508 Dr. Davy’s observations and experiments 
right to state what I have observed relative to a topic so in- 
teresting and obscure ; and to notice such facts as seemed to 
bear more immediately on the question, in hope of exciting 
farther inquiry, by which alone the true source of the azote, 
apparently evolved in the preceding instance, can be ascer- 
tained. 
The effect of nitrous gas introduced into the pleura now 
requires consideration. I have made several trials farther 
with this gas. When admitted nearly pure into the pleura 
it produced very serious symptoms, but did not prove fatal, 
provided the lung on the opposite side was free to act. The 
distressing symptoms usually subsided in about twelve hours ; 
and then, on killing the animal, the greater part of the 
nitrous gas was found to be absorbed ; the pleura was free 
from inflammation, the substance of the lungs very slightly 
inflamed, and the blood exhibited a brownish hue. From 
these circumstances it may be conjectured, that nitrous gas 
produces its deleterious effects after it has been absorbed, 
either by acting on the blood immediately, or on the air cells 
of the lungs and the blood conjointly, when converted into 
nitrous acid in the course of the pulmonary circulation. 
On the admission of nitrous oxide into the pleura, I have 
made one experiment only. About 30 cubic inches of this gas, 
contaminated with 25 per cent, common air, were passed into 
the pleura of a dog. The animal exhibited no uneasy feeling, 
and immediately after appeared to be rather exhilirated. It 
continued apparently in good health for 24 hours, when it 
was killed. Five cubic inches of air were procured from the 
pleura, which consisted of 10 per cent, oxygene and go azote, 
being quite deprived of nitrous oxide. The pleura and lung 
