492 
OBSERVATIONS ON 
pulsion from the lungs, undergoes “ a degree of compression as 
equal to three, whilst the avenues through which the air has to 
escape are in conjunction as equal only to one;” and that, 
while undergoing this degree of compression, or condensation, a 
certain portion of caloric, which the air contained, is forced out 
or made “ to escape in a sensible form , and which immediately 
becomes communicated to the blood circulating in the lungs, as 
palpable heat: in fact, that instead of the principle of heat being 
conveyed to the blood in the lungs in a concealed or latent form, 
as has generally been imagined, it is actually evolved from the 
cells of the lungs themselves in a sensible form, and consequently 
the great work of the arterialization of the blood is effected by a 
very simple and purely mechanical process.” 
Now, as Mr. Turner has given us a very brief and candid state¬ 
ment of his new theory respecting the generation of animal heat 
in the lungs, he will not, I am sure, object to my making a few 
observations, and putting a few questions to him on this most 
interesting subject. 
In the first place, we ought to have been informed of the 
degree of mechanical pressure necessary to increase the tem¬ 
perature of a given quantity of atmospheric air when in a 
partially confined state out of the living body; and, in the next 
place, to have made the thing at all substantial, we ought to have 
been told that the air underwent a similar degree of mechanical 
pressure during its immediate expulsion from the lungs. Instead 
of this, Mr. Turner has only told us what he considers to be the 
degree of pressure necessary to simply expel the air from the 
lungs, and the correctness of which statement I very much doubt. 
We are informed, that the “ degree of mechanical pressure ne¬ 
cessary to produce the required effect on the distended air-blad¬ 
ders of the lungs is equal to three , whilst the avenues through 
which the air has to escape are, when taken in conjuction, equal 
only to one” Now, if this statement is correct, the air only re¬ 
ceives two degrees of pressure during its expulsion from the lungs; 
and Mr. Turner must remember, that even then there is, after 
each expiration, a considerable portion of air still remaining in 
the lungs: consequently, if the air receives only two degrees of 
pressure during its expulsion, this I contend is not sufficient to 
affect the temperature of any given quantity of it, whether in or 
out of a living animal body; for, if I mistake not, I believe it 
will require several hundred degrees of mechanical pressure to 
affect the temperature of atmospheric air contained in a gun- 
barrel syringe: while even then the object is not effected unless 
the compression is produced in a very rapid manner. There is also 
a doubt in my mind, whether the increase of temperature of the 
