
178 STORRS AGRICULTURAL EXPERIMENT STATION. 
stored in the body when the food is in excess of its demands, 
or consumed from the previous supply in the body when the 
digested food is not equal to the demands of the latter, there 
still remains a certain quantity of nitrogenous material which 
is not completely oxidized but is eliminated by the kidneys in 
urea and allied compounds. Assuming that all of the digested 
nitrogen excreted from the body is in the form of urea, we 
may roughly calculate the amount of the potential energy of 
protein which thus fails to be transformed into kinetic energy 
in the body. 
Urea contains 46.67 per cent. N., hence N. X 2.143 = urea. 
N. X 6.25=protein. Hence protein divided by 6.25 X 2.143 
— the urea corresponding to the protein. ‘The heat of com- 
bustion of one gram of urea is 2.53 calories. ‘The fuel value 
of the urea corresponding to one gram of protein would there- 
fore ber (gram of protein) 6.25 X 2.143 X 2.53 somone 
calories.* 
According to this computation, which is theoretical and 
but approximately correct, there would be for each gram of 
digested protein 0.87 calories of energy in the unconsumed 
urea and other compounds. Subtracting this value from the 
total fuel value of the digested nutrients the remainder may be 
assumed to represent the proportion of the total energy of the 
digested nutrients which becomes actually available to the body. 
This is designated in the tables as ‘‘ net fuel value of the food 
digested.’ In estimating the coefficients of digestibility for 
the fuel values this net fuel value is used rather than the total 
fuel value of the digested nutrients. 
SUMMARY OF RESULTS OF DIGESTION EXPERIMENTS. 
The results of the experiments as expressed in the quantities 
of nutrients in the food eaten and the coefficients of digestibility 
are recapitulated in table 53. In this table it will be observed 
that experiments 1-5 and 9-12 were made with the laboratory 
janitor, who was used to moderately hard muscular work, while 
the subjects of Nos. 13 and 14 were assistants in the laboratory, 
whose ordinary labor involves somewhat less of muscular exer- 
cise. In experiments 11, 12, 13 and 14, however, the sub- 
jects were in the respiration apparatus and without muscular 

* For further explanations of this matter see Report of this Station, 1894, pp. 125, 126. 
