The main subjects proposed for study have been the following: 
(1) The application of the law of the conservation of energy in the 
body. An experimental demonstration of the action of this law was 
the first object sought. The fundamental principle once proven, the 
apparatus and methods can be utilized for the study of some of the 
fundamental problems of the science of food and nutrition. 
(2) The quantities of nutrients and energy metabolized by men under 
different conditions of rest and muscular and mental exercise. 
(3) The amounts of nutrients and energy required for internal phys- 
iological work, as that of respiration, circulation, and digestion. 
(1) The relation between external muscular work and the nutrients 
and energy metabolized in its performance. This general problem 
includes the narrower one of the power of the body as a machine to 
convert the potential energy of its food and of its previously stored 
material into muscular energy. Viewed from one standpoint this 
latter phase of the subject is the same as that to which the expression 
"the animal body as a prime motor" is frequently applied. From 
another standpoint it includes the comparison of the animal body with 
steam engines and other sources of power in respect to the economy 
with which the energy of fuel is utilized, the fuel in the case of the 
animal being its food, while in the case of the ordinary machine it is 
coal, oil. gas. or wood. 
(5) The transformations of nutrients and energy in mental work. 
(6) The capacities of the different classes of nutrients to supply the 
body with material and energy, the proportions in which they may 
replace one another in building tissue or yielding energy as heat or as 
muscular work, and their power to protect one another and the mate- 
rials of the body from consumption. 
(7) The nutritive values of food materials and the fitting of food to 
the needs of the consumer. 
Of the above problems all have received considerable attention 
except No. 5, which has to do with food and mental work. This has 
as 3^et been made the especial subject of only one experiment. It is 
hoped that the study of this problem may also be entered upon in the 
not too distant future. Besides the problems thus detailed a number 
of others have received attention. Among these are: 
(8) The digestion and assimilation of food material-. 
(9) The quantities of carbon dioxid. water, nitrogen, and other 
materials excreted by the body as well as the energy given off as heat 
and as external muscular work under different conditions of work and 
rest, together with the rates of elimination at different periods of the 
day and night. In this connection the respiratory quotient has also 
been considered. 
(10) The temperature of the body and its variation during different 
periods of the day and under different conditions of work. rest, and 
sleep. 
