. Digestion is a very simple process in those cases in which it takes place within a single cavity, having but one opening, and no complementary apparatus of any kind, compared with what it is when connected with an apparatus for bruising the food, for mixing it with saliva, for macerating it in a crop or a series of reticulated and foliaceous pouches, mixing it with bile, pancreatic juice, &c. &c., and transmitting it along a muscular canal, of six, eight, or ten times the length of the body to which it belongs. Absorption, in like manner, among the most inferior classes is essentially one and undi- vided either in kind or destination. It is in itself adequate to the entire office of nutrition, seizing and transmitting the matters which are fitted for this end, elaborating the food and atmospheric air at the same instant of time, and effecting immediately the composition of the whole animal organism. In animals higher in the scale, we perceive, in the first place, that there are several species of absorption : there is, in the first place, the absorption from the surface of the digestive passages and that from the surface of the lungs, gills, skin, &c. or of the respiratory apparatus. Again, absorption is not limited to furnishing materials for the com- position of the organism ; it is also entrusted with the office of abstracting from its interior the particles which are worn out and no longer fit to continue the ends of their existence in the places they occupy. Nor is this all ; for it is by absorption that the amount of those exhaled fluids which moisten internal cavities, having no external communications, is regu- lated, and by which, as it would appear, many of the secreted fluids, the bile, and the sper- matic fluid in particular, are inspissated and rendered more fit to accomplish the important ends they subserve in the economy. Absorp- tion in the highest classes of all is even per- formed by two, and perhaps three different orders of vessels, the lacteals, namely, the lymphatics, and the veins. Further, absorption is not in the higher as it is in the lower classes of animals a function effecting immediately the composition and de- composition of the parts and particles of the organization. It is intermediate to the pre- paration of the nutritious juices and their ap- propriation or assimilation by the organism. The lacteals or absorbent vessels of the in- testines collect the fluid called chyle from the pultaceous alimentary mass in its progress through the intestines. But this fluid is not yet fitted to subserve nutrition ; as a pre- liminary it lias 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 or-jans, 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 d 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 trachea of those animals whose respira- tion is diffuse, and that exist on the surface of the earth, consequently are filled vvitli air; those of the creatures that exist in water are conduits for the constant transmission of this fluid. When the respiration is concentrated, corresponding modifications in the function are encountered according to the medium in which animals live : the air is either received immediately into the body, when the apparatus is known as a lung, or, suspended among water, it is passed over the surface of the respiratory organ, which is then denominated gill. Quadrupeds and birds respire univer- sally by means of lungs, fishes and the mol- lusca by means of gills. In certain reptiles the function is carried on by means both of lungs and gills, and as it would appear even by the general surface of the body either vica- riously, or at one and the same time. These are the only true amphibious animals. A circulation, properly so called, is the ap- panage of an organization already somewhat complicated, consequently of an animal con- siderably raised in the scale of creation. This function, it is evident, as implying in its sim- plest sense a progressive motion of the general nutritive fluid or blood, can only exist where such a fluid is encountered. It is altogether wanting, therefore, among those animals in which nutrition is accomplished immediately. We ascend but a little way in the scale before we find the function consisting not only of an outward or progressive motion of the nutritive fluids, but of a retrograde motion also of these same fluids modified in their nature, and re- quiring exposure to a greater or less degree in some form of respiratory apparatus to fit them anew for distribution to the organization at large. The fluid in this instance parts from a centre, and returns thither after having made the round of the system. Circulation in this acceptation only occurs among those animals that have a separate respiratory apparatus, and in which we meet with absorption of nutri- ment from without, and of lymph, &c. from within. The pabulum of nutrition is taken up by lacteals and veins from the digestive apparatus, and by veins and lymphatics from the rest of the organism for transmission, under the name of venous blood, to the apparatus of respiration, whatever its form. In this the fluid, still immature and unapt for assimilation, is exposed in vessels of infinite minuteness and extreme tenuity to the action of the at- mospheric air, and having undergone in these a certain change, it begins to be collected by another set of vessels, which form branches suc- cessively of larger and larger size, until finally it is projected from the respiratory apparatus in one or more trunks, under the name of arterial blood, fitted for assimilation by the organization at large, and proving the principal stimulus under the influence of which its various par- ticular organs accomplish their offices. Circulation, however, as a function, is com- plicated in the same degree as the apparatus by which it is effected. In some classes we find the circulation taking placing through vessels 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 secretion, properly so called. In the lowest tribes excretion is quite simple, consisting of a mere exhalation from the general surface of the body. In the more elevated we find another and very important form of excretion super- added, that, namely, of the urine, the nature of which, and the mode in which it takes place, we have already indicated in speaking of the structure. Secretion, however, even in the classes but a little raised above the lowest, is a function of much more varied import, and con- sists of a great many other processes than that by which the bodies of animals are depurated and their blood maintained in a state fit to supply all the wants of the system. We ad- vance but a little way before we begin to detect distinct organs destined for the secretion of peculiar fluids from the general mass of cir- culating nutriment, evidently subservient in many cases to the most important ends of the economy, and by no means destined to be rejected from the system as useless, like the excretions properly so called. It seems even that it is by a process analogous to secretion that the imponderable matters — the heat, light, and electricity, which we have acknowledged as elements in the constitution of organized beings, are eliminated. All animals possess sensibility or sensation, though evidently in the most dissimilar degrees. Some have been supposed to possess the faculty of perceiving impressions made