e internal organs were found to be
healthy, short epileptiform attacks occurred, in one of which death took
place. The autopsy gave no indication of the cause of death. Two
examinations of the blood were made in the course of the three days he
was under observation. In one of these, out of =ten cover-glass
preparations, not a single white blood corpuscle was found=, and in the
second only one example.

We have mentioned this case here, because it is remarkable as an extreme
leukopenia never before observed. An explanation however is impossible
owing to the obscurity of the general clinical condition.

For the rest the conditions, under which a considerable diminution of
the leucocytes occurs, are very well-known. We distinguish two chief
groups:

1. Leukopenia from =destruction of a portion of the white blood
corpuscles= (Loewit);

2. Leukopenia from =deficient inflow of white corpuscles=:

[alpha]. in infectious diseases from =negative chemiotaxis=;

[beta]. in anaemia etc. from =defective action of the bone-marrow=.

We have entered more fully into the leukopenia experimentally produced
by Loewit, in the chapter on leucocytosis. We there explained, that
according to present views, we have to deal, not with an actual
destruction of the white elements, but merely with an altered
distribution within the blood-stream.

Amongst the infectious diseases where an hypoleucocytosis occurs,
typhoid fever must first be mentioned. The diminution is chiefly at the
expense of the polynuclear cells. Uncomplicated measles too, generally
runs its course with a marked leukopenia, specially distinct during the
breaking out and at the height of the exanthem. These cases of
infectious leukopenia are to be explained, not by a destruction of white
corpuscles, but rather by a diminished inflow, brought about by the
circulation of substances negatively chemiotactic for the polynuclear
elements.

Leukopenia has still another meaning in certain cases of severe anaemia,
where it indicates a highly unfavourable prognosis. Ehrlich has
described (_Charite Annalen_ 1888) a case of posthaemorrhagic anaemia
ending fatally, where an extreme diminution of the leucocytes occurred.
Exact figures shewed that the greater proportion (80%) of white blood
corpuscles consisted of lymphocytes, whilst the polynuclears amounted to
14% (instead of 70-72% normally). Eosinophil cells and nucleated red
blood corpuscles were entirely absent. Ehrlich explained