No.573.

LONDON, SATURDAY, AUGUST 23, 1834.

UNIVERSITY OF LONDON.

LECTURES

ON

C O M P A R A T I V E A N A T O M Y

AND

ANIMAL PHYSIOLOGY,DELIVERED BY

ROBERT E. GRANT, M.D., F.R.S.E.,&c., &c. ;

Fellow of the Roy. Coil. of Physicians of Edin.,and Professor of Comparative Anatomy and Ani-mal Physiology in the University of London.

LECTURE XLIV. IOK THE DIGESTIVE ORGANS OF FISHES,AMPHIBIA, AND REPTILES. I

OF all the organs of nutrition, or ofvegetative life, the digestive are thosewhich are most immediately related to

the kind of food, the peculiar instinctsand habits, and the whole structure andinternal economy, of animals. We haveseen, throughout the invertebrated tribes,that the form and the development oftheir digestive apparatus are most inti-mately and necessarily connected withtheir means of perceiving, distinguishing,and obtaining their food, their organs ofperception and locomotion; so that the

organs of the senses, the nervous system,and even the muscular and the osseoussystems, have their structure, and forms,and extent of development, in perfect ac-cordance with the condition of the diges-tive organs. Indeed the organs of animal

life, notwithstanding their importance andtheir high physiological character, are

subordinate to those more general organsof individual nutrition or of vegetative life,and are developed in accordance withtheir condition. The monad is ciliatedto move about, and select and seize itsprey, because it has many hungry sto-

machs to satisfy with particular kinds offood ; but the poriferous animal, feedingon the simplest forms of organic matterdiffused through the mass of the ocean,needs no such power of locomotion, andit grows, fixed like a lichen, on the rocks.When the digestive apparatus becomesmore exquisitely organized, and adjustedfor the assimilation of matter only in aparticular condition, it must necessarilybe provided with numerous organs ofsense, and organs of locomotion and pre-hension, to distinguish and obtain thispeculiar form of matter. These mutualrelations necessarily exist between all theparts of the same animated machine, andtheir study leads to the discovery of thoseinteresting laws which regulate the co-

I existence of organs and parts in animalbodies. It is by an acquaintance with.these laws that we are enabled, from thestructure of one organ, to infer that ofmany others, and from the examination of: part of an animal to construct its wholefabric.

In the class of fishes we see the first-and lowest vertebral condition of the ali-mentary canal, and of the whole digestiveapparatus. Fishes, voracious to a proverb,subsist almost entirely on animal food.The ocean teams chiefly with animal life.It is a dense and rich and moving andtempestuous element, where vegetation iscomparatively small, contrasted with itsdevelopment in the light and unresistingelement of the atmosphere. This richand re&i&tmg element of water abounds,! in every latitude and in every drop, with.all forms of animated beings. We observe,! thus, that fishes have the means of easily! satisfying their voracious appetites with aselection of all kinds of food in the ani-! mals that team through every latitude, andthrough every stratum of the ocean whichencompasses so large a portion of th3globe. Their teeth are not generally in-struments for mastication, but, as we haveseen, are formed for prehension, and areoften fixed, with a solid osseous connexion,to the gums, by the ossification of their

pulp, without roots or alveoli, not opposedto each other like flat-crowned teeth;

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they are sharp, recurved, similar, dense tand pointed cones ; they are often loosely (attached to the jaws, disposed in nume- i !

Tous rows, consisting chiefly of bone, with IIlittle or no enamel, and therefore it is that I i

we find their central pulp so frequently i :

ossified and anchylosed to the surface of Ithe jaws in more advanced life. Thosecrowns of teeth are obviously mere pre- ihensile organs, as you observe frequently ideveloped in different parts of the mouth- in other classes, as on the tongue in birds, Bon the vomer of amphibia, on the pala-Itine bones of serpents, on the tongue ofmolluscous animals, and even on the Itongue of fishes. Those prehensile or-

gans, adapted to grasp and retain everyliving thing that moves in the waters, areplaced in all parts of the mouth of theseall-devouring animals; they are placed Ioften on the branchial arches, on the os I

hyoides, on the intermaxillary bones, on I

the palatine bones, on the vomer, on thepharyngeal bones, as well as on the upperand lower jaw-bones. Some fishes are

entirely destitute of teeth of every kind.The tongue is generally very short, broad,and fleshy, in fishes; their oesophagus isgenerally very wide and short, and withinternal folds of the mucous coat, andopens directly into their capacious sto-mach. Thus the food of fishes not beingmasticated in the mouth does not dwellthere, and as there is abundance of mois-ture with their food, they require no sali-vary glands, and have none. Their aeso-phagus is wide, because their food is swal-lowed entire.Now then fishes, which are but hungry

