TISSOT APPARATUS WITHOUT AUTOMATIC COUNTERPOISE. 219 



The uniformity in the results with the two methods of breathing has 

 been calculated and the curves based upon these calculations are given 

 in figure 72. These show that practically the same uniformity obtains 

 with the additional dead space as in the experiments without this 

 increase. 



It will be seen, therefore, from the results obtained in this series of 

 comparisons, that it is possible to increase the dead space of the Bene- 

 dict respiration apparatus by attaching a long tube to the three-way 

 valve without affecting the accuracy of the measurements of the 

 respiratory exchange. This enables the experimenter to adapt the 



PER CENT CF VARIATION 



Fig. 72. — Probability curves for the series of comparison experiments with and without addi- 

 tional dead space (spirometer unit). 

 The ordinates indicate the percentage of the total number of periods and the abscissa? represent 

 the percentage of variation from the average. 



apparatus more readily to different positions taken by the subject than 

 would be practicable if it were necessary to keep the dead space as small 

 as possible. While no series of experiments was carried out with other 

 forms of apparatus, it would seem probable that the results could be 

 applied to them as well as to the Benedict respiration apparatus. 



TISSOT APPARATUS WITH AND WITHOUT AUTOMATIC COUNTERPOISE ON THE 



SPIROMETER BELL. 



The Tissot spirometer is so arranged that each position of the bell 

 is exactly counterpoised by means of a column of water in the counter- 

 poise tube. 1 A siphon connects this column of water with the water in 



»See p. 64. 



