ORGANS AND PROCESSES OF DIGESTION 57 



XXXV. PREPARATION OF DIGESTIVE FLUIDS (OPTIONAL). 



A. Collection of Saliva. Wash the mouth out thoroughly 

 with warm water to remove all foreign matter. Bow the 

 head forward, turn out the lower lip, and collect the clear 

 saliva as it flows over the center of the lip. Collection should 

 be made only a short time previous to use in experimenting. 

 The saliva should give no reaction with Fehling's solution. 



B. Artificial Gastric Juice. Obtain a pig's stomach. Cut 

 it open and wash its contents out by gently flushing it with 

 water. Remove the mucous membrane from the cardiac 

 end, and after drying this with filter paper mince it and bottle 

 with four or five ounces of glycerine. (The glycerine dis- 

 solves the pepsin.) After three days filter through muslin. 

 The filtered solution may be kept indefinitely. When 

 required for use add 0.2% hydrochloric acid 1 in the 

 ratio of one part of the acid to ten parts of glycerine 

 solution. 



A substitute for the above is solid pepsin powder dis- 

 solved in water. For use, this should be treated with 

 0.2% hydrochloric in the same way as the glycerine so- 

 lution. , 



C. Artificial Pancreatic Juice. Soak the pancreas of a 

 pig in water over night. Then remove it from the water, 

 mince, and add ten times its volume of glycerine. (Glyc- 

 erine dissolves the pancreatin.) Filter as with gastric juice. 

 This preparation is suited to the digestion of starches and 

 proteids. For action on fats add ten volumes of 1.5% solu- 

 tion of sodium carbonate, shake well, and filter. 



A substitute for the glycerine solution may be made by 



1 That is, dilute hydrochloric acid containing 2 parts of the concentrated 

 commercial acid to 998 parts of water. 



