THE PROTEINS 9 



ble, that is, they are changed to proteans, and it is 

 believed by some protein investigators that nearly 

 every protein may assume a protean state. 



The metaproteins may be formed from simple 

 protein by the action of acids and alkalies. In this 

 instance, however, the change is undoubtedly more 

 profound than in the case of the proteans. Formerly, 

 metaproteins were termed albuminates, that formed 

 by acid being called acid albuminate, that from the 

 action of alkali being designated alkali albuminate. 

 These substances are insoluble in neutral fluids but 

 are readily soluble in an excess of acid or alkali. The 

 metaproteins are of interest when it is recalled that 

 the acid metaprotein arises as the first step in gastric 

 digestion of protein and that likewise alkali meta- 

 protein may be formed during pancreatic digestion. 



The coagulated proteins can be produced from 

 simple proteins by the long continued action of alco- 

 hol, stirring or shaking of their solutions, or by the 

 influence of heat. In one instance, namely, the trans- 

 formation of fibrinogen into fibrin in shed blood, the 

 process has long been assumed to be induced by an 

 enzyme. More recent work, however, tends to show 

 that enzyme action is not concerned in the reaction. 



The class of derived proteins called Secondary 

 Protein Derivatives represent a more profound change 

 from simple proteins than is true for the proteans, 

 metaproteins and coagulated proteins which are 

 grouped together as Primary Protein Derivatives. 

 Of the secondary protein derivatives the proteases 



