CLASS AMPHTRfA 



481 



tr- 



end, but constricted at the posterior or pyloric end where it joins 

 the small intestine. The walls of the stomach are thick, con- 

 sisting of four layers : (i) the outer thin peritoneum; (2) a tough 

 muscular layer; (3) a spongy layer, the submucosa; and (4) an 

 inner folded mucous layer, the mucosa. The mucosa is made 

 up of glands lying in connective tissue. 

 Near the cardiac end the glands are 

 longer than at the pyloric end. 



The anterior portion of the small in- 

 testine is known as the duodenum; this 

 leads to the much-coiled ileum, which 

 widens into the large intestine. The ali- 

 mentary canal, as well as the urinary 

 bladder and reproductive ducts, open 

 into a sac-like cavity called the cloaca. 

 The inner layer of the intestine, the 

 mucosa, is much folded ; it consists of 

 ordinary absorptive cells and goblet 

 cells. 



The digestive glands are the pancreas 



The pancreas lies between G, glottis; /, lower jaw; 



L, lateral subrostral fossa; 

 M, median subrostral 

 fossa: N, posterior nares; 

 0, oesophagus; P, pulvinar 

 rostrale ; S, opening of 



empties it into the common bile-duct, vocal sac; T, tongue; v, 



r^, ; , ,, i t. j j j i_ vomer ; tp, tuberculum pre- 



The liver is a large three-lobed reddish linguale (From Ho lmes.) 

 gland which secretes an alkaline diges- 

 tive fluid called bile. This fluid is carried by bile capillaries 

 into the gall-bladder, where it is stored until food enters the in- 

 testine, when it passes into the duodenum through the common 

 bile-duct. 



Digestion begins in the stomach. The alkaline fluid secreted 

 by the mucosa layer of the oesophagus and the acid gastric juice 

 secreted by the glandular walls of the stomach digest out the 

 proteid portion of the food by means of & ferment, called pepsin, 



2 I 



and liver. 



the duodenum and the stomach. It is 

 a much-branched tubular gland which 

 secretes an alkaline digestive fluid and 



T-- 



FIG. 411. Mouth of 

 the frog widely opened. 

 E, Eustachian tubes; 



