74 THE BIOLOGY OF THE FROG CHAP, iv 



into the body cavity from in front are two thin, very disten- 

 sible sacs, with a reticulated appearance, the lungs. With a 

 blowpipe they may be inflated from the glottis and swell 

 enormously. When the air is expelled from them, they con- 

 tract to a very small size. 



The different parts of the alimentary canal vary consider- 

 ably in size and texture. Above and projecting behind the 

 liver is the stomach, a thick-walled, muscular organ which 

 tapers toward the posterior end where the pyloric constric- 

 tion marks its point of separation from the small intestine. 

 Anteriorly the stomach is connected with the short esopha- 

 gus leading from the posterior end of the buccal cavity. 

 The small intestine, which proceeds from the pyloric end of 

 the stomach, at first bends forward and runs nearly parallel 

 with the stomach; this portion is called the duodenum; the 

 portion behind this, or the ileum, curves abruptly backward, 

 and, after forming several coils, suddenly widens out into 

 the large intestine. The anterior portion of the large intes- 

 tine is called the rectum; posteriorly it narrows into the 

 cloaca, which passes above the ventral part of the pelvic 

 girdle and terminates in the anus, or vent. Along its whole 

 extent the alimentary canal is suspended from the mid-dor- 

 sal portion of the body cavity by a thin, transparent sheet 

 of membrane, the mesentery. 



In the U-shaped loop between the stomach and intestine 

 lies an elongated, light-colored organ of irregular shape, the 

 pancreas. There is a dark red, rounded body, the spleen, 

 attached to the mesentery near the anterior end of the large 

 intestine. 



The reproductive organs, or gonads, lie on either side of 

 the alimentary canal and are supported from the dorsal body 

 wall by special sheets of membrane like the mesentery. The 

 gonads of the female, or ovaries, during the breeding season 



