EXPERIMENT STATION RECORD. 



Vol. IX. Xo. 11. 



In order to establish the rational feeding of man and the domestic 

 animals on a thoroughly scientific basis it is essential that the income 

 and outgo of both matter and energy should be accurately measured. 

 This has led to the development of what are known as metabolism 

 experiments and the devising of special methods and apparatus for 

 such experiments. A digest of the published accounts of metabolism 

 experiments has recently been issued as a bulletin of this Office. 1 The 

 present number of the Record contains a brief abstract of that bulletin 

 (p. 1073), together with an article by one of its authors showing the rela- 

 tion of metabolism experiments to other investigations regarding the 

 food and nutrition of man and animals. A complete metabolism experi- 

 ment involves a determination of the income and outgo of the various 

 chemical elements, especially nitrogen, carbon, hydrogen, and oxygen, 

 which make up the substance of the animal body or are connected with 

 its life processes, as well as of the physical factors involved in the 

 income and outgo of energy. A few brief statements regarding the 

 present status of this subject may serve to indicate its importance and 

 show what remains to be done to work out these problems. 



In respiration experiments which have been made in the past the 

 income and outgo of nitrogen and carbon have been successfully meas- 

 ured. The determination of hydrogen has, however, been far from 

 satisfactory. This fact, among others, was brought out iu the compila- 

 tion of experiments with man and animals above referred to. The 

 correctness of such determination depends upon the accuracy of the 

 measurements of water in the respiratory products. The usual plan 

 followed has been to analyze only aliquot portions of the respired air. 

 Some difficulty has been experienced in the accurate measurement of 

 the samples and of the total amount of air. Although the greater 

 part of the water can be easily determined, a satisfactory determination 

 of the total amount has been difficult of accomplishment. All these 

 factors render the measurement of hydrogen a difficult matter. In 

 connection with work on the respiration calorimeter the Storrs Experi- 

 ment Station, in its investigations carried on in cooperation with 

 Wesleyan University and this Department, has devised a method for 

 determining the water in respiratory products with the desired accuracy. 

 Reference has been made to the method iu previous publications, 2 



1 U. S. Dept. Agr., Office of Experiment Stations Bui. 45. 



2 U. S. Dept. Agr., Office of Experiment .Stations Bui. 44. 



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