This monograph summarizes the large amount of experimental data accumulated during many years of studying the functions of the blood system and its regulatory mechanisms under the action of diverse morbific factors within the models of pathological processes (e.g. immobilization stress, blood loss, inflammation, cytostatic and radiation myelosuppressions, experimental encephalopathies, neuroses, and spontaneous leucosis). These data are is analyzed with the understanding that hematopoietic tissue is an integrated system that can react to the challenges of both the internal and external environments. This analysis helped develop the theory of hematopoiesis control describing the regularities in the work of basic subdivisions of the hematopoietic tissue under normal and pathological conditions, as well as the performance and interaction of the local and long-ranged control systems. The monograph is recommended for Physiologists, Pathophysiologists, Hematologists, Oncologists, Pharmacologists and other professionals.