But the fact, that a transition from neutrophil to oxyphil cells has never really been observed in the blood, is decisive evidence against the hypothesis of Mueller and Rieder. Were the hypothesis true, transitional stages ought to be found with ease in every sample of normal blood. Rieder and Mueller themselves are unable to bring forward any positive result of this kind, else they would hardly have been contented to fall back on the authority of Max Schultze, who professed to shew the transitional forms between the finely and coarsely granular leucocytes in the circulating blood. The authority of Max Schultze in morphological questions stands high, and very rightly; but one ought not to rely upon it for support in problems that are really histo-chemical, and which should be solved by their appropriate methods. As a logical consequence of their view, and in decided opposition to Ehrlich, Mueller and Rieder assume that the eosinophil cells of the bone-marrow "are far rather the expression of a storage than of a fresh formation there. =The bone-marrow therefore should be regarded in reference to the coarsely granular cells of the blood more as a storage depot, where these cells serve other purposes, which for the present cannot be more closely defined.=" The chief reason for this assumption, these authors see in the fact, that the majority of the eosinophils in the bone-marrow are mononuclear, whilst those of normal blood possess a polymorphous nucleus. Mueller and Rieder should themselves have raised the obvious objection that the same holds good for the nucleus of the neutrophils. They would then have seen the fault in their theory; for according to it the most important blood preparing organ constitutes as it were, not the cradle of the blood cells, but their grave. The simplest and readiest explanation, based too upon histological observation, is surely this: that the mononuclear eosinophil cells grow into polynuclear in the bone-marrow, but that the latter only reach the blood by means of their power of emigration. As this view has been accepted by the great majority of authors since Ehrlich's paper "On severe anaemic conditions," we believe we may content ourselves with the above objections to the Mueller-Rieder theory, although it has even quite recently found supporters (_e.g._ B. Lenhartz). H. F. Mueller moreover in his paper on bronchial asthma (1893) takes a position different from his earlier, and approaching that of Ehrlich. In considering the production of polynuclear eosinophilia we may best start from an experiment of E. Neusser's. Neusser found in a pemphigus patient, whose blood shewed a considerable increase of the eosinophils, that the contents of the pemphigus bulla consisted almost entirely of eosinophil cells. Neusser now produced a non-specific inflammatory bulla in the skin by a vesicant, and found that the cellular elements in it were exclusively the polynuclear neutrophil concerned in all ordinary inflammations.