THE BLOOD OF CHICK EMBRYOS
221
very numerous in precirculatory stages; they cannot be regarded as
phagocytic cells.
The last 'formed' component consists of the pericellular filaments or
haematexodies, studied in supravital blood preparations from 60-70hour-old embryos under phase contrast microscope by Borghese et al.
(1954a, b). These filaments, surrounding primitive red blood cells and
showing quick movements and changes, are regarded as extensions of
the cytoplasm of the red cells. Haematexodies appear to a greater
extent under less favourable conditions of explantation in vitro.
Filamentous threads resembling the haematexodies described by these
authors are sometimes seen near badly damaged cells in blood smears.
The so called 'degenerate cells' were mentioned in the sub-section on
thrombocytes (Section II, B).
E. Total Blood Volume and Related Values throughout the Incubation Period
In recent years three attempts have been made to determine the
circulating blood volume in chick embryos (Fig. 6A). Yosphe-Purer
et al. (1953), using a dye-dilution method to determine plasma volume
and haematocrit values for packed blood corpuscle volume, found much
higher plasma volume values for the incubation period studied (11th18th day) than did Rychter et al. (1955a, b) who used the same method
from the 2nd day of incubation till the 1st postembryonic day. The
circulating blood volume was found to rise from 9-3 cu.mm on the 2nd
day to a maximum of 2870 cu.mm on the 18th day, decreasing slightly
thereafter, most probably because the circulation ceases in the embryonic
membranes, especially in the allantois, coinciding with the beginning of
air breathing between the 18th and 19th day of incubation. The chick
thus became the first vertebrate embryo in which the development of
the blood volume was estimated throughout the entire prenatal period.
The data of Barnes and Jensen (1959) employing radioactively labelled
erythrocytes on day 9, 12, 15 and 18 of incubation lie between the data
of the other two groups (Fig. 6A).
The total amount of haemoglobin in circulation could be calculated
when blood volume and haemoglobin content of the blood were simultaneously determined (Rychter et al., 1955a; Barnes and Jensen, 1959).
The increase in total haemoglobin (Fig. 6B) is slow up to the 10th day,
but thereafter it increases rapidly reaching a maximum of 221 mg on the
18th day. These values (Rychter et al., 1955a) correspond nearly
perfectly with Ramsay's (1950) measurements of haem-iron content of
the embryonated hen's egg from the 8th day till hatching and with
Sch0nheyder's (1938) data for 2-day-old chicks. The three values given
by Sendju (1927) for the 7th, 14th and 18th day of incubation are much
lower. The total haemoglobin content calculated from Barnes and
221
very numerous in precirculatory stages; they cannot be regarded as
phagocytic cells.
The last 'formed' component consists of the pericellular filaments or
haematexodies, studied in supravital blood preparations from 60-70hour-old embryos under phase contrast microscope by Borghese et al.
(1954a, b). These filaments, surrounding primitive red blood cells and
showing quick movements and changes, are regarded as extensions of
the cytoplasm of the red cells. Haematexodies appear to a greater
extent under less favourable conditions of explantation in vitro.
Filamentous threads resembling the haematexodies described by these
authors are sometimes seen near badly damaged cells in blood smears.
The so called 'degenerate cells' were mentioned in the sub-section on
thrombocytes (Section II, B).
E. Total Blood Volume and Related Values throughout the Incubation Period
In recent years three attempts have been made to determine the
circulating blood volume in chick embryos (Fig. 6A). Yosphe-Purer
et al. (1953), using a dye-dilution method to determine plasma volume
and haematocrit values for packed blood corpuscle volume, found much
higher plasma volume values for the incubation period studied (11th18th day) than did Rychter et al. (1955a, b) who used the same method
from the 2nd day of incubation till the 1st postembryonic day. The
circulating blood volume was found to rise from 9-3 cu.mm on the 2nd
day to a maximum of 2870 cu.mm on the 18th day, decreasing slightly
thereafter, most probably because the circulation ceases in the embryonic
membranes, especially in the allantois, coinciding with the beginning of
air breathing between the 18th and 19th day of incubation. The chick
thus became the first vertebrate embryo in which the development of
the blood volume was estimated throughout the entire prenatal period.
The data of Barnes and Jensen (1959) employing radioactively labelled
erythrocytes on day 9, 12, 15 and 18 of incubation lie between the data
of the other two groups (Fig. 6A).
The total amount of haemoglobin in circulation could be calculated
when blood volume and haemoglobin content of the blood were simultaneously determined (Rychter et al., 1955a; Barnes and Jensen, 1959).
The increase in total haemoglobin (Fig. 6B) is slow up to the 10th day,
but thereafter it increases rapidly reaching a maximum of 221 mg on the
18th day. These values (Rychter et al., 1955a) correspond nearly
perfectly with Ramsay's (1950) measurements of haem-iron content of
the embryonated hen's egg from the 8th day till hatching and with
Sch0nheyder's (1938) data for 2-day-old chicks. The three values given
by Sendju (1927) for the 7th, 14th and 18th day of incubation are much
lower. The total haemoglobin content calculated from Barnes and