larvae, have thus their large stomach almost openihg on their outer surface, so

wide and short generally is the cesopba-gus. They are all stomach, like the larvseof other classes, and are chiefly intent

upon the gratification of their voraciousappetites. All other sense seems to beabsorbed in this. No soft sounds to charmtheir ears are heard in the silent deep.No roaring of lions, or other fierce ani,mals, to excite their alarm. They are

dumb, because they have no lungs norlarynx; and so they should be, as they areso deaf. Their huge eyeballs, what canthey see to engage their attention but theirprey in the vast dark deep, clouded withmud, or the ever-moving sands? Yousee, therefore, that all their senses butthat of hunger are obtuse. Look at theirsmall brain; it is permanently in the veryembryo state, the very earliest con-

dition of the human foetal brain. Andthus fishes have little to mind but theirstomach, which is a crucible adapted forthe decomposition of all kinds of organizedmatter. The stomach of fishes is often, in

the form of a large spherical sac, with itscardiac orifice near to its pyloric, as yousee in this lophius, and with strong mus-cular parietes. We observe the cesopba-gus often very thick and muscular, andmarked by longitudinal or transverse foldsof the mucous coat, which extend alongthe cavity of the stomach, and the begin-! ning of the stomach is often indistinguish-able from the ossophagus. Sometimes thisstomach is more of a flask form, dilatinggradually from its commencement at thecardiac orifice to the middle, then taper-

! ing downwards to its lower closed extre-

mity, as you see in the polypterus, thexiphias, and many other fishes.The pyloric orifice is variously situate

upon the polymorphous stomach. Some-times it is placed near to the cardiac ori-fice, as you see in the sword-fish, and thelophius; sometimes, as in the tetraodon andthe lamprey, we observe it placed at thelower extremity of the stomach; some-times the stomach bends upon itself, as

we see in the rays and the sharks; this is. the common form in the higher cartilagi-nous fishes. The stomach here, in the3shark, passes down wide and then forms1 an angle, turning upwards, and becoming1 narrower and more muscular towards thepyloric extremity. The pyloric muscularpart of the stomach in fishes is often

strong as a gizzard. At this pyloric ex.- tremity of the stomach we observe themucous coat, passing freely inwards, andforming a circular projecting fold of themucous coat, with rough margin, extend.

ing into the interior; this is the pyloricvalve, which is remarkable for its con-

stancy in this class. In the molluscousanimals similar valvular folds are common.In the class of fishes, beyond this pyloricvalve we observe the orifices of the hepa-tic and the pancreatic glands.Those pancreatic glands in the osseous

fishes have the form of small appendiculaetrea, more or less numerous, that openaround the pyloric extremity of the stom-ach immediately beyond the pyloric valve,pouring their secretion, of a turbid whiteappearance and thick consistence, into thecommencement of the duodenum. This isthe form and position of the pancreas inthe osseous fishes; but those pyloric cseca.vary very much in their number and forms.Sometimes there are hundreds of themcommunicating with each other, and col-lected together in this situation aroundthe pyloric end of the stomach, as in themackerel; or opening by one great orificeat the commencement of the duodenum,as in the sturgeon and in the sword-fish,We find the number diminishing untilwe are left, in the perch, with only three

cæca, and in the lophius and the pleu..

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ronectes with only two. The nature andrelations of those appendices, however,are not in the least altered by there

being only two, or as many as two hun-dred. In the cartilaginous fishes the pan-creas has a conglomerate appearance,from these casca being so much lengthenedand so much subdivided. ’

In the digestive organs of the xiphia8 gla-dius (Fig. 160), which is a powerful preda-

ceous fish inhabiting the open seas, weobserve a very strong muscular oesophagusleading to a closed, lengthened, bottle-

shaped stomach (Fiy. 160, a), with verythick parietes and a strong cardiac sphinc-ter. The pyloric orifice (Fig. 160, b) isnear the cardiac, at the anterior extremityof this long narrow sac, and has a verydistinct internal fold of the mucous coatforming a circular valve. Immediatelybeyond this valve is seen the entrance ofthe ductus communis claoledoeh2cs, and thewide opening of the general duct (Fig. 160,f) of all the pancreatic cæca, which hereform a large reniform mass (Fig. 160, e),covered with a muscular tunic and the pe -ritoneum. The liver (Fig. 160, c) is un-divided, rather small, and sends out threelong hepatic ducts, which enter the cysticnear to its termination in the duodenum.The gall-bladder (Fig. 160, d) is curved,pyriform, with a long cystic duct. Thesmall intestine (Fig. 160, b, g) is long, nar-row, and muscular, and presents an inter-nal circular fold of the mucous coat pro-jecting free where it terminates in the veryshort, wide, and straight colon (Fig, 160, h),forming a distinct valvula coli. The pan-creas (Fig. 16 1) of this animal when openedshows its innumerable component caeca

