8 ABSORBENT POWER OF MEMBRANES 



that, after they have continued for some time, the 



pressure required to force the liquid through the 



membrane does not continue equal. If during the 



first 6 hours a pressure of 12 inches of mercury were 



necessary, we often find that after 24 or 36 hours, 



8, or even 6 inches will suffice to produce the same 



effect, obviously because by long-continued contact 



with water the membrane undergoes an alteration, 



in consequence of which the pores are widened. 



The pas- From these experiments it appears, that the 



ujuids power of a liquid to filter through an animal mem- 



membranes hrane bears no relation to the mobility of its par- 



portion P to" tides; for under a pressure which causes water, 



their fluid- b rmej or O ji to p ass through, the far more mobile 



alcohol does not pass. 

 The ab- The capacity of the animal membrane for being- 



sorbent 



power of moistened by, and its power of absorbing, the liquid, 



the mem- . 



brane for nave a certain share in producing the result of its 

 has a share filtration through the membrane. 



The following table will shew this fact : 



100 parts, by weight, of dry ox-bladder, take up 

 in 24 hours, 



Absorption of pure water 268 volumes 



saturated solution of sea salt (brine) ... 133 



,, alcohol of 84 per cent 38 



oil of marrow 17 



100 parts, by weight, of ox-bladder, take up in 

 48 hours, 



of pure water 310 parts by weight 



a mixture of water and f brine ... 219 



