Mitchell on the Penetrativeness of Fluids. Ill 



strate all this, yet M. Dutrochet did not perceive it, as is evident 

 from his reference of the phenomena to a source to which, in latter 

 years, the French naturalists and philosophers have been accustomed 

 to look with almost superstitious reverence. Electricity is the great 

 key of scientific explanation ; and the theory of Du Fay is relied 

 on, though badly itself sustained, as the point d'appui of almost all 

 other theories. M. Dutrochet has accordingly ascribed the trans- 

 missions to that power, and supposed, in the very teeth of some of 

 his most striking facts, that the current was from a less dense to a 

 more dense fluid, or from positive to negative, dependent not on an 

 inherent power of infiltration, and of course for the same membrane 

 always the same, but varied, or even inverted, at pleasure, by 

 arrangements productive of supposed electrical powers. He says, 

 p. 139, 



' Ces re'sultats nous font de"jk pressentir que 1'impulsion qu'eprou- 

 vent les liquides dans ses experiences, depend d'un courant dlec- 

 trique determine par le voisinage de deux fluides de densite' ou de 

 nature chimique diffe'rentes, fluides que se*pare imparfaitement une 

 membrane permeable. Cette membrane ne joue evidemment aucuii 

 role propre dans cette cir Constance, ; elle ne fait fonction que de 

 moyen de separation entre les deux Jluides auxquels elle est cepen- 

 dant permeable : les liquides la traversent, soit dans un sens, soit dans 

 Vautre, au gre de r action reciproque des deuxjliddes qui baignent 

 ses parois opposees.' 



As he used water and solutions in water, by which the former 

 became denser, he found, as might be expected, that it infiltrated 

 the tissue more readily than most of its solutions ; hence, in such 

 cases, the water penetrated more quickly than they, and the current 

 usually set most rapidly from less dense to more dense. But when 

 he used essentially different liquids, he yet found the water going 

 through at Us high rate, as we perceived to be the case with sul- 

 phuretted hydrogen and ammonia. Water traversed the animal 

 membrane rapidly to join alcohol, which, according to his electrical 

 theory, should not have been the case, as the alcohol is less dense 

 than water. For this and some other exceptions Dutrochet attempts 

 to account, by reference to influence derived from chemical quali- 

 ties. 



If, however, as in the case of the gases, two liquids of different 

 rates of penetrativeness be placed on opposite sides of an animal 

 membrane, they will in time present the greater accumulation on 

 the side of the less penetrant liquid, whether more or less dense, 

 but will finally thoroughly and uniformly mix on both sides, and at 



