CHARACTER OF KATABOLISM 75 
1.423 grams. On the other hand if 90 per cent of the residual gas is argon, 
the weight of a liter of the gas would be 1.4375 grams, an increase of over 
1 per cent. It has formerly been our custom to apply a correction of +0.4 
per cent to the weight of oxygen, but if the impurity is argon, the correction 
should have been —0.6 per cent. The values for the oxygen consumption 
as originally calculated, therefore, were all 1 per cent too high, and they 
have consequently been reduced by this percentage which represents a defi- 
nitely established error. Since a decrease of 1 per cent in the values for the 
oxygen affects the respiratory quotient by 1 per cent, all of the respiratory 
quotients as originally calculated were too low, and accordingly throughout 
the whole report they have been raised by 0.01. 
In all experiments in which oxygen made from liquid air is used, the 
correction for argon must be of significance and necessary, this being one of 
the relatively few instances where the actual difference between argon and 
nitrogen has entered extensively into the computations of chemical or physio- 
logical routine technique. In all future publications of this laboratory, the 
correction will be made without further comment. 
Physiological Sources of Error rx Gas Measurements. 
The carbon-dioxide output of the body may be equal to that expired 
in a given time, it may exceed the amount eliminated, or, under certain con- 
ditions, it may be much less. If the subject artificially or unintentionally 
ventilates the lungs excessively by labored respiration, the composition of the 
alveolar air may be considerably changed, and carbon dioxide may leave 
the blood so that a large amount of carbon dioxide may be "pumped out" 
of the body that was not simultaneously produced. Under these conditions 
there would be an excessive elimination of carbon dioxide with a consequent 
abnormal respiratory quotient — the respiratory quotient being much too 
large. After a period of excessive ventilation, with a large "pumping out" 
of carbon dioxide, the equilibrium between the alveolar air and the blood 
may be again established by the retention of carbon dioxide. Under these 
conditions the amount of carbon dioxide expired would be less than that 
produced, and consequently the respiratory' quotient would again be abnormal 
in that it would be too low. Recognizing the great influence that an abnormal 
ventilation of the lungs, or an abnormal elimination or retention of carbon 
dioxide would have upon the respiratory quotient, and hence upon the inter- 
pretation of the character of the metabolism, every precaution was taken 
with these subjects to secure a normal respiration during the work experi- 
ments. This was done by having the subject ride on the bicycle ergometer 
for a preliminary period of not less than 15 minutes before the experiment 
began, the conditions being the same as during the actual experimental 
period. As a general rule, the work continued for approximately an hour, 
and sometimes longer, the measurements being made at intervals throughout 
the working period, so that the subject previous to the different periods of 
the experiment had been working for a length of time varying from 15 min- 
utes to an hour or more. 
Only in the experiments following work was there a possibility of the 
retention of carbon dioxide playing any great role. This was studied in ob- 
servations made of the respiratory exchange immediately after the work ex- 