connected together into a large kidney-shaped mass by means of intervening cel-lular tissue and capillary vessels. Thiz-large pancreas is composed of innumerableshut sacs, each about a line in diameter;the closed ends of which are seen all ovet

the surface of the organ. These little cseca.are filled with a thick white secretion, andare formed by the successive divisions ofthe single great duct by which they allpour their contents into the duodenumimmediately below the pyloric valve, as Idescribed many years ago in the Medico-Chiricsgical Transactions of Edinburgh.Each caecum composing the pancreas

of the sturyecn does not open separatelyinto the duodenum as stated by CUVIER,but by one great orifice, as shown byMoNRO, and as I have shown also in thexiphias. If we are reduced in the class offishes to this very simple form of the pan-creas, consisting of two caeca, obviouslytraced to be this organ, by following itfrom man downwards, or from this formup to man’s, in what form should youexpect to find this organ when you looked

for it lower down in the scale of animals ?Somewhat, surely, of the same simplestructure as we saw it in the gasteropods,in the condition of a single pyloric caacum,conjectured rightly by CARUS to be the

analogue of this organ.It is interesting to ti ace downwards theforms of those well-known glands, and toseek thus for their simplest forms in thevertebrata, in order that we may recog-nise the still simpler forms of the sameorgans when they present themselves

among the invertebrated classes.In the cartilaginous fishes the pancreas

assumes the conglomerate form which itpresents in the higher forms of vertebrata.In the sword-fish, that organ is very large;it is larger than the liver itself; it weighssix ounces more than the liver; it con-sists in the sturgeon, as in the xiphias,of numerous casca. enclosed in one massin a muscular sheath, hundreds of cseca.

that are all ramified from one great ductor orifice, and that orifice opens intothe duodenum close to the anal side ofthe pyloric valve, and to the terminationof the ductus eommasnis choledochus. This

complex pancreas is surrounded exter-nally by a peritoneal and a muscularcoat. This muscular structure of the exte-rior tunic compresses that large glandularorgan, and forces out the secretion whichits numerous component caeca contain.In the cartilaginous fishes there is a trueconglomerous gland, the most highly de-veloped form.The intestine of fishes varies consider-

ably in its length, according to the kindof food; it is for the most part short, andsometimes is much shorter than the

length of the body. In the flying-fish you! will observe that it passes in a straight! line from the mouth to the anus, and isthus not half the length of the body, andyet this is in a vertebrated animal. It is

740

almost equally short and straight in thelamprey. At other times it has numerousand long convolutions. At a short dis-tance before it terminates in the rectum,we observe that it sends inwards a fold of’the mucous coat, which forms a valvularprojection into the interior of the cavityof the intestine; that is the valve of thecolon ; the colon from that part is gene-rally somewhat, though very little, en-

larged to the extremity of the rectum. In- the river lamprey, petromizon fluviatilis,’before you, you observe the oesophagus, I,stomach, and intestine, passing nearly in,a straight line from the mouth to the anus, Ithe whole alimentary canal being shorter I-than the length of the body. In the car-tilaginous fishes we observe, in the raysand sharks, that on the exterior the in-testine appears remarkably short, and al- Imost straight from the pyloric extremityof the stomach to the anus, but the foodhas a very extensive course to pass throughin going through this apparently straight.intestine, in consequence of a convolutedfold that is seen to wind round in a spiralmanner through its whole interior. Thisconvoluted fold is seen also in the stur-

geon and most chondropterygii. In the

rays it presents an extensive surface, fromthe close approximation of those convolu-tions; but in the sharks, the spiral turnsof this mucous fold are placed at a greaterdistance from each other, although thekind of structure is essentially the sameas in the rays, formed like the turns of astair, along the whole course of whichthe food has to pass. We observe the in-testine of considerable length in severalof those fishes, although their food is notvegetable. This is frequently on accountof the low degree of organization of theanimals upon which these fishes chieflysubsist, and, consequently, the degree ofelaboration which such food has to un-dergo before it can be brought to the con-dition of their body. There is no cæcum

on the colon, but only the valvula coli.The alimentary canal in fishes passes Ismooth, without valvulæ conniventes, butwith villi, and often rugae, and terminatesin a short general cloaca, which receivesthe terminations of the two oviducts inthe female, as well as the terminations ofthe urinary organs, and in the male theterminations of the two spermatic vessels.They are differently placed here, however,from the position which they occupy withrelation to each other in quadrupeds; forif you consider their position in this spe-cimen of the father-lasher, you observethat on the anterior part is the openingof the intestine; the rectum is seen pass-ing down in front of the ovaries. Themiddle part presents the single opening of

