Role of Salts in Preservation of Life 191 



phenomena of streaming inside the cell, changes in the surface 

 film of the protoplasm occur, whereby this film is more easily 

 injured by the salts. If we suppress the oxidations we suppress 

 also the processes leading to cell-division and thereby retard 

 the deleterious action of the abnormal salt solution upon the 

 surface layer of the protoplasm of the egg. 



XI 



If we now raise the question as to why salts are necessary 

 for the preservation of the life of the cell we can point to a 

 number of cases in which this answer seems clear. Each cell 

 may be considered a chemical factory, in which the work can 

 only go on in the proper way, if the diffusion of substances 

 through the cell-wall is restricted. This diffusion depends on 

 the nature of the surface layer of the cell. Overton and others 

 assume that this layer consists of a continuous membrane of 

 fat or lipoids. This assumption is not compatible with two 

 facts, namely, that water diffuses very rapidly into the cell, 

 and second, that life depends upon an exchange of water- 

 soluble and not of fat-soluble substances between the cells 

 and the surrounding liquid. The above-mentioned facts of the 

 antagonism between acids and salts suggest the idea that the 

 surface film of cells consists exclusively or essentially of certain 

 proteins. 



The experiments mentioned in this paper indicate that the 

 role of salts in the preservation of life consists in the '' tanning" 

 effect which they have upon the surface films of the cells, 

 whereby these films acquire those physical qualities of dura- 

 bility and comparative impermeability, without which the cell 

 cannot exist. 



On this assumption we can understand that neutral salts 

 should be necessary for the preservation of life although they 

 do not furnish energy. 



As far as the dynamical effects of salts are concerned it is 



