PftACTICAL PHYSIOLOGY. 



[IX. 



(d.) Instead of (a.) or (b.) use Benger's liquor pepticus, or the 

 pepsin of Burroughs, Wellcome, & Co., or that of Park, Davies, 

 & Co. 



All the above artificial juices, when added to hydrochloric acid 

 of the proper strength, have high digestive powers. 



2. Pepsin and Acid (HC1) are necessary for Gastric Diges- 

 tion. 



(a.) Take three beakers or large test-tubes, label them A, B, C. 

 Put into A water and a few drops of glycerin extract of pepsin or 

 powdered pepsin. Fill B two-thirds full of hydrochloric acid 0.2 

 per cent., and fill C two-thirds full with 0.2 per cent, of hydrochloric 

 acid, and a few drops of glycerin extract of pepsin. Put into all 

 three a small quantity of well-washed fibrin, and place them all in 

 a water-bath at 40 C. for half an hour. 



(b.) Examine them. In A, the fibrin is unchanged ; in B, the 

 fibrin is clear and swollen up ; in C, it has disappeared, having 

 first become swollen up and clear, and completely dissolved, being 

 finally converted into peptones. Therefore, both acid and ferment 

 are required for gastric digestion. 



The results obtained, all the tubes being at 40 C., are : 



