agnosis of myelogenic leukaemia, 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 Tuerk's
investigations, in the critical period of pneumonia as parts of a
general leucocytosis, the danger of confusion with leukaemic 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 leukaemic 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
Tuerk'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 leukaemia, 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 leukaemia. These are to
be regarded as for the most part identical with the mononuclear
eosinophil cells, noticed by Mueller 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 leukaemia, 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 leukaemia 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
leukaemia, Ehrlich stated that the absolute number of polynuclear
eosinophils is always much increased in myelogenic leukaemia. 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 Mueller and Rieder has mor