PHYSIOLOGICAL EFFECTS 147 
PHYSIOLOGICAL EFFECTS OF MUSCULAR WORK. 
MECHANICS OF RESPIRATION. 
Since throughout this whole series of experiments much use is made of 
the respiratory quotient in determining the character of the katabolism, 
all the factors which could possibly affect this relationship between the carbon 
dioxide and the oxygen must be considered. Abnormal respiration has been 
shown by Zuntz and his associates to produce almost instantly abnormal 
respiratory quotients by virtue of a pumping out or excessive removal 
of carbon dioxide from the alveoli. In view of the very great ventilation of 
the lungs during the severe muscular work in these experiments, it became 
necessary to find whether or not there was an excessive pumping out of 
carbon dioxide which persisted throughout the entire experiment, since this 
removal of carbon dioxide would materially increase the output and thus 
abnormally raise the respiratory quotient. Furthermore, it is conceivable 
that after the work had ceased, there may have been a marked retention of 
carbon dioxide with a consequent lowering of the respiratory quotient, this 
low quotient implying the combustion of a relatively greater proportion of fat. 
The professional subject, M. A. M., showed throughout all the resting 
experiments an irregularity in respiratory rhythm that at times made it 
difficult to carry out the experimental routine, as occasionally he inspired 
deeply and again the respiration would be shallow for a moment or two. 
Since the experimental data are obtained by connecting the subject with 
the respiration apparatus at the end of a normal expiration, great care was 
necessary with this irregularity in respiration to secure the right conditions 
for beginning an experiment. During the excessive ventilation of the lungs 
and the rapidity of respiration incidental to severe muscular work, it was 
possible to determine the moment for throwing the 3-way valve at the end 
of an expiration either by the sound of the air rushing through the valve 
or by holding the hand in front of the open end. At the end of an experiment, 
the time for throwing the valve could be determined by noting the position 
of the rubber tension-equalizer. When the air was being expired from the 
lungs, the tension-equalizer rose; as soon as the tension-equalizer ceased rising, 
i. e., at the end of the expiration, the valve was thrown. Care was always taken 
to have the subject breathing through the mouthpiece and the 3-way valve for 
several minutes before the valve was thrown, to make sure that he had accus- 
tomed himself perfectly to the conditions of experimentation before the experi- 
ment began. Accordingly we have no reason to believe that there was any 
"pumping out" of carbon dioxide due to an altered respiratory type. 
Following the excessive muscular work, there was again an altered respi- 
ration as the volume of respiration perceptibly decreased. A special study was 
therefore made of the ventilation of the lungs before, during, and after work; 
furthermore, in order to secure evidence regarding the possibility of the reten- 
tion of carbon dioxide in post-work periods, a careful study was made of the 
carbon-dioxide tension of the alveolar air. 
Ventilation of the Lungs as Affected by Musculab Work. 
Many experiments on animals and a few on men indicate that following 
muscular work there is an excessive ventilation of the lungs which continues 
for some time; in fact, the muscular work incidental to the large ventilation 
