CHAPTER III 

 PROTOPLASM AND COLLOID-CHEMISTRY 



WE have been told in the foregoing chapter 

 that protoplasm is a slimy mass contain- 

 ing numerous organic compounds which chiefly 

 belong to the groups of proteins, carbohydrates, 

 and fatty bodies. The substances named here 

 represent for the chemist chemical bodies of 

 certain physical properties which, since the 

 famous investigations of Thomas Graham on 

 Liquid Diffusion applied to Analysis, in 1861, are 

 well known as colloidal properties. Colloids, the 

 prototype of which is glue, TO KoAAa, were charac- 

 terised by Graham as substances which scarcely 

 or not at all show diffusion through animal mem- 

 branes, and which cannot possibly be brought into 

 the shape of crystals. Colloids, therefore, form a 

 striking contrast to the common mineral salts 

 which readily show diffusion or Osmosis through 

 membranes, and which regularly appear as crystals 

 when the solution is concentrated and evaporated. 

 Graham spoke of this stage as the Crystalloid 

 Stage. For him, to use his own words, Colloids 

 and Crystalloids were two worlds of matter, 

 quite distinct and without any transition from one 

 to the other. 



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