INFLUENCE OF MUSCULAR EXERTION UPON METABOLISM. 223 
blood during the same time. The average results, computed in 
milligrams per minute, were: 
During Rest, | During Work, 
Merms. Merms. 
Oxygen from blood... 1.0... 0... cece cece ee eee 0.11803 2.48490 
in CO, produced.........0.... 0.02 cee eee 0.08424 3.15052 
«required to oxidize dextrose taken up from 
bloods. ics axon domes va gheey eee sue eee Meese 0.58305 2.35055 
Carbon of CO, produced. ............00 000s eens 0.03160 1.18128 
“dextrose taken up... .........0-.000005 0.21862 0.88118 
During rest the muscle was storing up both carbohydrate (gly- 
cogen) and oxygen, thus supplying itself with a reserve of potential 
energy. During activity this reserve, as well as the supply brought 
by the blood, was drawn upon for the performance of work. 
The fluctuations of the respiratory quotient resulting from mus- 
cular exertion are explained by Chauveau in outline as follows: 
At first there is a rapid oxidation of the stored glycogen of the 
muscles and of the dextrose of the blood, resulting in a respiratory 
quotient approaching unity. As the work progresses the store of 
carbohydrate material in the organism becomes relatively exhausted, 
unless there is a large supply of it in the food, and to meet the 
demands of the muscles an increased production of dextrose from 
the fat of the food or of the body takes place in the liver. This 
change, however, according to the equation proposed on p. 38, con- 
sumes 67 molecules of oxygen for each 18 molecules of carbon diox- 
ide produced. This process, superadded to the combustion of 
carbohydrates in the muscles, results in the observed lowering of 
the respiratory quotient. The further lowering of the quotient 
during a succeeding rest period results from the great diminution 
in the amount of carbohydrates oxidized in the muscles, the for- 
mation of carbohydrates from fat in the liver still continuing 
for a time in order to replenish the exhausted store of muscular 
glycogen. 
Fat as a Source of Muscular Energy.—According to the above 
theory, fat is only indirectly a source of muscular energy, in 
that it serves for the production of dextrose in the liver, and the 
