16 ORGANIZATIONOFREPTILES. 



horny points in the oesophagus, directed backwards or towards the stomach, which 

 may be useful in preventing the escape of food. 



The stomach is in all extremely simple in structure and arrangement. In some 

 it seems a mere continuation of the oesophagus, and it is not always easy to mark 

 the point of separation; in others, as in Frogs and Tortoises, we meet with an 

 enlargement like a sac; this gradually decreases in size, and terminates in the 

 small intestine; its termination being marked externally by a slight contraction, 

 and by the greater thickness of the walls. In many, the parietes of the organ are 

 thin, the muscular coat being delicate; in others, as in the Green Turtle, which 

 feeds on vegetables, the muscular covering of the stomach is remarkably thick 

 and strong, resembling in this structure the gizzards of Birds. 



The gastric juice is poured out from the inner surface of the stomach, mixes 

 with the food, and produces in it certain chemical changes. This fluid is possessed 

 of several curious properties; as the power of correcting or arresting putrefaction, 

 of coagulating albumen, &c.; but of all these its solvent power is the most remark- 

 able; even the bones of other animals cannot withstand its action. It varies, 

 however, in activity in different genera; in Serpents and Frogs, where the walls 

 of the stomach are thin, it is most abundant, and most active; in the Green 

 Turtle it is much less so, digestion being assisted by the strong coats of the 

 stomach. The numerous experiments of Spallanzani would seem to prove that 

 the gastric juice is only active on such substances as form the natural diet of the 

 animal, since he found that the fluid taken from the stomach of one subsisting 

 entirely on flesh, would not act on vegetable matter, and that the gastric juice of 

 an herbivorous, had no effect on the food of a carnivorous animal, while the same 

 fluid of an omnivorous being, acted equally well on animal or vegetable substances. 



The intestinal canal is the last portion of the digestive organs, where the greatest 

 change is wrought in the aliment by the admixture of bile and pancreatic juice, 

 and whence the nutritious parts are absorbed into the blood. It is subdivided into 

 small and large intestines, the first or small intestine being of greater length. A 



