'38 



THE BIOLOGY OF THE FROG 



CHAP. 



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 

 _M 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- 

 tral side arises a second 

 sheet of peritoneum (the 

 gas tro-hepato-ditodenal liga- 

 ment), which extends to the 

 duodenum and liver. The 

 wall of the stomach is much 



i 



Fig. 38. — Alimentary canal of Rana es- 

 culenta. A, opening of the rectum into 

 the cloaca, CI; Du, duodenum ; D, 

 ileum ; f, boundary between the lat- 

 ter and the large intestine, R ; ///?, 

 urinary bladder ; M, stomach ; Mz, 

 spleen ; Oe, esophagus ; Py, pylorus. 

 (After WiediTsheim.) 