’the two united oviducts. The oviducts,which in osseous fishes are only the ante-rior portions of the ovaries, communicatewith each other before their final opening,and form thus, apparently, one ovary oroviduct, with its upper part divided intotwo. The posterior part of this generalvent, that next to the tail, presents theopening of the urinary organs, sometimeswith and sometimes without a bladder.In the mammalia the rectum is placed be-hind the urinary organs in front, and thegenital organs in the middle. On eachside of the anus in the cartilaginous fishes,there is a valvular oblique opening whichleads into the cavity of the peritoneum, asyou observe in all the rays and sharks.These two peritoneal openings at thesides of the anus are seen in other fishes,as the lamprey, the sturgeon, the sword-’ fish, the salmon, and also in animals ofaquatic habits belonging to the class of

reptiles, as we see in the gavials, the cro-> codiles, and the alligators, and may serveto allow some peritoneal fiuid secretionto escape, though their valvular oblique3 orifice will permit nothing to enter. The- anus in fishes is never at the end of thetrunk, and is generally considerably ante-

) rior to the end even of the abdominal

-cavity, which often extends far backwardss into what appears to be the caudal part ofr the trunk.

Now as this digestive apparatus offishes is its simplest form met with in thevertebrata, we find it to present all thatdiversity which we commonly observe inthe lowest conditions of organs. The dis-tinction of great and small intestine issometimes obvious, and sometimes quiteimperceptible. Although there are yet novalvulæ conniventes, the mucous surfaceis often greatly extended by longitudinalor transverse rugs’ or plicae, or by its vil-lous surface. The alimentary canal isshort in fishes, because they are yet low inthe scale, and their food has less change toundergo to bring it to their condition;but their short canal possesses the powerof quick and effective digestion, by meansof the strong muscular coat of the sto-mach and intestine; and by the great de-velopment of the liver, and’ of the pan-creas, and other glandular cryptæ openinginto its interior. Swallowing everythingthey meet, they can reject from their sto-mach the shells and other indigestibleparts of their food, like rapacious birds.Their liver is always large, and generallylight-coloured and oily, but their pancreaswe have seen to present every stage ofdevelopment, from two simple caeca to itsmost conglomerate form, and often it isentirely wanting. The rudiments of sali-

vary glands are seen in the numerous

741

small glandular cryptæ, which often givea spongy or cellular appearance to their

. palate, as shown by RATHKE in the carp.The spleen, sometimes single and some-times divided, is found attached to the Istomach or to the intestine, and the me-sentery is now a constant part, to give the ’’

intestine attachment to the vertebral co-lumn, and to support the ramifications ofbloodvessels, lacteals, and nerves. The

air-bag generally communicates with theintestine, the stomach, or the oesophagus,by the ductus pneumaticus, but does notyet serve as an organ of respiration. The

cavity of the abdomen is here separatedfrom that which contains the heart andthe respiratory apparatus, by a diaphragmstill entirely membranous, and its perito-neal serous cavity opens, often externally,by the two lateral anal passages.The tadpoles of amphibia are all stomach

and voracity, like the fishes-the greattadpoles of the sea, and like the voraciouslarvæ of many insects; but by the meta-morphosis of the tadpole, as by the changeof the larva to the perfect insect, the longand capacious intestine is greatly reducedin extent, and adapted to the change offood, and the new condition of all theother organs of the body. The jaws andmuscular apparatus for mastication arestill feeble in the amphibia, and the foodis mostly swallowed entire. The teethare mere prehensile, slender, conical,sharp spines, placed sometimes, as in Ifishes, in numerous rows on the palate andjaws, as in the siren, or, more serpent-like,in single rows on the palatine bones and on 1both jaws, as in the common tritons, or ’only on the upper jaw and the palatinebones, as in the frogs; but the toad andthe pipa have both jaws destitute of teeth.The long, free, and cleft tongue of the frogapproaches much more to the ordinaryform of the bifurcated tongue of higherreptiles than the short, thick, fleshy formof that organ in the perenni-branchiatespecies of amphibia. The strong muscularand dilatable cesophagus leads to a length-ened narrow stomach, directed trans-

