
INVESTIGATIONS ON METABOLISM. LO) 

The weight of CO, in outgoing air during the periods of rest 
and mental work ranged from 8.1-13.4 mg. per liter, but aver- 
aged not far from 11 mg. per liter. During the period of 
muscular work, however, the range was from 9.9 mg. per liter 
in the hours of rest, ¢. ¢., at night, to 24.6 mg. per liter in the 
hours of severe work. 
Authorities on ventilation commonly estimate the maximum 
of carbon dioxide permissible in the air of inhabited rooms at 
one part per thousand by volume, which corresponds to 1 cc. or 
about 1.97 mg. CO, per liter. It will be observed that the 
amounts of CO, in the air in the respiration chamber during 
these experiments was from 8-25 mg. per liter, and averaged | 
10-12 mg. per liter. In other words, the subjects of hese 
experiments lived constantly in an atmosphere containing from 
five to six times the amount of CO, in the standard just 
Teferred to. In experiment No. 4 the CQ, rose to nearly 
thirteen times the amount in the standard. The interesting 
fact in this connection is that no one of the subjects appeared 
to experience any inconvenience whatever from either this 
large amount of carbon dioxide or from any other products of 
exhalation. In experiment No. 2 the subject was for a time 
somewhat ill, but, apparently, the reason for this was entirely 
separate from the ventilation. , 
The subject who remained in the apparatus during the five 
days of the third experiment was as comfortable in every way, 
according to his repeated statements both during the experi- 
ment and afterwards, as if he had been breathing the air of 
an ordinary well-ventilated room. Even in the fourth experi- 
ment the subject was not aware of the least inconvenience or 
sense of discomfort during the twelve days of his sojourn in 
the chamber. | 
It may be added that these results are in accord with the late 
experiments by Messrs. Billings, Mitchell, and Bergey,* which 
imply that the discomfort experienced in poorly ventilated 
rooms is not due to the excess of carbon dioxide. 
We venture the suggestion, however, that one cause of the 
discomfort felt in ill-ventilated rooms occupied by a number of 

* ‘The Composition of Expired Air and its Effects upon Animal Life. By J. S. Bil- 
lings, M. D.; S. Weir Mitchell, M. D.; and D. H. Bergey, M. D. City of Washington. 
Published by the Smithsonian Institution, 1895. From Smithsonian Contributions to 
Knowledge, vol. xxix. (No. 989. Hodgkins Fund. ) 
