TECHNIQUE FOR METABOLISM DURING REST. 79 



ALVEOLAR AIR. 



The determination of the alveolar air tension was made with a modi- 

 fied form of the Haldane apparatus on samples of alveolar air obtained 

 by a method previously described.^ In this method of collection a 

 3-way valve is used which is attached to a 6-foot length of rubber 

 tubing and a mouthpiece. The subject at first breathes through the 

 short arm of the valve, and is cautioned to breathe normally and no 

 deeper than usual and to hold the lips firmly about the mouthpiece. 

 While he breathes through the side opening of the valve the operator 

 watches the rise and fall of the chest or abdomen. At the end of an 

 expiration, the time is noted and the valve is turned to such an angle 

 that the subject breathes quietly into the long rubber tube. After 20 

 seconds and at the end of an expiration, the valve is turned back quickly 

 to the original position. At the usual respiratory rate, 20 to 22 seconds 

 will allow for 4 or 5 respirations. A small light feather fastened across 

 the outlet of the long tube will indicate by its movements the end of the 

 expiration. After the valve is turned, the samples are quickly drawn 

 from the rubber tube through an aperture near the valve and analyzed 

 as usual by the Haldane method. Prior to the second test, the long 

 tube is thoroughly ventilated to expel the residual air from the pre- 

 ceding respirations. The results for each test are based on the average 

 of the analysis of two samples taken successively. 



TECHNIQUE FOR DETERMINING GASEOUS METABOLISM 

 DURING REST. 



The considerable amount of experimental attention given to the 

 technique for determining the gaseous metabolism led, as would be 

 expected, to an unusual extension of the gaseous metabolism measure- 

 ments. When the experiment was first proposed, it was intended to 

 obtain occasional records of the respiratory exchange for the individual 

 men. As the program developed, it appeared desirable to get as fre- 

 quent records for each man as possible. Therefore all of the facilities 

 of the Laboratory were drawn upon to meet the emergency of having 

 to determine the gaseous metabolism of 12 men as nearly as possible 

 once each day. It was believed that in some of the observations, 

 methods could be used in which a high degree of accuracy might be 

 sacrificed to expedition, but it was also desirable to make determina- 

 tions of the respiratory exchange by means of thoroughly tested stand- 

 ard methods, if only rarely. Finally, it was planned to make observa- 

 tions of the squad as a whole in a newly perfected respiration chamber 

 in the Nutrition Laboratory in Boston, which had been thoroughly 



1 Roth, Journ. Am. Med. Asso., 1915, 65, p. 413; also Boston Med. and Surg. Journ., 1918, 

 179, p. 130. 