versely from left to right, and generallywith thick fleshy parietes, covered aboveby the two lobes of the liver, and having asingle lengthened spleen attached to itsleft side. The stomach is most lengthenedand narrow in the tadpole and the aquaticspecies, and these exhibit the least dis-tinction between the small intestine andthe colon. The young tadpole of thecommon frog (Fig. 161), with its fish-likeform and its small round sucking mouth,feeds on all kinds of soft animal and ve.getable matter found in the fresh-waterponds and stagnant pools, and possessesan alimentary canal of extraordinary

length adapted to this simple and mixedkind of food. The intestine is nearly equalthroughout and only a little enlarged to-wards the end of the rectum, so that there

is still as little distinction of great andsmall intestine as in the fishes, and thisequality of the alimentary tube is its em-bryo condition in all higher animals. Thelong intestine is easily seen through thetransparent abdominal parietes of theyoung tadpole, coiled in a circular man-ner upon itself, and distending the abdo-men by its numerous convolutions. Pro-portioned to the trunk of the young tad-pole, the intestine has at this period manytimes the length which it has in the adultanimal, when the food consists entirely ofprey of a higher character, as snails,worms, caterpillars, and similar animals.found creeping on the ground or on plants,During the metamorphosis there is nopart of the economy of these most mu-table animals that undergoes greaterchanges than the intestine and the wholealimentary apparatus. Those changes wehave already traced in the osseous system,.especially in the os hyoides and the ver-tebral column, and in the nervous system,as well as in the disposition of their mus-cular apparatus connected with respim-tion and locomotion. In the intermediatestages of the metamorphosis we observethe different conditions of their alimentarycavity, it becomes gradually shorter, as thefood changes, and in the adult state of the

742

frog (Fig. 162) it is not one-quarter ofthe length, proportioned to the magnitude Iof the body, which it had in the tadpole- state, when its numerous long convolutionsdistended the abdominal cavity.

The stomach presents a thick muscular Iand pyriform sac in the adult of the com-mon frog (Fig. 162, m n) and in the toad ;and it is still of a lengthened form, as inmost of the amphibious animals, as you ob-serve in this land salanaander, and in thiscommon aquatic crested triton, where youobserve it covered entirely, above and be-fore, by the two lobes of the liver, andhaving the spleen fixed by cellular sub-stance and vessels to its left side. Theintestine performs a few convolutions ofinconsiderable width in the adult state ofthe frog, and is marked in the duodenumby several transverse folds of the mucouscoat. It presents a little difference be-tween its small and its large intestine,which is wider and more straight in itscourse; and it terminates in a generalcloaca, which also receives, as in the fishesand other oviparous vertebrata, the ter-minations of the urinary and genitalorgans. At the back part of the length-ened stomach we almost always find a longnarrow pancreas, which partakes of thelengthened form of the liver and spleenand stomach. These viscera have gene-rally a more lengthened form in the tailedamphibia than in those which lose that

organ of motion. You observe that samelengthened and undivided form of the

liver, of the pancreas, of the spleen, and ofthe whole alimentary canal, in this a:rolotlof Mexico, and in other aquatic species.Thus we observe that, in the different con-stitutions of these changeable amphibiousanimals, the intestine and the whole ali-mentary apparatus undergo changes to

adapt them to the different kinds of food onwhich they subsist in the different stagesof their metamorphosis. Feeding at firston the minutest animals and the softestaquatic plants, of which there is a never-

failing abundance in the rich aquatic me-dium in which they are at first developed,we observe they are at length able by thedevelopment of their legs and their lungsto come to the banks of the pools of waterthey inhabit, and gradually to seize larva",snails,,worms, and similar nutritious food,until at last their aquatic, fish-like careerterminates in an almost terrestrial

reptile condition. In this last stagethey are confined thus to animal foodof a higher character. So that the ali-

mentary canal in those which undergoa metamorphosis is twice changed in itsessential condition. It begins in the veryyoung tadpole by being very short andsmall, and, equal throughout, as in all othervertebrata in the early embryo state; itthen rapidly assumes the long convolutedform of intestine, where the stomach is

but imperfectly marked in the more

mature tadpole; and at length it again

becomes shortened in the adult frog, whenall the divisions of the intestine becomemore distinct and obvious.The serpents still present teeth on the

palatine and intermaxillary bones, as wellas in both jaws, but like the teeth ofinferior vertebrata, they are still nearlysimple crowns, sharp, conical, incurvated,and are adapted for prehension, not formastication. Neither their loose jaws northeir slender sharp unopposed teeth areadapted for this function. Like theworms and larvæ they consist of themere trunk of higher animals, and alltheir internal organs partake of the longcylindrical form of their body. The sali-

vary glands vary in the extent of their deve-lopment, as we see also the accompanyingdestrttctive poison gland. They feed onliving prey, and their scaly lips and longfiliform bifurcated tongue, emploved as anorgan of touch, are little adapted to giveacute feelings from their food, which passes

through their mouth and oesophagus un-divided. The oesophagus is therefore

capable of enormous distention, and in its

. collapsed state presents a longitudinallyl plicated appearance, with thin and very: elastic parietes, lubricated by a most

