128 STORRS AGRICULTURAL EXPERIMENT STATION. 
than large. The period of the preliminary digestion experi- 
iment which preceded the metabolism experiment was depended 
upon to bring the body into approximate nitrogen equilibrium 
in the rest experiments and in some of the earlier work experi- 
ments. In the later work experiments, especially those with 
J. C. W., the quantity of protein was intended to be a little 
less than needed for nitrogen equilibrium. The reason for 
making the supply of protein rather small is found in one of 
the purposes of the experiments, which was to compare the 
relative efficiency of the non-nitrogenous materials of the ra- 
tion. It was thought that the action of these latter might per- 
haps be partially obscured with an abundant supply of protein. 
It was with this same general idea that the whole food supply 
was made small rather than large. Considering that the body 
has a well proven power of adapting the output of nitrogen to 
the income, within wide limits, it is evident that the quantities 
of protein katabolized in these experiments cannot be taken as 
an exact measure of the normal permanent demand of these 
subjects for protein in the daily food. Still less can the quan- 
tities be taken as the measure of the average permanent de- 
mand for men in general with corresponding muscular activity. 
The case with the supply and consumption of energy is 
somewhat but not wholly similar. The supply was nearly or 
quite sufficient in the rest experiments; but in the work ex- 
periments, especially those with J. C. W., it.was so small that 
the body made considerable drafts upon its reserve store of 
both non-nitrogenous and nitrogenous compounds. How much 
of the loss of body protein is to be ascribed to the lack of pro- 
tein and how much to the lack of total energy in the diet it is 
impossible to say. Special experiments with different quanti- 
ties of both protein and energy would be required to settle this 
question. ; | 
As regards the energy, however, the case is perhaps less ob- 
scure. It is safe to say that the body requires a given amount 
of total energy for maintenance and the production of a given 
amount of muscular work and that this demand varies more or 
less with the amount of muscular activity. It is also fair to 
assume that when the energy of the food does not meet its 
needs, it will draw upon such reserve materials as it can most 
conveniently utilize. The general testimony of metabolism 



