72 EVERS's COMPARATIVE ANATOMY. 



REPTILIA. 



The ophidian and saurian reptiles chiefly subsist on animal food, 

 therefore their digestive apparatus will be found to differ from that 

 of the chelonia which live on vegetable substances. The teeth of 

 serpents are sharp, conical, inverted, unopposed, and set in loose, 

 movable bones, adapted for seizing and lacerating their prey, they 

 are attached to the maxillary, inter-maxillary, sphenoid, and palate 

 bones, and the poison fangs of the venomous species are perforated 

 and grooved in front to transmit, the secretion of the poison gland 

 forced out by muscular pressure. The tongue is long, smooth, 

 sheathed, and bifurcated. The salivary glands vary in the differ- 

 ent species; the sublingual is always present, and the poison gland, 

 which is analogous to the parrotid, is confined to the noxious spe- 

 cies, and is placed below and behind each orbit. The long, disten- 

 sible oesophagus, copiously supplied with mucus, leads to the long, 

 straight, capacious stomach, longitudinally plicated and capable of 

 being distended to many times the size of the body ; it tapers to the 

 pyloric orifice, which is provided with a distinct valve, and embraced 

 by sphinctorial fibres. The duodenum presents a villious surface, 

 and receives the pancreatic and biliary ducts; the remainder of the 

 small intestine is narrow and convoluted to the commencement of 

 the short, dilated colon, where there is generally a circular valve 

 and a small coecum. The colon ends in the cloaca together with 

 the ureters, oviducts, or vasa deferentia, and the male organ of 

 generation, single or divided, also passes through the cloaca, as in 

 other oviparous vertebrata. The liver, spleen, pancreas, the kid- 

 neys, the testes, and the ovaria present an elongated form conform- 

 able to the shape of the body. The small intestines are attached 

 to a mesentery, and the large are often sacculated for the purpose 

 of retarding the passage of the food. 



As most of the sauria are carnivorous like the ophidia, they pre- 

 sent a form of alimentary apparatus equally simple. Their prehen- 

 sile teeth are fewer and chiefly restricted to the jaws; the stomach 

 is short and round in the form of a gizzard, with a pair of central 

 tendons ; the small intestine is long in the phytophagous species 

 as the scincus and iguana, and in all other respects they resemble 

 the ophidian reptiles. 



The phytophagous chelonia present a higher development of 

 alimentary canal than the carnivorous species. The place of teeth 

 is supplied by the sharp horny margins of the jaws ; the tongue is 

 covered with long papilla?; and the salivary glands are variously 

 developed in the different species. The long, wide, muscular oeso- 

 phagus leads to a large fleshy stomach, extended transversely, and 

 without a pyloric valve. The intestine is about six times the length 

 of the body, and the colon presents a short, wide coecum, and a 

 circular valve at its commencement in the terrestrial, but not in the 

 aquatic species. The alimentary canal is wide and muscular, and 



