THE quantitative analysis of granulopoiesis requires knowledge not only of the complex relations between cytologic compartments within the bone marrow but also of the distribution and fate of cells capable of leaving the vascular bed after only a brief sojourn in the bloodstream and under conditions not readily accessible to observation. The genesis of many of the granulocytopenic states has thus remained obscure. In certain types increased peripheral destruction by a variety of mechanisms has been invoked. In others it is possible to relate the lack of granulocytes in the blood to a primary disturbance in bone-marrow function leading to . . .