743

copious secretion of mucus. This highly ! t tdilatable character of the first portion of 1 1the alimentary canal, for the swallowing of entire prey, corresponds with their (want of prehensile hands or feet, andaccords with the condition of the bonesaround the mouth, so that they are able Ito convey through the mouth and the!!oesophagus animals many times the ! sdiameter of their own body, as you ob- I :serve in the dissected specimen before you,where a snake with the neck smaller than Ithe point of the little finger has yet con-veyed into its stomach without subdivisiona large full-grown frog ten times thatsize. The oesophagus thus passes insen- Isibly into the stomach as one wide length-ened pouch. The stomach is thus capableof being dilated to many times the diameter

Bof the natural condition of the trunk, asyou observe in the stomachs of the boaconstrictors before you. The œsophagus,the stomach, and the whole external partsof the trunk of the body, we observe to Ipossess alike the power of dilatationwhich we already saw in the jaws. Theexterior integuments are highly elastic,and are covered not by large plates ofhorny suhstance, as in the crocodiles, orwith fixed bones and large plates of horn,as in the chelonian reptiles, but withsmall detached pieces, that can easily beseparated to a distance from each other,and allow the trunk to expand. Themucous coat here is remarkably thin andvillous, and presents an immense surfacefor the secretion of mucus. At the loweror pyloric extremity of this longitudinallyextended stomach we observe a contractionwhere the muscular coat is thickest, andthe sphincter muscle and valve of the

Ipylorus are placed. From this point ofthe commencement of the duodenum, theintestine, in this boa, presents numerous Bvery small convolutions for about a sixth

part of its length. The whole of thesmall intestine is here convoluted into a

very small space; these convolutions arefixed to each other by cellular substanceand by numerous bloodvessels. You require Ito cut this cellular connecting tissue inorder to separate those convolutions fromeach other, and to perceive the length ofthis small intestine. At first view, onopening the boa constrictor or any of theseserpents, this intestine appears twisted, asif it were the spiral intestine of a ray orof a shark, with a spiral fold passing intothe interior ; it has that appearance untilyou have dissected its turns asunder, andshown the simple convolutions of thissmall intestine. Where the small intestineterminates in the large, there is a smal’caecum of the colon ; that csecum has E

tapering form, and in a boa constrictor o

ten feet long the cæcum of the colon isbetween three and four inches in length,and about an inch and a half in breadth ;commencing wide, from the beginning ofthe colon it tapers up to its shut extremity.It is bound to the small intestine likewiseby cellular tissue and by the peritoneum ;and if you did not dissect out this cæcum.of the colon, you would not ascertain thatit had such a caecum at all; indeed youwill generally fmd it stated that reptilesare destitute of a cæcum of the colon, buthere I have dissected it out and left it

exposed to view. The colon proceeds wideand straight to the termination in thecloaca, which receives also the termina-

tions of the two oviducts in the female,the two ureters, and, in the male, also thetwo grooved organs of intermission whendouble, as well as the terminations of thetwo spermatic vessels which end at thebase of the grooved male organs. The

liver and the other glandular organs ofthe abdomen, as the spleen, the pancreas,the kidrieys, and the testes or ovaria,present the same lengthened form whichwe observe in the stomach and in theother parts of the alimentary cavity in theophidian reptiles. The pancreas in the

serpents is divided into numerous lobes,and those lobes send out each a separateduct which continues free into the duo-denum. That structure has lately beendescribed by my friend Dr. DuvERNOY.It appears to me to point out a beautiful

!! transition from that simple condition of thedetached pyloric cxcaiu fishes where those

little glandular portions of the pancreasIoden separately into the intestine, to thestill more concentrated form which we meetwith in birds, where there are still separatelobes and pancreatic ducts, and thence tothe mammiferous form, where there is onegland and one duct. In the lowest rep-tiles, as the cæcilia, we still find the in-

testine, as in the lowest fishes, passingstraight through the body, and shorterthan the trunk, and we observed the sameshort course followed by the alimentarycanal in the carnivorous serpentine formsof the articulated classes.

