38 
CHEMISTRY: H. C. SHERMAN 
Proc. N. a. S. 
Furthermore, these methods are capable of increasing the resistance of 
mice to replants of their own spontaneous tumors. From the evidence 
at hand it seems then that the immunity aroused by these two physical 
agents has at least one other point of similarity to that induced by tissue 
injection, namely, a period of latency after the exposure before the immunity 
becomes evident. Whether the tissue injection, the small dose of X-rays, 
or the dry heat induce changes in the organism other than those associated 
with increase in the lymphoid tissue which would account for the im- 
munity, is impossible to state at the present time; but the evidence now 
at hand points at least to the lymphoid tissue as an important agent in 
the immunity reaction to transplanted cancer of mice. 
The work reported in this paper was carried out with the assistance of 
Herbert D. Taylor, John J. Morton, W. D. Witherbee, Waro Nakahara, 
and Ernest Sturm. 
THE PROTEIN REQUIREMENT OF MAINTENANCE IN MAN 
By H. C. Shearman 
Department of Chemistry, CoIvUmbia University 
Communicated by W. A. Noyes, November 17, 1919 
During the past four years a number of experiments have been carried 
out to test the nutritive requirements of maintenance in healthy men and 
women, and the efficiency of diets derived chiefly from the cereal grains 
in meeting these requirements. In connection with this work the results 
of all available data from previous investigations which seemed to lend 
themselves to direct quantitative comparison, have been brought together. 
Probably the best present indication of the amount of protein or nitrogen 
actually required for the maintenance of the average adult is to be obtained 
by averaging the observed output of nitrogen in all available experiments, 
upon normal men and women, in which the energy value of the food was 
appropriate to the size and activity of the subject and the intake of nitrogen 
appears to have been just about sufficient to result in equilibrium of intake 
and output. Since a considerable and rather variable amount of time is 
required for the body to adjust its rate of nitrogen output to the rate of 
intake, it is probable that the "indicated protein requirement" obtained 
by averaging all available experiments will be somewhat greater than the 
minimum amount of protein on which the same subjects could actually 
have established and maintained equilibrium had the experiments been 
sufficiently prolonged. In other words, for the practical purpose of indi- 
cating how much protein the food must furnish in order to provide for 
adult maintenance such an average will err on the side of safety in that it 
may be expected to be appreciably above the minimum which would ac- 
tually suffice to keep normal individuals in equilibrium. Two other in- 
