202
LEO LEMEZ
predominantly circular in outline, 'hyperchromia in later stages due to
the thickness of their cytoplasm (Dantschakoff, 1908a; Alexander and
Schjeide, 1953), with a more or less round vesicular nucleus containing
in most instances discernible chromatin blocks even in mature cells.
The definitive elements (Ε II) first appear in circulating blood on the
5th day of incubation as round basophilic cells called erythroblasts
(Fig. 1A) which gradually attain a more polychromatophilic cytoplasm
and a coarser nuclear pattern. Thereafter they become somewhat oval
in outline, changing into proerythrocytes (Fig. 1A) and finally become
distinctly oval, resembling those of the hen, but exceeding them in both
length and width. Simultaneously the structure of the nucleus becomes
indistinct because the chromatin blocks are squeezed together.
The size of both the cell and nucleus (length and width, or diameter)
was measured more or less systematically in red blood cells of chick
embryos by Keller (1933), Fennell (1947), Perri (1948c), Sandreuter
(1951), Bernardelli et al. (1953), Alexander and Schjeide (1953) and
Lemez (1953). As maturation proceeds, the dimensions of the cell
decrease slightly in primitive erythrocytes only, while the nuclear
dimensions decrease to a much greater extent in both primitive and
definitive elements.
The sequence of maturation of both primitive and definitive red
blood cells has been investigated by many workers over different
periods, the data being expressed in terms of erythrocyte differential
counts (Sugiyama, 1926, from day 1-5 to day 7 ; Dawson, 1936, from the
2nd to the 18th day; Fennell, 1947, from the 3rd to the 20th day;
Sandreuter, 1951, from the 8th day to hatching (in both chick and
starling embryos); Astaldi et al., 1952, from the 2nd to the 9th day;
Lemez, 1953, from the 7th to the 18th day; Lemez and Rychter, 1956,
and Lemez, 1958, from the 2nd day of incubation to the 1st postembryonic day).
The red differential count is characterized as follows :
(1) There is a rapid change in the proportion of primitive (EI) and
definitive (Ε II) elements between the 4th and the 7th days of incubation, when the relative proportion of primitive erythrocytes decreases
from 100% to about 20% (Sugiyama, 1926; Dawson, 1936; Fennell,
1947; Lemez and Rychter, 1956; Lemez, 1958). This, together with a
relatively high proportion of thrombocytes (degenerated cells—Section
II, B) led Schechtman (1952) and Schechtman and Hoffman (1953) to
the conclusion that there must be a rapid destruction of primitive
erythrocytes during this period. This is an example of how dangerous it
can be to consider a decrease in the relative proportion of one cell group
in a growing organism as evidence for their disintegration; in this
instance, estimation of the total count (survival curve) reveals that there
LEO LEMEZ
predominantly circular in outline, 'hyperchromia in later stages due to
the thickness of their cytoplasm (Dantschakoff, 1908a; Alexander and
Schjeide, 1953), with a more or less round vesicular nucleus containing
in most instances discernible chromatin blocks even in mature cells.
The definitive elements (Ε II) first appear in circulating blood on the
5th day of incubation as round basophilic cells called erythroblasts
(Fig. 1A) which gradually attain a more polychromatophilic cytoplasm
and a coarser nuclear pattern. Thereafter they become somewhat oval
in outline, changing into proerythrocytes (Fig. 1A) and finally become
distinctly oval, resembling those of the hen, but exceeding them in both
length and width. Simultaneously the structure of the nucleus becomes
indistinct because the chromatin blocks are squeezed together.
The size of both the cell and nucleus (length and width, or diameter)
was measured more or less systematically in red blood cells of chick
embryos by Keller (1933), Fennell (1947), Perri (1948c), Sandreuter
(1951), Bernardelli et al. (1953), Alexander and Schjeide (1953) and
Lemez (1953). As maturation proceeds, the dimensions of the cell
decrease slightly in primitive erythrocytes only, while the nuclear
dimensions decrease to a much greater extent in both primitive and
definitive elements.
The sequence of maturation of both primitive and definitive red
blood cells has been investigated by many workers over different
periods, the data being expressed in terms of erythrocyte differential
counts (Sugiyama, 1926, from day 1-5 to day 7 ; Dawson, 1936, from the
2nd to the 18th day; Fennell, 1947, from the 3rd to the 20th day;
Sandreuter, 1951, from the 8th day to hatching (in both chick and
starling embryos); Astaldi et al., 1952, from the 2nd to the 9th day;
Lemez, 1953, from the 7th to the 18th day; Lemez and Rychter, 1956,
and Lemez, 1958, from the 2nd day of incubation to the 1st postembryonic day).
The red differential count is characterized as follows :
(1) There is a rapid change in the proportion of primitive (EI) and
definitive (Ε II) elements between the 4th and the 7th days of incubation, when the relative proportion of primitive erythrocytes decreases
from 100% to about 20% (Sugiyama, 1926; Dawson, 1936; Fennell,
1947; Lemez and Rychter, 1956; Lemez, 1958). This, together with a
relatively high proportion of thrombocytes (degenerated cells—Section
II, B) led Schechtman (1952) and Schechtman and Hoffman (1953) to
the conclusion that there must be a rapid destruction of primitive
erythrocytes during this period. This is an example of how dangerous it
can be to consider a decrease in the relative proportion of one cell group
in a growing organism as evidence for their disintegration; in this
instance, estimation of the total count (survival curve) reveals that there