The crocodiles and the lizard tribes aremostly carnivorous, like the serpents, andfeed generally on entire and living prey;;so that we still find in them the shortmembranous and simple alimentary canal.Their digestive apparatus is for the mostpart short and capacious, particularly inits first or anterior part. In most of theselizards, we perceive the stomach to be stcomparatively small sac, with its aperturesplaced at the opposite extremities, havingseldom any appearance of a fundus or

csecum, or any means of retarding thepassage of food through that cavity. In

744

these loricated crocodilian animals, how-ever, we observe a stricture of the stomach,rather remarkable. The stomach there isof a globular form, and is provided withthick, strong, muscular parietes, consti.

tuting a true gizzard. The strong muscu.lar parietes of this gizzard of the croco-dile you observe in the specimen beforeyou, the crocodile of the Nile, in the cen-tral shining silvery tendon on each side ofthe stomach, to which the lateral radiatingmuscles are attached. Now these animalsare observed to have in their stomach

frequently along with their food, stonesand gravel, as if to assist in its subdivi-sion. We still find in the sauria, traces ofthe pyloric and colic valves, so large infishes. There is but little difference be-tween great and small intestines ; the

large intestines do not yet present thatpuckered wide appearance which we ob-serve in the large intestine or colon of themammalia. Some of the saurian reptilesfeed on vegetable food, though compara-tively few. In those, as in the iguanaand the scinck before you, the intestine islong and convoluted and capacious. Thewhole habits and dispositions of these ani-mals correspond with their kind of food.The flesh of the yguana is very differentin its quality from that of the saurian rep-tiles that feed on animal food. The fleshof the large crocodilian reptiles is toughand rancid, and is not eaten, but the pa-latable flesh of the iguana is prized as anarticle of food in South America, wherethe animal abounds. We observe thisalso with regard to the flesh of the scinck,which feeds on vegetable substances, ananimal well known to the Arabians, andthe flesh of which was supposed to be an an-tidote to many diseases. But most sauriaare carnivorous, and hence the constancyof their gall-bladder, as in the carnivoraof other classes. The intestines varythus with their kind of food, like the sto-mach. The tongue is often long and fili-form, and cleft, as in the monitors andlizards, or short and fleshy, as in the cro-codilian sauria; it is a very long projec-tile slender organ in the chameleon, witha broad clavate termination for seizingflies. The caecum coli, though generallypresent, is very small and short, and thecolon is furnished with a valve. The liveris always provided with a gall-bladder,the spleen has a lengthened form, and thepancreas has generally a more compactform than in the serpents. The caecum ofthe colon is wanting in the crocodile andsome of the monitors, which, notwith-

standing, possess the ordinary valvulacoli, like most of the other sauria whichhave a small cæcum.

In the chelonian reptiles we observe

animals that, for the most part, whetherthey live upon the land, or inhabit thewater, feed upon vegetable substances.

They possess salivary glands of variousdegrees of development, and in some theyhave not been detected. Those that in-habit the deep, or the great turtles thatare so much sought after as an article offood, and the shells of which-the horny

’ coverings of the ribs-are so highly prizedin commerce for the uses that are madeof them in the arts-they feed chiefly onmarine plants; and we have seen thesharp horny bills by which they were

enabled to divide and to bruise those’ succulent marine plants which rendertheir flesh so delicate, and colour it green.We find, in the land-tortoises, likewise,

which feed upon vegetable food, that the, intestine is comparatively wide, long, andconvoluted; that the tongue is short,

fleshy, and villous ; the oesophagus is wide,with longitudinal plicae, and of consider-able length, on account of the great lengthof the neck.The oesophagus of the chelonia is strong

and muscular, and is marked with longi-

tudinal plicae, folds of the mucous coat,which extend into its inner surface. Those; longitudinal plicæ of the thick muscular

œsophagus in the chelonia we observe topass along a considerable portion of thestomach, along the whole of the mem-branous or cardiac half, and to be even

slightly perceptible upon the strong mus.cular pyloric extremity of the stomach,; which is so remarkable for its strengthand thickness in this part in the chelonianreptiles. Those animals have always thetongue short and fleshy, and covered withnumerous long papillae directed back-

