THE DIGESTIVE SYSTEM 83 



domen between the kidneys and at the left of the inferior 

 vena cava. 



The pancreas secretes a digestive fluid, the pancreatic 

 juice, which contains three enzymes, trypsin, steapsin, and 

 amylopsin. The gastric juice of the stomach contains pep- 

 sin which reduces protein food substances to soluble pep- 

 tones. These, in turn, the trypsin breaks down into amino 

 acids, which are absorbed in the intestines. Steapsin de- 

 composes fats into fatty acids and glycerin. Amylopsin 

 reduces all digestible carbohydrates to glucose, which is 

 absorbed and stored in the liver as glycogen. 



The pancreas of the rat is irregular in shape and divided 

 into many large and small lobes. Some of these lobes 

 anastomose with each other. The pancreas is suspended 

 in the descending limb of the great omentum, and through- 

 out the mesoduodenum. It bends dorsally in the mesen- 

 terial junction of these membranes, and also sends a lobe 

 to the pyloric region of the stomach. Its left end is 

 dorsal to the spleen. Pancreatic tissue lies close against 

 the mesenterial side of the duodenum throughout the 

 duodenal loop. 



The pancreatic juice enters the bile duct, as it crosses 



the pancreas, through several small ducts. The openings 



of these ducts into the bile duct may be seen if the latter 



is slit and its inner surface examined under the dissecting 



microscope. The bile duct conducts the pancreatic juice, 



with the bile, to the duodenum. These ducts are identified 



with difficulty unless a careful dissection be executed 



using a microscope. 



Exercise XXI. Make an enlarged drawing of the opened ab- 

 dominal cavity, showing as many as possible of the contained 

 organs and mesenteries. 



