One question that naturally arises in considering the possible effects of a diminished proteid intake upon bodily health is whether a continued diminution of proteid food will have any influence upon the character and composition of the blood. It might be claimed, for example, that a lowering of the quantity of proteid food below the ordinarily accepted standards will eventually result in a deterioration in the character of the blood. Obviously, if such should prove to be the case, it would at once emphasize the necessity for higher standards of proteid feeding. Further, there might result marked changes in the hæmoglobin-content of the blood in connection with a lowered proteid metabolism long continued. With these thoughts in mind, a careful study of the blood of the soldiers has been made from time to time, with special reference to determining the number of erythrocytes and leucocytes in the fluid, attention also being paid to the percentage of hæmoglobin. Four distinct observations were made, as a rule, upon each man, namely, in the months of October, December, January, and March. The results are tabulated in the accompanying tables. Examination of these results shows that, as a rule, the number of erythrocytes, or red blood corpuscles, was somewhat increased during this period of lowered proteid feeding. We are not disposed, however, to lay very much stress upon this apparent increase, because it is not sufficiently marked to carry much weight, especially in view of the difficulties attending the obtaining of great accuracy in blood counts in general. Regarding the leucocytes, the figures are less definite, but may be fairly interpreted as indicating practically no appreciable change in the number of white corpuscles. Similarly, the hæmoglobin-content shows no distinct alteration. Hence, the conclusion is that the physiological economy practised by the soldiers during their six months’ stay in New Haven, and especially the marked diminution in the amount of proteid food consumed, did not result in any deterioration of the blood, so far as it can be measured by the number of contained erythrocytes and leucocytes, and by the content of hæmoglobin.