THE BLOOD OF CHICK EMBRYOS
223
Jensen (1959) deviates greatly on the 18th day from all other findings
(Fig. 6B).
From the physiological point of view the blood volume and total
haemoglobin content during development cannot be related to embryo
body weight only, because the membranes contain a substantial part of
the vascularized living matter in the embryonated egg and should
contain an appropriate amount of blood. Complete data on yolk sac
(corrected for ingested yolk) and allantoic weights are given by Byerly
(1932) supplemented for amnion weight by Romanoff (1952). These are
commonly used by investigators, with corrections for embryonic weight,
as a reference weight of extraembryonic living matter in the developing
eggInformation on the distribution of blood between the embryo body
and embryonic membranes was provided by Ramsay (1951) (Fig. 6A—
inset), who estimated the distribution of haem-iron in the embryo and
its membranes between the 8th and the 21st day of incubation. It is
apparent that up to the 14th day more than 50% of the blood is present
in the membranes (including haemopoietic tissue). This contrasts with
Byerly's (1932) measurements showing that the wet weight of the
membranes exceeds that of the embryo body only until the 9th or 10th
day of incubation.
The ratio of blood volume to unit weight of embryo + membranes
(Fig. 6B) was found to decrease by 50% from 19-8 ml/100 g on the 8th
day to 9*9 ml/100 g at hatching when it was still much higher than in the
adult hen (6-3% of the body weight according to Pino et al., 1951, or
6-5% according to Medway and Kare, 1959). We cannot therefore agree,
at least for newborn chicks, with the statement of Korzujev and Galkina
(1957) that the relative amount of blood in newborn chicks, ducks,
turkeys, and pigeons does not exceed that of the adult bird. A decrease
in relative blood volume per unit weight of embryo and placenta during
development was also found in mammalian foetuses (Barcroft, 1946).
In contrast to the blood volume, the relative amount of haemoglobin
per unit weight of embryo + membranes remained fairly constant from
the 8th day onwards, decreasing only by 15% (Rychter et al., 1955a, b)
(Fig. 6B). The relative amount of haemoglobin computed from the data
of Barnes and Jensen (1959) is again extremely high for the 18th day of
incubation.
F. Mitoses in Circulating Blood Cells and their Role in
Primitive Erythrocyte Proliferation
1. Occurrence during Normal
Development
Division of the primitive erythrocytes (Ε I) of chick embryos was
observed and illustrated by Remak (1841, 1858) long before the nature
H
223
Jensen (1959) deviates greatly on the 18th day from all other findings
(Fig. 6B).
From the physiological point of view the blood volume and total
haemoglobin content during development cannot be related to embryo
body weight only, because the membranes contain a substantial part of
the vascularized living matter in the embryonated egg and should
contain an appropriate amount of blood. Complete data on yolk sac
(corrected for ingested yolk) and allantoic weights are given by Byerly
(1932) supplemented for amnion weight by Romanoff (1952). These are
commonly used by investigators, with corrections for embryonic weight,
as a reference weight of extraembryonic living matter in the developing
eggInformation on the distribution of blood between the embryo body
and embryonic membranes was provided by Ramsay (1951) (Fig. 6A—
inset), who estimated the distribution of haem-iron in the embryo and
its membranes between the 8th and the 21st day of incubation. It is
apparent that up to the 14th day more than 50% of the blood is present
in the membranes (including haemopoietic tissue). This contrasts with
Byerly's (1932) measurements showing that the wet weight of the
membranes exceeds that of the embryo body only until the 9th or 10th
day of incubation.
The ratio of blood volume to unit weight of embryo + membranes
(Fig. 6B) was found to decrease by 50% from 19-8 ml/100 g on the 8th
day to 9*9 ml/100 g at hatching when it was still much higher than in the
adult hen (6-3% of the body weight according to Pino et al., 1951, or
6-5% according to Medway and Kare, 1959). We cannot therefore agree,
at least for newborn chicks, with the statement of Korzujev and Galkina
(1957) that the relative amount of blood in newborn chicks, ducks,
turkeys, and pigeons does not exceed that of the adult bird. A decrease
in relative blood volume per unit weight of embryo and placenta during
development was also found in mammalian foetuses (Barcroft, 1946).
In contrast to the blood volume, the relative amount of haemoglobin
per unit weight of embryo + membranes remained fairly constant from
the 8th day onwards, decreasing only by 15% (Rychter et al., 1955a, b)
(Fig. 6B). The relative amount of haemoglobin computed from the data
of Barnes and Jensen (1959) is again extremely high for the 18th day of
incubation.
F. Mitoses in Circulating Blood Cells and their Role in
Primitive Erythrocyte Proliferation
1. Occurrence during Normal
Development
Division of the primitive erythrocytes (Ε I) of chick embryos was
observed and illustrated by Remak (1841, 1858) long before the nature
H