138 



THE BIOLOGY OF THE FROG 



CHAP. 



-~0e 



D 



The Esophagus and Stomach. - - The esophagus is very 

 short and remarkably distensible, as is proven by the rela- 

 tively large animals the frog is capable of swallowing. The 



inner surface is thrown into 

 longitudinal folds which ex- 

 tend also into the stomach. 

 There is no sharp line of 

 demarcation separating the 

 jf esophagus from the phar- 

 ynx on the one hand and 

 from the stomach on the 

 other. The anterior end 

 of the stomach is consider- 

 ably wider than the esopha- 

 gus, and the organ tapers 

 gradually to the posterior 

 or pyloric end, where it is 

 separated by a constric- 

 tion, the pylorus, from the 

 small intestine. The stom- 

 ach lies mainly in the left 

 half of the body, and is 

 curved so that the convex 

 side is toward the left. It 

 is suspended dorsally by a 

 fold of peritoneum, the mes- 

 ogaster, and from the ven- 



FIG. 38. - Alimentary canal of Rana es- tral side arises a second 

 culenta. ,4, opening of the rectum into sheet of peritoneum (the 

 the cloaca, Cl; Du, duodenum; D, 7 , , j / / 



zastro-hepa to- duo a en a I aga - 



ileum ; f, boundary between the lat- => 



ter and the large intestine, K ; HB, ment^), which extends tO the 



urinary bladder; Af. stomach; Mz, duodenum and liver. The 

 spleen ; Oe, esophagus ; Py, pylorus. 



(After Wiedersheim.) wall of the stomach is much 



