y increased.

C. A third morphological variation which anaemic blood may shew in the
more severe degrees of the disease, is the appearance of =nucleated red
blood corpuscles=.

Though we do not wish to enter here upon the latest questions concerning
the origin of the blood elements, we must shortly indicate the present
state of our knowledge of the nucleated red corpuscles.

Since the fundamental work of Neumann and Bizzozero, the nucleated forms
have been generally recognised as the young stages of the normal red
blood corpuscles. Hayem's theory, on the contrary, obstinately asserts
the origin of the erythrocytes from blood-platelets, and has, excepting
by the originator and his pupils, been generally allowed to drop.

Ehrlich had in the year 1880 pointed out the clinical importance of the
nucleated red blood corpuscles, in as much as he demonstrated that in
the so-called secondary anaemias, and in leukaemia, nucleated corpuscles
of the normal size, "normoblasts"; in pernicious anaemia excessively
large elements, "megaloblasts," "gigantoblasts" are present. At the same
time Ehrlich mentioned that the megaloblasts also play a prominent part
in embryonic blood formation.

In 1883 Hayem likewise proposed a similar division of the nucleated red
blood corpuscles into two,

(1) the "globules nuclees geantes" which he found exclusively in the
embryonic state, (2) the "globules nuclees de taille moyennes" which he
found invariably present in the later stages of embryonic life, and in
adults. Further, W. H. Howell (1890) found in cats' embryoes two kinds
of erythrocytes, (1) very large, equivalent to the blood cells of
reptiles and amphibia ("ancestor corpuscles"), and (2) of the usual size
of the blood corpuscles of mammalia. And similarly more recent authors,
H. F. Mueller, C. S. Engel, Pappenheim and others, have adhered to the
division of haematoblasts into normo- and megaloblasts. And it is on the
whole recognised, that, physiologically, normoblasts are always present
in the bone-marrow of adults, as the precursors of the non-nucleated
erythrocytes; that the megaloblasts, however, are never found there
under normal circumstances, but only in embryonic stages, and in the
first years of extra-uterine life.

S. Askanazy on the contrary has expressed the view, that the normoblasts
may arise from the megaloblasts, and thereby denies the principal
distinction between them. Schaumann also holds that the separation of
th