FOODS— HUMAN NUTEITION. 1() ( .> ( .) 



tion very importanl changes in the apparatus have been introduced and the method 

 of experimenting has been modified to Include the direct determination of oxygen. 

 A quantity of air circulates through the apparatus and the carbon dioxid and water 

 eliminated in the respiratory products are removed by passing the air currenl through 

 soda-lime mixture and through sulphuric arid. As the air currenl passee back into 

 the respiration chamber oxygen is added to make up for thai used by the subject, 

 the amount being determined b) weighing the cylinder containing the oxygen before 

 and after t he addition is made. 



.The calorimeter maybe fairly designated an instrument of precision and serves 

 for the very accurate measurement of energy, carbon dioxid, water, and oxygen in 

 experiments with man extending over a number of days, under various conditions 

 of work and rest. 



[n connection with the experiments, the balance of income and outgo of nitrogen 

 and other food constituents is taken into account so that the experiments furnish 

 data for considering the total income and outgo of matter and energy in addition t<> 

 the respiratory quotient. 



"In experiments with man as carried out with this apparatus and acccessories, 

 the following determinations of intake and output of material are made: 



" The intake [as regards matter] consists of food, drink, and oxygen from respired 

 air. The amounts are determined by weighing. The analyses include determina- 

 tions of water, ash, nitrogen, carbon, hydrogen (organic), and at times sulphur and 

 phosphorus. The output of material consists of products of respiration and perspira- 

 tion, urine, and feces. The dry matter of \n'i~< and urine is subjected to a series of 

 analyses similar to those for food, and tin- water and carbon dioxid of perspiration 

 and respiration are determined according t<> the method- discussed in this report. 

 The determinations of nitrogen in perspiration are made, when necessary. . . . 



" [In the ease of energy] the intake is derived from the potential energy, i. e., heats 



of combustion of the f 1. The output consist- of sensible heat given off from the 



body, the latent heat of the water vaporized, and the potential energy, i. e., heat of 

 combustion of the unoxidized port ions of the dry matter of urine and feces. In cer- 

 tain eases, e. g., work experiments, a not inconsiderable portion of the output is in 

 the heat equivalent of external muscular work. . . . 



"The heats of oxidation are determined by burning the Bubstances in the bomb 

 calorimeter; the heat given off from the body is measured by the respiration calorim- 

 eter; the external work is measured by a specially devised ergometer. Allowance 



is made for heat introduced and removed by the ventilating air current, f 1. u-rv<, 



and urine, and for that involved in changes of body temperature, which is also 

 measured. . . . 



"Since the completion of the new apparatus, 22 experiments with 5 different sub- 

 jects, covering a total of 60 days, have been conducted. These experiments la-ted 

 from 1 to 13 days, during which time the subject remained inclosed in the calorim- 

 eter chamber. Ordinarily the experiment lasts :'> or -t days. In general, each 

 experiment is preceded by a preliminary period outside the chamber, during which 

 the subjeet is given the special diet to be tested, and his habits of life bo modified as 

 to conform with those to be followed in the chamber. When the subject is to he 

 engaged in muscular work, he devotes considerable time in the preliminary days to 

 riding a bicycle in the open air. the amount of work performed being as nearly as 

 can be judged equivalent to that to he done later on the bicycle ergometer inside 

 the chamber. 



"The food for the whole experimental period, including the preliminary days, is 

 carefully weighed, sampled, and daily portions placed in proper container- ready for 

 consumption. The more easily decomposed materials, such as milk and cream, are 

 sampled, weighed, and analyzed each day. The bread and meat when used arc 



33747— No. 11—06 



