INVESTIGATIONS ON METABOLISM. IO5 
The methods for calculating the results from the observed 
data, which were found by weighings, measurements, and 
analyses—and are quite extensive—are explained in the publi- 
cation just referred to. The estimates of income and outgo 
and gain or loss of protein are made by multiplying the nitro- 
gen by the factor 6.25. The corresponding estimates for fats 
are made by assuming the protein to contain 53 per cent. 
and the fats, 76.5 per cent. of carbon. The carbon in the 
protein gained by the body is added to, or that in the protein 
lost 1s subtracted from, the carbon of the outgo; the resulting 
amount is subtracted from the total carbon of the income, and 
the difference, divided by .765, is taken as representing the 
gain or loss of fat. The estimates of potential energy are based 
upon direct determinations of the heats of combustion of food, 
feces and urine. In the estimates in which fat gained or lost 
by the body are involved, however, each gram of fat is assumed 
to contain 9.4 calories of potential energy. In the correspond- 
ing estimates of fuel value of the protein gained or lost it is 
assumed that incompletely oxidized nitrogenous compounds 
excreted in the urine will have the fuel value of the urea cor- 
responding to the nitrogen of the protein. 
DISCUSSION OF RESULTS. 
VENTILATION AND PRODUCTION OF CARBON DIOXIDE. 
The observations regarding ventilation and the effects of the 
presence of carbonic acid in large quantities are of decided 
interest. 
The results are epitomized in table 9, from which it will be 
seen that the quantity of CO, in the incoming air, which was 
ordinary, fresh air from the outside of the building, was normal, 
ranging from .55 to .60 milligrams per liter. The ventilation 
in experiments 1 and 2, taken collectively, was at the rate of 
about 50 liters of air per minute; the CO, in the outgoing air 
varied from 8.0 to 12.7, and averaged 10.7 milligrams per 
liter. In experiment No. 3, with an average ventilation of 75 
liters of air per minute, the range of CO, in the air was from 
Mmcmtoec-ontie per uter and the average 7.4 mg. per liter. 
The smaller quantity of CO, in the air as compared with expert- 
ments 1 and 2 was due to the larger ventilation, since the 
average weight of CO, given off in 24 hours was 806.4 grams . 
