362 PRINCIPLES OF ANIMAL NUTRITION. 
With one exception, the results per square meter agree very well 
with those of Rubner, both absolutely and relatively. 
Rubner has also shown in later experiments * that the same 
thing is substantially true of guinea-pigs, both at zero and at the 
temperature of about 30 degrees, at which the heat production is at 
its mimimum (critical temperature). He likewise points out t 
that the well-known rapid metabolism of children as compared 
with adults is, so far as the available data show, quite closely pro- 
portional to their relative surface, and observations on the diet of 
a dwarf { gave a like result. 
Richet,§ working with an air-calorimeter of constant pressure, 
in which the heat production was measured by the amount of 
water displaced by the expansion of the air, obtained the following 
results on rabbits, and similar results upon guinea-pigs are also 
reported: 
Total Heat 
: . Heat ; The Same 
Sea tive me | perKe, | Scr Water | Por Unit of 
als. Displaced. Surface. 
2.0-2.2 4.730 119 
2.2-2.4 3.985 110 130 
2.4-2.6 3.820 115 129 
2.6-2.8 3.650 119 127 
2.8-3.0 3.570 125 128 
3.0-3.2 3.320 * 130 127 
It would appear from the description of the experiments that 
only the heat given off by radiation and conduction was measured, 
no specific statements being made as to ventilation or as to the loss 
of heat as latent heat of water-vapor. The experiments were also of 
short duration, ranging from sixty to ninety minutes. 
The same author in later experiments || determined the respi- 
ratory exchange of rabbits of different weights. Computing the 
* Biologische Gesetze, pp. 17-18. 
t Zeit. f. Biol., 21, 390. 
t Biologische Gesetze, p. 9. 
§ Archives de Physiol , 1885, II, 237. 
|| Jbzd., 1890, pp. 17 and 483; 1891, p. 74; Comptes rend , 109, 190. 
4] By means of an apparatus described briefly in Comptes rend., 104, 435 
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