200 COMPARISONS OF RESPIRATORY EXCHANGE. 



abnormal. The carbon-dioxide elimination for the other two periods 

 with this method does not compare well with the values obtained with 

 the spirometer unit and if the last two values for the Mueller valves 

 were considered abnormal, the value for the first period might be taken 

 as normal. The average values in this experiment for the spirometer 

 unit are influenced by the figures for the second period with this appa- 

 ratus, as the values for the carbon-dioxide output and oxygen intake 

 in this period are both abnormal; but there is no indication of error in 

 the manipulation and the figures are accordingly included. If the values 

 for the carbon-dioxide elimination and oxygen consumption for this 

 period are excluded, the average respiratory quotient would be raised. 



The values obtained with the subject J. J. G. present just the oppo- 

 site picture to that for W. J. T., and it is difficult to state whether the 

 value for the Mueller valves or that for the spirometer unit is correct. 

 Both series of periods show good uniformity. The differences between 

 the results with the two methods are not large, except that on March 

 20 the oxygen consumption is noticeably larger with the Mueller valves. 



The degree of uniformity in the results shown by the curves in figure 54 

 is about the same with both apparatus, except that the respiratory quo- 

 tient is more nearly uniform with the spirometer unit than with the 

 Mueller valves. 



Before a final conclusion is drawn regarding these two methods, the 

 comparison experiments with the Mueller valves and the Tissot valves 

 will be considered. 



MUELLER VALVES AND TISSOT VALVES. 



In addition to the preceding comparison, a series of experiments was 

 carried out in which the Tissot valves and the Mueller valves were 

 compared, the 200-liter Tissot spirometer being used to collect the 

 expired air. In the first two of these experiments the regular routine 

 for the use of the Tissot spirometer was not strictly followed. The 

 bell of the spirometer is partly counterpoised by means of a weight 

 suspended from a wheel 1 and the increase in weight of the bell due to its 

 rise when expired air is collected is automatically counterpoised by 

 water running through a siphon from the spirometer tank to the coun- 

 terpoise tube. In the first two experiments the siphon tube was not 

 used, but the counterpoise tube was three-quarters full of water. 



The methods of obtaining the various measurements were the 

 same as in the previous comparison. The subjects used for the pre- 

 ceding series of experiments were subjects in this series, and one experi- 

 ment was also made with a third subject. Thus two of the subjects 

 were accustomed to both the Mueller and the Tissot valves. The third 

 subject, J. H. H., had had no previous experience with the Mueller 

 valves, but had been used in a number of experiments with the Tissot 

 valves. The statistics of the seven experiments in this series follow. 



1 See p. 64. 



