Since it was demonstrated that erythropoiesis is subject to hormonal control (1), the search site of production of this factor and the appropriate source from which the erythropoietic hormone could be isolated, has been the subject of multiple investigations. Erythropoietic activity has been found in a variety of fluids including creónlcos plasma, urine (2) milk (3) and isolation of active eritropoyéticamente anterior pituitary (4, 5) material. However, such activity demonstrated in organic fluids in primary form, followed some procedures which showed decrease in capacity utilization of oxygen by the blood (Phenylhydrazine (6), bleeding (7), hypoxia, etc...) In pathological or after administration of cobalt (8) states ; such entity has not been possible to isolate sufficient active fractions to a suitable chemical and biological research. In observations made in large numbers of patien...