536 GENERAL CHARACTERS OP REPTILE!?. 



(Fig. 31 1, c) situated in the front of the mouth, are separate from 

 the rest, very sharp and pierced by a small canal, which termi- 

 nates near their extremity ; they are fixed upon very small 

 maxillary bones (Fig. 310), and these bones, supported upon a 

 long pedicle, are very movable ; so that when the animal does 

 not intend to use these poison-fangs, it turns them backwards, 

 and conceals them in a fold of its gum, from which it can erect 

 them at any moment. One of these long teeth is seen on each 

 side ; and there are, behind eacli of them, several germs, destined 

 to replace it, if it should break in the act of biting ; but the 

 maxillary bones do not bear any other teeth ; and there are only 

 seen in the roof of the mouth, two rows of palatine teeth, instead 

 of four ranges, as in the common Snakes. These last animals, 

 like several other Reptiles have the palate furnished with teeth, 

 as well as the jaws. Some Reptiles are, on the contrary, com- 

 pletely destitute of teeth ; such as the Tortoises, in which the 

 jaws are covered with a horny plate, having cutting edges, 

 and bearing a considerable resemblance to the beak of Birds ; 

 but there are never fleshy and movable lips like those of Mam- 

 malia. 



477. As the aliment does not require to remain in. the mouth, 

 in order to be ground down there, the veil of the palate would 

 have been in general useless ; and in fact, it very seldom exists. 

 In the greater number of these animals, the pharynx is not dis- 

 tinct from the mouth, and frequently there is not even any well- 

 drawn line of separation between the oesophagus and the 

 stomach, which is simple and of varied form. The intestines are 

 short and deprived of the ccacal appendage ; the large intestine 

 differs little from the small intestine, and terminates in a cloaca, 

 into which open also the urinary canals and organs of reproduc- 

 tion. Reptiles have, like the higher animals, lymphatic vessels, 

 destined to absorb the products of digestion, and to pour them 

 into the current of the circulation. 



478. Their blood is not rich in solid matter; and the oval 

 corpuscles, which swim about in it, are of a greater size than in 

 any other class. The arrangement of the circulating system 

 varies ; but there is always a direct communication between the 



