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A paper was read, entitled, "An Experimental Investigation of the 

 Phenomena of Endosmose and Exosmose." By William Ritchie, Esq., 

 M.A., F.R.S., Professor of Natural Philosophy in the Royal Institu- 

 tion of Great Britain. 



M. Porret had, in the year 1816, announced the discovery, that if 

 a vessel containing water be divided into two compartments by a dia- 

 phragm of bladder, and placed in the voltaic circuit, the water would 

 rise on the negative side above its level in the positive compartment. 

 M. Dutrochet discovered, that if alcohol be placed in one of the cham- 

 bers, and water in the other, without employing the voltaic battery, 

 the water will percolate through the bladder, and the fluid will rise in 

 the chamber containing the alcohol: an action to which he gave the 

 names of Endosmose and Exosmose, according to its direction with 

 regard to the side of the membrane considered • comparing its two 

 sides to those of a Leyden jar in opposite electrical states. This 

 electrical theory has been combated by M. Poisson: but the true ex- 

 planation of this singular phenomenon does not appear to have been 

 yet given. 



The experiments of the author, of which an account is given in this 

 paper, were made with a glass tube, about an inch in diameter, one 

 end being drawn out into a slender tube of the interior diameter of 

 one eighth of an inch, and having a piece of bladder tied over the 

 other end. When this Endosmomeier, as it has been called, is by means 

 of a small funnel introduced into the narrow end filled with alcohol, 

 and immersed in water, the water penetrates through the blad- 

 der, and the spirit rises rapidly in the narrow stem. The author 

 found on trial that this action was apparently not affected by a pow- 

 erful current of voltaic electricity passed through the bladder, by in- 

 troducing positive and negative wires on both sides of it. On sub- 

 stituting a strong solution of sulphate of zinc for the alcohol, the same 

 negative result was obtained. 



The author considers the action of the animal membrane to be the 

 consequence of its strong attraction for water, an attraction to which 

 it owes its hygrometric properties; while, on the other hand, the 

 membrane has no attraction for alcohol, which has itself a powerful 

 attraction for water. The water, therefore, finds its way easily through 

 the membrane, and uniting with the alcohol, is carried off by it, and 

 diffused through the liquid, making room for the other portions that 

 successively come over. Whalebone and quills have similar hygro- 

 metric properties, and may be substituted for membranes with the 

 same effect. All substances readily soluble in water give rise to the 

 phenomena of endosmose, on the same principle as alcohol, such as 

 gum, sugar, and salts. The phenomenon bears a striking resem- 

 blance to the rise of the sap in the capillary vessels of plants, both 

 being probably dependent on the same principle; the filamentous 

 texture of the roots performing the function of the membrane, and 

 the contained sap that of the attractive fluid ; by the agency of which 

 that external moisture of the earth is imbibed and raised into the 

 interior of the plant. 



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