604 
PHYSIOLOGY: T. M. CARPENTER 
bag) ; masks, rubber mouthpiece, glass and pneumatic nosepieces, Muel- 
ler valves, and Haldane gas-analysis apparatus (laboratory form and 
portable form). 
The subjects were healthy young men, mostly medical students and 
laboratory assistants. The comparison of any two apparatus was made 
by determining the respiratory exchange of a subject with both appa- 
ratus on the same day, preferably in alternate periods. The subject was, 
in both tests, in the post-absorptive condition with as complete muscular 
repose as possible. 
Measurements were made of the elimination of carbon dioxide and the 
absorption of oxygen from which the respiratory quotients were calcu- 
lated. Records were also obtained of the average pulse-rate, the aver- 
age respiration-rate, the total respiratory ventilation, and the volume 
per respiration. A record of the degree of muscular repose was secured 
by means of a special device. The accompanying table gives a general 
summary of the results obtained in the principal comparisons of appa- 
ratus and their modifications. 
From a study of the details of the experiments, it is considered that all 
of the apparatus employed are suitable for the determination of the total 
carbon-dioxide elimination and the oxygen consumption and that the 
simplest and quickest method is the Benedict universal respiration ap- 
paratus. Of the apparatus with breathing appliances, the t3rpe involving 
the analysis of the expired air is considered the best for the determina- 
tion of the respiratory quotient. The use of a rubber-lined cloth bag for 
collecting the expired air affords the most favorable opportunity for thor- 
oughly mixing the portion collected, but care must be taken to select a 
bag which is not appreciably permeable to carbon dioxide. A spirom- 
eter for collecting the expired air is preferable to a meter, as all of the 
air can be collected and sampled. The Tissot valves were found to be 
the most reliable and efficient of the various kinds tested. In the ma- 
jority of the experiments the respiratory exchange was the same irrespec- 
tive of the kind of breathing apphances used. The Haldane gas-analysis 
apparatus is considered to be the best for the analysis of expired air but 
the analyses should be frequently controlled, using the constancy in 
composition of outdoor air as a basis. 
Adequate control tests, in which such combustible materials as alco- 
hol, ether, or other substances, whose composition is known, are ad- 
vised as a means of checking the accuracy of respiration apparatus 
in general. A sufficient number of experiments with any given condi- 
tions and conservatism in the acceptance of results are also strongly 
recommended. 
