172 PROCESS OF CALORIFICATION IN ANIMAL BODIES. 
amount of muscular power is no precise measure of the 
animal heat, or the flea and the dragon-fly, travelling at the 
rate of 200 miles per hour, would, in proportion to its size, 
have a more elevated temperature. Dr. Davey had affirmed, 
that the sympathetic nerve is the source of this heat ; but no 
unwonted development of that system had been detected in 
birds. He believed in the chemical theory, and affirmed, in 
opposition to the late Mr. Barlow, that the fat from the 
combustion of which heat is derived is a natural production, 
and is constantly met with in wild animals. 
Mr. H. Lee agreed with Dr. Winn, that there are certain 
conditions of the system as to heat which cannot be accounted 
for by the chemical theory. The limbs of a dying person 
become cold, while the trunk retains its natural warmth ; and 
he had observed, that the body of a patient suffering from 
injury to the head, became and continued colder than the 
surrounding media. 
Dr. E. Smith related the experience of the inhabitants of 
warm climates in reference to the value of the action of the 
skin. He had observed, when travelling near the Gulf of 
Mexico, that, while riding on the high rolling prairies, with 
the temperature of the sun’s rays at 120° or 130°, no incon- 
venience was experienced beyond that of direct burning, for 
the lungs acted freely, and the clothing was constantly 
dripping with perspiration. This was owing to the dryness 
of the atmosphere ; but, whenever he crossed the wooded 
bottom of a river, and w r as entangled for a time in the trees 
and mud, the respiration became laborious, and the perspira- 
tion, instead of flying off rapidly, rolled down in streams. 
This was attributable to the lessened evaporation resulting 
from increase of moisture in the air, and the absence of the 
breeze. When the perspiration w 7 as free, there w r as a less 
rather than a greater tendency to the action of the kidneys. 
Those persons who live in low, marshy places in hot countries, 
do not readily eliminate the effete matter by the skin and 
kidneys, and therefore become liable to fever. In the Russian 
winters the inhabitants are said to have a custom of entering 
into ovens heated to 240° before setting out for the chase, 
and, as the air is dry, and the perspiration free, the effect is 
exhilarating. 
I)r. Gibb gave similar experience in reference to cold, and 
affirmed, that while he could enjoy the intense cold of 
Canada, because it was dry, he had suffered much from the 
comparatively trifling but damp cold of this country. He 
also called attention to the fact, that emigrants from this 
country bear the first year’s cold of Canada with impunity, 
