ENDOSMOSIS. 



water with the positive pole. I soon saw the 

 water rise in the tube of the instrument : en- 

 dosmosis had taken place. The similarity of 

 effects led me to admit that some particular 

 and unknown mode or form of electricity was 

 the cause of the endosmosis produced by the 

 heterogeneous nature of fluids. It was in 

 vain, however, that I tried to discover signs of 

 this electricity with the most delicate electro- 

 meters. 



In reflecting afterwards upon what might be 

 the common cause of the phenomenon pre- 

 sented in Porret's experiment and that of or- 

 dinary endosmosis, I was inclined to think 

 that electricity might not be the immediate 

 cause of the effects exhibited, and that it only 

 acted in the case cited by producing heteroge- 

 neousness of quality in the two fluids subjected 

 to the positive and negative poles. Experience 

 seems to have confirmed my doubts on this 

 point. I took a small endosmometer of glass, 

 closed by a piece of bladder, and filled its re- 

 servoir with water coloured blue with the co- 

 louring matter of violets ; I plunged the reser- 

 voir of this endosmometer into the same co- 

 loured water contained in a small glass vessel ; 

 I put this latter fluid in communication with 

 the positive pole of the voltaic pile, and the 

 interior fluid of the endosmometer in commu- 

 nication with the negative pole. The exterior 

 blue fluid soon became red, and consequently 

 acid, and the interior blue fluid became green, 

 and consequently alkaline. These two fluids 

 having thus become heterogeneous, to this may 

 be ascribed the endosmosis which manifested 

 itself, and which increased the volume of the 

 interior fluid at the expense of the volume of 

 the exterior fluid. Thus electricity would not 

 be in this case the immediate cause of endos- 

 mosis, but the remote one ; it would only act 

 in producing the heterogeneous quality in the 

 two fluids, and it would be this quality which 

 would produce the passage of fluids as in the 

 experiments on endosmosis, the discovery of 

 which belongs to me. 



But let us now inquire in what way hetero- 

 geneousness of quality in two fluids, separated 

 by a membranous partition, occasions the phe- 

 nomenon of endosmosis. Upon this point 

 opinions are greatly divided. M. Poisson and 

 Mr. Power have each, in his own way, given 

 an analytical explanation of the phenomenon, 

 and ascribed it to the action of the capillary 

 canals of the porous septum interposed be- 

 tween the two fluids. In this explanation the 

 phenomenon of the current of exosmosis is set 

 aside, or regarded as occurring merely acciden- 

 tally. Now this is entirely opposed to the fact, 

 we have constantly evidence of the simulta- 

 neous existence of the two opposite and une- 

 qual currents of endosmosis and exosmosis. 



Endosmosis by others has been held to be 

 simply the effect of the viscidity of one of the 

 fluids divided by a porous septum. This visci- 

 dity prevents the upper fluid from permeating 

 the interposed septum, whilst the inferior fluid, 

 little or not at all viscid, filters readily through 

 the septum and mingles with the upper fluid, 



whose volume it continently increases. ThiV 

 opinion, published by a man of distinction, de- 

 serves to be seriously investigated. 



When an equal weight of gum arabic and of 

 sugar is dissolved in two equal weights of water, 

 the viscidity of the different solutions is by no 

 means the same, the solution of the gum is ob- 

 viously more viscid than that of the sugar. 

 Now if these two solutions be divided by a 

 piece of bladder, the current of endosmosis 

 will be found to flow from the solution of the 

 gum towards that of the sugar ; in other words, 

 from the more viscid to the less viscid fluid; 

 in this instance, consequently, we see the more- 

 viscid fluid permeating the membrane with 

 greater facility or in greater quantity than the 

 less viscid fluid. More than this, the same 

 phenomenon takes place if the quantity of the 

 gum be made double that of the sugar. 1 have, 

 for instance, tried a solution of two parts of 

 gum arabic in thirty-two parts of water, (den- 

 sity 1.023,) and a solution of one part of sugar 

 in the same quantity of the menstruum, (den- 

 sity 1.014,) divided by a piece of bladder, and 

 found that the endosmotic current was still 

 directed from the solution of the gum towards 

 that of the sugar. These facts suffice to prove 

 that the endosmotic current does not always 

 flow from the less towards the more viscid 

 fluid. It is not, therefore, the inequality of 

 vicosity in these two fluids which is, in this 

 instance, the cause of their unequal permeation 

 across the porous lamina which separates them. 



In order to place these facts beyond a doubt, 

 the comparative viscidity of the gum-water and 

 the sugar-water which were made use of in the 

 experiments of which I have been speaking, 

 required to be accurately measured. Such a 

 comparative estimate of the viscidity of fluids 

 may be obtained by observing the time which 

 an equal quantity of each of them, at the same 

 temperature, takes to run through a glass capil- 

 lary tube. In this way I tried, 1st, pure water; 

 2d, a solution of one part of sugar in thirty-two 

 parts of water; 3d, a solution of one part of 

 gum-arabic in thirty-two parts of water; 4th, and 

 lastly, a solution of two parts of gum in thirty- 

 two of water. With a temperature of +7 cent. 

 I found that fifteen centilitres of pure water 

 passed through a capillary tube of glass in one 

 hundred and fifty-seven seconds; that fifteen 

 centilitres of the solution of one part of sugar 

 in thirty-two of water passed through the same 

 tube in one hundred and fifty-nine seconds and 

 a half; that fifteen centilitres of the solution of 

 one part of gum in thirty-two of water passed 

 through in two hundred and sixty-two seconds 

 and one-third ; and that the same quantity of 

 the solution of two parts of gum in thirty-two- 

 of water required three hundred and twenty-six 

 seconds to pass through. 



From these experiments it appears that the 

 viscidity of the solution of sugar, in the propor- 

 tion of one to thirty-two of water, (density 

 1.014,) is very little above that of pure water; 

 that the viscidity of the solution of gum-arabic, 

 in the proportion of one to thirty-two of water, 

 is much greater than that of the sugared water 



