PLATK 



.*. 6- 



Vie, 9, 10. 



Pig. II. 



Pwdef 



reptile*. 



10 



upon itself; and that portion which is opposite the 

 prmciiul curvature, has it- sid.-^ thicker than the rest, 

 and i internally pla te.l with longitudinal folds. The 

 nun of tin- gullet in the>e animals is distinguished 

 by the sudden dilat ition funned by the stomach Among 

 the S.iuriniK, the crocodile has the stomach of a glpbu- 

 l.ir figure, divided, however, into two unequal portions. 

 The stomach of the Guana is oval, and very long, with- 

 out curvature, and not easily distinguished from the 

 gullet. In the Tupinainbis the stomach form* a long 

 tube, bent nearly into a circle. The stomach of the 

 Chameleon liegins by an inflated portion, then takes the 

 form of a long cylinder, and bends back upon itself. 

 In the Dragon, this organ is strait, and has nearly the 

 shape of a pear. In the Balracians, the form of the 

 stomach resembles that in tortoises, but is proportionally 

 more dilated. In Salamanders it is long, not much ex- 

 panded, and strait, except near its farthest extremity. 



The intestinal canal of reptiles is not easily to be di- 

 vided into small and large by any particular appendage, 

 like the ctecum of quadrupeds; though the distinction, in 

 point of diameter, holds in most species. All the Chelo- 

 isiam, most of the Saurians, and all the Balracians ex- 

 cept the Sireu, have a long small intestine inserted into 

 one extremity of a short great gut, into which it is 

 usually prolonged, so as to form a valve. In the Igua- 

 na only is there any thing like a caecum. 



The intestines of reptiles in general are very short. 



In the Clielonians, what may be called the small in- 

 testine, is largest at its juncture with the stomach, and 

 gradually diminishes in diameter till it terminates in 

 the great intestine, where its diameter is only about 

 one-fourth of that of the latter. The coats of the in- 

 testines in this order are thicker than in those of most 

 other reptiles. See Fig. 8. 



In the nilotic crocodile, the small intestine is divided 

 into two portions, of which one is of greater diameter, 

 and has thinner coats than the other. This intestine is 

 remarkable for a thin layer of a pulpy glandular sub- 

 stance, between the muscular and the villous coats. 

 The large intestine of the nilotic crocodile is cylindri- 

 cal; but in another species, the gavial, it is pear-shaped. 

 In the lizird tribe, the large intestine is cylindrical, and 

 of much greater diameter than the rest of the canal. 

 In the chameleon, the whole intestinal canal is nearly of 

 equal diameter, except at one part, where it forms a 

 sort of valve. In the dragon, the intestines make about 

 two circumvolutions and a half, before terminating in 

 the anus. In most of the smaller saurians the coats of 

 the intestines are thin and transparent. 



The most remarkable differences in the intestinal ca- 

 nal of the Batracians, are those which take place in the 

 same species at different periods of its existence. In the 

 tadpole, or young animal, the intestines are very long, 

 small, and nearly of equal diameter, without any val- 

 vular distinction, and have numerous circumvolutions. 

 In the perfect animal, the whole intestinal canal is 

 much shorter, the distinction into small and large in- 

 testines very evident, and the circumvolutions much 

 fewer. In frogs, the large intestine is cylindrical ; in 

 toads, it is more or less conical. The difference of dia- 

 meter between the large and small intestines is most 

 evident in salamanders, whereas in the siren this dis- 

 tinction is scarcely to be noticed. See Fig. 11. 



The food of most reptiles consists of worms, insects, 

 and other small animals, which they swallow whole. 



< >t course the process of digestion takes place almost 



< olirely in the stomach, where the gastric juice is evi- 

 dently possessed of considerable solvent power. Some 



IIERPETOLOGY. 



Reptiles. 



Abstinence 

 of reptiles. 



of theCheloni.in order, indeed feed partly on sea-plants, 

 thence called turtle grass, which they bite off with their 

 horny mandibles, and swallow whole. 



Many of these animals are extremely voracious, and 

 will gorge themselves with living worms or insects, 

 till they become nearly incapable of motion, and till the 

 animals they have swallowed crawl again out of their 



mouths. 



The process of deglutition, in most reptiles, is effect- 

 ed by repeated contractions and dilatations of the throat 

 and gullet, which are very evident to an observer. It 

 is supposed by some physiologists, that part of the 

 prey in some species undergoes a degree of solution in 

 the gullet ; but this seems to us not very probable. 



Though the solvent power of the gastric juice in 

 reptiles is undoubted, its action is sometimes very slow, 

 einecially on living animals, these having been found 

 undissolved, and sometimes even still alive at the end 

 of several days. 



Notwithstanding the voracity of some reptiles, it is 

 astonishing how long almost all these tribes can sup- 

 port the want of food. Turtles and tortoises, even when 

 not in a torpid state, have lived for 10, or even 18 

 months, without taking any kind of food. Newts have 

 lived for two months, a chameleon for eight, salaman- 

 ders for an equal period, protei for two years, and toads 

 for a much longer time under the most perfect absti- 

 nence. It is most extraordinary, and the circumstance 

 forms a strange anomaly in animal physiology, that al- 

 though these reptiles gradually lose their vitality from 

 the want of food, they do not lose weight in proportion, 

 and in some instances suffer no sensible diminution or 

 flaccidity of musc.le. 



CHAP. IV. 



Of Circulation and Absorption in Reptiles. 



THERE are several peculiarities in the circulation of 

 reptiles, and the organs vary considerably in the dif- 

 ferent orders. In some they are similar to those of 

 the higher classes of animals, except that the principal 

 cavities of the heart communicate more or less freely 

 with each other ; in others, the circulating system is 

 entirely different from that of Mammalia, and much 

 more simple. 



In the Chelonian tribes, the heart is very broad in 

 proportion to its length, but differs in figure in the 

 two genera, being nearly hemispherical in the proper 

 Chelonias, and of an oblong squareform in the Tesludines. 

 In both it has two auricles, and a ventricle divided in- 

 to compartments. It is situated below the lungs, and 

 between the lobes of the liver. The auricles are very 

 large, forming each about one-third of the whole heart, 

 and spread wide at the base of the ventricle. Their- 

 sides are thin, and their cavities do not communicate. 

 The ventricle is strong and fleshy, and its cavity, 

 which is naturally small, is still more diminished by nu- 

 merous fleshy bundles that proceed from its sides, and 

 are separated from each other in such, a manner as to 

 leave spaces between them. The auricles communicate 

 .,with the ventricle by large apertures, guarded by mem- 

 branous valves ; and on each side of the ventricle are 

 orifices, also furnished with valves, that lead to the 

 great arterial trunks. The pericardium is large, and . 

 closely attached to the contiguous membrane, as to the 

 diaphragm in quadrupeds. 



In the Saurians, the heart is also provided with two Saurian*. 