upon them by external objects, but to have no power of re- acting upon external nature, they being without the faculties which in the higher classes prompt to action. This state; however, of animal ex- istence is rather hypothetical than demonstrable, and in animals generally we observe not only the aptitude to be impressed, but inherent capacities inducing reaction upon the world around them. The sensitive life of these beings consequently consists of two items — the senses and their organs, external and internal, by which im- pressions are received and cognized, and the affective and intellectual faculties by which the motives to action, the propensities, sentiments, instincts, appetites, &c., are originated, and the means and modes of accomplishing their promptings are supplied. Animals evidently differ immensely in the degrees in which they are endowed with ex- ternal and internal senses. Some appear to possess none of the external senses save touch ; others, in addition to this, have taste and smell ; the most perfect besides these three reckon sight and hearing. The internal senses, in like manner, are more or less acute, more or less numerous, according to the consitution of ani- mals : those of hunger and thirst are probably universally distributed, and the most keenly felt; then come those which induce the respira- tory act, the sexual act, &c. ; and here we find ourselves among the propensities which exist in very different numbers and kinds in every different species of animal. Some tribes tend their offspring, others leave their progeny to the care of accident, which in this case always suffices for their protection ; some con- gregate in herds or shoals, others live solitary or in pairs; some are bold and rapacious, others timid and gentle, See. 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. 1-15 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 thev still perform those partial motions which their preservation as individuals require — taking their food, respiring, voiding their excretions, &c. Those that can move from one place to another have organs in relation to the mode in which this motion is accomplished, whether it be by creeping, by swimming, by running, leaping, flying, &c. &c. Every partial movement ex- ecuted by the higher animals has, farther, its own special apparatus : the intestinal canal has its muscular parietes; the necessity that is felt to communicate internal sensations and ideas has its pathognomonic means in the looks, gestures, sounds of the voice, and so on. Nor is it only in the greater or less degree of complexity of their general structure, in the num- ber and diversity of their particular organs, or in those of the actions whose sum constitutes their vitality,thatanimals differ from oneanother; they vary farther in the degree in which these organs and these functions are enchained or mutually dependent. In the most simple animals so complete is the independence of the several parts, that their bodies may be divided into numerous pieces without injury to the vitality of any one of them, each possessing in itself the capacity to commence a separate existence. In animals somewhat more elevated in the scale we observe very extensive powers of reproduc- tion at least, of parts that have been lost, and even of continuing existence in very insignificant remainders of their bodies. In the most ele- vated tribes, however, the dependence of every part upon the whole becomes such that neither will the body essentially mutilated survive, nor will any part of the slightest consequence con- tinue to live. Among the beings at the bottom of the scale we have in fact found the organiza- tion to be homogeneous, or without distinction of parts, and nutrition to be accomplished by means of an immediate absorption and exhala- tion; and as 'every part possesses the structure which makes it capable of these two acts, every 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 VOL. I. contain the organs of every one of the functions essential to nutrition. Further, it is certain that the nervous system, when once it has fairly made its appearance, strictly dominates the nutritive function, and that every part of the nervous system itself becomes progressively more and more dependent on one of its portions, the encephalon or brain, as animals stand higher in the scale of creation, and as the functions over which the nervous parts preside respectively are themselves of a higher order. These are new and additional reasons for the centraliza- tion of life, or for the complete dependence of the organs and their functions one upon another among the more perfect animals — man, the quadrumans and quadrupeds, birds, &c. So much for the acts that minister to the preservation of the individual. Let us now turn to the interesting series by which species are continued. In the very lowest grades this end is accomplished without the concurrence of sexes : at a determinate period of its life the animal either separates into several fragments, which become so many new and independent individuals, or it throws out a number of buds or germs from its external surface or from a particular internal cavity. The first of these modes of reproduction is entitled fissiparous, the second external gemmiparous, and the third internal gemmiparoit-s. 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, arid it is only subsequently, under the in- 116 ANIMAL fiuence of a certain temperature, and after the lapse of a certain time, that the young being bursts the shell and commences its independent existence ; this is the case among oviparous animals. Or otherwise : the fecundated egg makes its way so slowly through the passages that lead from the ovary outwards, that it is hatched before it can escape, so that the young one passes from the body of the mother imme- diately. Animals in whom this happens are justly said to be ovo-vivipuroits. In the third and last place, the fecundated ovum is imme- diately loosened from the ovary, but instead of being laid, or extruded from the body immedi- ately, it only passes along a canal to a certain distance from the ovary, where it meets with a reservoir or cavity (the uterus) to which it at- taches itself, and within which it commences a series of evolutions, at the expense of the mother, preliminary to its final expulsion with instincts ready formed, and an organization so perfect as enables it to begin its separate ex- istence. The classes in which this mode of reproduction obtains, and they are the highest of all, including quadrupeds and man, are en- titled viviparous, so that in these, besides the connection of the sexes and the fecundation of the germ, we have the phenomena of utero- gestation and labour. And here the proper work of reproduction ends; but the young are so generally born in some sort immature, that in the higher classes the connection between the offspring and pa- rent does not cease immediately. In the class of mammalia, indeed, the connection is little less intimate during the earlier periods of extra uterine life than it was during the whole term of mtra-uterine existence ; the young being still depends upon its mother for the whole of its nourishment, and very generally for the supply of warmth it requires and the protection needful to it till able to provide for itself. 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