CHARACTER OF KATABOLISM 85 
have been drawn, first, for the 34 days on which such values were obtained, 
and second, for the 16 days on which the after-periods were of such length 
that a subdivision could be made of the values obtained for the first and second 
hours after work, respectively, this last average necessarily including only 
data secured in the experiments with the subject M. A. M. In the grand 
average for 34 days, it will be seen that the respiratory quotient of 0.85 was 
raised during work to 0.88, falling after work to 0.78. An inspection of the 
data shows that this rise and fall was present in the majority of the experi- 
ments, although in several of the earlier experiments there was a fall in the 
respiratory quotient^ during work, with a further lowering — very rarely a rise 
— during the period after work. The greater number of the experiments 
included in the average for the 16 days were made in the latter part of the 
experimental year, for, with the exception of the experiment of December 21, 
there were none prior to January 9. This average also shows a slight, 
though definite, rise in the quotient during the work, with a subsequent 
marked fall in both periods after work. 
From the research as a whole, therefore, the significant conclusions can 
be drawn that there was a distinct, though numerically small, increase in 
the respiratory quotient during work, with a very appreciable decrease in 
the quotient following work, especially in the first hour of rest. This rise 
and fall may be interpreted in various ways. The rise in the quotient during 
work would distinctly imply that a larger proportion of carbohydrates was 
burned during this period than before or after work, especially as the rise in 
the quotient could not have been produced by an excessive disintegration of 
protein, since practically all of the quotients obtained in the period before 
work were above 0.8. It also seems probable that the marked fall and general 
continued lower level of the respiratory quotient after work indicates the 
combustion of a larger proportion of fat than was the case in the period 
before work, the lower quotients showing that the supply of carbohydrates 
in the body had been materially depleted. The increases in the respira- 
tory quotient during the work-period as compared with the period before 
work was but small, namely, from 0.85 to 0.88 and from 0.84 to 0.86 — 
an increment that might almost be considered within the limit of experi- 
mental error when the great differences in the physiological condition of 
the man are taken into account. Of themselves, therefore, these increases 
do not indicate a selective combustion of carbohydrates during muscular 
work, since it is possible that the combustion of carbohydrates in the period 
after work was proportionally the same as in the period preceding work, 
and that the low quotients in the last rest-periods were simply due to a natural 
depletion of the storage of carbohydrates during muscular work. 
Furthermore, a close inspection of the data in table 92 shows that there 
are variations in the respiratory quotients obtained with the professional 
bicycle rider, M. A. M., between the earlier and the later experiments. 
To bring this out more clearly, the quotients may be averaged in the follow- 
ing way: For the 20 comparable days from December 15 to January 31 the 
average quotients for this subject were 0.85 before work, 0.85 during work, 
and 0.78 after work, while for the 12 comparable days from February 1 to 
April 16 the average quotients were 0.85 before work, 0.91 during work, 
and 0.78 after work. Dividing the experimental year with this subject 
