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actions, the crystalloidal appears the energetic form, and the colloidal 

 the inert form of matter. The combining equivalent of the colloid 

 appears always to he high, and it has a heavy molecule. Among the 

 colloids rank hydrated silicic acid, and a number of soluble hydrated 

 metallic peroxides, of which little has hitherto been known ; also 

 starch, the vegetable gums and dextrin, caramel, tannin, albumen, 

 and vegetable and animal extractive matters. The peculiar structure 

 and chemical indifference of colloids appear to adapt them for the 

 animal organization, of which they become the plastic elements. 



Although the two classes are widely separated in their proper- 

 ties, a complete parallelism appears to hold between them. Their 

 existence in nature appears to call for a corresponding division of 

 chemistry into a crystalloid and a colloid department. 



Although chemically inert in the ordinary sense, colloids possess 

 a comparative activity of their own, arising out of their physical pro- 

 perties. While the rigidity of the crystalline structure shuts out ex- 

 ternal impressions, the softness of the gelatinous colloid partakes of 

 fluidity, and enables the colloid to become a medium for liquid 

 diffusion, like water itself. The same penetrability appears to take 

 the form of a capacity for cementation in such colloids as can exist 

 at a high temperature. Hence a wide sensibility on the part of 

 colloids to external agents. Another eminently characteristic quality 

 of colloids, is their mutability. Their existence is a continued meta- 

 stasis. A colloid may be compared in this respect to water while 

 existing liquid at a temperature below its usual freezing-point, or to 

 a supersaturated saline solution. The solution of hydrated silicic 

 acid, for instance, is easily obtained in a state of purity, but cannot be 

 preserved. It may remain fluid for days or weeks in a sealed tube, 

 but is sure to gelatinize at last. Nor does the change of this colloid 

 appear to stop at that point. For the mineral forms of silicic acid, 

 deposited from water, such as flint, are found to have passed, during 

 the geological ages of their existence, from the vitreous or colloidal 

 into the crystalline condition (H. Rose). The colloidal is in fact a 

 dynamical state of matter ; the crystalloidal being the statical con- 

 dition. The colloid possesses ENERGIA. It may be looked upon 

 as the probable primary source of the force appearing in the pheno- 

 mena of vitality, as living matter without form. To the gradual 

 manner also in which colloidal changes take place (for they always 



