106 Mitchell on the Penetrattveness of Fluids. 



that it was considerable could be seen by looking at the stout mem- 

 branes broken by it. 



By greatly increasing the length of the taller limb of an inverted 

 syphon, similar to the one already described, I was able to bring to 

 bear on the common air imprisoned in the shorter limb, a very con- 

 siderable column of mercury. Up to a pressure of sixty-three inches 

 of mercury or rather more, equal to more than the power of two 

 atmospheres, the penetrative action was found capable of conveying 

 the gases, the subject of the experiment, into the short leg, through 

 the gum elastic membrane. The entrance of the gas into the short 

 leg was expressed by the ascent of the long column of mercury in 

 the other, which as it entered, it was compelled to heave up. At 

 the height of sixty-three inches, the membrane, though supported 

 by cloth, could scarcely sustain the weight, and would not bear any 

 increase of height. Although, therefore, at present, I do not know 

 the limit of this power, I believe it will be found very much greater, 

 because the power of the column which was tried did not, until a 

 leak was sprung, seem to very sensibly affect the rate of entrance. 



To the mind of a physician, the repetition of the foregoing experi- 

 ments, substituting animal membranes for gum elastic, would natu- 

 rally suggest itself. Should animal membranes present the same 

 phenomena, the interest of the investigation would be vastly en- 

 hanced, and a very important service done to the cause of ' Physi- 

 ological Medicine.' That animal membranes would act in the same 

 manner was rendered probable by the well-known experiments of 

 PRIESTLEY, who affected by means of oxygen the colour of blood 

 confined in a bladder. It had also been observed by him that a 

 closely tied bladder, containing hydrogen gas, is found, after a 

 considerable lapse of time, to contain only atmospheric air, and that 

 in quantity perhaps equal to the hydrogen lost. Several other facts 

 of the same kind are detailed by him. Finally in the Journal of the 

 Royal Institution, I find the following * Notice of the Singular 

 Inflation of a Bladder. By THOMAS GRAHAM, A.M.,F.R.S.E., Lec- 

 turer on Chemistry, Glasgow/ 



* In the course of an investigation of mixed gases through capil- 

 lary openings, the following singular observation was made. 



* A sound bladder with stop-cock was filled about two thirds with 

 coal gas, and the stop-cock shut ; the bladder was passed up in this 

 flaccid state, into a bell-jar receiver, filled with carbonic acid gas 

 over water. The bladder was thus introduced into an atmosphere 

 of carbonic acid gas. In the course of twelve hours, instead of 

 being in the flaccid state in which it was left, the bladder was found 

 distended to the utmost, and on the very point of bursting, while 

 most of the carbonic acid gas in the receiver had disappeared The 



