The confused state of the idiopathic anemias, so far as the classification and nomenclature are concerned, has become more evident since the modern methods of investigation were disclosed. The regrouping of those cases which were previously included under von Jaksch's and Banti's anemia have clarified the situation to some degree. The true picture of aplastic anemia as is held by most clinicians consists of a severe anemia which develops rapidly over a period of from six weeks to four months ending fatally within six months or less. The other formed elements of the blood stream, the leukocytes and the platelets, show a similar numerical reduction. Associated with this, according to Lucas, there may or may not be an increase in the lymphoid structures, the lymph glands, the spleen and the liver. The postmortem finding of a marrow with the active elements replaced by fatty tissue has been included as the