156 ORIGIN AND NATURE OF LIFE 



stances by means of which it first arose from 

 inorganic nature. 



Whatever may be the reason, simple 

 inorganic salts are indispensable in all living 

 cells, and exist in union with the proteins 

 forming crystallo-colloids. 



The peculiar energy properties of colloidal 

 solutions and the bearing of such proper- 

 ties upon the life-processes were clearly 

 expressed by Graham, who writes, " Their 

 peculiar physical aggregation with the chemi- 

 cal indifference referred to, appears to be 

 required in substances that can intervene 

 in the organic processes of life. The plastic 

 elements of the animal body are found in 

 this class. As gelatin appears to be its type, 

 it is proposed to designate substances of the 

 class as colloids, and to speak of their peculiar 

 form of aggregation as the colloidal condition 

 of matter. Opposed to the colloidal is the 

 crystalloidal condition. Substances affecting 

 the latter form will be classed as crystalloids. 

 The distinction is no doubt one of intimate 

 molecular constitution. " Although chemi- 

 cally inert in the ordinary sense, colloids 

 possess a compensating activity of their own, 

 arising out of their physical properties. 

 While the rigidity of the crystalline structure 

 shuts out external impressions, the softness 





