MODIFICATIONS OF ENDOSMOSIS. 497 



i 



In physiological absorption, the salts of the blood exert a 

 certain amount of endosmotic force, but of all its constitu- 

 ents, albumen is the most efficient in this regard. The 

 greater the relative proportion of albumen to the watery con- 

 stituents, the greater will be the activity of endosmosis. It 

 is in this way that the hydragogue cathartics, by largely di- 

 minishing the watery constituents of the blood, at the same 

 time that they diminish the pressure, increase the activity of 

 absorption. The albumen of the blood also opposes exosmo- 

 sis, or transudation ; and when its proportion is considerably 

 diminished, dropsies into the areolar tissue and the serous 

 cavities are apt to occur. 



Modifications due to Movements of the Liquids. Move- 

 ments of the liquids, in endosmotic experiments, are capable 

 of increasing the activity of the currents in two ways. In 

 the first place, by agitating the liquids the rapidity of diffu- 

 sion is increased and fresh layers of liquid are brought in 

 contact with the membrane. It is well known to all that 

 have experimented on this subject, that in an ordinary en- 

 dosmometer, after the current has become very feeble or has 

 entirely ceased, it may be again excited by simply agitating 

 the liquids. This fact was accurately described and explained 

 by Poiseuille. He placed an endosmometer filled with a 

 solution containing four per cent, of phosphate of soda in a 

 vessel of serum. The liquid mounted in the tube to the 

 height of thirty-four millimeters, but after some hours .of 

 complete repose, it descended to about three millimeters 

 above the level of the external liquid. On slightly agitating 

 the apparatus, the ascent recommenced at the rate of four 

 millimeters per hour. 1 Poiseuille explains this fact on the 

 principle that endosmosis and exosmosis had gone on in that 

 portion of the liquid near the membrane until the density of 

 the saline solution had been reduced to a point at which the 



1 POISEUILLE, Reclierches Experimentales sur les Medicaments. Comptca 

 Rendus, Paris, 1844, tome xix., p. 997. 

 82 



