PRODUCTION OF ANIMAL HEAT. 
387 
instead of being conveyed to the blood in the lungs in a con¬ 
cealed or latent form, as generally imagined, is actually evolved 
from the cells oj the lungs themselves in a sensible form, and imme¬ 
diately communicated to the blood circulating in the lungs as 
palpable heat; and that the great work of arterialization of the 
blood is effected by a very simple process, and purely on mecha¬ 
nical principles. 
I regard each minute air-cell of the lungs as a separate furnace ; 
the common atmospheric air inhaled as the fuel; and that, in conse¬ 
quence of a wise provision of nature in the construction of the 
respiratory apparatus, the inhaled air is opposed in its ejection 
from the cells, until it has undergone a certain degree of com¬ 
pression in the act of expiration, which forces it to leave a part 
of the caloric that it contains. 
A reference to the internal structure of the respiratory organs 
will exhibit every facility to the free and rapid admission of the 
external air, whilst the same organization evidently allows of its 
return ; but, I contend that it presents numerous obstacles to its 
rapid ejection in ordinary breathing; and it appears to me to 
be just such a piece of mechanism as a mechanic would devise 
for the effectual compression of atmospheric air. 
The inflated lungs being comprised of myriads of minute cells 
or bladders in a state of distention, each cell, having a separate 
communication with the bronchise bv a neck of inconceivable 
• - ^ 
smallness, its calibre being impervious to any thing of greater 
density than air, has to encounter suddenly, in the effort of ex¬ 
piration, the force of combined impressions : first, the contrac¬ 
tion of the cell itself, in virtue of its own inherent elasticity ; 
secondly, the powerful contraction of the diaphragm aided by the 
abdominal and intercostal muscles, all conspiring at the same 
instant to reduce the area of the chest in every direction, consti¬ 
tute a joint pressure on the distended air-bladders as equal to 
three , whilst the avenues through which the air has to escape are 
in conjunction only as equal to one; consequently as the air-cells do 
not rupture when the sides of the chest suddenly approximate, the 
contained air necessarily undergoes that degree of compression 
or condensation which causes a certain quantity of caloric to 
escape from it in a sensible form. 
How far this process of compressed atmospheric air within the 
lungs may afford a vehicle for the transmission of electric fluid 
into the blood and nervous system, I shall not pretend, at present, 
to enlarge upon. 
No. 311, Regent Street, June 14th, 1832. 
