262 ON TflE EXTERNAL CAUSES OF DISEASE. 
formed a part of the animal, they become decomposed by the 
nutritive process. 
Our ideas of life have generally been so much connected with 
organic bodies, and principally those endowed with visible action, 
that it requires a new bend to the mind to make it conceive that 
the circumstances are inseparable. Mr. Hunter alleges, that in 
the nature of things there is not a more intimate connection 
between life and a solid, than between life and a fluid. For 
althouoh we are more accustomed to connect it wdth the one 
o 
than the other, yet the only real difference which can be shewn 
between a solid and a fluid is, that the particles of the one are 
less moveable among themselves than those of the other. 
An argument produced by Mr. Hunter to prove that the blood, 
in common with the solid parts, is possessed of wdiat he calls 
the materia vitce diffusa ” is that the blood becomes vascular 
like other living parts'^. This is very commonly seen after 
amputations, when the coagula on the extremities of arteries 
may be injected by injecting these arteries. Mr. Hunter con¬ 
sidered it also as a strong proof of the blood being alive, that 
when taken from the arm in the most intense cold which the 
human body can bear, it raises the thermometer to the same 
height as blood taken in the most sultry heat, as living bodies 
alone have the power of resisting great degrees of heat and cold, 
and preserving in every situation, while in health, thut uniform 
temperature which is distinguished by the name of animal heat. 
It is also capable of being acted upon by a stimulus. In proof 
of this, Mr. Hunter observes, that it coagulates from exposure, 
as certainly as the cavities of the abdomen and thorax inflame 
from the same causes. ‘‘The more it is alive ,he says, “ that 
is, the more the animal is in health, it coagulates the sooner on 
exposure; and the more it has lost its living principle, as in the 
case of violent inflammations, the less is it sensible to the stimulus 
produced from its being exposed, and it coagulates the later.’^ 
* Sir E. Home lias explained the manner in which this is produced in 
the “ Philosophical Transactions accompanied with some beautifully ex¬ 
ecuted engravings, shewing th6 new -forincd vessels rising from the centre of 
what had been a coagulurn of blood, and opening into the stream of the 
circulating finid. 
