478 ABSOKPTKXN-. 



Influence of Membranes upon Osmotic Currents. 



The force with which liquids pass through membranes, 

 called endosmotic or osmotic force, is to a great degree de- 

 pendent upon the influence of the membranes themselves. 

 This influence is always purely physical, in experiments 

 made out of the body ; and physiological absorption can be 

 explained, to a certain extent, by the same laws. It must be 

 remembered, however, that the properties of organic struc- 

 tures, which are manifested only in living bodies, are capable 

 of modifying these physical phenomena to a remarkable de- 

 gree. For example, all living tissues are capable of selecting 

 and appropriating from the nutritive fluids the materials ne- 

 cessary for their regeneration ; and the secreting structures of 

 glands also select from the blood certain principles which are 

 used in the formation of their secretions. At the present day 

 these phenomena, and their modifications through the ner- . 

 vous system, cannot be fully explained. This is true, also, 

 of many of the phenomena of absorption and their modifica- 

 tions, which are probably dependent upon the same kind of 

 action. In view of these undoubted facts, the influence of 

 the structures through which liquids pass in physiological ab- 

 sorption may be divided : first, into physical influences, which 

 may be illustrated by endosmotic experiments with organic 

 membranes out of the body ; and second, modifications of 

 these phenomena, which are presented only in the living 

 organism. 



One of the earliest theories which was offered in expla- 

 nation of the passage of liquids through membranes, makes 

 it dependent . entirely upon the laws of capillary attraction 

 and of the diffusion of liquids ; and to appreciate fully the 

 views of those who adopt this purely physical theory, it will 



the whole be immersed in pure water, in the course of about twenty-four hours, 

 one-half or three-fourths of the crystalloid matters will be found in the surround- 

 ing liquid, entirely separated from the colloid matters. An apparatus of this 

 land, called a dialyser, has been found very useful in certain inorganic analyses. 



