Familial blood diseases are, in many instances, directly related to the hemolytopoietic system, the special pathology of which is but meagerly understood. The physiologic activity of this system controls the cellular elements of the blood by maintaining a proper balance between blood cell formation and destruction.
The reticulo-endothelial system would seem to comprise the most important portion of the hemolytopoietic mechanism, and consists of the endothelium and related reticular cells of the spleen, lymph and hemolymph glands, the star cells of the liver and the reticulo-endothelium of the bone marrow. The large, wandering endothelial cells are best considered in this system. In the embryo, the liver and spleen contribute to the formation of red blood cells, whereas in postnatal life the bone marrow constitutes the essential seat of the formation of most of the cellular blood elements, unless protracted strain causes a reversion to the embryonic functions of red and