THE PANCREAS 131 



Certain glands in the lining of the intestine secrete a juice called 

 succus enter ictis or intestinal juice. Near the region where the 

 small intestine leads from the stomach is the opening of a duct 

 formed by the union of ducts from the liver and pancreas. 

 Through this duct, juices from the liver and pancreas are emptied 

 into the small intestine, where they mingle with the secretions of 

 the intestinal glands. 



The pancreas. The pancreas is a flat, pear-shaped gland, about 

 five inches in length, that lies slightly back of the stomach, between 

 the lower part of the stomach and a fold of the intestine. It 

 secretes an alkaline digestive juice called pancreatic juice. This 

 juice contains three enzymes : (1) An amylase, amylopsin, similar 

 to the ptyalin of the saliva, continues the conversion of starch 

 into simple sugars. (2) A protease, formed as trypsinogen, is con- 

 verted into trypsin by the action of a substance, enterokinase, 

 secreted by the mucous membrane of the small intestine. Tryp- 

 sin, similar to, but more powerful than pepsin, changes the pro- 

 teins into the simpler products, peptones and amino-acids. (3)' A 

 lipase, steapsin, breaks down fats into fatty acids and glycerol. 

 Some of these fattv acids then combine with the alkaline salts, 

 present in the juices of the intestine, to form soaps. Fats are 

 insoluble, but these soaps are readily soluble in water. Soap- 

 making, saponification, is part of the digestive process. The 

 breaking down of the fats and the saponification that follows are 

 made easier by emulsification, that is, the breaking up of the fat 

 into very tiny particles. 



Problem. JJliat is the effect of an alkali on a fat f 



Place in each of two test tubes a small amount of olive oil. Add an equal 

 amount of sodium hydroxide (an alkaline material) to the oil in one of the 

 tubes. Let it stand for forty-eight hours, shaking occasionally. 



I. What difference do you observe between the oils in the two test tubes ? 

 The change you have brought about in the one is called an emulsion. 



II. Mount a drop of oil under the niicroscope. 



