INTERNAL WORK. 369 
to the two-thirds power of the volume of the body, while below 
this point there is superadded a stimulating effect upon the heat 
production, which, since it acts through the surface, we may 
assume to be proportional to the latter. 
Comparison of Species.—In the foregoing discussion compari- 
sons have been made between large and small animals of the same 
species, with the result that both their internal work and their 
total fasting metabolism appear to be closely proportional to their 
surface. Going a step further and comparing the average results 
of the several species with each other, E. Voit * reaches the inter- 
esting and striking result that the same relation of total fasting 
metabolism to surface is substantially true as between different 
species. The following table contains the averages, with the addi- 
tion of the fasting metabolism of the horse as computed by Zuntz 
& Hagemann, which Voit believes with good reason to be too 
low: 
Fasting Metabolism. 
Average Tem- Average 
perature, Weight, Kgs. 
Deg. C. Per Kg., Per Square 
Cals. Meter, Cals. 
Horse............. 9.1 (2) 441 11.3 > 948 
Swine............. 20.1 128 19.1 1078 
Mai i622 auistn ee oes 14.3 64.3 32.1 1042 
Dog ...........05. 18.0 15.2 51.5 1039 
Rabbits os ae. sie cae 18.2 2.3 75.1 776 
Goose............. 15.0 3.5 66.7 967 
FAC bie ice, aanaa cohansae 18.5 2.0 71.0 943 
With the exception of the rabbit, the average heat production 
of these various animals per unit of surface does not show any 
greater variations than have been observed between different 
animals of the same species, more or less of which, as we have seen, 
can probably be accounted for by errors in the estimate of the 
surface of the body. 
Accepting the fact of the general proportionality of heat pro- 
duction to surface, and passing over for the moment the excep- 
tional case of the rabbit, it is plain that the considerations which 
have been adduced in discussing the results upon the same 
* Loc. cit., p. 120. 
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