LIFE 



osmosis, which is connected with the variations in the 

 quantity of water in the living substance and its power of 

 diffusion. The plasm, which is of a spongy or viscous 

 consistency, can take in dissolved matter from without 

 (endosmosis) and eject matter from within (exosmosis). 

 This absorptive property (or "imbibition-energy") of 

 the plasm is connected with the colloidal character of the 

 albuminoids. As Graham has shown, we may divide all 

 soluble substances into two groups in respect of their 

 diosmosis — crystalloids and colloids. Crystalloids (such 

 as soluble salt and sugar) pass more easily into water 

 through a porous wall than colloids (such as albumen, 

 glue, gum, caramel). Hence we can easily separate by 

 dialysis two bodies of different groups which are mixed 

 in a solution. For this we need a flat bottle with side 

 walls of india-rubber and bottom of parchment. If we 

 let this vessel float in a large one containing plenty of 

 water, and pour a mixture of dissolved gum and sugar 

 into the inner vessel, after a time nearly all the sugar 

 passes through the parchment into the water, and an 

 almost pure solution of gum remains in the bottle. This 

 process of diffusion, or osmosis, plays a most important 

 part in the life of all organisms; but it is by no means 

 peculiar to the living substance, any more than the 

 absorptive or viscous condition is. We may even have 

 one and the same substance — either organic or inorganic 

 — in both conditions, as crystal or as colloid. Albumen, 

 which usually seems to be colloidal, forms hexagonal 

 crystals in many plant-cells (for instance, in the aleuron- 

 granules of the endosperm), and tetrahedric hoemoglobin- 

 crystals in many animal-cells (as in the blood corpuscles 

 of mammals). These albuminoid crystals are distin- 

 guished by their capacity for absorbing a considerable 

 quantity of water without losing their shape. On the 

 other hand, mineral silicon, which appears as quartz in 

 an immense variety (more than one hundred and sixty) 



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