[ 457 ] 
was more ealily killed than an old one ; as alfo the youngeft 
part of the fame plant. 
This power of generating heat feems to be peculiar to 
animals and vegetables v/hile alive. It is in both a power 
only of oppofition and refiftance ; for it is not found to 
to exert itfelf fpontaneouily and unprovoked ; but mud: 
always be excited by the energy of fome external frigo- 
rific agent. In animals it does not depend on the motion 
of the blood, as fome have fuppofed, becaufe it belongs to 
animals who have no circulation; belides, the nofe of a 
dog, which is nearly always of the fame heat in all tem- 
peratures of the air, is well fupplied with blood : nor can 
it be faid to depend upon the nervous fyftem, for it is 
found in animals that have neither brain or nerves. It 
is then mod probable, that it depends on fome other 
principle peculiar to both, and which is one of the proper- 
ties of life; which can, and does, a61 independently of cir- 
culation, fenfation, and volition ; viz, that power which 
preferves and regulates the internal machine, and which 
appears to be common to animals and vegetables. This 
principle is in the mod perfedf date when the body is in 
health, and in many deviations from that date, we find 
that itsadlion is extremely uncertain and irregular; fome- 
times riling higher than the dandard, and at other times 
falling much below it. Indances of this we have indiffer- 
ent difeafes, and even in the fame difeafe, in very ihort 
intervals of time. A very remarkable one fell under my 
own obfervation, in a gentleman who was taken with an 
P p p 2 apo- 
