may be added to the facts set forth already to prove, in the most decided manner, that the greater power of permeation manifested by one of the two fluids in experiments on endosmosis does not follow from any greater viscidity it may possess than the fluid opposed to it. In sixteen parts of water I dissolved two parts of sugar and one part of oxalic acid. In this so lution I plunged the reservoir of an endosmo meter, closed with piece of bladder, and filled with pure water : this did not show any diffe rence of level in the tube during the two hours that I continued the experiment. There was consequently no endosmosis. Nevertheless, I found that the water contained endosmo meter contained a large quantity of oxalic acid, whether tested by the addition of lime-water or by the palate, which last also detected the presence of sugar. Thus the sweet-sour fluid, exterior to the endosmometer, had penetrated the water contained within its cavity. If this circumstance was proclaimed by no increase in the volume of the water, this undoubtedly was owing to the included water having lost by the descending counter-current an amount exactly equal to the amount it had gained by the in ward or ascending current. There was no en dosmosis in the sense in which I use that word, although it is certain that there were two active antagonist currents athwart the membrane which separated the two fluids. It must not be lost sight of that I only give the title of cndosmosis to a stronger current opposed to a weaker counter-current, antagonists to each other, and proceeding simultaneously athwart the septum, dividing the two fluids which are made the subjects of experiment. The instant these two antagonist currents become equal, there is no accumulation of fluid on one side, and there is then no longer any effort at dilatation or im pulsion; in a word, there is no longer any endosmosis.
The opposite directions in which the endos mosis towards water, effected by acids of deter minate density, and the endosmosis from water occasioned by other fluids, would lead us to conclude that in placing such a fluid as gum water or sugar-water in an endosmorneter fur nished with an animal membrane, and in con tact externally with an acid solution of appro priate density, we should have a much more rapid endosmosis towards the included fluid than if it were pure water in which the endos mometer was plunged ; and this in fact is what I have found to be the case by experiment. Into an endosmometer, closed with a piece of bladder, I poured a solution of five parts of sugar in twenty-four parts of water. Having plunged the reservoir of the instrument into water, I obtained in the course of an hour an ascent of the included fluid, which may be re presented by the number 9. The reservoir of the same endosmometer filled with a portion of the same saccharine solution, having been plunged into a solution of oxalic acid, the den sity of which was 1.014, (3.2 parts acid to 100 solution,) I obtained in the course of an hour an ascent of the included fluid, which required to be represented by the number 27. The substitution of a solution of oxalic acid for pure water consequently caused the amount of endosmosis in the same interval of time to be tripled. I obtained like results with the tarta ric and citric acids, employed of the densities required to enable them to produce endosmosis towards water. From thee experiments it would appear that water, charged with a small proportion of one of the acids, of which men tion has been made, possesses a power of pene tration athwart animal membranes greater than that inherent in pure water. But a direct ex
periment, detailed in an earlier part of this paper, proves that this is not the case; pure water used by itself is still the fluid that pos sesses the greatest power of penetrating through animal membranes. lf, consequently, in those experiments which I have last described, the water charged with acid passed more readily and more copiously into the saccharine solu tion than pure water, this happens undoubtedly from other causes or conditions which I cannot take upon me to explain, but which appear to be : 1st. A reciprocal action between the two heterogeneous fluids, an action which modifies, which even completely inverts the natural power of penetration possessed by each of the fluids when employed singly ; 2d. A particular action of the membrane upon the two fluids which penetrate it, an action which, with the animal membrane, gives the stronger current or current of endosmosis to the acid solution of due density, and the weaker current or coun ter-current of exosmosis to the pure water. It seems to me impossible to deny this peculiar action to the animal membrane, when we see that a vegetable membrane in the same circum stances produces endosmotic phenomena di rectly the reverse. The peculiar influence of the membranous septum is likewise manifested in a very striking way in the experiment in which I have shown that the current of endos mosis flows from water towards alcohol when these two fluids are divided by an animal membrane, and, on the contrary, that the cur rent of endosmosis flows from alcohol towards water when the two fluids are separated by a membranous septum of caoutehone.
Endosmosis, in the present order of things, is a phenomenon restricted to the realm of or ganization ; it is nowhere observed in the inor ganic world. It is in fact only among organ ized beings that we observe fluids of different density separated by thin septa and capillary pores; we meet with nothing of the same kind among inorganic bodies. Endosmosis, then, is a physical phenomenon inherent exclusively in organic bodies, and observation teaches us that this phenomenon plays a part of the high est importance in their economy. It is among vegetables especially that the importance of the phenomenon strikes us ; I have, in fact, de monstrated that it is to endosmosis that are due, in great part, the motions of the sap, and particularly its very energetic ascending motion. I have also shown that all the spontaneous mo tions of vegetables are referable to endosmosis. The organic vegetable tissue is composed of a multitude of agglomerated cells mingled with tubes. The whole of these hollow organs, the parietes of which are extremely thin, and which contain fluids the densities of which vary, ne cessarily make mutual exchanges of their con tents by way of endosmosis and exosmosis. Nor can we suppose but that the same pheno mena take place among the various cells and cavities exhibited by the organism of animals. But the effects of endosmosis, its influence on the physiological phenomena presented by ani mals, has yet to be determined ; and here, un doubtedly, the physiologist has an ample field before him for inquiry. I shall only say in conclusion, and with reference to this very in teresting part of the subject, that I have satis fied myself that it is to endosmosis that the motions of the well-known spiral spring tubes of the milt of the cuttlefish, when put into water, are owing.
(II. Dutrochet.)