LECT. III. EXOSMOSE. 73 



others. But a great number of difficulties are met with in 

 considering the phenomena in this manner. We refrain 

 from enumerating them, as they must present themselves to 

 any one who has followed us in the exposition of the facts 

 we have observed. We shall merely observe that, in 

 ascribing every thing to endosmose, the presence of the 

 solution of gum, or of sugar, in the interior of the endos- 

 mometer, gives us no explanation of the phenomena which 

 are observed with the internal membrane of the stomach of 

 the lamb, and with the mucous membrane of the bladder of 

 the ox ; and that these phenomena are susceptible of a more 

 easy and natural explanation, by assuming that, by exosmose, 

 the various membranes give to the different liquids a more 

 or less easy passage towards the water, according to the 

 surface with which these liquids are in contact; and by 

 supposing that the passage of the water towards the denser 

 liquid is always constant, in accordance with the almost gene- 

 ral law of endosmose. But it was necessary to have recourse 

 to experiment to determine whether our mode of consider- 

 ing the phenomenon was correct ; and it was requisite not 

 only to prove the existence of exosmose, as M. Dutrochet 

 had done, but also to measure it in the same manner as 

 endosmose. 



In these researches we preferred using the skins of frogs 

 and eels, and employing saltwater as the denser liquid, and 

 also, in some cases, a solution of sugar. 



We began by preparing two endosmometers in the usual 

 way ; in one, putting the skin of the frog or eel with its 

 internal surface towards the interior of the instrument ; and, 

 in the other, placing the membrane in the contrary posi- 

 tion. We introduced into the two endosmometers equal 

 volumes of salt water of known density, and plunged these 

 instruments into two separate glass vessels, each contain- 

 ing a volume of distilled water equal to that of the salt 



