ATTRACTION OF THE MEMBRANE FOR THE LIQUIDS. 47 



The kind of influence which the nature of the The nature 



,1 i. . i , ofthemem- 



partition, or its attraction for the liquids in contact bnme has 



11 . i an iinpor- 



with it, exerts on the phenomenon, is seen by com- ta nt in- 

 paring the action of an animal membrane with that 

 of a thin sheet of caoutchouc. 



In a tube, closed with bladder, which is filled Experi- 

 ment with 

 with alcohol, and immersed in pure water, the bladder, 



volume of the alcohol is increased; more water 

 passes to the alcohol than alcohol to the water. 



If, without making any other change in the ex- and with 



caoutchouc. 



penment, the tube be closed with a thin sheet or 

 caoutchouc, the volume of the alcohol now dimi- 

 nishes, while that of the water increases. 



Here, all the circumstances of the mixture of 

 the two liquids have remained the same, except the 

 nature of the partition, which makes the difference 

 in the result. 



When we fill with brine a tube Experi- 



ment to 



closed with bladder (Fig. 8), and prove the 



attraction 



place it in a vessel of water, so that of the biad- 



i der for t* 16 



the bladder and water only commu- liquid, 

 nicate by a single drop, the liquid in 

 the tube increases in bulk, and rises 

 in the tube, as if the bladder had been 

 immersed in the water ; but the drop 

 becomes gradually smaller, till after 

 an hour or two, a complete separation takes place, 

 and the drop tears itself away from the water.* 



* If we pour into a tube, ^ of an inch wide, and closed with 

 bladder, as much mercury as covers the surface of the bladder, 



