138 



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 



^-M 



-Mz 



Fig. 38. — Alimentary canal of Rana es- 

 culenta. A, opening of the rectum into 

 the cloaca, CI; Z?«, duodenum ; D, 

 ileum ; \, boundary between the lat- 

 ter and the large intestine, R ; HB, 

 urinary bladder ; M, stomach ; Mz, 

 spleen ; Oe, esophagus ; Py, pylorus, 

 (After Wiedersheim.) 



longitudinal folds which ex- 

 tend also into the stomach. 

 There is no sharp line of 

 demarcation separating the 

 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 py lpric end, where it is 

 separated by a constric- 

 tion, the pylorus, from the 

 small intestine. The sto?n- 

 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 

 gastro-hepa to-duodenal liga- 

 ment^, which extends to the 

 duodenum and hver. The 

 wall of the stomach is much 



