ON ANIMAL HEAT. 
569 
37. An objection might be urged against the position I have 
taken, to the effect that the elastic tissue would absorb as much 
caloric, on its re-assuming its usual dimensions, as it gave out 
during its distention. It is probable that it does again absorb 
heat ; but it would appear, in operating with a single artery re- 
moved from the body, that on its resumption of its primary form 
it receives caloric from whatever surrounds it, and thus its own 
temperature is actually increased. The same thing, on a more 
extended scale, takes place throughout the body, and the fact 
cannot be controverted . The extensive admittance given to the air 
through the internal parts of birds and insects may operate, by 
supplying a ready source of latent heat, to exalt their temperature 
so considerably beyond what might have been anticipated. 
38. As the distention of the arteries depends on the quantity 
of blood contained in them, so, when that quantity is decreased 
by blood-letting, or other means, might it not be expected that 
the animal heat would be less, from the fact that the elastic 
coats of the arteries being less exercised, consequently supply a 
diminished quantity of caloric? 
39. If the heat of the body were entirely ruled by the respira- 
tory process, would it not be found that when respiration were 
quickened the heat of the frame would be increased proportion- 
ately ? but the contrary is often the fact, and the body and ex- 
tremities become cold when that process is abnormally increased. 
40. The independent heat which trees and plants support 
above that of the atmosphere may be also referred to the exer- 
cise of their elastic properties when agitated by the winds. Should 
this be the case, their temperature ought to be greatest in windy 
weather. 
41. Upon an examination of all the circumstances affecting 
the generation of vital heat, it will, I think, be admitted, — 
That the elastic and contractile tissues of the body are a fertile 
source of its heat , and that they form the main , if not the sole , 
means of its production. 
42. In the course of this investigation I have given the princi- 
pal facts attendant on the phenomena of animal heat from the 
authority of scientific examiners. I have not perverted them to 
meet my own peculiar views on the subject, but have endeavoured 
to shew, as briefly as I possibly could, the close connexion which 
exists between these phenomena and what I imagine to be their 
principal cause. If there be any merit in this essay, it consists 
in the assertion of the discovery of a principle in physics, i. e., 
that the distention of elastic bodies generates heat, and the en- 
deavour to apply that principle to account for the production of 
the thermal properties of animals. Lancet. 
