e two kinds rests on doubtful foundation, since occasionally it is
questionable whether particular cells are the normoblasts or the
megaloblasts.

We distinguish three kinds of nucleated red blood-corpuscles on the
grounds of the following characters;

1. =The normoblasts.= These are red corpuscles of the size of the usual
non-nucleated disc, whose protoplasm as a rule shews a pure haemoglobin
colour, and which possess a nucleus. Occasionally there may be 2-4
nuclei. The sharply defined nucleus lies generally in the centre,
comprises the greater part of the cell, and is above all distinguished
by its intense colour with nuclear stains, which exceeds that of the
nuclei of the leucocytes, and indeed of all known nuclei. This property
is so characteristic that the free nuclei, which occur occasionally in
anaemias, and particularly often in leukaemia, may be recognised as nuclei
of normoblasts, although surrounded by traces only of haemoglobin, or by
none at all.

2. =The megaloblasts.= These are 2-4 times as large as normal red blood
corpuscles. Their protoplasm, which constitutes by far the chief portion
of the body of the cell, very often shews anaemic degeneration to a
greater or less degree. The nucleus is larger than that of the
normoblasts, but does not form so considerable a fraction of the cell as
in the latter. It is often not sharply defined, and is of a rounded
shape. It is distinguished from the nucleus of the normoblast by its
much weaker affinity for nuclear stains, which may often be so small
that little practised observers perceive no nucleus.

Occasionally very large cells are present of the kind just described,
which are therefore called =gigantoblasts=, but which are not
distinguishable in other respects from the megaloblasts.

It cannot be denied that it is often difficult to decide whether a
particular cell is to be regarded as a specially small megaloblast or a
large normoblast. In such cases one would naturally search the
preparation for perfect forms of haematoblasts, and for the presence of
free nuclei or of megalocytes, in order to obtain an indirect conclusion
concerning the cells in question.

3. =The microblasts.= These are occasionally present, _e.g._ in traumatic
anaemias, but they are very seldom found, and have not so far attracted
particular attention.

* * * * *

The question of the meaning of the =normoblasts= and =megaloblasts= has led
to lively