188 



COMPARISONS OF RESPIRATORY EXCHANGE. 



Since the increased carbon-dioxide elimination is not accompanied 

 by an increase in the total ventilation, it is evident that there must 

 have been a slightly more economical ventilation with mouth-breath- 

 ing than with nose-breathing. 



The probability curves for these comparison experiments are given 

 in figure 49. The curves for the carbon-dioxide elimination do not 

 show very much difference, but those for the oxygen consumption are 

 slightly more uniform with the mouth-breathing. The pulse-rate is 



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PER CtNT OF VARIATION 



Fig. 49. — Probability curves for the series of comparison experiments with nose- and mouth- 

 breathing (Tissot apparatus). 

 The ordinates indicate the percentage of the total number of periods and the abscissae the per- 

 centage of variation from the average. 



noticeably more uniform with the mouth-breathing. The respiration- 

 rate and the volume per respiration have about the same degree of 

 uniformity with both types of breathing, while the total ventilation 

 is slightly more uniform with the nose-breathing. 



The results of this comparison substantiate in the main the results 

 obtained with the two preceding comparisons with the Benedict respi- 

 ration apparatus, t. e., that the differences in the respiratory exchange 

 between mouth- and nose-breathing are not large enough to be of 

 great significance in a study of the respiratory exchange. 



