378 PHILOSOPHY OF ZOOLOGY. 
From these experiments it appears, that the temperature 
of the human body may be raised 4° above its natural 
standard, and sunk 15° below it, by the operation of ex- 
ternal circumstances. In the mouse, the heat was dimi- 
nished 16° below,—and in the dog, raised 7° above the 
natural standard. 
The same law extends to the cold-blooded animals. Dr 
Hunter found the temperature of a healthy viper, when 
exposed to 108°, rise to 923°; and the same animal, when 
placed in a temperature of between 10° and 20°, had its 
heat sunk to 37°, 35°, and even 31° *. 
It is in consequence of the unceasing influence exerted 
on the animal frame, by the varying temperature of sur- 
rounding objects, that the different parts of the body are 
seldom of the same degree of heat. The stomach, heart, 
and liver, are always nearest the standard, the other parts, 
which are more remote, varying one or two degrees in the 
warm-blooded animals, when not greatly acted upon by 
deranging causes. 
2. When the body is exposed to a temperature greatly 
above the ordinary standard of the animal, a counteract- 
ing influence is exerted, and cold is generated.—In all ani- 
mals, whether hot or cold blooded, the heat may be raised 
a limited number of degrees. But, even when the exter- 
nal temperature continues high, the heat of the body re- 
mains stationary at its maximum of elevation+. Thus, in 

* Phil. Trans. 1778 p. 25. 
+ Governor Ex.is, in a letter to the celebrated Joun Exuxis, dated Geor- 
gia, 17th July 1758, makes a slight reference to this law, which was after- 
wards developed by Dr Fonpyce. ‘* I have frequently (says the Governor) 
walked an hundred yards under an umbrella, with a thermometer suspended 
from it by a thread, to the height-ef my nostrils, when the mercury has 
rose to 105°; which is prodigious. At the same time, I have confined this 
