368 PRINCIPLES OF ANIMAL NUTRITION. 
pina dy cite ace Teer et | Carbon Dioxide in 12 Hours. 
Tempereuars, 
egrees. 
Bee Relative. qo. Relative. 
30.8 7.2 1.0 12.03 1.00 
20.1 17.9 2.5 14.34 1.19 
12.3 25.7 3.6 17.76 1.48 
0.2 37.8 5.25 18.24 1.52 
—5.5 43.5 6.0 19.83 1.65 
It would appear from these figures that even below the critical 
temperature the “physical” regulation plays a large part in the 
regulation of the body temperature, being simply supplemented 
by the “chemical” regulation, and that therefore the demand for 
heat has not the determining influence upon the heat production 
which Rubner supposes. According to v. Hésslin the apparent 
dependence of the total metabolism upon the surface is only a par- 
ticular case of a general morphological law and he points out: 
First, that since, according to him, the velocity of the circula- 
tion does not vary greatly in large and small animals, the average 
amount of blood passing through the organs, and consequently 
their supply of oxygen, will be proportional to the total cross- 
section of the blood-vessels, which again, similar form being 
assumed, will be proportional to the two-thirds power of the 
volume (or weight) of the body. 
Second, that the capacity of the alimentary canal to digest and 
resorb food and thus to supply material for metabolism is limited 
in the same proportion. 
Third, that the work of locomotion—substantially the only 
form of external work in the wild state—at a given speed is pro- 
portional to the two-thirds power of the weight. 
In short, v. Hésslin claims that all the important physiological 
activities of the body, including, of course, its internal work and the 
consequent heat production, are substantially proportional to the 
two-thirds power of its volume, and that since the external surface 
bears the same ratio to the volume, a proportionality necessarily 
exists between heat production and surface. According to this 
view, then, the heat production of the fasting animal at the criti- 
cal temperature represents the internal work, which is proportional 
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