MEMBRANES SATURATED WITH WATER. 13 



tion of salt, the salt contained in which diffuses itself equally in the water of the 

 bladder. Of the 310 volumes of water which become thus saturated with salt, 

 only 133 volumes are retained in the bladder; and in consequence of this diminu- 

 tion of the absorbent power of the bladder for the brine, 177 volumes of liquid are 

 expelled, and run off in drops from the surface of the bladder. 



Membranes, fibrine, or a mass of flesh, behave exactly in a similar manner when 

 in contact with alcohol. If placed in alcohol in the fresh state, that is, when they 

 ?re thoroughly charged with water, there are formed, at all points where water and 

 alcohol meet, mixtures of the two, and as, the animal texture absorbs much less of 

 an alcoholic mixture than of pure water, more water is, of course, expelled, than 

 alcohol taken up. 



9-17 grammes of bladder, fresh, that is saturated with water (in which are con- 

 tained 6'95 grammes of water, and 2-22 of dry substance,) when placed in 40 

 cubic centimetres of alcohol, weigh, at the end of 24 hours, 4'73 grammes, and 

 have, consequently, lost 4'44 grammes.* In the 4-73 grammes which remain, are 

 2-22 grammes of dry bladder, and, of course, 2-51 grammes of liquid. If we 

 assume that this liquid has the same composition as the surrounding mixture 

 (which is found to contain 84 parts of alcohol to 16 of water,) it will consist of 

 2-11 grammes of alcohol and 0-40 of water; and consequently, of the 6-95 gram- 

 mes of water originally present, 6-45 grammes have been expelled, and replaced 

 by 2-11 grammes of alcohol. For 1 volume of alcohol, therefore, retained by the 

 bladder, rather more than 3 volumes of water have been expelled from it. 



t Since, in this case, so much more water is expelled than is taken up of alcohol, 

 the first result is a shrinking of the animal substance^ 1 ) 



If the bladder could take up or absorb equal volumes of brine and water, or of 

 alcohol and water, then when the fresh bladder was strewed with salt, or laid in 

 alcohol, the volume of the absorbed liquid would be unaltered, and an equal volume 

 of saline solution, or of diluted alcohol, would be retained by the animal tissue. 

 But since the absorbent power of the tissue for water is diminished by the addition 

 of salt, or of alcohol, it follows plainly, that a certain quantity of water must be 

 expelled as soon as its character is changed by the addition of one of these 

 substances. 



The relation of bladder, fibrine, and other animal substances, when saturated 

 with water, to alcohol and brine, proves, that the shrinking (diminution of volume') 

 of these tissues does not depend on a simple abstraction of water in virtue of the 

 affinity of alcohol and of salt for that liquid ; for it is quite certain that the attrac- 

 tion of alcohol to water, and that of water to alcohol, are respectively equal.J The 

 attraction of the water within the tissue for the alcohol without, is just as strong as 

 the power of the alcohol without to combine with the water within. Less alcohol 

 is taken up, and more water given out, because the animal tissue has less attraction 

 for the mixture of alcohol and water than for pure water alone. The alcohol with- 

 out becomes diluted, the water within becomes mixed with a certain proportion of 

 alcohol, and this exchange is only arrested when the attraction of the water for the 

 animal tissue, and its attraction for alcohol, come to counterpoise each other. 



If we regard a piece of skin, or bladder, or fibrine as formed of a system of capil 

 lary tubes, the pores or minute tubes are, in the fresh state, filled with a watery 

 liquid, which is prevented from flowing out by capillary attraction. 



But the liquid contained in these capillary tubes flows out of them as soon as its 

 composition is altered by the addition of salt, alcohol, or other bodies. 



( } ) Fibrine and other animal matters exhibit results quite similar to those obtained 

 with bladder. 26'02 grammes of fibrine saturated with water (containing 6*48 grammes 

 of dry fibrine and 19'54 of water) were reduced, in 45 grammes of absolute alcohol, to 

 16-12 grammes, losing, therefore, 9'90 grammes. Admitting the absorbed liquid to have 

 the composition of the unabsorbed residue (70 per cent, of alcohol,) it appears, that for 

 1 volume of alcohol absorbed by fibrine rather more than 2 volumes of water are 

 separated. 



* Amount of water expelled from bladder by alcohol. 



tMoist membranes shrink when strewed with salt, or placed in alcohol. 



J The cause of this is the less affinity of the tissue for alcohol, &c., than for water. 



