SUGGESTED METHOD OF STUDY. 355 



lightly movable and gives perfect closure without backlash is suitable. The 

 spirometers are of the Tissot model. A complete description of this spirometer 

 is given in a former publication from this Laboratory. 1 Any spirometer which 

 is lightly movable and fairly well counterpoised is practicable for this purpose. 

 The 100-liter spirometer is the most adaptable for general use. The portable 

 gas-analysis apparatus is the one devised by Haldane 2 for the analysis of atmos- 

 pheric, mine, and expired air. Its accuracy should be controlled by analyses 

 of atmospheric air. The apparatus, when properly set up, should give 0.03 

 per cent CO 2 and 20.93 to 20.95 per cent O 2 for atmospheric air. We insist 

 on this as a proof of the accuracy of the analysis of the expired air. Such 

 analyses should be reported in connection with the results of metabolism 

 measurements. 



With the combination of apparatus outlined in the foregoing paragraphs, a 

 trained subject awake, and a complete absence of external muscular activity, 

 it is possible to measure the peak effect of either the metabolism or of the 

 respiratory quotient, or to measure the effects of the ingestion of exceedingly 

 small amounts of material. During the past two years the gaseous exchange 

 and respiratory quotients of trained subjects have been measured for 6 to 7 

 hours in consecutive experimental periods as short as 10 minutes, with no 

 great degree of discomfort to the subject and with a high degree of accuracy. 



When the increments in metabolism are likely to be large and to extend over 

 a considerable period of time, and when it is possible to repeat the experiment 

 several times, the clinical respiration apparatus (a chamber apparatus) 3 is 

 probably the most feasible. In this apparatus it is not necessary for the sub- 

 ject to remain absolutely immovable and the possibility of movement makes 

 it pleasanter for the subject in long experiments. 



Summary. From the foregoing it can be seen that the ideal method for 

 determining the effect of the ingestion of food upon the metabolism is the use 

 of trained subjects; a measurement of the basal metabolism on the same day 

 as that following the ingestion of food ; an absolute absence of external muscu- 

 lar activity; a subject awake; graphic records of both the absence of activity 

 and any evidence of drowsiness or sleep; as short periods as possible; spiro- 

 meters, respiratory valves, face mask, and portable Haldane gas-analysis 

 apparatus, with determinations controlled by analyses of atmospheric air. 



l Carpenter, Carnegie Inst. Wash. Pub. No. 216, 1915, p. 61. 



'Haldane, Methods of air analysis, 1912, p. 47. 



'Benedict and Tompkins, Boston Med. and Surg. Journ., 1916, 174, pp. 857, 898, and 939. 



