ENDOSMOSIS, (14or, intus, arobtoc, im pulsus).—Accitlent having mademe acquainted with the fact that a small animal bladder, con taining an organic fluid, became considerably distended by remaining for some time plunged in water, and that the water even expelled the thicker fluid contained within the bladder, when there was a hole by which it could escape, I be thought me of the probable cause of this pheno menon, and soon came to the conclusion that it depended on the difference of density between the included or interior fluid, and the water or exterior fluid. I found that the cceca of fowls filled with milk,thin syrup, &c. and secured with a ligature, became turgid and even excessively distended when treated in the same way. I now discovered that the fluids contained in the urea permeated their coats, and were diffused in the surrounding water. I saw, further, that two opposite currents were established through the parietes of the cceca; the first and stronger formed by the exterior water flowing towards the fluid contained in the cceca ; the second and weaker, by the thick included fluid flow ing towards the water. To the first of these currents I gave the name of Endosntosis, and to the second that of Exosmosis. These titles, I must allow, are objectionable, and perhaps badly chosen. The first conveys the idea of an entrance and the second of an exit. Now, the phenomenon, regarded in its proper point of view, consists in a double permeation of fluids, abstracted from any idea of entrance or exit. Besides, the current of endosmosis, which, etymologically speaking, expresses an in-going current, may nevertheless be, experimentally speaking, an out-going current ; this, for exam ple, happens when a hollow membranous organ, containing water, comes to be placed in contact exteriorly with a fluid more dense than water. There is then a current of endosmosis which goes out of the bladder, and a current of exos mosis which enters it. Thus facts are found in contradiction to the terms, and these I should not have hesitated to change, if their general adoption did not render this change very diffi cult, and subject to great inconvenience. I have, therefore, resolved to retain them, wishing it to be understood by naturalists that no attention is here paid to their etymological signification.
To estimate the amount of endosmosis I contrived an apparatus to which I gave the name of endosmometer; it consists of a small bottle, the bottom of which is taken out, and replaced by a piece of bladder. Into this bottle
I pour some dense fluid, and close the neck with a cork, through which a glass tube, fixed upon a graduated scale, is passed. I then plunge the bottle, which I entitle the reservoir of the endosnnneter, into pure water, which, by en dosmosis, penetrates the bottle in various quan tities through the membrane closing its bottom. The dense fluid in the bottle, increased in quan tity by this addition, rises in the tube fitted to its neck, and the velocity of its ascent becomes the measure of the velocity of the endosmosis.
To measure the strength of endosmosis, I have made use of an endosmometcr in which the tube was twice bent upon itself, the as cending branch containing a column of mer cury, which was raised by the interior fluid of the endosmometer in proportion as the en dosmosis increased the volume of this By means of these two instruments I have found that the velocity and strength of endos mosis follow exactly the sante law. Both are in relation to the quantities which express, in two comparative experiments, the excess of density of two dense fluids contained in the endosmorneter, above the density of water, which in these two experiments is exterior to the instrument. Thus, for example, in putting successively into the same endosmometer, syrup of which the density is 1.1, and syrup of which the density is 1.2, and in plunging in both cases the reservoir of the endosmometer into pure water, von obtain in the first case an en dosmosis, of which the strength and velocity are represented by 1, and in the second case an endosmosis, of which the strength and velocity are represented by 2 ; that is to say, by the numbers relative to the fractionals 0.1 and 0.2, which express the excesses of density of the two solutions of sugar above the density of water, which is 1. 1 have ascertained by ex periment that the strength of endosmosis is such that, with syrup of which the density is 1.11, and an endosmometer, the opening of which is closed by three pieces of bladder, one over the other, you obtain an endosmosis which raises the mercury to 1 metre 238 millimetres, or 4.5 inches 9 lines, which is equivalent to an elevation of water of 16 metres 77 centimetres, or 51 feet 8 inches. It follows from this, that in employing syrup, of which the density was 1.33, (its ordinary density,) you would obtain an endosmosis, the strength of which would be capable of raising water more than 150 feet.