ZUNTZ-GEPPERT AND BENEDICT METHODS. 119 



ZUNTZ-GEPPERT RESPIRATION APPARATUS AND BENEDICT RESPIRATION APPARATUS 



(TENSION-EQUALIZER UNIT). 



In the first series of experiments comparing the respiratory exchange 

 as measured by the Benedict respiration apparatus and the Zuntz- 

 Geppert apparatus, 1 the tension-equalizer unit was used and, in all but 

 one experiment, the pneumatic nosepieces. With the Zuntz-Geppert 

 apparatus, the ordinary form of rubber mouthpiece was employed, also 

 the common form of valve (see fig. 18, page 54) with fish-membrane 

 or thin rubber covering. The samples of expired air in the experiments 

 with this apparatus were collected in the burettes of the Zuntz-Geppert 

 gas-analysis apparatus and analyzed immediately after the experi- 

 mental period. The volume of expired air was converted to 0° C. 

 and 760 mm. by means of the readings of the thermo-barometer. The 

 expired air was conducted from the subject to the Elster meter through 

 a rubber tube with an internal diameter of 20 mm. and a length of 1 to 

 2 meters. 



The regular routine was followed in carrying out the experiments, any 

 exceptions being noted in the statistics. 2 While the apparatus first used 

 varied in the different experiments, in all cases they were alternated 

 with each period. The total number of periods varied from 6 to 

 8, following each other as rapidly as technique would permit. They 

 were usually 15 minutes in length, but in some cases varied from 

 this by 5 minutes, either more or less. Prior to the periods with the 

 Zuntz-Geppert apparatus, a preliminary determination was made of 

 the rate of ventilation of the lungs by noting with a stopwatch the time 

 required for the expiration of 20 liters of air. When it was found that 

 the rates for two successive periods were uniform, the experimental 

 period with the Zuntz-Geppert apparatus was begun. 



The pulse-rate in all of the experiments was obtained by means of 

 the Bowles stethoscope; usually three separate counts were made in 

 each period. The respiration-rate was secured during the first few 

 experiments by noting the time for 10 respirations and then calculating 

 the rate per minute; three counts were obtained in this way. Subse- 

 quently a pneumograph around the lower part of the chest was used, 

 by means of which a graphic record was made of the respiration for the 

 whole period. The muscular activity was noted by the observer, 

 although in the experiments in which the respiration was obtained with 

 the chest pneumograph incomplete graphic records of the activity were 

 also secured. The methods used in later experimenting for securing a 

 graphic record of the muscular activity were not developed at the time 

 when this series of experiments was carried out. 



The subjects were members of the Laboratory staff, and while all 

 of them were more or less familiar with the tension-equalizer unit, they 

 were not all accustomed to the Zuntz-Geppert apparatus. 



'See p. 53. 2 For the routine followed with the Zuntz-Geppert apparatus, see p. 60. 



