CAUSES OF THE MOTIOX OF JUICES. 395 



Water is imbibed by the membrane of bladder much 

 more freely than alcohol ; on the other hand, a film of 

 collodion (cellulose nitrate left from the evaporation of 

 its solution in ether) is penetrated much more easily by 

 alcohol than by water. If, now, these liquids be sepa- 

 rated by bladder, the apparent flow will be towards the 

 alcohol ; but if a membrane of collodion divide them, 

 the more rapid motion will be into the water. 



When a vigorous chemical action is exerted upon the 

 membrane by the liquid or the dissolved matters, osmose 

 is greatly heightened. In experiments with a septum of 

 porous earthenware (porcelain biscuit), Graham found 

 that in case of neutral organic bodies, as sugar and alco- 

 hol, or neutral salts, like the alkali-chlorides and nitrates, 

 very little osmose is exhibited, i. e., the diffusion is not 

 perceptibly greater than it would be in absence of the 

 porous diaphragm. 



The acids, oxalic, nitric, and hydrochloric, mani- 

 fest a sensible but still moderate osmose. Sulphuric 

 and phosphoric acids, and salts having a decided alka- 

 line or acid reaction, viz., acid potassium oxalate, sodi- 

 um phosphate, and carbonates of potassium and sodium, 

 exhibit a still more vigorous osmose. For example, a 

 solution of one part of potassium carbonate in 1,000 

 parts of water gains volume rapidly, and to one part of 

 the salt that passes into the water 500 parts of water 

 enter the solution. 



In all cases where diffusion is greatly modified by a 

 membrane, the membrane itself is strongly attacked and 

 altered, or dissolved, by the liquids. When animal 

 membrane is used, it constantly undergoes decomposi- 

 tion and its osmotic action is exhaustible. In case 

 earthenware is employed as a diaphragm, portions of its 

 calcium and aluminium are always attacked and dis- 

 solved by the solutions upon which it exerts osmose. 



Graham asserts that to induce osmose in bladder, the 



