164 A RESPIRATION CALORIMETER. 



spiration amounting to not far from i to 2 grams per minute, and hence 

 it was our effort to have the weight of the man recorded at exactly the 

 same moment after 7 o'clock. Theoretically, inasmuch as the quantities 

 of carbon dioxide and water vapor in the air are determined precisely 

 at 7 o'clock, the three weighings should be made at exactly this hour ; 

 but, as a matter of fact, this was distinctly impracticable, and we believe 

 that the routine here employed gives results that are not far from 

 correct. With a subject who had never been inside the chamber before, 

 this routine of weighing man, then chair plus bedding, then absorbing 

 system, took not far from 10 to 12 minutes each morning. 



Checks on the accuracy. This method of weighing was very carefully 

 checked by weighing the subject in the chair and then placing several 

 brass weights in his lap. It was found that, allowing for the slight loss 

 from perspiration and respiration, the gain noted by the observers on 

 the platform balance above corresponded exactly to the weights added. 

 The accuracy of the weighing of the absorbing system was determined 

 in a similar way. A small wire basket was constructed so as to hang 

 directly from the hanger itself or in any position on the trough, and 

 thus correspond to varying quantities of moisture. By placing weights 

 in the basket in different positions, the accuracy and sensitiveness of 

 the whole system could thus be easily tested. Frequently weights 

 were placed on the lead counterpoises, and the apparent loss of weight 

 of the system, as detected on the platform balance, always agreed very 

 satisfactorily with the weights thus added. 



It seems fair to assert, therefore, that it is possible to weigh a man,, 

 his bedding and clothing, and the absorbing system to within 5 grams, 

 if not less, and thus the weighing of these objects is now sufficiently 

 accurate to serve as a check on the oxygen determinations. Indeed, it 

 is not impossible that the indirect determination of oxygen by this means 

 may ultimately take the place of the direct method now employed. 



THE ERGOMETER. 



Many problems in metabolism require for proper study a knowledge 

 of the external muscular work performed by the body. The utilization 

 of the various nutrients as sources of muscular energy, the isodynamic 

 replacement of the nutrients in diets for muscular work, and the 

 efficiency of the body as a machine may be mentioned as among the 

 problems of this nature. Considerable attention has therefore been 

 devoted by investigators to securing an accurate measurement of external 

 muscular work. 



The first method used in connection with the experiments with the 

 respiration calorimeter consisted of raising and lowering a weight by 



