GASTRIC DIGESTION. 51 



previously been heated to boiling with 5 c.c. water and again 

 cooled) + 5 c.c. of 0.2% HC1. 



(h) Fibrin + 5 c.c. of solution 3 + 5 c.c. of 0.8% lactic 

 acid. 



(&) Fibrin + 5 c.c. of solution 3 + 5 c.c. of 1% oxalic acid. 



(ro) " +5 " " " 3 + 5 " "5%HC1. 



(n) " +5" " " 3 + 5" "0.5%Na,CO,. 



(p) " +5 " " " 3 + 3 " "bile. 



Note carefully, in each case, the relative rapidity with 

 which the flock of fibrin is disintegrated. 



PEPTIC PROTEOLYSIS. 



The previous experiments have indicated that the action 

 of pepsin is directed toward the transformation of the proteins 

 by a process of cleavage into soluble and diffusible products. 

 The question concerning the characterization, separation, 

 and identification of these soluble digestive products appears 

 at present to rest in a state of uncertainty, but in a general 

 way they are conventionally divided into the proteoses, pep- 

 tones, and a mixture of nitrogenous substances ("amino" 

 bodies) only characterized by not giving the biuret reaction. 

 The current method for the separation of these bodies is 

 based, first, upon the precipitation of the proteoses by com- 

 plete saturation of their solution with (NH 4 ) 2 S0 4 , and, second, 

 upon the precipitation of the peptones in the filtrate (from 

 the proteoses) by means of iodo-potassium iodide,, The 

 remaining substances are removed from their solution 

 by the addition of phosphotungstic acid. The proteoses 

 allow of a further separation by means of fractional precipi- 

 tation with (NHJ 2 S0 4 , and the peptones are divided into 

 two fractions by 95 per cent alcohol. This method isolates 



