NUTRITION 



155 



The pancreas, or sweetbread, may be regarded as the chief 

 digestive gland in the Vertebrate body though it also performs 

 additional functions. The gland lies just below the stomach in 

 Man, and each day secretes into the small intestine nearly two pints 



Common bile duct 



Hepaticjiuct 

 \Y v<f( iftX Liver 



Cystic ducts 



Gall bladder 



Pancreatic 



duct 



Stomach 



Small intestine. 



Pylorus 



Fig. 112. — Liver and pancreas of the Frog, showing their ducts. Lobes of 

 liver turned forward. The cystic ducts unite with hepatic ducts and finally 

 lead into the common bile duct. The latter passes through the pancreas, 

 receives further hepatic ducts and the pancreatic duct and leaves the pan- 

 creas, opening into the upper part of small intestine. 



of strongly alkaline pancreatic juice containing three enzymes — 

 trypsin acting on proteins, amylase on starches, and lipase on 

 fats. (Fig. 113.) ' 



Thus food that has run the gauntlet of the enzymes of the upper 

 digestive tract is now attacked by the pancreatic juice. But this 

 is not all: the process of progressive simplification of the food is 

 carried on by the secretions of innumerable minute glands embedded 

 in the intestinal wall. This intestinal juice supplies several 

 enzymes — the erepsin group to change the protein products into 

 amino acids, and the others to convert complex sugars into simple 



