ao6 THEPHILOSOPHY 



It wlli, conlequently, during the circulation, imbibe this principle 

 from thofe parts which retain it with the leaft force, or fi-ora the 

 putrefcent parts of the fyftem : And hence the venous blood, when 

 it returns to the lungs, is found to be highly impregnated with 

 phlogifton. By this impregnation, its capacity for containing heat 

 is diminifhed. In proportion, therefore, as the blood, which had 

 been dephlogifllcated by the procefs of refpiration, becomes again 

 combined with phlogifton, in the courfe of the circulation, it will 

 gradually give out that heat which it had received in the lungs, 

 and diffufe It over the whole fyftem *.' 



The Do6lor afterwards proceeds to affign a reafon why the heat 

 of animals is always equal. ' As animals,' fays he, ' are continu- 

 ' ally abforbing heat from the air, if there were not a quantity of 

 ' heat carried off, equal to that which is abforbed, there would be an 

 ' accumulation of it in the animal body. The evaporation from 

 ' the furface, and the cooling power of the air, are the great caufes 



* which prevent this accumulation. And thefe are alternately in- 

 ' creafed and diminilhed. In fuch a manner as to produce an equal 



* effea. When the cooling power of the air is dimlniflied by the 



* fummer heats, the evaporation from the furface is increafed ; and 



* when, on the contrary, the cooling power of the air is Increafed 



* by the winter colds, the evaporation from the furface is propor- 



* tionally diminilhed f.' 



This theory, though not fupported by mathematical evidence, is 

 not only Ingenious, but feems to make a nearer approach to truth 

 than any that has hitherto been Invented J. 



Refpiration, 



* Crawford on Animal Heat, pag. 73. f Ibid. pag. 84. 



1 If the reader is defirous of feeing fome pertinent remarks on Doitor Crawford's 



Theory 



