In the description of the condition of benign aplastic anæmia in pigs, attention is directed, among other things, to changes in the bone-marrow which seem of fundamental importance in understanding normal erythrogenesis. It is possible that an indirect van den Bergh reaction can be converted into an immediate direct by controlling the H-ion concentration suitably, either with buffer solutions or with less dissociable acids, such as acetic, used in preparing the van den Bergh reagent. The question of the interpretation of direct and indirect reactions, therefore, would seem to be reopened. Following Minot and Murphy's work, a pig with aplastic anæmia was fed with liver. The lesions in the liver, considered with the marked improvement in the blood which followed on liver feeding in this case, lead one to regard the condition as one of blood and marrow inefficiency due primarily to hepatic insufficiency. A comparison of pernicious anæmia with the benign aplastic anæmia of pigs seems to indicate that in pernicious anæmia there is more than a mere functional disturbance of the marrow. The marrow appears to be fundamentally and organically affected, and this appears to be the pathological basis of the disease—a point which has already been discussed more fully elsewhere [14]. A parallel may be drawn between the varieties of aplastic anæmia, such as already exists for ordinary anæmias. We have, thus, the secondary or benign anæmias on the one hand; and, on the other, the primary or malignant anæmias, such as pernicious anæmia. Correspondingly, we have such benign or secondary aplastic anæmias as that described in the pigs; and malignant or primary aplastic anæmias such as those in benzol poisoning, etc. That aplasia should be so marked a feature in iron deficiency, as compared with other secondary anæmias, is probably due to the persisting nature of the cause.
Leukopenic Myelosis