TECHNIQUE FOR METABOLISM DURING REST. 95 



even greater degree of accuracy was possible. Indeed, with their 

 apparatus it was possible to determine the carbon dioxide with an 

 accuracy of 0.0001 per cent. This extraordinary accuracy made it 

 possible for the Stockholm investigators to utilize their large respiration 

 chamber for studying the metabolism of a single individual in complete 

 muscular repose. It is obvious, however, that an apparatus of this 

 type requires an especially capable gas analyst. 



The dimensions of the Stockholm and Helsingfors chambers seemed 

 to us much too large for ordinary observations on groups of individuals 

 or with severe muscular work. It was therefore considered that in 

 building the group chamber for the Nutrition Laboratory it would be 

 advantageous to minimize the volume in so far as would be consistent 

 with flexibility in adapting it to the types of experiment desired. 

 Accordingly, a chamber with approximately one-half the volume of the 

 Helsingfors chamber was constructed. 



The first research in which the group respiration apparatus was 

 employed was one which has been in progress for a year or more in 

 cooperation with Simmons College, namely, the study with a group of 

 young women of college age of both the resting requirements and the 

 carbon-dioxide production during various domestic activities. The 

 original intention was to describe this apparatus in detail in the pub- 

 lished report of the research with the Sinomons College students. The 

 exigencies of the situation, however, demand that a somewhat lengthy 

 description should be given here of the technical apparatus used for 

 a considerable number of observations in this research on under- 

 nutrition. 



The entire apparatus has been built by the construction staff of the 

 Nutrition Laboratory. To Mr. W. E. Collins and his assistant, Mr. 

 F. A. Renshaw, our appreciation is here expressed for the skilful way in 

 which the apparatus was constructed. 



GENERAL PRINCIPLE OF GROUP RESPIRATION APPARATUS. 



The respiration chamber is of air-tight construction and supplied 

 with a current of outdoor air by means of a rotary air-impeller. At a 

 diametrically opposite corner of the chamber from this air-impeller is a 

 pipe which conducts the air to a second rotary air-impeller of the same 

 type and size. By means of a simple system of butterfly valves the 

 absolute amount of air passing through the chamber can be adjusted 

 at will. The air leaving the chamber is aliquoted by a method devel- 

 oped for this apparatus. A large portion of air is discharged freely into 

 the laboratory room and two smaller portions, ahke in amount, are 

 discharged under special conditions into containers from which the air 

 is withdrawn as desired. The air sample may be analyzed by volu- 

 metric analysis or, as is actually done in this case, the carbon dioxide 

 may be removed by passing the air through soda lime. 



