METHODS OF INVESTIGATION. 77 
The division of the increments of the respiratory gases was accord- 
ingly— 
Oxygen Carbon Dioxide 
Consumed. Produced. 
BY latina weer duarwee ee enews 0.6939 c.c. 0.4905 c.c. 
By carbohydrates........... 0.9765 “ 0.9765 “ 
“ 
Otalsnchete usec ae 1.6704 “ 1.4670 “ 
From these data the actual amounts of fat and carbohydrates 
metabolized can be readily computed, one gram of fat requiring for 
its oxidation 2.8875 grams (2.028 liters) of oxygen and producing 
1.434 liters of carbon dioxide, while one gram of a carbohydrate of 
the composition of starch requires 1.185 grams (0.832 liter) of 
oxygen and produces the same volume of carbon dioxide. 
CoMPUTATION OF F'aT FROM CARBON BaLANcE.—While the use 
of the Zuntz type of respiration apparatus may afford invaluable 
information regarding the nature of the chemical changes going 
on in the body, a satisfactory determination of the gain or loss of 
carbon by the body usually requires the employment of one of the 
other types of apparatus.* Having by such means added a deter- 
mination of the carbon balance to that of the nitrogen balance, we 
have the data necessary for computing the gain or loss of fat as well 
as of protein by the schematic body. 
For this purpose we first compute the gain or loss of protein 
in the manner already described. Using Kohler’s factor for pro- 
tein (p. 67), a gain of 16.67 grams of nitrogen is equivalent to a 
gain of 100 grams of protein. This 100 grams of protein will 
contain, according to Henneberg, 53 grams, or according to Kohler, 
52.6 grams of carbon. Any gain of carbon in excess of this amount 
must therefore be in the form of non-nitrogenous organic matter, 
while if less than this amount of carbon has been gained the non- 
nitrogenous matter of the body must have been drawn upon to 
supply the difference. The only non-nitrogenous organic substance 
assumed to be present in the schematic body, however, is fat, con- 
taining on the average 76.5 per cent. of carbon (p. 61). Neces- 
*For a direct comparison of results obtained upon the horse by the Zuntz 
and the Pettenkofer forms of apparatus, see Lehmann, Zuntz, & Hagemann, 
Landw. Jahrb., 23, 125. 
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