INFLUENCE OF MEMBRANES UPON OSMOTIC CURRENTS. 487 



the mercury with the negative pole. This experiment sim- 

 ply illustrates the fact that attractive force can be generated 

 by galvanic action. It is well known that endosmosis can 

 be greatly modified by galvanism, but the supposition that 

 capillary attraction is an electric phenomenon is purely hy- 

 pothetical and is entertained by few physicists. The numer- 

 ous publications by different experimenters, which immedi- 

 ately followed the publication of the observations of Dutro- 

 chet, 1 many of them in this country, did little more than 

 confirm the facts demonstrated by Dutrochet, differing only 

 on theoretical points. A consideration of these, however, 

 belongs more to physics than to physiology. 



It was first supposed by Dutrochet that the endosmotic 

 current always took place from the rarer to the denser li- 

 quid ; and it was found, in using different saline solutions, 

 that within certain limits, the activity of the current was 

 in proportion to the density of the solution in the endos- 

 mometer. But this error was soon corrected by more ex- 

 tended experiments, in which endosmotic currents frequently 

 took place from the denser to the rarer liquids, as is the case 

 with water and alcohol, and with alcohol and ether. 2 It is 

 now fully recognized that the osmotic currents are not ne- 

 cessarily dependent upon the different densities of the liquids, 

 but are due chiefly to their different affinities for the in- 

 tervening membrane. 



The osmotic currents may be modified with the same li- 



1 TONGO, Experiments to prove the Existence of a peculiar Physico-organic Ac- 

 tion, inherent in Animal Tissues, called Endosmose and Exosmose. American 

 Journal of the Medical Sciences, May, 1829, p. 73. 



JACKSON, On Absorption, Ibid., Feb., 1830, p. 277. 



MITCHELL, On the Penetrativeness of Fluids, Ibid., Nov., 1830, p. 36. 



VALK, Microscopical Observations on Portions of Animal Tissue, with addi- 

 tional Experiments on Endosmose and Exosmose, Ibid., Feb., 1831, p. 405. 

 DRAPER, Experiments on Absorption, Ibid., May, 1836, p. 13. On the Phys- 

 ical Action of the Capillary Systems, Ibid., Feb., 1838, p. 289; and, On some Me- 

 chanical Functions of Areolar Tissues, Ibid., May, 1838, p. 23, and August, 

 1838, p. 302. 



2 DUTROCIIET, Op. tit., p. 40. 



