108 Mitchell on the Penetrativeness of Fluids. 



discovery. Made at an earlier period, his observation was published 

 in the Journal for October, 1829, and has since attracted appa- 

 rently no scientific attention. Such is usually the fate of the most 

 pregnant facts which are not perceived to bear on some generality. 

 This one passed from my mind along; with all the other isolated phe- 

 nomena of that number of the Journal, and only shone importantly 

 when illuminated by the reflected light of an extensive principle, 

 subsequently developed. These remarks are made, not to throw any 

 discredit on the character of the accomplished gentleman to whom 

 they refer, but to correct the baneful error of ancient dogmatism, 

 which yet weighs so heavily on the cause of nature and truth. It 

 was true that the carbonic acid entered a closed bladder, and that 

 too with power, and it was equally true, that oxygen had done 

 the same thing in the experiment of Priestley, and that, in his 

 hands, even common air had penetrated to replace hydrogen in 

 a similar viscus, and yet he ascribed the phenomenon observed 

 by him to the capillaries, and the conducting power of aqueous 

 canals. 



In what manner the power of ' rising into the air' was given, and 

 whether it was dependent on the force of water, or some other cause, 

 does not and could not be made to appear from the single fact, as 

 presented by Mr. Graham. A very little practical interrogation, 

 following the word just uttered by nature, would have obtained an 

 answer fraught with new and important truth. 



But to return to the immediate subject of this essay. Analogy, 

 the experiments of M. Dutrochet, and the observations of Priestley 

 and Graham, gave me almost the certainty of finding animal mem- 

 branes performing relatively to the gases the same function which 

 belongs to those formed of the inspissated juice of the Jatropa elas- 

 tica. Accordingly, each gas was subjected to the action of animal 

 membranes, which replaced the gum elastic at the mouth of the 

 short limb of an inverted syphon. Dried bladder, and gold-beater's 

 skin, moistened to cause an approach to a normal state, and sections 

 of various recent tissures, were successively tried, and found to act 

 on the gases in the manner and order in which they were affected 

 by gum elastic. The more recent the membrane, the more rapid 

 and extensive the effect produced ; and in living animals the trans- 

 mission was very rapid. 



Besides the estimates of comparative movement made with the 

 syphon, experiments in a different manner were resorted to, to more 

 clearly show the general truth. Thus a piece of the strong intestine 

 of a goose connected with the oesophagus and gizzard, being par- 

 tially inflated with common air, and firmly tied, was left in an 



