escribed as artificial necrobiosis, seems in this connection worthy of
consideration.

Just as with regard to the formation of erythrocytes the views differ
one from another, so also with regard to the "free" nuclei which come
under observation in numerous preparations. Koelliker has taught that
these nuclei are not quite free, but are always surrounded by a minute
border of protoplasm. On the other hand Rindfleisch regards these nuclei
as having migrated from, or having been cast off by the erythroblasts;
and Neumann explains them as the early forms of erythroblasts. Ehrlich
was the first to endeavour to effect a compromise between the directly
opposed views of Rindfleisch and Neumann. He taught that both kinds take
part in the production of the red discs. From blood preparations which
contain numerous normoblasts, for instance in "blood crises" (see p.
62), an unbroken series of pictures can easily be put together shewing
how the nucleus of the erythroblast leaves the cell, and at last
produces the appearance of the so-called free nucleus. It must be
expressly mentioned that these pictures are only to be found in
specimens in whose preparation pressure of any kind upon the blood has
been avoided. Further, however rich a blood may be in normoblasts, the
metamorphosis of the nucleus as described by Neumann, is practically
never to be observed. It is quite otherwise with the megaloblasts.
Amongst them, few examples are to be found in which traces at least of
the destruction and solution of the nucleus are not shewn, and in a
blood preparation of pernicious anaemia, which is not too poor in
megaloblasts, one can construct step by step the unbroken series from
megaloblasts with a complete nucleus through all stages of Karyorrhexis
and Karyolysis to the megalocytes, as the process is described by
Neumann[9].

From Ehrlich's observations it follows, that the normoblasts become
normocytes by extrusion or emigration of the nucleus, the megaloblasts
become megalocytes by degeneration of the nucleus within the cell.

M. B. Schmidt without making use of the principal distinction made by
Ehrlich, also concludes from his researches on sections of the
bone-marrow of animals in extra-uterine life, that both kinds of
erythrocyte formation occur.

Quite recently Pappenheim, partly in conjunction with O. Israel, has
carried out very thorough researches on these particular points. As the
subject for observation he chose the blood of