THE BLOOD OF CHICK EMBRYOS
205
red cell line derivatives and the manner in which they originate have
been described. Lemez (1953) showed that at the end of the incubation
period nearly all erythroplastids belong to the definitive series. Previously
cells of the primitive line were believed to be their only source, thus
prolonging considerably the survival of primitive elements after hatching.
About the 14th day Lemez (unpublished) observed some definitive
diploid erythrocytes, each with a large nucleus frequently undergoing
fragmentation. Some erythrocytes with round nuclei and round cell
outline were observed in samples taken during the last third of the
incubation period; these undoubtedly belong to the definitive line
(E IIj type), the erythrocytes having matured without changing shape
from the round erythroblast into the oval mature erythrocyte. They do
not represent a recurrence of primitive erythrocytes.
The genesis of primitive binucleate erythrocytes (Ε I) was observed
and recorded by microcinematography, in vitro by Borghese et al. (1955)
and by Rondanelli and Strosselli (1957). In the former study the onset
of mitosis was normal, but cytoplasmic division began and then
regressed, i.e., caryokinesis was not followed by cytokinesis. Rondanelli
and Strosselli, on the other hand, observed that, following a normal
mitotic process, the separated twin cells subsequently amalgamated
forming a typical binucleate cell.
2. Erythrocyte Number, Haemoglobin Content,
Haematocrit
Values, Characteristics of the 'Average
Erythrocyte'
The number of erythrocytes per cu.mm is a much investigated
aspect of chick embryo haematology. One of the first to determine this
value was Ascarelli (1895) who published an uninterrupted series of
data from the 7th day of incubation to the 7th postembryonic day. The
high values given by him for the last third of the incubation period and
the postembryonic period have not been confirmed by subsequent
workers. In many cases there are gaps in the incubation period studied
(Sümegi, 1932, started with day 13 of incubation; Zorn and Dalton,
1937a, b—day 9; Penionschkevitch, 1937, and Ogorodniy, 1939, quoted
by Romanoff, 1960—day 12; Burmester et al., 1941—day 15; Weller
and Schechtman, 1949—day 14 to 16; Sandreuter, 1951—day 10; Hsu
et al., 1952—day 18; Alexander and Schjeide, 1953, and Lemez, 1953,
1955—day 7; Pilipenko, 1957, and Barnes and Jensen, 1959—day 9).
Some workers examined only a few embryos per incubation day. None
of them extended Ascarelli's data to an earlier developmental stage
until Rychter (1955) and Rychter et al. (1955a) covered the entire
incubation period, starting with the 2nd day of incubation (25 somite
stage on average) and extending the study to the 1st day after hatching
(Fig. 2B).
205
red cell line derivatives and the manner in which they originate have
been described. Lemez (1953) showed that at the end of the incubation
period nearly all erythroplastids belong to the definitive series. Previously
cells of the primitive line were believed to be their only source, thus
prolonging considerably the survival of primitive elements after hatching.
About the 14th day Lemez (unpublished) observed some definitive
diploid erythrocytes, each with a large nucleus frequently undergoing
fragmentation. Some erythrocytes with round nuclei and round cell
outline were observed in samples taken during the last third of the
incubation period; these undoubtedly belong to the definitive line
(E IIj type), the erythrocytes having matured without changing shape
from the round erythroblast into the oval mature erythrocyte. They do
not represent a recurrence of primitive erythrocytes.
The genesis of primitive binucleate erythrocytes (Ε I) was observed
and recorded by microcinematography, in vitro by Borghese et al. (1955)
and by Rondanelli and Strosselli (1957). In the former study the onset
of mitosis was normal, but cytoplasmic division began and then
regressed, i.e., caryokinesis was not followed by cytokinesis. Rondanelli
and Strosselli, on the other hand, observed that, following a normal
mitotic process, the separated twin cells subsequently amalgamated
forming a typical binucleate cell.
2. Erythrocyte Number, Haemoglobin Content,
Haematocrit
Values, Characteristics of the 'Average
Erythrocyte'
The number of erythrocytes per cu.mm is a much investigated
aspect of chick embryo haematology. One of the first to determine this
value was Ascarelli (1895) who published an uninterrupted series of
data from the 7th day of incubation to the 7th postembryonic day. The
high values given by him for the last third of the incubation period and
the postembryonic period have not been confirmed by subsequent
workers. In many cases there are gaps in the incubation period studied
(Sümegi, 1932, started with day 13 of incubation; Zorn and Dalton,
1937a, b—day 9; Penionschkevitch, 1937, and Ogorodniy, 1939, quoted
by Romanoff, 1960—day 12; Burmester et al., 1941—day 15; Weller
and Schechtman, 1949—day 14 to 16; Sandreuter, 1951—day 10; Hsu
et al., 1952—day 18; Alexander and Schjeide, 1953, and Lemez, 1953,
1955—day 7; Pilipenko, 1957, and Barnes and Jensen, 1959—day 9).
Some workers examined only a few embryos per incubation day. None
of them extended Ascarelli's data to an earlier developmental stage
until Rychter (1955) and Rychter et al. (1955a) covered the entire
incubation period, starting with the 2nd day of incubation (25 somite
stage on average) and extending the study to the 1st day after hatching
(Fig. 2B).