on air found in the pleura, &c. 505 
sion of hydrogene into the pleura of dogs, and in each instance 
after death I found that the hydrogene had disappeared, and 
that its place was supplied by a small quantity of azote. 
Did the azote found in these instances exist in the pleura 
previous to the experiment ? 
A remark of Dr. Laennec, would seem to countenance this 
notion. He says, “ M. Ribes assures me, that he has found 
in opening the serous cavities of dogs a small quantity of air 
constantly to escape/'* On the contrary, in opposition to 
this, are the experiments of Haller and other accurate ob- 
servers, recorded in the controversy which Hambergerus gave 
rise to, by reviving and maintaining the opinion of Galen, 
that air is contained between the lungs and the pleura.-f 
In doubt between these contending authorities, with the 
desire of satisfying myself on the point, I have made some 
experiments on dogs, the results of which convince me, that 
in a healthy state, no air is contained in the pleura of this 
animal. When I opened, under water, the chests of dogs 
killed by drowning, not the smallest globule of air escaped ; 
but, when the right side of the chest was opened in the atmos- 
phere, an appearance presented itself, at first favourable to 
the idea of a little air being contained in the left pleura, for 
the mediastinum was pressed from the left side towards the 
right, (the body lying on the left side) evidently by air 
within the transparent membrane. This appearance on 
examination proved to be fallacious, for the air was found to 
* A Treatise on the Diseases of the Chest, See. translated from the French of 
R. T. H. Laennec, M. D. by John Forbes, M. D. p. 208. 
f Haller’s Not. in Praelect. Boerh. dcvi. Haller’s Opuscula Anatomica, 
de resp. Gott. 1751, p. 91, and 345. Marherr’s Praelect. in Boerh. Inst. vol. iii. 
P- 39 1 * 
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