CHARACTER OF KATABOLISM 81 
Immediately before work 0.75 
During the first 5 minutes of work 0.84 
Between the 10th and 15th minute 0.87 
Between the 40th and 45th minute 0.95 
At the end of work, between the 65th and 70th minute 0.84 
After 1 hour of rest 0.74 
Unfortunately Chauveau gives this merely as a sample experiment, 
and states that it is neither the best experiment nor the most conclusive. The 
only evidence with regard to the intensity of the work and the gaseous ex- 
change is the statement that it is four times that during rest; on this basis 
Chauveau computes the theoretical respiratory quotient as follows: If the 
subject burned exclusively fat, using a respiratory quotient for fat katabolism 
, Aim « . , . 0.70x3+0.75x1,, .. . , 
of 0.70, the computation would oe , thus giving a respiratory 
4 
quotient of 0.71. He argues from this that if the subject burned only fat 
during muscular work, the tendency would be to lower the respiratory quo- 
tient. On the other hand, if the combustion were exclusively of carbohy- 
drates, using a respiratory quotient for carbohydrate katabolism of 1, the 
computation would be '■ , or a respiratory quotient of 0.94. 
4 
This was essentially the value found at the end of 40 to 45 minutes of work. 
Chauveau argues from this that the work during the experiment with Tissot 
was done exclusively at the expense of carbohydrates. He points out, how- 
ever, that the quotient does not stay at this high value but gradually falls 
as the work progresses. While he considers that the data indicate without 
doubt that the muscular work cannot be done simply by the combustion of 
fat, he brings up the question as to why the quotient is lowered if the work 
is done exclusively by the combustion of glycogen. These lower values he 
explains by the statement that there is a draft upon the store of carbohydrates 
which is immediately compensated by the conversion of fat into carbohydrate 
and this partial combustion of fat results in a lowering of the respiratory 
quotient. 
As is too frequently the case, the details of this important experiment are 
not given, and its shortness has been frequently criticized. Whether or not 
there was a cessation of work during the collection of samples or whether the 
samples were collected by means of a portable apparatus is not known, 
but the possible alterations in the character of the respiration at the cessation 
or the beginning of work may all play an important role in determining the 
measurements of the character of the katabolism. 
The experiments as a whole have been severely criticized by Zuntz,* 
who points out that while Chauveau attempts to explain the low respiratory 
quotient toward the end of work, he does not explain why the respiratory 
quotient was low at the beginning of the work-period when the store of car- 
bohydrates was abundant. Zuntz argues that the quotient obtained during 
the first 15 minutes agrees with the theory of himself and his associates that 
during work the nutrients oxidized are essentially the same as during rest, 
but that there is some increase in the utilization of the carbohydrates because, 
a Zuntz, Verhandl. Bert, phyaiol. Geselleh., Archiv f. Physiologie, 1896, p. 538. 
