390 ORGANS OF DIGESTION. 



amphibia, in the similarity and the extensive distribution 

 over the buccal cavity of the small conical fangless teeth, the 

 shortness of the tongue, the great development of the cornua 

 of the os hyoides, the want of salivary glands, the shortness 

 and width of the oesophagus, the elongated form and muscu- 

 larity of the stomach, the similarity of the small intestine 

 and the colon, the want of coecum coli and fundus of the 

 stomach, and the great size of the liver. In many of the 

 animals of this class, however, we discover approximations 

 to the higher vertebrata, in the more restricted distribution 

 of the teeth, the elongation of the tongue and the body of 

 the os hyoides, the greater distinctness of the gastric cavity, 

 and its fundus, and of the small and large intestine, the 

 absence of pyloric valve and valvula-coli, the development 

 of transverse folds in the duodenum, and of a slight ccecum 

 on the colon. The gall-bladder and the mesentery are now 

 always developed, the pancreas is always conglomerate, and 

 the tadpoles of all the species commence with the same short 

 strait, simple alimentary tube as in the embryos of all the 

 higher vertebrata, although some of them are destined to 

 undergo a double metamorphosis in this part, to adapt it 

 to the difference of food and habits of the larva and the 

 adult. 



XXI. Reptilia. As most of the ophidian and saurian 

 reptiles are carnivorous animals, and most of the chelonia 

 phytophagous, there is great diversity in the form and struc- 

 ture of the masticating organs, the alimentary cavities and 

 the chylopoietic glands in the different species of this class. 

 The serpents, like most of the lower vertebrata, swallow en- 

 tire prey, and have their teeth, like those of amphibia and 

 the simpler fishes, in form of mere conical crowns, sharp, 

 incurvated, unopposed to each other, attached to loose move- 

 able bones, and adapted for prehension, not for mastication. 

 The teeth of serpents are still attached to the palatine, ptery- 

 goid, and intermaxillary bones, as well as to the upper and 

 lower jaws ; they are wielded by powerful muscles, to enable 

 them to wound and secure their prey, they are deeply im- 

 bedded in the soft gums, but rest in shallow osseous grooves ; 

 they are limited to single rows, as in higher vertebrata ; the 

 palatine rows are more constant in their characters than the 

 maxillary ; they are excavated by a large nutritious canal, 





