360 THE HUMAN BODY AND ITS FOOD 



pancreatic juice. The ferments of the pancreatic juice 

 are 



(1) Amylopsin, which completes the digestion of starchy 

 foods ("amylum" means starch). 



(2) Steapsin, which digests fats ("stear" means fat). 



(3) Trypsin, which completes the digestion of proteids 

 (its name means " something that ' wears down/ or 

 digests"). 



The pancreatic juice is a thin, watery liquid, like saliva. The 

 pancreas, which secretes it, is a tongue-shaped gland about 6 inches 

 long and one inch in diameter. It lies behind the stomach (see 

 Fig. 273, 350). The pancreas of the lower animals, such as the pig, is 

 called sweetbread. The duct from the pancreas unites with that 

 from the liver, so both the bile and the pancreatic juice enter the 

 small intestine through the same opening. 



368. Changes in Food by Digestion. Let us now look at 

 the process of digestion as a whole, and ask : ' ' What is the 

 fundamental thing that digestion in the mouth, stomach, 

 and intestines does?" The answer is that this digestion 

 makes food soluble, so that it can go through the wall of 

 the alimentary canal into the blood and lymph. Most of 

 the proteids do not dissolve in water; neither do the fats 

 and starch. How, then, can food be made to dissolve? 

 We have already learned that scientists believe that mat- 

 ter consists of particles called molecules (cf. 61). While 

 all molecules are extremely small, yet some are very com- 

 plex as compared with others. The molecules of most 

 food materials are especially complex. To make these 

 food materials dissolve, their molecules must be broken 

 down into simpler molecules. This is the work that the 

 ferments, or enzymes, perform in digestion. 



