6 ~ Dr. Bell on the Generation of, &c. 
covered with moifture. It is, perhaps, for this 
purpofe alfo, that it is rough and uneven ; which, 
by extending the furface, caufes a greater evapo¬ 
ration. 
Thefe may be faid to be the means through 
which the human body is preferved, in nearly the 
fame temperature, when it happens to be placed, 
for a time, in an atmofphere of a fuperior degree 
of heat. They feem to me fo adequate to this 
effed, that I would even venture to impute the 
increafe of the temperature of the body, from 
96 to 100 degrees, which happened in the expe¬ 
riments, rather 'to the acceleration of the blood, 
than to the influx of heat from the external air. 
While the caufe of animal heat remains unknown, 
it would be prefumption to aflert, that thefe are 
the only means, by which the body is enabled 
to refill the effeds of external heat. There may 
be others; and it is not unreafonable to fuppofe, 
that as external cold, perhaps by its tonic influ¬ 
ence, increafes the power of the body to generate 
heat, fo external heat may diminifh that power, 
and thus leflfen the quantity of heat generated 
within, while the evaporation, produced by the 
fame caufe, guards it againfl receiving any accef- 
fion from without. 
