THE BLOOD OF CHICK EMBRYOS
215
MalenSek, 1932; Fennell, 1947, at the 6th; Lemez, 1955, sporadically,
i.e., in less than 7 smears out of 12 per day, on the 4th day, constantly
from the 6th day onwards). Eosinophils, basophils and lymphocytes are
always present in smears from the 14th day onwards (Sugiyama, 1926;
Sandreuter, 1951; Lemez, 1955) though eosinophils were seen sporadically from the 11th day and basophils and lymphocytes from the 12th
day of incubation onwards (Lemez, 1955) (Fig. 4). Reports of their
earlier appearance must be regarded as an error. Monocytes were first
encountered on the 18th day (Sugiyama, 1926; Sandreuter, 1951;
Lemez, 1955), but did not occur constantly until the 20th day. It should
be mentioned that the early lymphocytes and monocytes do not exhibit
all the features of mature cells, so that they were described as prolymphocytes up to the 16th day and the majority as promonocytes until
hatching (Sandreuter, 1951 ; Lemez, 1955).
Though many authors mentioned the presence of leucocytes in chick
embryo blood smears, only Sandreuter (1951) and Lemez (1955)
published a systematic differential count, the former author from the
8th day till hatching, the latter from the 4th day, when neutrophils
were first encountered, until the 1st postembryonic day. From the 15th
day of incubation till the 7th day after hatching the percentages of
neutrophils and lymphocytes are given in the data of Burmester et al.
(1941). Some fragmentary data are given by Sugiyama (1926) and
Fennell (1947). The leucocyte differential count in starling embryos from
the 8th day of incubation is given by Sandreuter (1951).
When the haemocytoblasts are excluded (Section II, A), then the
general trend in the differential count shows very slight change from
the original 100% dominance of the neutrophils until the lymphocytes
begin to appear; these continue to increase in proportion until a week or
more after hatching ; for on the 20th day of incubation the lymphocytes
represent only 10%, but have increased to 25% on the first day after
hatching (Fig. 4). Such high granulocyte counts are typical for chick
embryo blood. Of course, considered in terms of number per cu.mm,
the total number of eosinophils and basophils is much lower, and that of
neutrophils somewhat higher, on the first day after hatching than in the
adult hen (Fig. 4). The repeatedly expressed opinion of Lucas and
Jamroz (1956, 1958) that the circulating blood of chick embryos
normally contains only 2 cell types, erythrocytes and thrombocytes, all
other cell types being held in tissue depots, cannot be accepted.
When every white blood cell line is considered separately, there is an
overall shift towards more mature stages. The degree of neutrophilic and
eosinophilic maturation might be quantitatively estimated, using the
so-called Hynek's number (Hynek, 1909). The sum of the number of
segments (young forms count as zero) encountered in one hundred
215
MalenSek, 1932; Fennell, 1947, at the 6th; Lemez, 1955, sporadically,
i.e., in less than 7 smears out of 12 per day, on the 4th day, constantly
from the 6th day onwards). Eosinophils, basophils and lymphocytes are
always present in smears from the 14th day onwards (Sugiyama, 1926;
Sandreuter, 1951; Lemez, 1955) though eosinophils were seen sporadically from the 11th day and basophils and lymphocytes from the 12th
day of incubation onwards (Lemez, 1955) (Fig. 4). Reports of their
earlier appearance must be regarded as an error. Monocytes were first
encountered on the 18th day (Sugiyama, 1926; Sandreuter, 1951;
Lemez, 1955), but did not occur constantly until the 20th day. It should
be mentioned that the early lymphocytes and monocytes do not exhibit
all the features of mature cells, so that they were described as prolymphocytes up to the 16th day and the majority as promonocytes until
hatching (Sandreuter, 1951 ; Lemez, 1955).
Though many authors mentioned the presence of leucocytes in chick
embryo blood smears, only Sandreuter (1951) and Lemez (1955)
published a systematic differential count, the former author from the
8th day till hatching, the latter from the 4th day, when neutrophils
were first encountered, until the 1st postembryonic day. From the 15th
day of incubation till the 7th day after hatching the percentages of
neutrophils and lymphocytes are given in the data of Burmester et al.
(1941). Some fragmentary data are given by Sugiyama (1926) and
Fennell (1947). The leucocyte differential count in starling embryos from
the 8th day of incubation is given by Sandreuter (1951).
When the haemocytoblasts are excluded (Section II, A), then the
general trend in the differential count shows very slight change from
the original 100% dominance of the neutrophils until the lymphocytes
begin to appear; these continue to increase in proportion until a week or
more after hatching ; for on the 20th day of incubation the lymphocytes
represent only 10%, but have increased to 25% on the first day after
hatching (Fig. 4). Such high granulocyte counts are typical for chick
embryo blood. Of course, considered in terms of number per cu.mm,
the total number of eosinophils and basophils is much lower, and that of
neutrophils somewhat higher, on the first day after hatching than in the
adult hen (Fig. 4). The repeatedly expressed opinion of Lucas and
Jamroz (1956, 1958) that the circulating blood of chick embryos
normally contains only 2 cell types, erythrocytes and thrombocytes, all
other cell types being held in tissue depots, cannot be accepted.
When every white blood cell line is considered separately, there is an
overall shift towards more mature stages. The degree of neutrophilic and
eosinophilic maturation might be quantitatively estimated, using the
so-called Hynek's number (Hynek, 1909). The sum of the number of
segments (young forms count as zero) encountered in one hundred