chap, xxi i.] IMBIBITION. 247 



forces are able to overcome the forces of recoil, but as 

 soon as sufficient resistance has developed, the two 

 forces corne to be in equilibrium, and further imbibi- 

 tion ceases. The forces which determine imbibition 

 are sometimes enormous. As an example, take the 

 splitting asunder of rock by means of wedges of dry 

 wood placed in clefts and then allowed to imbibe water. 

 Various observers have made a large number of ex- 

 periments on the differences of imbibition dependent 

 on the nature of the liquid into which the solid body 

 is plunged. Some of those made by Liebig, and pub- 

 lished in 1848, in his Recherches sur quelques-unes des 

 causes du mouvement des liquides dans I'organisme 

 animal, may be quoted here. 100 parts by weight of 

 dry ox-bladder took up, in 24 hours, 268 volumes of 

 pure water ; the same quantity in a saturated solution 

 of sea salt took up only 133 volumes ; a third quantity 

 took up 38 of alcohol (84 per cent.), and a fourth 17 

 of oil of marrow. " Of all liquids, pure water is taken 

 up in the largest quantity ; and the absorptive power 

 for solution of salt diminishes in a certain ratio as the 

 proportion of salt increases. A similar relation holds 

 between the membranes and alcohol ; for the mixture 

 of alcohol and water is taken up more abundantly 

 the less alcohol it contains." The same has been found 

 to hold good for other animal tissues. The extent of 

 imbibition 'depends, therefore, both on the tissue and 

 on the liquid which moistens it. Membrane has less 

 affinity for brine than for pure water. If salt be 

 sprinkled on a membrane whose pores are occupied 

 with pure water, the water dissolves some of the salt, 

 forming a solution, and this brine solution diffuses 

 itself through the bladder. The pores of the mem- 

 brane come to be occupied by salt solution instead 

 of pure water ; but the membranes can contain less 

 of salt solution than of pure water, and, consequently, 

 it has to expel a quantity of the water, which collects 



