l and considerable.

That the absolute and relative number of eosinophil cells may markedly
sink in certain complications of leukaemia, constitutes no exception to
the law that the eosinophil cells are increased in myelogenic leukaemia.
In this connexion the self-evident principle must be observed, that only
analogous conditions are comparable. The standard of comparison for a
leukaemic patient suffering from severe sepsis is not the blood of a
healthy person with normal numerical proportions, but that of a patient
similarly attacked by a severe sepsis. Now we know that in sepsis the
number of eosinophil cells is enormously diminished, so that Zappert, in
five cases of this nature, was unable to recognise any eosinophils in
the blood. In contrast to this stands a case of myelogenic leukaemia
described by Rieder and Mueller, complicated by a severe and lethally
ending suppurative process. In consequence of the acute neutrophil
leucocytosis brought about by the septic infection, the number of
eosinophils sank rapidly from 3.5% to 0.43% (4 hours before death). The
absolute number of eosinophil cells however in this terminal stage still
amounted to 1400-1500 per mm.^{3}, and was therefore, in comparison with
an uncomplicated sepsis, very much raised. Writers should not have
disputed the importance of the eosinophil cells for the diagnosis of
leukaemia from cases like these; on the contrary they should have seen in
them a decisive confirmation of the constancy of the absolute increase
of the eosinophils in leukaemic blood.

At the time when Ehrlich formulated his proposition on the diagnostic
importance of the eosinophil cells in leukaemia, the simple eosinophil
leucocytosis (see p. 148), first discovered later by the investigation
of asthma etc., was unknown. For no confusion can arise between
leukaemia, and conditions accompanied by eosinophilia, as they can be
distinguished on clinical grounds alone. The blood moreover provides
ample means for a differential diagnosis: (1) the total increase of the
white cells in this case seldom reaches degrees that remind one of
leukaemia; (2) the eosinophil cells are exclusively polynuclear; (3) mast
cells and neutrophil myelocytes are almost entirely absent.

In favour of the diagnostic value of the absolute increase of the
eosinophil cells are those cases too, where with a blood condition
closely recalling leukaemia, the absence of eosinophil cells excludes the
diagnosis of that di