202 . PHYSIOLOGY. 



the effect of putrefaction, towards which there is certainly some 

 approach in animal bodies ; but the opinion is still very doubt- 

 ful. For, first, the effect of any degree of putrefaction in pro- 

 ducing heat is not well ascertained. Secondly : It is not sup- 

 ported by any analogy, that putrefaction, in the degree to which 

 only it proceeds in living bodies, is capable of producing the 

 heat appearing there. And, lastly, whatever is the degree to 

 which putrefaction proceeds in living bodies, it does not appear 

 that there is any increase of heat correspondent to the increase 

 of putrefaction, and rather the contrary. 



CCLXV. The suppositions either of mixture, or of putre- 

 faction, as the cause of animal heat, are both of them rejected 

 by this, that the generation of heat in animal bodies is mani- 

 festly dependent on another cause, that is, the motion of the 

 blood. For the power of generating heat in any animal is not 

 perfect, till the motion of the blood in it is fully established ; 

 and, when the generating power is established, we perceive the 

 heat to be increased or diminished, as various causes increase or 

 diminish the motion of the blood. In dying animals, the heat 

 grows less as the motion of the blood grows less ; and when at 

 death this ceases altogether, the heat ceases also, commonly, at 

 least, as soon after death as we can suppose a body of the same 

 bulk to lose the heat it had acquired. 



CCLXVI. This connexion between the heat and motion of 

 the blood seems in general to be well proved ; and, though it 

 may be difficult to reconcile certain appearances to it, we would 

 so far admit of the supposition as to inquire, in the next place, 

 into the manner in which the motion of the blood may generate 

 heat. 



CCLXV II. On this subject the most common opinion is, 

 that the heat is produced by the attrition of the particles of the 

 blood upon one another, or of these on the internal surface of 

 the vessels in which they move. But we cannot find any anal- 

 ogy to support either the one or the other supposition. 



The attempt made to support the latter supposition, by en- 

 deavouring to shew that upon this the equality of heat in the 

 different parts of the same body is well explained, deserves 

 little regard, as it is founded on doubtful principles and mis- 

 taken facts. 



