58 CAUSES OF ABSORPTION OF OTHER 



pores and on both surfaces of the bladder changes 

 its place, and the original difference in the quality 

 of the two liquids is renewed. 



Motion of If we suppose a tube, formed of a membrane (an 

 liquids. intestine, for example), and filled with water, and if 

 we assume that a current of saline solution flows 

 round this tube, in consequence of a mechanical 

 force, the increase of volume of the brine (the pas- 

 sage into it of a certain amount of water) will be 

 effected in a far shorter time than if the brine were 

 not in motion. 



Difference The velocity of transference will diminish with 



tilf of P the" the amount of difference in properties between the 



liquids. twQ ]jq u j^ g ^ t h e Different amount or per-centage of 



salt) ; it will be greatest at first, and diminish as 



the dilution of the brine increases, in proportion, 



that is to say, as water is transferred from the con- 



tents of the tube to the liquid without. 



Effect of The greatest effect, therefore, must occur and be 



tinued re- permanent, when the water transferred to the brine 



is continually again removed from it, that is, when 

 the concentration of the brine is kept uniform. 

 To this end, if we suppose the membrane to be 

 difficultly permeable for one liquid, while the other 

 is easily taken up into its pores, and if we reflect, 

 that this second liquid, on entering into the pores 

 of the bladder, in virtue of the attraction of their 

 walls for it, acquires a certain velocity which per- 

 mits it to pass beyond the extremities of the canal 

 or of the pores, so as entirely to fill the pores, and 



