118 COMPARISONS OF RESPIRATORY EXCHANGE. 



per cent for the oxygen consumption. If the ordinates in figure 37 

 are examined, it will be noted that of the two apparatus the spirometer 

 unit shows the larger number of periods having a variation from the 

 average carbon-dioxide elimination greater than 2.5 per cent, the 

 number of periods showing such excess variation being some 40 per 

 cent larger than with the tension-equalizer unit. The curves for the 

 oxygen consumption, however, show a greater uniformity in the results 

 obtained with the two forms of apparatus. This greater difference in 

 variation for the carbon-dioxide elimination with the spirometer unit 

 and the parallelism in the oxygen consumption is shown at all points 

 in these curves for the two apparatus. The curves for the respiratory 

 quotient show a difference similar to that in the carbon-dioxide curves. 



The pulse-rate curves are remarkably parallel, indicating that the 

 conditions of the experiments were, in general, about the same so far as 

 activity and metabolic intensity were concerned. Not much stress 

 can be laid upon this parallelism, however, as the measurement of 

 the pulse-rate was the least accurate of the data obtained. All of the 

 other observations were made for the entire period and the average is 

 therefore a true average, but the pulse-rate was taken only at intervals, 

 the entire time occupied in taking the records amounting to only one- 

 third of the experimental period. From our general experience with 

 pulse-rates, it is evident that no assumption can be made that five 

 counts of one minute each at intervals during the 15-minute experi- 

 mental period will give an average as accurate as the averages obtained 

 for the other measurements. It is believed, however, that the lack 

 of refinement in measuring the pulse-rate applies in equal degree to the 

 results obtained for both apparatus and the average pulse-rates for 

 the two apparatus are therefore comparable. The figures would there- 

 fore indicate that the variations in the pulse-rate are nearly the same 

 in both series of experiments. 



The cause for the lesser uniformity of results for the carbon-dioxide 

 measurement with the spirometer type of apparatus lies, probably, 

 in the differences in ventilation of the lungs with this apparatus. 

 Since the ventilation was not measured with either type of apparatus, 

 these variations are not known. The difference, however, can not be 

 ascribed to greater irregularities in the respiration-rate when the spiro- 

 meter unit was used, as the percentage variations in the respiration-rate 

 for the two apparatus are nearly parallel. 



In summarizing, it may be stated that on the average the two forms 

 of apparatus give the same results in the measurement of the respira- 

 tory exchange under like conditions and that the tension-equalizer unit 

 gives somewhat more uniform results in the determination of the carbon- 

 dioxide elimination and the respiratory quotients. 



