152 ORIGIN AND NATURE OF LIFE 



colloids was also suggested by Graham as a 

 method, called dialysis, of separating colloids 

 from crystalloids for analytical purposes. For 

 example, such a crystalloid as strychnine 

 can easily be separated from proteins and 

 other colloids, in the mixed contents of the 

 stomach, when investigations are being con- 

 ducted in a case of supposed poisoning, and 

 so minimal amounts may be detected in a 

 mixture that looks at first sight a hopeless 

 mess to analyze. 



In many important industrial processes 

 this property is now employed, and it is one 

 of the most important of the colloidal pro- 

 perties from both theoretical and practical 

 points of view. 



When a solution of colloidal silica separated 

 from admixed crystalloids by prolonged 

 dialysis is examined, it is a perfectly clear 

 and very limpid body, which remains so for 

 some days, but very slowly it undergoes the 

 process of coagulation and sets into a clear, 

 slightly opalescent, jelly. 



Graham's researches were published in 

 1862-4, and even at that early date he had 

 realized the importance to the physiologist 

 of the study of the properties of his new-found 

 bodies, for colloids, as he says, form the 

 active part of all living cells. Thus he states 



