354 CAPILLARY ATTRACTION, ETC. [MEMOIR XXVI. 



strong, and so the endosmosis of the water and exosmo- 

 sis of the alcohol take place ; the current of the former 

 greatly preponderates over that of the latter, and an ac- 

 cumulation 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 earthenware, 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 gravities of the liquid, 

 and that the lighter liquid always moves towards the 

 denser more abundantly than the denser towards the 

 lighter. But water endosmoses equally well to alcohol, 

 which is lighter than it, and to gum-water or salt-water, 

 which are heavier. 



The force with which a liquid will thus pass through 

 a pore to mingle with another liquid beyond is, as we 

 shall presently see, very great. 



It has sometimes been affirmed that living organic 

 textures possess a so-called selecting power, permitting 

 some substances to pass through them and refusing a 

 passage to others. But this so-called selecting power is 

 purely physical, as are the separations and apparent de- 

 compositions to which it gives rise. 



If we take a glass tube, a a, Fig. 79, over the lower 

 end of which a piece of peritoneum or other delicate 

 membrane, b b, is tightly tied, and half fill it with litmus- 

 water, and then place it in a glass of alcohol, c c, the lev- 

 els of the liquids inside and outside being adjusted ac- 

 cording to their specific gravities, so that there may be 



