305 
nitrogen ; and, after the experiment, it contained 
147.52 ; so that 50.12 cubic inches of nitrogen had 
been obtained from the animal. This increase of 
nitrogen, it is added, was much more than equal to 
the cubic contents of the animal's body *. In ano- 
ther experiment, the excess of nitrogen was 34.20 ; 
and in a third, made with a mixture of oxygen and 
hydrogen gases, the nitrogen obtained from the lungs 
of a Guinea pig amounted to 57.40 cubic inches ! 
These experiments seem clearly to shew, that, under 
certain circumstances, a volume of nitrogen gas is 
obtained from the lungs, greater than the actual ca- 
pacity of those organs, and greater, consequently, 
than, in conformity with the mechanical properties of 
elastic fluids, they can be considered able to contain. 
603. Is then this excess of nitrogen, as these che- 
mists suppose, really given off from the blood ? This 
question necessarily involves the previous considera- 
tions, Does this gas, at any time, exist in that fluid, 
and from what sources can it be derived ? Now we 
have no evidence that nitrogen gas is contained in 
the blood, but the base of that gas is known to ex- 
ist in it ; and, by chemical agents, which effect the 
entire decomposition of the blood, it may be obtained 
from it in a gaseous form. It can hardly, however, 
be contended, that, because the blood affords nitro- 
gen gas under decomposition, it yields it spontaneous- 
ly in the healthy living system, where no such de- 
composition takes place ; though this, indeed, is the 
* Phil. Trans. ISOp, p. 417- t Ibid. 
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