FORCE OF ENDOSMOTIC MOVEMENT. 107 



will not exude from them, and accumulate in the interior of the viscus, 

 for, as we have seen, a capillary tube can not establish a continued cur- 

 rent or flow. But the case becomes totally different when the bladder is 

 filled with alcohol ; for then, as fast as the water presents itself on the in- 

 ner end of the pore, it is dissolved away by the alcohol, and the necessary 

 condition for a continuous flow is complied with. Meantime, through . 

 the pore itself a little alcohol passes in the opposite way by infiltrating 

 through the incoming water, provided that the current be not too strong, 

 and so endosmosis of the water and exosmosis of the alcohol take place, 

 the current of the former greatly preponderating over that of the latter, 

 and an accumulation of liquid in the interior of the bladder ensues. 



That in all this there is nothing specially dependent on the organic 

 texture employed is obvious from the fact that the same results arise 

 when any inorganic porous body is used. Vessels of unglazed earthen- 

 ware, pieces of baked slate or stucco, answer the purpose very well, as 

 will also a^glass vessel with a minute fissure or crack in it. 



An incorrect representation of the conditions under which endosmosis 

 takes place is often made. It is said to depend on the relative specific 

 gravity of the liquids. Thus it is stated that the lighter liquid always 

 moves toward the denser, more abundantly than the denser to the lighter. 

 The error of this is readily shown by many simple illustrations. Thus 

 water endosmoses equally well to alcohol, which is lighter than it, and 4o 

 gum water or salt water, which are heavier. The relation of specific 

 gravity has nothing whatever to do with the action. 



The force with which a liquid will thus pass through a pore to mingle 

 with another liquid beyond is very great. I have observed -p orce against 

 these motions occurring against a pressure of many atmos- which these 



A-,.,,.. , ^ movements 



pneres. And, indeed, in practice we have no means of measur- ma y take 

 ing its actual intensity ; for when a pressure of a certain de- P lace - 

 gree has accumulated, hydraulic leakage takes place backward through 

 the pore, and conceals the true action. 



From the preceding statements respecting capillary attraction and en- 

 dosmosis, we may therefore conclude that, whenever a liquid is in con- 

 tact with a porous body the substance of which it can wet, it will freely 

 pass into the pores thereof, and, if the necessary conditions for its re- 

 moval are present, will percolate or transfuse with very great mechanical 

 power ; that this will take place through pores that are not only invis- 

 ible to the eye, but imperceptible by the aid of the microscope ; that 

 some liquids pass thus with more readiness, some with less, some not at 

 all the result in these respects depending on the electro-chemical rela- 

 tions subsisting between them and the solid they are in contact with, 

 and their own force of cohesion; that organic membranes present no 

 peculiarities, their action arising, not because they are organic, but be- 



