28 
CAUSES INTERFERING WITH 
diameter than a human hair, the two gases will 
immediately begin to mix, and after a short in- 
terval will be found equally distributed between 
both vessels. If the upper vessel be filled with 
oxygen, nitrogen, or any other gas, the same 
phenomena will ensue ; the gases will be found, 
after a short time, to be in a state of mixture, 
and at last there will be equal portions of each 
in both vessels. The permeability of animal 
membranes by gases has been fully proved by the 
researches of Drs. Faust and Mitchell. It fully 
appears from their experiments that animal mem- 
branes, both in the living and dead subject, both 
in and out of the body, are freely penetrated by 
gaseous matter ; that the phenomena of endos- 
mose and exosmose, observed in liquids by Du- 
trochet, are likewise exhibited by gases. If a 
glass full of carbonic acid be closed by an animal 
membrane, or sheet of caoutchouc, and be then 
exposed to the atmosphere, a portion of air will 
pass into the glass and some of the confined gas 
escape from it ; and if the experiment be reversed 
by confining air in the glass, which is then placed 
in an atmosphere of carbonic acid, the latter 
passes in and the former out of the glass. Similar 
phenomena ensue with other gases ; so that when 
any two gases are separated by a membrane, both 
of them pass through the partition. But though 
