ON THE EXTERNAL CAUSES OF DISEASE. 267 
the carbon of this fluid, and thus forms carbonic afcid gas. Ac¬ 
cording to this view, not a particle of the inhaled air is absorbed 
by the blood, and the office of the lungs is supposed to be simply 
that of receiving the atmospheric air, and expiring carbonic acid 
gas. With respect to the nitrogen, which forms the other con¬ 
stituent part of the atmosphere, as it was returned exactly in the 
same state and quantity as it was inhaled, it was supposed to 
have little influence on the animal economy. 
The reader will perceive that we have taken a different view 
of the subject. For, from the experiments of Dr. Edwards and 
others, we are led to believe that a part of the atmospheric air 
enters directly into the circulatory current. ‘‘The oayyge?^,” he 
says, “ which disappears in the respiration of atmospheric air, 
is w'holly absorbed. It is afterwards conveyed wholly or in part 
into the blood. It is replaced by exhaled carbonic acid, which 
proceeds wholly or in part from that which is contained in the 
mass of the blood. 
The absorbed azote is replaced by exhaled azote, which pro¬ 
ceeds wholly or in part from the blood.” 
According to this view, respiration is not a purely chemical 
process, a simple combustion in the lungs, in which the oxygen 
of the inspired air unites with the carbon of the blood, to form 
carbonic acid to be expelled ; but a function composed of several 
acts. On the one hand, there are absorption and exhalation, at¬ 
tributes of all living beings ; on the other, the intervention of the 
two constituents of atmospheric air,—oxygen and nitrogen. 
It would exceed the limits of our paper to follow the doctor in 
the different experiments by which he arrived at these conclusions; 
we must, therefore, refer our readers to the work itself: but 
the following detail of experiments is too interesting, in this 
point of view, to be omitted here. 
. “ Three puppies, a day or two old, were introdueed into separate vessels, 
containing 150 centilitres, or 91-5 cubic inches of air. They remained there 
five hours. During the experiment it was evident that there w as an ab¬ 
sorption of air ; for the mercury rose in the tube, and it was necessary to 
"pour a fresh supply into the vessel in which it was immersed. It w as evi¬ 
dent that the absorption was considerable, but the exact measure of it could 
not be ascertained. From the analysis of the respired air, it appeared that 
the three puppies had produced nearly the same (juanlity of carbonic acid, 
