162 NATURE AND LIFE. 



suiting phenomena deserve the liveliest interest from a 

 theoretical point of view, as well as from their applied 

 uses. 



Dutrochet proved, by remarkable experiments, that, 

 when a tube closed below by a membrane, and containing 

 gum-water, is placed in a vessel containing pure water, the 

 level of the gum-water rises little by little through the grad- 

 ual introduction of pure water into the tube, while a certain 

 quantity of the gum-water inside mingles with the pure 

 water outside. In a word, a mutual exchange takes place 

 between these two fluids, communicating by the membrane, 

 and the current, passing from the thinner liquid toward the 

 denser one, is ascertained to be more rapid than that 

 moving in the opposite direction. 



This experiment reveals one of the most important phe- 

 nomena of life in plants and animals, noted by the word 

 endosrnosis. Now, Dutrochet had before observed that if 

 the positive pole of a battery be inserted in the pure water, 

 and the negative pole in the gum-water, the acts of endos- 

 mosis are effected more energetically. Qnimus and Legros 

 discovered, further, that, if the contrary arrangement be 

 adopted, that is, if the positive pole be placed in the gum- 

 water, and the negative pole in the pure, the level of the 

 liquid in the tube descends noticeably, instead of rising. 

 Electricity, therefore, can reverse the usual laws of endos- 

 mosis. It exerts an influence not less distinct on all the 

 other physico-chemical movements, taking place deep in 

 the organs. In them it decomposes the salts, coagulates 

 the albuminoid elements of the blood and the tissues, just 

 as it does in the vessels of the laboratory. Take a very 

 curious instance : In chemistry, on decomposing the iodide 

 of potassium, iodine is freed, and betrays itself by the 

 tinge of intense blue which it develops on contact with 

 starch. Now, if an animal be injected with a solution of 

 iodide of potassium, and then electrified, it is noticed, after 



