14 PHYSICAL CHEMISTRY IN MEDICINE. 



the pure Si curve. In other words in a definite salt- 

 protein mixture the addition of an indefinite amount 

 of another salt does not change the coagulation- 

 point. 



These experiments, which are given here only in part, 

 seem to show for the first time that compounds of a certain 

 stability are formed when salts are mixed with pro- 

 teins. 



The additive ion effects of the salts show also a depen- 

 dence upon .certain quantitative relations. We must 

 probably attribute this to an affinity between salt and 

 protein which, as indicated by other observations, is 

 of such a character that the metallic ion and the acid 

 ion of a salt unite with different, asymmetric parts of 

 the protein molecule. 



An investigation of the conditions determining the 

 solubility of egg globulin has shown that this is dependent 

 upon the presence of ionized compounds. In even a 

 highly concentrated solution of dextrose or urea, in other 

 words substances which do not dissociate into ions, 

 globulin is precipitated in the same way as in the almost 

 entirely non-ionized water. 



We may point out in passing the biological significance 

 of these facts which show the importance of the mineral 

 constitutents of the organism in a new light. 



There can be little doubt that ion-protein compounds 

 are present in the animal organism, in fact we have 

 every reason for believing that all protein constituents of 

 the protoplasm enter into the composition of this sub- 

 stance only in combination with ions. 



As shown by numerous observations, the salts are 

 held fast in the organism with great force. This affinity-, 



