7 o> 7 
eee 
t 4 i 
124 STORRS AGRICULTURAL EXPERIMENT STATION. 
nutrients was contained in the food eaten and how much was 
left in the undigested residue. The difference is taken as the 
measure of the amount digested. In the same way, it is the 
potential energy of the digested material which is made available 
to the body in the forms of heat and muscular power. The 
energy of the undigested material is lost to the body. To 
learn how much of the energy of the food is available we must 
find how much potential energy was contained in the food eaten 
and how much is left in the residues not used in the body. 
The difference will be the amount set free and made available 
for fuel. 
The potential energy of the food and the unconsumed residues 
is learned by burning the materials in the calorimeter and meas- 
uring the heat produced. This method has been followed in 
connection with the digestion experiments referred to. 
The experiments here described are, so far as the writers know, 
the first attempt in this direction.* The results are far from 
being all that could be desired. We have not yet found a per- 
fectly satisfactory method for determination of the heat of 
combustion of the solid matters of the urine, though we hope 
for better success in due time. A number of collateral sub- 
jects call for study, some of which are already entered upon. 
The purpose here is simply to report some of the first results 
obtained. 
The much needed study of the general subject requires the 
taking into account of the total income and outgo of the body as 
expressed in terms of matter and of energy. This is the pur- 
pose of the respiration calorimeter which is now being elaborated 
by codperation of the Station in the chemical laboratory of 
Wesleyan University, to which reference was made in the last 
Annual Report of this Station.+ 
The purpose of the present article is to record some of the 
observations already made. An explanation of the way in which | 
the principal data are obtained is given with the details of the 
latter in the case of experiment No. 1. For the other experi- 
ments only the data arecited. The results of all the experiments 
are summarized in table 44. 

* Prof. H. P. Armsby, of the Pennsylvania Experiment Station, has conducted a series of 
feeding experiments in which the heats of combustion of food and residues were determined by 
one of us with the calorimeter used in the experiments here described, but the results are not 
yet published. 
+ Report for 1893, page 16. 

