DIGESTION AND ABSORPTION OF NUTRIENTS 97 



the amount equal to about the size of a pea, and also 

 add five to ten drops of diluted hydrochloric acid. 

 (Water, pepsin, and hydrochloric acid are the three 

 principal ingredients of gastric juice.) Label the test 

 tube No. 3, shake the mixture, and put it in a warm 

 place beside test tubes 1 and 2. (Since it is difficult 

 to get the exact proportion of the three ingredients of 

 gastric juice, it is well to prepare several tubes as de- 

 scribed above, labelling each test tube No. 3.) At the 

 end of a few hours or a day examine the test tubes con- 

 taining the minced egg and the artificial gastric juice, 

 comparing them with test tubes 1 and 2. Has the egg 

 been digested ? How do you know ? 



V. The Small Intestine and its Functions 



133. Position, form, and size. — The small intestine is a 

 much-coiled tube, filling the larger portion of the abdominal 

 cavity (Fig. 2). It is usually twenty feet or more in length, 

 and therefore constitutes nearly four fifths of the whole 

 length of the alimentary canal. Beginning at the stomach, 

 it decreases somewhat in size until it opens into the large 

 intestine. 



134. Peritoneum. — The whole abdominal cavity is lined with 

 thin, smooth membrane called the peritoneum. Sheets of peritoneum 

 likewise inclose the various organs found in the abdominal cavity, 

 and help to connect these organs to the walls of the abdomen. 

 Peritonitis is an inflammation of any portion of this membrane. 



135. Digestion in the small intestines. — In the intestines 

 important digestive processes are carried on (1) by the juices 

 secreted in the glands found in the inner wall of the intestine 

 (intestinal glands), (2) by the pancreatic juice secreted by the 

 pancreas, and (3) by the bile secreted by the liver. All 

 these juices, when mixed with the food in the intestine, 



