498 ABSOBPTION. 



current takes place in the opposite direction ; as he had pre- 

 viously demonstrated that with one per cent, solutions of 

 phosphate of soda, the current was always from the saline 

 solution to the serum. This great diminution in density, 

 however, he assumed to be only local ; and the endosmotic 

 current recommenced when general diffusion was hastened 

 by agitation of the liquids. In experiments such as those 

 performed by Matteucci and Cima, in which fluid is made 

 to pass in a current through a portion of a vein which is 

 immersed in a vessel of acidulated water, the rapid pene- 

 tration of the acid is due in part to the suction force pro- 

 duced by the current, and in part to the constant renewal of 

 liquid on one side of the membrane. In an experiment of 

 this kind, Matteucci found that an acid reaction was almost 

 immediately manifested in the liquid flowing from the vein 

 when a current was established, but the penetration required 

 some time when the liquids were motionless. 1 



In the vascular system, all the conditions are realized for 

 the greatest development of the influence exerted upon en- 

 dosmosis by the movements of liquids. The blood is circu- 

 lating in the small vessels under a pressure much less than 

 that in the general arterial system. It contains a large pro- 

 portion of albumen, the fluid of all others which powerfully 

 attracts an endosmotic current without itself passing through 

 membranes. The circulation is so rapid that what enters 

 through the walls of the vessels is immediately carried on to 

 the heart, and in less than thirty seconds (the estimated du- 

 ration of the entire circuit of the blood), by the churning 

 action of this organ as well as the diffusion produced by the 

 force of the current, is mixed with the whole mass of the 

 circulating fluid. The substance absorbed must then mod- 

 ify the whole mass of blood (which is estimated at eighteen 

 pounds, in a man of ordinary size) before the activity of ab- 

 sorption can be diminished by an alteration in the density of 



1 MATTEUCCI, Lemons sur les Phenonenes Physiques des Corps Vivants, Paris, 

 1847, p. 78. 



