THE COLLOIDS 81 



exists no life process that is not accompanied by 

 changes in the crystalloidal and colloidal substances 

 of the cells and tissues. The physico-chemical laws 

 which govern changes in crystalloids and colloids 

 in vitro may be taken in general as governing the 

 changes which take place in the same substances in 

 living matter. 



The biological significance of the crystalloids is 

 however not yet fully understood, and is one of the 

 chief objects of research in bio-chemistry. Experi- 

 ment has shown that there are physiological effects 

 solely attributable to the ions. " The vital pro- 

 perty of the ions to keep in solution the widely dis- 

 tributed globulins cannot be replaced by any other 

 kind of dissolved crystalloid."* It is also known 

 that differences in the concentration of the ions are 

 the source of differences in the electrical potential ;t 

 and the mineral constituents of the human body are, 

 in the concentration in which they are present, 

 almost completely dissociated. This is equally true 

 of metallic or alkaloidal salts introduced into the 

 body for therapeutical purposes. Loeb was the 

 first who recognised the importance of ions in the 

 electrical changes of organisms, and that changes 

 in the ionic constitution were the causes of the 

 majority of electrical phenomena observed in 

 animal organs. In every dilute solution the salts 

 are almost completely dissociated into ions, and 

 the remaining or undissociated molecules are neutral 

 electrically ; therefore the effect of such a solution 



* Pauli's " Physical Chemistry in the Service of Medicine," 

 p. 42. 



f LOG. cit. 



6 



