ACTION OF THE ENZYMES. 119 



is being acted upon. HAMMARSTEN gives 0.08 to 0.1 per- 

 cent for fibrin; 0.1 percent for myosin, casein, and vegetable 

 proteins; 0.25 percent for coagulated white of egg. 



Alkalies and alkaline salts when present in a digestion 

 mixture are uniformly injurious in their action. If pro- 

 teins are present at the same time with the acid-proteinase, 

 alkalies act less destructively, no doubt because the alka- 

 lies combine with the protein. This is indicated by the 

 fact that the same concentration of alkali acts the less 

 deleteriously upon the acid-proteinase the greater the amount 

 of protein present. 1 Of other substances which, when 

 present, influence the activity of acid-proteinase and which 

 are of medical interest, the following may be mentioned: 

 Alcohol and tannic acid interfere with the action of the 

 ferment, as do most alkaloids and carbohydrates. Bile 

 also belongs in this group, for one part of this substance is 

 able to do away entirely with the proteolytic activity of 

 five hundred parts of gastric juice. Caffein and theobromin 

 further the action of the enzyme. 2 



Within certain limits the rapidity with which acid-pro- 

 teinase splits a protein increases with an increase in the 

 quantity of the ferment present in the reaction mixture. 

 But in no case is the digestion of the protein complete unless 

 the products of the reaction are removed. An accumulation 

 of the products of digestion retards markedly the further 

 analysis of the protein. It will be shown further on that 

 this is probably dependent upon the fact that the action of 

 acid-proteinase is reversible, and that the ferment synthe- 

 sizes from the products of the digestion the protein itself, 



1 See LANGLEY. Journal of Physiology, 1882, III, pp. 253 and 283; 

 LANGLEY and EDKINS: ibid., 1886, VII, p. 371. 



* WROBLEWSKI: Zeitschrift fur physiologische Chemie, 1895, XXI, 

 p. 1; also BUCHNER. Berichte der deutschen chem. Gesellschaft, 1897, 

 XXXIII, p. 1110; LABORDE: Comptes rendus Soc. biol., 1899, LI, p. 

 821; NIRENSTEIN and SCHIFF. Archiv fur Verdauungskrankheiten, 1902, 

 VIII, p. 559. BRUNO. PAWLOW'S Work ot the Digestive Glands. Trans- 

 lated by THOMPSON London, 1902, p. 158. 



