lus the cells stored up
in the blood-forming organs ("positive chemiotaxis"). In the cases in
which a diminution of the leucocytes in the blood is found, it is the
result of a repulsion of the leucocytes by the bodies mentioned,
=negative chemiotaxis=.

As the experimental investigation of leucocytosis was carried further,
it was found that leucocytosis, quite similar to that occurring in
infectious diseases, could also be brought about by the injection of
various chemical substances (bacterio-proteins, albumoses, organic
extracts and so forth); and it became evident that the explanation of
the process by chemiotaxis must be supplemented in many respects. Loewit
for instance found that when substances of this kind are injected, two
different stages can be distinguished in the behaviour of the
leucocytes. First came a stage in which they were diminished
("leukopenia," Loewit) and in such a way that only the polynuclear cells
were concerned in the diminution, whilst the number of the lymphocytes
was unchanged. After this came the phase of increase of the white blood
corpuscles; and here too exclusively of the polynuclear cells; the
=polynuclear leucocytosis=. This behaviour seemed to indicate that during
the first period a destruction of white blood corpuscles brought about
by the foreign substances took place, and that it was only the dissolved
products of the latter which caused the emigration of fresh leucocytes
by chemiotaxis. But new objections were raised against this view.
Goldscheider and Jacob, in particular, shewed by exact experiments that
the transient leukopenia of the blood was not true but merely apparent;
and was caused by an altered distribution of the white blood corpuscles
within the vascular system. For whilst in the peripheral vessels from
which the blood for investigation was usually obtained, there was in
fact a diminution of the leucocytes, "=hypoleucocytosis=," in the
capillaries of the internal organs, especially of the lungs, a marked
increase of the leucocytes, "=hyperleucocytosis=," was found.

There are other objections to the great importance that Loewit has given
to leukopenia. _A priori_ it is quite incomprehensible that the various
substances, which in the fundamental test-tube experiment are able to
exercise a distinct chemiotactic influence on the leucocytes, should
under other circumstances need the intervention of the products of
decomposition of the white blood corpuscles. Moreover