during the Year 1828. 415 



discovery Endosmosis ♦, or that property which, in two fluids 

 of different natures or density, separated from each other by 

 a thin porous division, produces the effect of the one pene- 

 trating the division rather than the other, and with sufficient 

 power to raise the latter much above the level at which it 

 would remain agreeably to the laws of equilibrium. M. Du- 

 trochet has taken great pains to verify the quickness and force 

 of this new power, as well as all the circumstances which 

 favour or oppose it ; and he has made the happiest applica- 

 tions of his discovery to those questions in vegetable physio- 

 logy, the solution of which has been despaired of by physiolo- 

 gists. He has invented a very simple instrument, which he 

 calls an endosmometer, and which consists of a tube, larger at 

 one end than the other, and which is closed at the largest end 

 by a bladder, or some other thin substance. This tube is 

 filled with a fluid, and the closed end is plunged into a vase 

 filled with another fluid, the action of which is to be ascer- 

 tained, on that contained in the tube. In general, when the 

 liquid in the vase is water, and that of the tube is more dense 

 than water, the liquid rises in the tube, because the water goes 

 up into it; and this ascension will extend several feet, and 

 constitutes endosmosis. If the position of the fluids be changed, 

 the movement will take place in an inverse direction, the water 

 in the tube will descend towards the denser liquor in the vase, 

 and will then form exosmosis. f There are even, properly 

 speaking, two currents in opposite directions : the endosmosis 

 and the exosmosis will take place at the same time, but one 

 of the two will have the ascendency. The quickness of the 

 endosmosic action is proportioned to the excess of density in 

 the interior liquid (that of the tube) over that of the exterior 

 (in the vase). It is supposed that this discovery will not only 

 greatly elucidate the ascension of vegetable fluids, but vege- 

 table irritability. By way of exemplifying this, we will ob- 

 serve, that the valves of the capsule of the ^alsamina have a 

 strong tendency to curve inwards, and as soon as the fibre 

 which unites them weakens, they curve in this manner with 

 as much force as rapidity. This is caused by their exterior 

 cells being larger than those of the internal surface, and con- 

 sequently by their containing most water, and swelling into 

 convexity. This elasticity of the valves diminishes by a partial 



* Derived from two Greek words, the one implying inward, and the othet 

 impulse; which, together, accurately describe the singular phenomenon 

 illustrated by the physiologist. 



t This is the reverse of the phenomenon described in the previous note, 

 and the term is also derived from the Greek, only expressing the outward 

 instead of the inward motion. 



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