144 COMPARISONS OF RESPIRATORY EXCHANGE. 



respiratory quotients with the Zuntz-Geppert apparatus being much 

 more uniform than those with the spirometer unit. For example, in 53 

 per cent of the periods with the spirometer unit the respiratory quotient 

 varies 3 per cent or more from the average for the experiment, while with 

 the Zuntz-Geppert apparatus only 39 per cent of the periods vary more 

 than 3 per cent. Both pulse-rate and respiration-rate have approxi- 

 mately the same degree of uniformity with both apparatus, while the 

 total ventilation and the volume per respiration are more nearly uniform 

 with the spirometer unit than with the Zuntz-Geppert apparatus. 



As will be seen from table 20, the averages of the differences between 

 the experiments are somewhat large, showing that, in general, the 

 agreement in the results with the two forms of apparatus is not par- 

 ticularly good . This lack of agreement is probably due in part to the fact 

 that the subjects were not familiar with the apparatus. The difference 

 between the averages of all the results with both types of apparatus is 

 small, however, (see table 19) and in general the two apparatus give essen- 

 tially the same results in the measurement of the respiratory exchange. 



TISSOT APPARATUS AND BENEDICT RESPIRATION APPARATUS 

 (TENSION-EQUALIZER UNIT). 



In the first series of experiments in which the Benedict respiration 

 apparatus and the Tissot apparatus were compared, the tension- 

 equalizer unit was used and the study was carried out in the same 

 manner as in previous comparisons. In five of the experiments the 

 50-liter Tissot spirometer was employed, the remaining comparisons 

 being made with the 200-liter Tissot spirometer. The pneumatic 

 nosepieces were used in all of the experiments but one. 



The expired air collected in the Tissot spirometer was sampled by 

 drawing portions through a glass tube inserted in a rubber stopper 

 placed in the opening at the top of the copper bell. (See Z in figs. 

 26 and 27, p. 64.) This tube was attached to a glass sampler, 

 with a capacity of 150 c.c. or 300 c.c., which was filled with mercury 

 and connected with a leveling-bulb. The sampler was provided with 

 three-way glass stopcocks. A sample of air was drawn by opening the 

 stopcocks and lowering the leveling-bulb ; when the sampler was full of 

 air, the leveling-bulb was raised and the upper stopcock turned so that 

 the air was expelled into the room. When the sampler was again full 

 of mercury, the leveling-bulb was lowered and the upper stopcock 

 turned so that a second portion of air was drawn from the spirometer; 

 this sample was also rejected. Finally, a third portion was drawn and 

 reserved for analysis. The analysis was made with the laboratory 

 form of the Haldane gas-analysis apparatus, in which the carbon 

 dioxide was absorbed by caustic potash and the oxygen by potassium 

 pyrogallate. Duplicate analyses of the sample usually agreed to within 

 less than 0.04 per cent for both carbon dioxide and oxygen. In some 

 cases two samples were drawn and one portion from each analyzed. 



