NET AVAILABLE ENERGY—MAINTENANCE. 405 
Per Grm. of Substance. Heat 
we Liter 
O Carb of Oxygen 
Cone’ | Dioxide | peat | gamed, 
sumed, |Pipduced,) Gai | “al. 
Albumin to fat and urea............ 0.481 | 0.4777 2.234 4.646 
ef “ dextrose and urea....... 0.713 | 0.5480 3.180 4.460 
io CO, HQ a aus 1.045 | 0.8720 4.857 | 4.647 
Stearin “ “ ‘ “ dextrose ...| 0.840 | 0.2257 3.417 4.067 
as e6 SEE and SEOs fs sae fade eia tel 2.043 | 1.4290 | 9.500 | 4.650 
Dextrose © ©  eaneewaas 0.744 | 0.7440 | 3.762 5.056 
determination of the respiratory products, the author assumes a 
scheme of metabolism in accordance with the theory, and finds that 
the heat production as computed on this assumption agrees quite 
closely with that actually determined. 
Aside from questions of method, particularly whether a five- 
hour period is sufficiently long, it is to be remarked that the results 
of Kaufmann’s experiments are ambiguous. They show that it is 
possible to interpret the facts in accordance with his theory, but 
they do not exclude the possibility of other explanations. For this 
reason it seems unnecessary to cite the experiments in detail, and 
for the same reason they are at best but confirmatory evidence in 
favor of the theory of isoglycosic values. 
§ 2. Modified Conception of Replacement Values. 
The theory of isodynamic replacement as announced by Rubner 
constituted the first systematic application of the general laws of 
energy to the problems of animal nutrition. As such it has exerted 
a profound influence upon subsequent study of the subject in that 
it has been chiefly instrumental in leading to a practical application 
of the long-known fact that the food is primarily a supply of energy. 
It was based, of course, upon the conception that the law of the 
conservation of energy obtains in the animal body, and in subsequent 
experiments, which have been described in Chapter IX, Rubner 
gave at least a partial demonstration of the truth of this concep- 
tion. 
Rubner’s general ideas still form the basis of our views regard- 
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