TECHNIQUE FOR METABOLISM DURING REST. 89 



12 minutes, the excursions of the bell are carefully watched and at the 

 conclusion of a normal expiration the 3-way valve is again turned, 

 disconnecting the subject from the ventilating air current; the time is 

 then noted. The mouthpiece and nose clips are removed, and the 

 subject lies quietly until another period is begun. 



It is a fundamental rule in this Laboratory that all subjects, prior to 

 measurements of the gaseous metabolism, must be lying down, resting 

 quietly for not less than 30 minutes. The length of time between 

 periods need be determined only by the activity of the operator in 

 recording his observations. After the end of the period 1 minute is 

 allowed to elapse to insure a thorough mixing of the air and removal of 

 carbon dioxide. When the pointer indicates that the level of the 

 spirometer is constant, this is read and the temperature is recorded. 



MODIFIED METHOD FOR DETERMINING THE OXYGEN CONSUMPTION. 



In testing several of these apparatus, Mr. Louis E. Emmes, of the 

 Laboratory staff, has had excellent success in determining the oxygen 

 consumption by using a modification of the method outlined in that he 

 reads the spirometer after the subject has been connected with the air 

 current. Noting the height to which the spirometer is raised at the end 

 of a series of regular normal expirations, he starts a stop-watch. The 

 experimental period then continues about 12 minutes, when again the 

 height of the spirometer at the end of a series of 3 or 4 normal expira- 

 tions is noted and recorded, and simultaneously the watch is stopped. 

 Using the difference between the two readings as an index of the oxygen 

 consumption, the usual calculations for temperature and pressure are 

 then applied. 



The obvious advantage of the Enunes method lies in the fact that 

 while the goose feather over the opening in the 3-way valve gives a fair 

 indication of the end of a normal expiration for determining the moment 

 to begin the experimental period, this point is much better indicated by 

 the actual excursions of the spirometer bell. Mr. Emmes thus uses the 

 excursions of the bell to begin as well as to end the period. The two 

 methods may be simultaneously applied and one period be made to 

 include another. This involves only two additional readings of the 

 height of the spirometer bell and two additional time records with a 

 second stop-watch. The use of the modified method is recommended 

 in all cases as a desirable check. A series of tests shows that a some- 

 what better agreement of duplicate periods may be secured with the 

 Emmes method. 



A still further check may be obtained by making the usual records 

 before and after the valves are turned at the beginning and end of the 

 period, and employing the Emmes method for two additional readings 

 10 or 20 seconds apart at the beginning of the period after the subject 

 has been connected with the air current and again before he is discon- 

 nected at the end of the period. Two stop-watches are used for these 

 intermediate records. Thus two sets of readings are secured for con- 



