6 THE FROG 



glands of the digestive system are the liver and the pancreas. Notice 

 again the three lobes of the liver, and, also, the gall bladder in which 

 the bile, a digestive juice secreted by the liver, is stored. Bile passes 

 from the gall bladder to the intestine through the bile duct, a very 

 delicate tube that lies in the mesentery and can be seen only in favor- 

 able specimens. The pancreas, a cream-colored gland of irregular 

 shape, is in that part of the mesentery which connects the stomach 

 with the first loop of the small intestine. Pancreatic juice is a di- 

 gestive juice secreted by the pancreas and discharged through pan- 

 creatic ducts into the bile duct where the latter passes through the 

 pancreas on its way to the intestine. What are the functions of the 



kidney 



sp/'na/corcf 

 \ 



posCoava/ v^/'n «. 



oyc/ry — — 



y/scena/ 



per/toneum 



coh/o/v 

 porieta/ parytorfcum cfi^estiye tract 



/ 

 / 



dbrsa/ m>rto 



- mesente'ftf 



y/scera/ 

 per/'toneufTt 



M/ri 



\ 



muscJes 



Fig. 10. — The frog; a transverse section in the region of the kidneys and 



reproductive organs. The specimen is shown as a male on the one side and 



as a female on the other; diagrammatic. 



bile and pancreatic juice? Other digestive glands occur in the walls of 

 the stomach and small intestine but are invisible without magnifica- 

 tion. 



(c) In order to see as much as possible of the digestive system 

 at one time for the purpose of drawing, it is necessary to snip the 

 mesentery, except jor that part which stretches between the stomach 

 and the first part of the small intestine and encloses the pancreas, and 

 spread the small intestine out on the animal's right side. Do not cut 

 the tract itself. The lobes of the liver may be turned toward the 

 head so that the stomach and pancreas are revealed. Push the urinary 

 bladder to one side to uncover the large intestine and cloaca. Draw 



