It is needful here to emphasise this hundred-fold repeated experience with special distinctness, for some recent authors do not even yet allow the full diagnostic importance of the blood examination. v. Limbeck says in the latest edition of his clinical Pathology of the Blood, "That one should not regard the blood changes as an invariably reliable diagnostic resource in myelogenic leukæmia; and that the diagnosis of leukæmia should not rest on the presence or significance of one or more cells. Not only the general features of the case, but the blood condition as well should be considered." To these remarks the objection must be made that up to the present no serious hæmatologist will have had to diagnose a leukæmic disease principally "from the presence of one or more cells." In the work of Ehrlich and his pupils at least, it has always been shewn that the character of a leukæmic condition is only settled by a concurrence of a large number of single symptoms, of which each one is indispensable for the diagnosis, and which taken together are absolutely conclusive. With these premises it is indisputable that the microscopic examination of the blood alone on dry preparations, without the assistance of any other clinical method, can decide whether a patient suffers from leukæmia, and whether it belongs to the lymphatic or myelogenic variety.
The microscopic picture of myelogenic leukæmia, disregarding the almost constant increase of the white blood corpuscles, has a varied, highly inconstant character. This arises from the co-operation of several anomalies, namely:
A. that in addition to the polynuclear cells, their early stages, the mononuclear granulated corpuscles likewise circulate in the blood;
B. that all three types of granulated cells, the neutrophil, eosinophil, and mast cells participate in the increase of the white blood corpuscles;
C. that atypical cell-forms appear, e.g. dwarf forms of all the kinds of white corpuscles; and further mitotic nuclear figures;
D. that the blood always contains nucleated red blood corpuscles, often in great numbers.
1. We begin with the discussion of the mononuclear neutrophil cells, Ehrlich's "myelocytes." They are present so abundantly in the blood of medullary leukæmia as to impart to the whole picture a predominantly mononuclear character. As we have frequently mentioned, myelocytes occur normally only in the bone-marrow, not in the circulating blood. Their eminent importance for the diagnosis of myelogenic leukæmia, where they have been regularly found by the best observers, is in no way diminished by their transitory appearance in a few other conditions (see pages 77, 78). Though they have been occasionally found, according to Türk's investigations, in the critical period of pneumonia as parts of a general leucocytosis, the danger of confusion with leukæmic blood changes is non-existent. This is guarded against by (1) the much smaller increase of the white cells; (2) the diminution of the eosinophil and mast cells; (3) the fact, that the myelocytes of leukæmic blood are nearly always considerably larger; (4) the preponderating polynuclear character of the leucocytosis, which is not effaced by the small percentage amount of myelocytes (at most 12%): (5) the incomparably smaller absolute number of myelocytes. In the most pronounced case of Türk's, for example, in which the percentage number of myelocytes amounted to 11.9, calculation of their absolute number gives at most 1000 myelocytes per mm.3 This is a figure which bears no comparison with that obtaining in leukæmia, where 50,000-100,000 myelocytes per mm.3 and over occur in cases that are in no way extreme.
2. The mononuclear eosinophil cells. Before the introduction of the staining method, Mosler had described large, coarsely granulated cells, "marrow cells," as characteristic for myelogenic leukæmia. These are to be regarded as for the most part identical with the mononuclear eosinophil cells, noticed by Müller and Rieder as peculiar, and aptly described by them as the eosinophil analogues of the preceding group. They appear as large elements with oval, feebly staining nucleus. Undeniably a valuable sign of leukæmia, they are not nearly so important as the mononuclear neutrophil cells, as follows from the numerical superiority of the latter. To regard the presence of "eosinophil myelocytes" as absolute proof of the existence of a leukæmia is inadmissible, since they are occasionally present in small numbers in other diseases.
3. The absolute increase of the eosinophil cells. In his first paper on leukæmia, Ehrlich stated that the absolute number of polynuclear eosinophils is always much increased in myelogenic leukæmia. This assertion of Ehrlich has been received under some protest; v. Limbeck in his text-book even speaks of an "alleged" increase of the eosinophil cells. The well-known work of Müller and Rieder has more particularly given rise to this opposition, and thrown doubt on the diagnostic importance of the eosinophil cells. These authors however base their contradiction on false premises.
For Ehrlich did not speak of a rise of the percentage of the eosinophil cells, but only of an increase in their absolute number. If in a case of leukæmia only the normal percentage number of eosinophils is found, it indicates, all the same, a great absolute increase; and Müller and Rieder would themselves have fully confirmed Ehrlich's statement, had they only calculated the absolute figures in a few of their cases. Selecting from the seven cases in this paper, those where it is possible from the given data to obtain the absolute number of the eosinophil cells, we get the following results: