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TEXTBOOK OF ZOOLOGY 



marked off from the small intestine and is wide and short. It passes 

 directly into a muscular part, the cloaca, which terminates in the anus 

 or vent. 



The buccal cavity has in its roof near the end of the snout two 

 patches of small conical teeth, called vomerine teeth. In addition, the 

 upper jaw has a single series of small conical teeth on its edge known 

 as maxillary teeth. These teeth serve primarily to help hold the cray- 

 fish, insect, or other animal captured for food, and they may help at 

 times in crushing it. The tongue is somewhat leaflike in shape and is 

 deeply notched behind, making it bicornute. Its anterior half is at- 

 tached to the floor of the mouth just back of the tip of the lower jaw. 



Vomerine teeth 



Fbor of orbit M/' 



Isophaqus M,.^^, 



Vocal 5ac 



Maxillary teeth 

 . InLcmol nares 



Sulojs marqinalis 



_ lustach'ian tuoe 

 Qlotth 



C Tonque 



Fig. 273. — Mouth or buccal cavity of the bullfrog. 



and its posterior end is free. In order to get the tongue out of the 

 mouth the posterior part has to somersault over the attached ante- 

 rior part. The tongue of the bullfrog is somewhat smaller pro- 

 portionally than that of the grass frog, as might be expected, for 

 the latter is more dependent on this organ when it hunts insects 

 inlajid. Taste buds are present on the tongue and palate. 



Esophagus, stomach, and intestine have an outer longitudinal and 

 an inner circular layer of smooth muscle. The peristaltic contrac- 

 tions of these muscles pass the food through the digestive tract and 

 aid in mixing it with the gastric juice in the stomach. They may 

 also be used to regurgitate a disagreeable substance swallowed by 

 the frog, in which case the stomach turns inside out and protrudes 

 into the mouth cavity. The stomach can be greatly expanded and 

 acts as a reservoir for food which may be available only at irregular 

 intervals and the frog has to take advantage of a food supply when 



