ORGANIZATIONOFREPTILES. 17 



circular fold of the small, projecting into the large intestine, often marks the termi- 

 nation of one and the beginning of the other; but this diflerence of size is not 

 equally evident in all Reptiles. Serpents have the canal nearly of the same dimen- 

 sions throughout its whole extent, and in the Siren the intestine is small and 

 without these subdivisions. In all, the intestinal canal is short and but little 

 convoluted; it is longer than in Fishes, but shorter than in Birds and Mammaha. 

 The length of the canal corresponding to the nature of the food of the animal, is 

 shortest in the carnivorous, as in the Serpents, longest in those that feed on plants, 

 as in the Gopher. It varies even in the same animal, according to its mode of 

 life. The Tadpole, living on vegetable substances, has the intestinal canal very 

 long; but when the animal becomes a Frog, the character of its food being different, 

 this canal decreases in length; and it is wonderful to observe the ease with which 

 nature changes an herbivorous to a carnivorous animal. In the Turtle, the internal 

 surface is covered with several thin processes, placed longitudinally and close to 

 each other; they are most abundant near the upper portion, where the valvulse 

 conniventes are fomid in man, and like them, increase the extent of the absorbing 

 surface. Before the termination of the large intestine at the vent, it enlarges and 

 forms a sac or common cavity, called the cloaca, into which opens the rectum, 

 the urinary, and the sexual organs; another link of organization connecting Reptiles 

 with Birds, as well as with the Maimnalia, through the Ornithorhynchus, where 

 the same disposition of parts prevails.* 



The liver is found here as in all other vertebrated animals, and is of large pro- 

 portionate size, being subdivided into lobes, of which the right is the larger. In 

 some of the Batrachia, as in the Frogs, it is very large, and consists of tlu'ee lobes: 

 in Serpents, there is but one lobe of great length. The shape, as well as the position 

 of the organ, varies m different tribes; in some it is placed near, in others more 

 remote, from the stomach. Its colour is dark brovra; darker than in the ox. 



A gall bladder, usually containing bile of a brovmish-yellow or greenish colour, 



* Carus, Vergleich. Zoot. Zweit. Theil., p. 508. 

 Vol. I.— 3 



