NUTRITION LABORATORY. 



189 



recorded to within a few tenths of a gram. Inasmuch as this apparatus was 

 provided with a method for determining oxygen directly, experiments were 

 made for comparing the direct and indirect determinations. The experi- 

 ments were all made with men sitting quietly in a chair suspended on a 

 balance inside the respiration chamber. A sample experiment is given in 

 the table herewith : 



Comparison of the Direct and Indirect Determinations of Oxygen. 

 [Metabolism Experiment, January 31, 1910.] 



The result of the experiment showed that while the indirect method with 

 extraordinary precautions could be used, the indications are that the errors 

 involved in the indirect determination of oxygen are such as to preclude its 

 use under the conditions that ordinarily obtain even in the most perfect forms 

 of respiration apparatus, and the accurate determination of the oxygen con- 

 sumption of man is practicable only by the use of the direct method. 



(2) Control tests of a respiration calorimeter. Francis G. Benedict, J. A. Riche, and 

 L. E. Emmes. Amer. Jour. Physiol., 26, p. i. 1910. 



Two of the respiration calorimeters now in use in the Nutrition Laboratory 

 were subjected to the most rigid control tests to show their capability for 

 determining the four important factors of metabolism in man, namely, 

 carbon-dioxide production, water vaporization, ox3^gen consumption, and heat 

 elimination, even in periods as short as one hour. 



Each apparatus has been first tested as a calorimeter by developing heat 

 electrically inside the chamber. Under these conditions a number of experi- 

 ments show that the two calorimeters give extremely accurate results. A 

 sample experiment is here given : 



Record of Heat Developed in Electrical Check E.rperiment zvifh 

 Chair Calorimeter, October 14, 1909. (i-hour Periods.) 



