COLLOIDAL SUBSTANCES 285 



tein ion through the collodion membrane and depends in no way 

 upon the existence of micellae. The existence of micellae could 

 only diminish the value of the osmotic pressure and of the P.D. 

 The results of our work lead to the conclusion that there is only 

 one source of colloidal behavior, namely, the Donnan equilibrium, 

 at least as far as the proteins are concerned. Without a Donnan 

 equilibrium there can be no colloidal behavior of proteins. A 

 Donnan equilibrium will always arise when the diffusion of one 

 kind of ions is blocked while the diffusibility of oppositely charged 

 ions is unrestricted, regardless of the nature of the block restrict- 

 ing the diffusibility and regardless of the nature of the ion the 

 diffusion of which is prevented. 



The writer hopes that the methods, experimental results, and 

 theoretical conclusions described in this book may be found of 

 use not only in the study of the colloidal behavior of other 

 substances than proteins but also in physiology. Life phenomena 

 cannot be dissociated from colloidal behavior, and the idea of an 

 organism or of living matter consisting exclusively or chiefly 

 of crystalloidal material or material with purely crystalloidal 

 behavior is inconceivable. Organisms have been defined as 

 chemical machines consisting essentially of colloidal material 

 capable of growing and automatically reproducing themselves. 1 

 If this be true, advance in physiology will be chiefly a hit or miss 

 game until science is in possession of a mathematical theory of the 

 colloidal behavior of the substances of which living matter is 

 composed. If Donnan's theory of membrane equilibria furnishes 

 the mathematical and quantitative basis for a theory of colloidal 

 behavior of the proteins, as the writer believes it does, it may be 

 predicted that this theory will become one of the foundations on 

 which modern physiology will have to rest. 



. J., "The Dynamics of Living Matter," New York, 1906. 



