84 COMPARISONS OF RESPIRATORY EXCHANGE. 



whenever a record is available. In all but the calorimeter experiments 

 the experimental periods approximated 15 minutes in length, varying 

 not more than 5 minutes from this. 



The pulse-rate in a few of the calorimeter experiments was counted 

 by the subject, but generally the count was made by the observer by 

 means of a Bowles stethoscope placed over the heart of the subject. 

 From 3 to 5 counts for each period were taken by the observer, every 

 count being a full minute in duration. 



In the earlier experiments the respiration-rate was counted by the 

 observer three times in each period for ten respirations and the rate per 

 minute calculated. Subsequently information regarding the rate and 

 general character of the respiration was obtained by means of a tam- 

 bour, pointer, and kymograph drum attached either to a pneumograph 

 fastened about the lower chest of the subject halfway between the 

 nipples and the umbilicus or by the recording apparatus on the spiro- 

 meter of the spirometer-unit respiration apparatus. 1 



In the experiments first carried out, the muscular activity was noted 

 by the observer, although an incomplete record of the degree of mus- 

 cular repose was obtained in many of the experiments by means of the 

 pneumograph used for recording the respiration; in some instances a 

 second pneumograph was placed about the hips, as suggested by Mr. 

 H. L. Higgins, of the Laboratory staff. In later experimenting a 

 special form of bed-rest was used which gave an exact record of the 

 muscular movements of the subject. 2 



A considerable number of the subjects used in this research were 

 members of the Laboratory staff; many of these had previously been 

 subjects of similar experiments or had assisted in carrying out the 

 experimental routine and were therefore familiar with the apparatus 

 developed in this laboratory; they were not, however, so familiar with 

 the other forms of apparatus. The subjects not members of the 

 Laboratory staff were mostly medical students. The ages of the men 

 experimented upon ranged between 18 and 35 years. 3 



To avoid repetition in presenting the statistics for the comparisons 

 of the various apparatus and varying conditions of use, a preliminary 

 statement is made of the general features peculiar to the series under 

 consideration. The details are then given of the individual experi- 

 ments, any exceptions to the general routineer changes in the apparatus 

 being noted. The results of the experiments are presented in a general 

 table accompanying the statistics for each series. In these tables the 

 data for the two forms of apparatus compared are grouped separately, 

 those for the periods with the apparatus first used preceding. The 

 tables show the time of beginning each period and in some series the 

 duration of the periods, the carbon dioxide eliminated and the oxygen 



1 See p. 39. 'Benedict, Carnegie Inst. Wash. Pub. 203, 1915, p. 311. 



The basal metabolism for these subjects has previously been reported together with age, height, 

 and weight. See Benedict, Emmes, Roth, and Smith, Journ. Biol. Chem., 1914, 18, p. 139. 



