DIGESTION AND ABSORPTION 169 



Tube (6) 2 per cent.: Add 2 c.c. of 10 per cent. HC1 and aqua 

 dest. q. s. ad 10 c.c. 



Tube (c) 1 per cent.: Add 1 c.c. of 10 per cent. HC1 and aqua 

 dest. q. s. ad 10 c.c. 



Tube (d) 0.5 per cent.: Add 5 c.c. of 1 per cent. HC1 and aqua 

 dest. q. s. ad 10 c.c. 



Tube 0) 0.4 per cent.: Add 4 c.c. of 1 per cent. HC1 and aqua 

 dest. q. s. ad 10 c.c. 



Tube (/) 0.3 per cent.: Add 3 c.c. of 1 per cent. HC1 and aqua 

 dest. q. s. ad 10 c.c. 



Tube (g) 0.2 per cent. : Add 2 c.c. of 1 per cent. HC1 and aqua 

 .dest. q. s. ad 10 c.c. 



Tube (h) 0.1 per cent.: Add 1 c.c. of 1 per cent. HC1 and aqua 

 dest. q. s. ad 10 c.c. 



Tube (y) 0.05 per cent.: Add 5 c.c. of 0.1 per cent. HC1 and aqua 

 dest. q. s. ad 10 c.c. 



Tube (k) 0.025 per cent.: Add 2.5 c.c. of 0.1 per cent. HC1 and 

 aqua dest. q. s. ad 10 c.c. 



Tube (1) 0.01 per cent.: Add 1 c.c. of 0.1 per cent. HC1 and aqua 

 dest. q. s. ad 10 c.c. 



Tube (m) 0.005 per cent.: Add 1.2 c.c. of 0.1 per cent. HC1 and 

 aqua dest. q. s. ad 10 c.c. 



Place these twelve tubes in the incubator and note conditions 

 every ten minutes for the first hour, every hour for the first six hours, 

 and then at the end of one or two days make the final observations. 



Tabulate results. Formulate conclusions. What range of strength 

 may, from the experiments with the artificial gastric juice under 

 artificial conditions, be considered the optimum strength for the acid ? 

 Is there any reason to doubt that the optimum strength as determined 

 above is essentially different from the optimum strength in normal 

 digestion ? 



(8) To Determine How Dilute the Pepsin May Be and Still Be 

 Efficient in Digestion. This experiment requires a standard solution 

 of pepsin to use as a basis. The U. S. Pharmacopoeia (p. 295 of the 

 7th Decennial Revision) gives the following formula for a standard 

 solution of pepsin: 



Hydrochloric acid (absolute), 0.21 grm. 



Pepsin (pure), 0.00335 grm. 



Water (distilled), q. s. ad 100 c.c. 



The following suggestions are made as to method of preparation: 

 To 294 c.c. of water add 6 c.c. of dilute hydrochloric acid sol. A. 

 In 100 c.c. of sol. A dissolve 0.067 grm. of standard pepsin sol. 

 B. To 295 c.c. of sol. A at 40 C. add 5 c.c. sol. B. The resulting 

 mixture is a standard artificial gastric juice of the formula given 

 above, and has the power of completely digesting at 38 to 40 C. 

 one-fifth its weight of coagulated egg albumin in six hours. 