, wards, and presenting a villous surface.The stomach lies transversely, below thetwo lobes of the large liver. The intes-tine you observe in those chelonian

reptiles to be of considerable length andconvoluted, occupying a considerable por-tion of the large and broad trunk of thebody. The small intestine, like the aeso-

phagus and stomach, is marked by longi-tudinal rugæ and folds of the mucous coat.Wehave here the digestive apparatuscon-

tainedin the abdominal or ventral portion ofthe great cavity of the trunk, which is oc-cupied upon its dorsal aspect by the largeand capacious lungs, extending backwardsto the pelvis itself, and separated by theperitoneum from the cavity containing the

digestive viscera. The position of thestomach, with the two large lobes of thebroad expanded liver hanging over it, andthe spleen on its left side, are seen in thepreparations before you. The gall-bladder,which is always present, enters the duo-denum very near to the pylorus, and be-

745

sides its duct there is a distinct hepaticduct which receives that of the pancreas,and opens into the duodenum. We ob-serve at the termination of the small in-testine in the wide colon, that it enters insuch an oblique manner as to leave a prettyconsiderable blind enlargement or caecumat the commencement of the colon. The

parietes of the alimentary canal are strongand muscular throughout. The mucouscoat is of great extent, as in other phyto-phagous animals; and although there areyet no valvulse conniventes, this innertunic forms numerous longitudinal foldsand cells in the course of the intestine, bywhich its secreting surface, and the sur-face for the distribution of the numerouslarger lacteal vessels, are greatly extended.The distinction of the small and large in-testine is more marked here than in theinferior reptiles, amphibia, or fishes, andthe long and capacious colon of the che-lonia is provided with a distinct valve, andoften with a wide and short caecum, so thatthe alimentary canal has now acquirednearly all those characters and divisionswhich it presents in higher stages of deve-lopment in the warm-blooded vertebrata.

ANATOMY AND PHYSIOLOGY.LECTURES

ILLUSTRATED BY THE

HUNTERIAN PREPARATIONS

IN THE MUSEUM OF THE ROYAL COLLEGE

OF SURGEONS, LONDON.

Delivered at the College in 1833, by

SIR CHARLES BELL, K.G.H., F.R.S.

LECTURE X.

RELATIONS EXISTING BETWEEN THE

NERVOUS AND MUSCULAR SYSTEMS,AND MENTAL AND BODILY EXPRES-

SION.

GENTLEMEN,—Hitherto you know Ihave taken sure ground; I have gone asfar as it was possible for me to be directedby the preparations and the arrangementsof Mr. HUNTER. But now I must either

go on alone, and unsupported, or I mustmove in another circle.Now I believe that you would rather

that I prosecuted the subject of muscularaction a little further. May I observe,then, that the muscular system may beconsidered as that part of the organiza-tion of the body which is under the direc,tion of the will by volition, and is used in

locomotion ; that, again, the muscular

system is used in performing all thosesecret functions which are going on with-out the cognizance of the mind, and allthe secret operations which are necessaryto the performances of the animal eco-

nomy.Now I wish to draw your attention to this,

- that the muscular texture which is so

directly under the influence of the mindand passions, which is expressive of thecondition of the mind, not by volition, butmade evident to the eye by certain symp-toms, is brought into action by certainnerves which are intermediate betweenthe internal parts of the body and theirexternal or muscular frame. This mayappear to some foreign to our proper sub-ject. Nothing, however, can be foreignon this occasion, which is a fair deductionfrom the facts presented to us by anatomy,a science which is highly cultivated onlywhen we observe all its relations. If youfind an interest in attending even to thenumber of bones in the wrist and the foot;nay more, if you find that you form as itwere another science by an attention tothe minutiae of animals, you will not con-sider that time to be lost which is spentin analysing the relation established be-tween the corporeal frame and the minditself, the moi especially as this is, infact, laying the foundation of the doctrineof sympathy, or the doctrine of symptoms,as I should more correctly express myself.For how are we to be alive to all thechanges in the body, and all the variationsof form in disease, unless we are familiarwith the condition and relation which areestablished between the nerves and emo-tions of the body ?

I will give you a familiar instance inillustration of my view. I had bought ahorse, and driven it to the door pf a pa-tient, who was looking out of the window,and who, on seeing me, said, " How longhave vou had that horse?" I told himthat I had bought it a fortnight since. Then,said he, " vou have made a bad bargainin it, for he is not sound." " How can

you presume," said I, " to say so, for youhave only looked at him from a dis-tance ?" " True," he replied, and I pressedhim to tell me how he knew the state ofthe animal. " By its breathing," he said;" by the inflation of the nostrils." I wasthen satisfied that he was wrong in hisopinion, for I found that I had not drivenhim in his own collar, and that he wasonly restrained in his respiration, and notunsound in his lungs. But I was well

pleased to find that this knowing gentle-man judged of the condition of the lungs.by the action of the nostril. I have seenthe same kind of thing in the hospital.