THE NOURISHMENT OF THE BODY 255 



pancreatic juice is poured into it. This juice is secreted by the 

 pancreas, a gland located beneath the stomach in a bend of 

 the intestine. In animals used for food, these glands are often 

 known as sweetbreads. The pancreatic juice has three fer- 

 ments or enzymes, namely amylopsin which digests starch, 

 trypsin which digests proteins, and steapsin which emulsifies 

 the fats by breaking them up into fatty acids and glycerine 

 and then, by combining them with alkalis, changing them 

 into soaps. The pancreatic juice, therefore, is the most 

 important digestive fluid in the body. When the pancreas 

 does not function properly, it causes the disease known as 

 diabetes. The contents of the stomach are acid (122, 123), 

 but the pancreatic juice can work only in an alkaline medium. 

 The neutralization of the food after it leaves the stomach is 

 accomplished by the bile, a strongly alkaline, yellowish fluid 

 poured into the intestine by the liver. The liver is a dark red 

 gland located on the right side of the body below the dia- 

 phragm. On the underside of the liver is a small sac, the gall 

 bladder, in which bile is stored when not needed in digestion. 

 The small intestine also secretes a digestive juice, but it appears 

 to be of little importance. The digestive juices are all pro- 

 duced by glands whose action is controlled by that part of the 

 nervous system not subject to the will. Many of their 

 processes are the result of reflex action. Often the sight or 

 smell of food will cause the glands to begin their secretions. 

 It is due to this cause that the mouth "waters" at the thought 

 of a particularly pleasing food. Under fear, grief, or strong 

 excitement, the glands do not always produce a sufficient 

 amount of their secretions, and if one takes food at such times 

 he may suffer from indigestion. 



219. The Teeth. Only the more complex animals have 

 teeth, though all but the simplest have some means of grind- 

 ing their food. Those forms which lack teeth have horny 

 jaws, beaks, mandibles, or other organs made from thickened 



