urs constantly in
lymphatic leukaemia according to the well-known results of Neumann, which
have since been generally confirmed. In these cases extensive tracts of
bone-marrow are replaced not by masses of malignant growth but by an
indifferent tissue, so to speak, a tissue which is unable to exercise
the above-described stimulating influence upon the remaining
bone-marrow. It is owing to this circumstance that we are able to
observe in the cases of lymphatic degeneration of the bone-marrow the
phenomena due to its exclusion, in their most uncomplicated form[19].

The most convincing results are obtained from cases of acute (lymphatic)
leukaemia, the pretty frequent occurrence of which was first noticed by
Epstein, and which has lately been very thoroughly studied by A.
Fraenkel. For the purpose in question, acute leukaemia is specially
suited, since the abnormal growth of the lymphatic tissue takes place
very rapidly, and for this reason brings about a quick and uncomplicated
exclusion of the bone-marrow tissue; as it were, experimentally. Under
its influence the neutrophil elements of the bone-marrow vanish rapidly,
and in many cases so completely that it needs some trouble to find a
single myelocyte, as for example in a case of Ehrlich's. The polynuclear
leucocytes are produced in the bone-marrow, consequently where the
bone-marrow is destroyed, as in this case, it is clear that their
numbers must be absolutely very much diminished in the blood.

Dock has also arrived at similar results, as we see from a preliminary
report; and he similarly explains the absence of neutrophil cells in
lymphatic leukaemia by the replacement of the myeloid by lymphatic
tissue.

Thus lymphatic leukaemia affords a striking proof that the lymphocytes
are cells of a peculiar kind, and which are quite independent of the
polynuclear cells. It is therefore exceedingly surprising that Fraenkel,
after accurately examining and analysing eight cases of acute lymphatic
leukaemia, believes he has found in them imperative reasons for the
assumption that the lymphocytes are transformed to polynuclear cells.
This can only be explained by the confusion which Uskoff's doctrine of
"young cells" has brought about.

We define lymphocytosis as an increase of the lymphocytes of the blood;
Fraenkel like Uskoff regards it as the emigration of the young forms of
the white blood corpuscles into the blood. He concludes logically from
the diminution of the poly