Mitchell on the Penctrativencss of Fluids. 117 



will represent the full penetrability of that membrane by water. 

 But if ether is less penetrable than that membrane, the rate of 

 accumulation will not represent the power of the animal tissue, 

 but that of the ethereal interstices, which^ on the supposition, 

 is less. 



The power of this process in liquids, like that of the gases, is not 

 yet measured. It is the power of infiltration in all such cases, and 

 must be eminently great. Like all processes having dependence on 

 molecular action, this one is influenced by electricity, when that is 

 brought to bear on it, but we can scarcely, after a fair estimate of 

 the value of facts, see anything more in the power than that of 

 common interstitial infiltration, a power marvellously great, but 

 insusceptible of demonstrative reference at present to any known 

 cause. 



The amount of force having been shown to greatly exceed that of 

 atmospheric pressure, we feel assured that the interstices are pene- 

 trated not by any vis a tergo. It must therefore be attributed to 

 some species of attraction, the force of which, as shown by the con- 

 densation of some gases by charcoal, sometimes equals a power of 

 forty atmospheres, or nearly six hundred pounds on the square 

 inch, a power amounting nearly to that of steam, at its maximum 

 density *. It is not chemical, because the quantity absorbed bears 

 no relation to known affinities ; it is not homogeneous attraction, 

 for it takes place solely among dissimilar substances, and often sub- 

 verts the condition produced by that power, as in some cases of 

 solution. 



After having proceeded thus far with my argument and experi- 

 ments, I felt as if it were important, if not essential, to my positions, 

 to test the power of gum elastic as an absorber of gases, indepen- 

 dently of the artificial arrangements which brought different gases 

 to the opposite sides of it. For that purpose I selected a hollow 

 cylinder of gum elastic, with thick parietes about an inch in length. 

 This specimen was placed in a cylindrical graduated test-glass, 

 filled with carbonic acid gas and placed over mercury. In less 

 than one minute the mercury began to rise, and in eight hours, 

 during which the observer was absent, it had risen to a considerable 

 height. A rough attempt to measure the bulk of mercury raised, 

 and of gum elastic used, showed that nearly an equal volume of 



* Found by comparing the experiments of Caguard de la Tour with those of 

 the Committee of the Institute of France. 



