on air found in the pleura , &c. 509 
exhibited no unusual appearances that could be referred to 
the gas absorbed. 
Mr. Abernethy, in his ingenious Essay on the Functions 
of the Skin, has proved that that texture is possessed of 
a power of absorbing and exhaling certain gases, which it 
exercises according to laws peculiar to the animal economy.* 
The preceding experiments seem to show that the pleura is 
possessed of a similar power in respect to absorption, and that 
in exerting this power, like the skin, it prefers one gas to 
another. Whether the analogy will hold good as regards 
exhalation also, must be decided by future inquiry 
Fort Pitt, Chatham, April iz, 1823. 
APPENDIX, 
CONTAINING 
An account of a case of Pneumato-thorax , in which the operation 
of tapping the chest was performed; with some additional 
observations on air found within the body ; and on the power of 
mucous membranes to absorb air. 
In the preceding pages I have given some particulars of a 
case of tubercular consumption, which proved rapidly fatal 
in consequence of the supervention of Pneumato-thorax; I have 
now the honour of communicating another case, in which the 
existence of air in the cavity of the chest was detected during 
life, and the patient was relieved from very distressing and 
* Surgical and Physiological Essays, Part II. by Johw Aberretht. 
