46 



ENDOSMOSE. 



LECT. III. 



pressure exercised by the solution, the water continually 

 Fi g- 3 - passes into the tube by filtration through the 

 membrane. The liquid within becomes thus 

 elevated to a certain extent, and may even 

 flow over by the upper aperture. At the 

 same time, a certain quantity of the mucila- 

 ginous or saccharine liquid escapes from the 

 tube through the bladder, and mixes with the 

 water ; but the quantity is necessarily less than 

 that of the water which passed in the oppo- 

 site direction through the membrane. Dutro- 

 chet has called the first of these phenomena 

 endosmose, and the second exosmose. 



Endosmose through Membranes, fyc. Mem- 

 branes produce endosmose until they begin to 

 putrefy, when the phenomenon ceases, and 

 the liquid which had risen into the tube, de- 

 scends and filters through the membrane. 



It is not membranes only which are en- 

 dowed with this property : very thin plates of slate, or bet- 

 ter still of baked clay, produce the same effect, though in 

 a more feeble degree. Calcareous and siliceous laminse, 

 on the contrary, have no effect of the kind : with them en- 

 dosmose does not take place. 



Intensity of the Current. The nature of the liquid em- 

 ployed greatly influences the phenomenon. Endosmose 

 is more obvious in proportion as the density of the liquid 

 in the tube exceeds that of the exterior liquid. It might 

 seem that the intensity of the current is proportional to 

 the difference of the densities of the two liquids; but alco- 

 hol, which is lighter than water, causes, when introduced 

 into the tube, endosmose of the water which is placed ex- 

 terior to it. Saline solutions produce, through membranes, 

 very energetic, but less durable effects. 



Endosmometer. 



