MUELLER VALVES AND BENEDICT APPARATUS. 195 



MUELLER VALVES AND TISSOT SPIROMETER AND THE BENEDICT RESPIRATION 

 APPARATUS (SPIROMETER UNIT). 



In view of the fact that the Mueller valves 1 are still used in a number 

 of laboratories for studying the respiratory exchange, it was considered 

 desirable to make a series of experiments to test their efficiency. In 

 these experiments the 200-liter Tissot spirometer was used with the 

 Mueller valves to collect the expired air, and the results were compared 

 with those obtained with the spirometer unit. 



In the periods with the Mueller valves, the valves were supported by 

 rods and wiring, so that with the subject lying on his back a valve hung 

 on either side of him, just outside of his shoulders. Care was taken to 

 have the valves hang perpendicularly in order that the water-level 

 might always be at right angles to the sealed end of the tubing. The 

 tee between the valves was so turned that the subject could breathe 

 comfortably through them. From the exit valve a piece of rubber 

 tubing led to the Tissot spirometer. The mouthpiece was used in all 

 of the experiments, as both subjects preferred it. 



Before sampling the air in the spirometer, a weight was placed on 

 the spirometer bell and 5 to 10 liters of air forced out. A 300 c.c. 

 gas-sampler was then connected with the tube at the bottom of the 

 spirometer (see A, B, fig. 27, page 64) and when about 5 liters of air had 

 been forced through the sampler the stopcocks were closed and the 

 sampler disconnected. The air sample was then analyzed by means of 

 the portable Haldane gas-analysis apparatus. 



The pulse-rate was secured in this series of experiments with the 

 Bowles stethoscope. In the periods with the Mueller valves, the record 

 of the respiration was obtained by means of the chest pneumograph, but 

 in the periods with the spirometer unit the respiration was recorded from 

 the movements of the spirometer bell. No graphic record of the degree 

 of muscular repose was obtained in this series, but both subjects were 

 very quiet in all of the experiments. They were somewhat trained with 

 the Benedict respiration apparatus and with the Tissot apparatus, but 

 had not previously used the Mueller valves. The statistics of the five 

 experiments are given in the following pages. 



STATISTICS OF EXPERIMENTS. 



W. J. T., March 18, 1913. — Spirometer unit, 3 periods; Mueller valves and 

 Tissot spirometer, 3 periods; preliminary period, 1 hour 4 minutes. First 

 period, spirometer unit; second and third periods, Mueller valves; periods with 

 each method alternating thereafter. Subject drowsy in some of the periods. 

 Pulse-rate for the most part uniform. Respiration-rate previous to experiment, 

 19 per minute. Respiration both in rate and character somewhat irregular 

 during the experiment, particularly in the first period with the Mueller valves. 

 Average barometric pressure, 780.5 mm. ; average temperature of the air in 

 apparatus with Mueller valves, 18.1° C; with spirometer unit, 20.5° C. 



W . J. T., March 29, 1913. — Mueller valves and Tissot spirometer, 4 periods; 

 spirometer unit, 4 periods; preliminary period, 46 minutes; periods with each 

 method in series. Pulse-rate very regular. Respiration-rate before experi- 

 ment, 19 per minute; during experiment respiration uniform except in first 



iSee p. 70. 



