220 COMPARISONS OF RESPIRATORY EXCHANGE. 



the tank, so that when changes in the position of the counterpoise tube 

 take place the water in the tube is automatically brought to the same 

 level as that of the water in the tank surrounding the bell. If it were 

 not necessary to have the spirometer bell counterpoised exactly at each 

 position the apparatus would be less complicated and there would be 

 no necessity of making sure that the water flowed freely through the 

 siphon between the two containers. A study was therefore made of the 

 effect upon the respiratory exchange of discontinuing the siphon 

 arrangement and partially, but not exactly, counterpoising the bell 

 of the spirometer. 



In some of the experiments the counterpoise tube was entirely 

 empty, so that at the end of the period there was a slight pressure of 

 air (less than 2 mm. of water) inside the bell of the spirometer. This 

 was due to the fact that the bell was heavier than the counterpoise 

 tube. In other experiments the counterpoise tube was half full of 

 water, so that at the beginning of the experiment there was a very 

 slight diminished pressure inside the bell. 



The Tissot valves were used in these experiments and either the 

 pneumatic nosepieces or the mouthpiece, according to the desire of the 

 subject. The pulse-rate was obtained with the Bowles stethoscope 

 and the record of the respiration-rate by means of the chest pneumo- 

 graph. The subjects, who were all more or less trained to the Tissot 

 apparatus, were very quiet, except as noted in the statistics. The 

 results of the seven experiments are given in the following pages. 



STATISTICS OF EXPERIMENTS. 



R. <•?., February 1, 1913. — With automatic counterpoise, 3 periods; without 

 automatic counterpoise, 2 periods; periods with the two methods in series. 

 During periods without counterpoise, the lead weight (see R, fig. 26) was 

 removed; there was no water running in the siphon, and none in the counter- 

 poise tube. Subject very quiet and awake all through experiment. Urinated 

 at 9 h 35 m a. m. Pulse-rate uniform in all periods. Average preliminary 

 respiration-rate 12 per minute. 1 Respiration-rate during experiment uniform. 

 Pneumograph so poorly adjusted that differences in character could not be 

 seen. Subject noted no difference between two methods, but stated respira- 

 tion was easy in all periods. Average barometric pressure, 752 mm. ; average 

 temperature of air in apparatus, 19.1° C. 



R. G., February 4. 1913. — Without automatic counterpoise, 3 periods; 

 with automatic counterpoise, 3 periods; preliminary period, 1 hour 2 minutes; 

 periods with and without counterpoise in series. In periods without automatic 

 counterpoise, counterpoise tube half full of water and no water running in 

 siphon. Subject quiet and awake; urinated at 10 h 40 m a. m. Pulse-rate 

 very uniform. Average respiration-rate in preliminary period, 16 per minute; 

 during experiment fairly uniform in rate. In first period, there was a tend- 

 ency to apncea; in the fourth period (the first with automatic counterpoise) 

 there was the same tendency. Average barometric pressure, 757.0 mm.; 

 average temperature of air in apparatus, 19.1° C. 



W. J. T., March 1, 1913. — With automatic counterpoise, 3 periods; without 

 automatic counterpoise, 2 periods; preliminary period 1 hour 25 minutes; 



x See note on experiment with L. E. E., p. 191. 



