558 
ON ANIMAL HEAT. 
maintain the balance of heat in the animal economy, will proba- 
bly give rise to improvements in the prevention and cure of dis- 
ease. (On Animal Heat, p. 438.) 
2. The source of animal heat, whether it be supplied by che- 
mical, vital, or purely physical action, has been a most fertile 
subject of theory ; but no position which has yet been assumed 
is considered fully explanatory. The celebrated John Hunter, 
who carefully examined the subject in all its bearings, declared 
himself dissatisfied with all the hypotheses that had been ad- 
duced to explain it. “ The theories hitherto brought forward do 
not in the least satisfy me, as I think that none of them accord 
perfectly with every circumstance observable in these cases.” 
(Hunter’s Works, by Palmer, vol. iii, p. 16.) Muller, in his late 
physiological work, after reviewing the various theories promul- 
gated on the subject, considers that some other supply of animal 
caloric is still undiscovered. Mr. Mayo is yet more confident 
“ that the source of vital heat remains unknown.” (Physiol., 
p. 96.) “ No attrition,” says Blagden, “ no fermentation, or 
whatever else the mechanical and chemical physicians have de- 
vised, can explain a power capable of producing and destroying 
heat, just as the circumstances of the situation require.” (Phil. 
Trans., 1775, p. 112.) 
3. By this peculiar property the animal maintains a tempera- 
ture apparently independent of extraneous circumstances, at once 
u constant, equable, and perpetual.” 
4. In the human being the degree of heat acquired is not so 
high as in some other classes of the mammalia. Blood heat is 
generally quoted at 98° of Fahrenheit’s scale, but this is certainly 
beneath the usual internal temperature. Dr. Beaumont, by 
placing a thermometer in the stomach of a living and healthy man, 
ascertained that the heat of that part of the frame averaged 100°. 
Muller found the temperature of the mouth and rectum to vary 
from 97.7° to 98.6° ; while that of the more internal parts of the 
body was from 100f° to 101 J°. Dr. Thompson places it at 101°, 
and Magendie at 101.75° Fahr. 
5. From the copious tables which Tiedmann has compiled of 
facts ascertained relative to the heat of different genera of the 
mammalia , it is seen that in some of them, such as the ox, horse, 
and elephant, the temperature is not quite so high as that of man ; 
while that of the squirrel, the ape (simia aigula ), the bat, and the 
whale, ranges rather above his natural standard. 
6. The heat acquired by many birds rises considerably above 
that of the mammalia. In the common pigeon it is 106°, in the 
vulture 107°, and in the raven sometimes as high as 109.23°. Dr. 
Edwards found the heat of sparrows to range from 105° to 110 g . 
