of
characteristic signs are necessary for the diagnosis of the latter, as
we shall have to explain in the next section. The presence of
mononuclear eosinophil cells in the blood should not be regarded, as is
the case in many quarters, as an absolute proof of leukaemia, for they
are also found in isolated cases of ordinary leucocytosis.

The increase of eosinophil cells is not always relative, but may be
absolute. The relative number, normally 2 to 4% of all leucocytes, rises
in eosinophilia to 10, 20, 30% and over; in a case described by Grawitz
90% indeed was found. The thorough researches of Zappert, carried out on
moist preparations by a suitable method, are particularly instructive
with regard to their absolute number. As the lowest normal value he
gives 50-100 eosinophil cells per mm.^{3}, as mean value 100 to 200, as
a high normal value 200-250. The highest absolute number he has ever
found was 29,000 per mm.^{3} in leukaemia, the highest number in simple
eosinophil leucocytosis 4800 (in a case of pemphigus). Reinbach indeed
once found about 60,000 eosinophil cells per mm.^{3} in a case of
lymphosarcoma of the neck with metastases in the bone-marrow.

Polynuclear eosinophil leucocytosis, apart from the form observed
in healthy children, occurs in varied conditions, and for
comprehensiveness we divide them into several groups. We distinguish
eosinophilia:

1. =In bronchial asthma.= Increase of the eosinophil cells of the blood,
often considerable, amounting to 10 and 20% and more has been regularly
found, first by Gollasch, later by many other observers. (For the
special clinical course of the eosinophilia in asthma see below.)

2. =In pemphigus.= Neusser first recorded that an extraordinarily great,
indeed a specific eosinophilia was found in many cases of pemphigus.
This interesting observation has been confirmed on many sides, in
particular by Zappert, who once observed 4800 oxyphil per mm.^{3}

3. In acute and chronic =skin-diseases=. Canon was the first to notice
that in a fairly large number of skin-diseases, especially in prurigo
and psoriasis, the eosinophil cells are increased up to 17%. The
observation of Canon is worthy of attention, that the increase of the
eosinophils is connected with the degree of extension of the disease,
rather than with its nature or local intensity. In a case of acute
widely distributed urticaria, A. Lazarus found the eosinophils increased
to 60% of the leucocytes, a number