
REPORT OF THE DIRECTOR. 13 
values likewise are only approximations. Much more experi- 
menting will also be needed to show, as accurately as we need 
to know, just how the different ingredients of the several classes 
of food materials are used in the body, and just what are the 
requirements of people in different classes, and under different 
conditions, for proper nourishment. When, however, we con- 
sider that, twelve years ago, we had extremely little accurate 
information about the chemical composition and nutritive values 
of American food materials, and were obliged to look to Euro- 
pean sources for nearly all of our information upon these sub- 
jects, and to depend upon analyses of European products for 
estimates of the composition of food materials produced in 
this country, the fact that such a table can be prepared from 
data which has been accumulated mostly in this country dur- 
ing so short a period is, most assuredly, a cheering mark of 
progress. 
Fleats of Combustion and Fuel Values of Foods and Feeding 
Stuffs.—In all the foods and feeding stuffs analyzed during the 
past year, the heats of combustion, which are taken as measures 
of the fuel value, have been determined by the bomb calorime- 
ter. An account of this apparatus was given in the Annual 
Report for 1894. It has since been further elaborated, and is 
now being made for other institutions, several of which already 
have it use. 
Experiments with Men in. the Respiration Calorimeter.— 
Previous annual reports have contained brief reference to this 
apparatus, which has been for some time in process of develop- 
ment. As was there explained, the more purely scientific pur- 
pose is the study of the application of the laws of the conservation 
of matter and energy in the living organism.” At the same time 
it has a most intensely practical purpose, namely, to learn more 
of the laws of nutrition and the ways the food is used in the 
body. ‘To obtain this most useful knowledge, abstract research 
of the highest order is necessary. 
The experiments are made by placing a man inside a box or 
chamber under conditions which permit the measurement of 
the income and outgo of his body. Arrangements are made 
for ventilating the chamber by a current of air which is meas- 
ured and is analyzed as it goes in and comes out, so that the 
