Protein — Modified Albuminoids 63 



properties unlike those possessed by the mother sub- 

 stances. 



A convenient division of these modified bodies, 

 though perhaps not strictly scientific, may be made 

 in accordance with the cause or manner of change. 

 These causes are: (1) coagulating ferments; (2) heat; 

 (3) action of acids and alkalies; (4) the ferments of 

 digestion; (5) combinations with other compounds. 



(1) Coagulating ferments. Reference has been 

 made to that interesting phenomenon, the coagula- 

 tion or clotting of blood. As stated, this is now 

 known to be due to a formation of a new compound, 

 called fibrin. The mother substance, fibrinogen, and 

 not the fibrin exists in the living blood, and it 

 seems to be well proven that the splitting of the fibrin- 

 ogen into two substances, one of which is fibrin, is 

 due to the action of a ferment, designated as a fibrin 

 ferment. It would be out of place to review the data 

 upon which this conclusion is based. There are, to 

 be sure, conflicting views, but the one stated seems to 

 be the most fully established. Fibrin, after thorough 

 washing, is an elastic white substance, which, in its 

 chemical properties, stands very close to the albumins 

 that are coagulated by heat. 



It has been held by various investigators that other 

 changes in animal fluids and tissues are brought about 

 in the same manner as the formation of fibrin, i. e., by 

 the action of a ferment. In one case, this is certainly 

 true, viz. ; the curdling of milk under the influence of 

 the ferment rennin. This ferment, which for cheese- 

 making purposes is extracted from the fourth stomach 



