20 On Respiration and Animal Heat. 
and the aqueous’ vapour. Upon a careful — 
examination of the facts, however, the results 
do not form a true equation; the quantity of 
aqueous vapour exhaled is undoubtedly greater 
than can be accounted for as above; the ex- 
cess of vapour is\supplied, we may suppose, 
by the natural exudation of moisture through 
the thin membranes of the lungs. 
In the Annales de Chimie for 1791, about 
three years after the 2d Edit. of Dr. Craw- 
ford’s book, we ‘find a memoir by Hassen- 
fratz on the subject of animal heat.—In the 
course of the memoir, M. de la Grange is 
introduced as objecting to Crawford’s theory, 
because it supposes all the heat to be given 
out in the lungs, which, he thinks, would be 
in danger of consuming them; he finds it ex- 
pedient, therefore, to invent another theory, 
as he conceives, in which the heat may be 
gradually given out, during the course of the 
circulation, to all the parts of the body.—It 
is scarcely possible for any one, who under- 
stands the doctrine of Crawford, to read the 
observations of La Grange, and his commen- 
tator, Hassenfratz, without smiling at their 
palpable ignorance of the doctrine under 
their review. The distinguishing feature of 
Crawford’s theory is, that of the greater capa- 
city of arterial blood for heat, than of venous 
