282 Dutrochet on the 



Other physiologists, observing that the phenomenon of en- 

 dosmosis does not take place when two liquids which are 

 not susceptible of being mixed (such as oil and water) are 

 placed in relation to each other, have supposed that the recip- 

 rocal dissolution of the liquids played a principal part in this 

 phenomenon, and that the gradual augmentation of the volume 

 of the liquid of the greatest density, was the result of the greater 

 facility of permeation possessed by the liquid of less density 

 which was opposed to it. This theory is destroyed by positive 

 facts ; thus, for example", sulphuric acid and water, which have 

 the greatest tendency to a mutual dissolution, do not produce 

 any endosmosis. 



The only mode of arriving at a certain theory upon the phe- 

 nomenon in question, is to observe and appreciate its effects 

 mathematically; this is what I have endeavoured to do by 

 determining, in the first place, the laws regulating the force 

 and velocity of endosmosis. I have ascertained that this 

 force is in proportion to the difference in the density of the 

 two liquids. Thus, for instance, if a solution of muriate of 

 soda, the density* of which is 1*06, be brought into relation 

 with water, the density of which is I, there will be a force of 

 endosmosis which will vary according to the extent of surface 

 of the membrane of the endosmometer. If, in the same 

 instrument, there be put a solution of the same salt, the 

 density of which is 1*12, this solution, being brought into 

 relation with water, will produce a force of endosmosis, which 

 will be the double of that produced, under the same cir- 

 cumstances, by the solution having the density of 1.06. 

 The two forces of endosmosis produced by these two 

 saline solutions will, therefore, be to each other as the two 

 excesses of density of these solutions above the density of the 

 water, that is : : 00-6 : OT2, or as 1 : 2. I have endeavoured 

 to ascertain whether there was any relation between this law 

 of the endosmosis and that regulating capillary ascension, and 

 for that purpose have examined the comparative forces of 

 capillary ascension of pure water, and of the two saline solu- 

 tions in question. I took a glass tube, the capillary attraction 

 of which raised water to a height of 12 lines (one inch) in a 

 temperature of 10 C. = 50 F., and found that the same 



