§44 
ANIMAL HEAT. 
The Measurement of Heat Production. 
The amount of heat produced by an animal can be determined by 
the measurement of the heat given off, and also by an estimation of the 
heat value of the chemical changes taking place in the body. The most 
exact method is that which embraces both of these determinations. 
Numerous attempts have 
been made to construct 
suitable calorimeters, but 
it is only within the last 
few years that exact 
methods have been de- 
vised. 
Calorimeters. 1 — In 
1780, Lavoisier and Lap- 
lace 2 employed the ice cal- 
orimeter, in which the heat 
produced by the animal is 
estimated from the amount 
of ice liquefied. The con- 
struction of this calorimeter 
is shown in the accompany- 
ing diagram. (Fig. 81). 
Important results were 
obtained by the use of this 
method, but they were not 
an exact measure of the 
heat produced by a normal 
animal. The exposure to 
such a low temperature causes an abnormal loss and production of heat, and 
it is impossible to rapidly and completely collect the water formed by the 
melting of the ice. 
Crawford, 3 in 1788, introduced the water calorimeter, and indicated the 
precautions necessary to obtain accuracy. The method was improved by 
Dulong and Despretz. 
Although this calorimeter was a great advance upon the ice calori- 
meter, yet it has been found by numerous observers to be unreliable. It 
is impossible, even by careful mixing, to obtain the exact heat of the water, 
for strata of different temperatures are formed, and thus errors easily 
arise. Further, the water responds very slowly to any change in the 
production of heat by the animal. This method was used by Dulong 4 
and Despretz, and has been again brought into use by Wood, Reichert, 
and others. 6 
The air calorimeter appears to have been first used by Scharling 7 in 1849, and 
1 A list of researches in which different kinds of calorimeters have been used, will he 
found in the paper hy Haldane, Hale White, and Washhourn, Journ. Physiol., Cambridge 
and London, 1894, vol. xvi. p. 124. 
2 Hist. Acad. roy. d. sc., Paris, 17S0, p. 355. 
3 " Experiments and Observations on Animal Heat," London, 1788, 2nd edition. 
4 Ann. de chim. etphys., Paris, 1843, Ser. 3, tome i. p. 440 ; Compt. rend. Acad. d. sc, 
Paris, tome xviii. p. 327. 
5 Ann. de chim. etphys., Paris, 1824, Ser. 2, tome xxvi. p. 337. 
"Wood, "Fever," Smithson. Contrib. KnoivL, Washington, 1880 ; Reichert, Univ. 
Med. Mag., Philadelphia, 1890, vol. ii. p. 173. 
7 Journ. f. prakt. Chem., Leipzig, 1849, Bd. xlviii. S. 435. 
