CHAP. L] OF NUTRITION. - 79 



of the fluid which they encounter. This explanation, proposed 

 by M. Ch. Robin, would, if well founded, furnish an explanation 

 of an extremely important fact. It would make us understand 

 why in the organisms themselves the composition of the fluid 

 absorbed is no longer on the hither side of the membrane or 

 living wall what it was on the thither side ; a phenomenon 

 peculiar to the biological osmosis, and never produced in the 

 endosmometers and the dialysing apparatus. 



But, well founded or not, this explanation seems to me by no 

 means needful to furnish a reason for the changes occasioned 

 in the composition of the fluids by physiological absorption. It 

 Eunices to explain this metamorphosis to take into account 

 chemical phenomena at the same time as physical phenomena- 

 Hitherto almost all the osmotic experiments effected in the 

 laboratories have borne upon liquids miscible indeed, but exercising 

 on each other no chemical action. Obviously this is not what 

 happens in the living tissues. There the fluids which have 

 traversed a living wall hold in solution unstable substances, 

 which are by the very fact of the osmosis in contact with other 

 fluids composed of substances of analogous complexity and of 

 different composition. There are evidently at the time of this 

 conflict, exchanges of molecules, chemical reactions; the new 

 substances arising repair the waste of the old, and for that 

 purpose are forced to enter into alliance and combination with 

 them. The residuum of these functions and that of the waste 

 of the substances previously organised are a blending of diverse 

 crystalloidal bodies, which is promptly dragged away from the 

 histological elements, the fibres, and the cells, to be afterwards 

 definitively expulsed from the organism. We have seen that 

 nothing is easier than to separate with a dialyser a crystalloidal 

 substance from a colloidal substance. It is very evident 

 nevertheless that the cellular wall is not inert in all this labour 

 of molecular mutation. It is as living as that which it contains, 

 and must consequently in like fashion participate in the 

 phenomena of transformation. 



