sease. In a case of carcinoma of the bone-marrow,
described by Epstein, with an anaemic constitution of the blood (nearly
always present it may be mentioned in leukaemia), there was found a
marked increase of the white blood corpuscles, numerous neutrophil
myelocytes and nucleated red corpuscles. Anyone holding, as Mueller and
Rieder do, that the number of eosinophil cells need not be considered in
the diagnosis, must in this case have diagnosed myelogenic leukaemia.
This however was according to Ehrlich's system impossible owing to the
complete absence of eosinophil cells.

From all these observations it follows that an absolute increase of
eosinophil cells is indispensable for the diagnosis of leukaemia.

4. =The absolute increase of the mast cells.= The mast cells are always
increased in myelogenic leukaemia. They may be counted in leukaemic blood
with the aid of the triacid or eosine-methylene blue stain. As shewn by
the former they appear as polynuclear cells free from granules, since
their granulation takes on no dye of the triacid mixture.

In all cases of myelogenic leukaemia the increase of mast cells is
absolute and considerable. Generally they are equally or half as
numerous as the eosinophils, occasionally they may exceed the latter in
number. Hence it follows that the mast cells undergo an increase in
number relatively greater than the eosinophil cells, for they normally
amount only to some 0.28%. They are perhaps of greater diagnostic value
than the eosinophils, because up to the present time we know of no other
condition (in contradistinction to eosinophil leucocytosis) in which a
marked increase of the mast cells occurs.

5. =Atypical forms of the white corpuscles.= Amongst these are to be
mentioned: (_a_) dwarf forms of the polynuclear neutrophils and of the
eosinophil elements respectively. As a rule they resemble normal
polynuclear cells on a small scale. (_b_) Dwarf forms of the mononuclear
neutrophil and eosinophil leucocytes, which correspond to the
pseudo-lymphocytes described elsewhere (see p. 78). The importance of
these dwarf forms for leukaemia is as yet insufficiently explained; and
it is difficult to decide whether they are already small forms on
reaching the blood-stream, or whether they are there produced by
division of a large cell. (_c_) =Cells with mitoses=. Formerly particular
weight was laid on the observation of mitoses, for they were regarded as
evidence that the increase of whit