When the problem of carcinoma is approached from the metabolic aspect, the first question which arises is: how does the metabolism of growing tissue differ from that of resting? The prospects of finding an answer to this question are good. Whether the mass of a given tissue is to remain constant, or, within a short period to increase many-fold, must be determined by the velocity of those processes which supply the driving forces for growth. Our task is to search for such processes and to compare their velocities in resting tissues and growing tissues.