52 CHEMICAL PHYSIOLOGY. 



(c.) Instead of (a.) and (b.) it is convenient to use Benger's 

 Liquor pepticus, or the pepsin preparation of Burroughs, 

 Wellcome & Co. 



All the above artificial juices, when added to hydrochloric acid 

 of the proper strength, have high digestive powers. 



2. Both Hydrochloric Acid and Pepsin are required for Gastric 

 Digestion. 



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

 A, B, C. Fill A two-thirds full of hydrochloric acid 0-2 

 per cent., put into B some water and a few drops of glycerin 

 extract of pepsin, or powdered pepsin, and fill two-thirds 

 full with 0-2 per cent, hydrochloric acid, and a few drops of 

 glycerin extract of pepsin. Put into all three a flake of 

 well-washed fibrin, and place them all in a water-bath at 

 40 C. for half an hour. 



(6.) Examine them. In A, the fibrin is swollen up ; in B, 

 unchanged; while in C, it has disappeared, having first 

 become swollen up and clear, and finally completely dis- 

 solved, being converted into peptones. Therefore, both acid 

 and ferment are required for gastric digestion. 



3. To Prepare Hydrochloric Acid of 0-2 per cent Add 6-5 cc. 

 of ordinary commercial hydrochloric acid to 1 litre of distilled 

 water, and shake together. 



4. Products of Peptic Digestion and its Conditions. 



(a.) Take three large test-tubes, labelled A, B, C, and fill 

 each one half full with hydrochloric acid 0-2 per cent. Add 

 to each 10 drops of a glycerin extract of pepsin. Boil B, 

 and make C faintly alkaline with sodic carbonate. The 

 alkalinity may be noted by adding previously some neutral 

 litmus solution. Add to each an equal amount a few 

 shreds of well- washed fibrin which has been previously 

 steeped for some time in 0'2 per cent, hydrochloric acid, 

 so that it is swollen up and transparent. Keep the tubes 

 in a water-bath at 40 G. for an hour, and examine them at 

 intervals of twenty minutes. 



(6.) After twenty minutes A begins to be turbid, and the 

 fibrin is dissolving. In B and C there is no change. After 



