THE BLOOD OF CHICK EMBRYOS
237
in the localization of erythrocyte-forming areas in the early chick
blastoderm based on in vitro cultivation ranging from the beginning of
incubation to 9 somite stages. He summarized in 11 successive diagrams
the localization of regions of potential haemopoiesis in the blastoderm
from the late prestreak to the 4-6 somite stages. Establishment of
haemoglobin-forming potentiality occurs before the appearance of the
embryonic shield in the preprimitive streak blastoderm and is relatively
uninfluenced by the course of the subsequent movement of the tissue
through the primitive streak to its definitive site.
2. Autodifferentiation
of Various Gell Types
Sabin (1921) studied chick blastoderms in vitro. The endothelial cells
during the 2nd day gave rise to red blood cells, while during the 3rd
day they gave rise to monocytes intravascularly and to histiocytes
(macrophages, clasmatocytes) extravascularly. On the 3rd day also, the
granulocytes (neutrophils) developed extravascularly from mesenchymal
cells. Silberberg and Orzechowski (1928) found in young explanted
blastoderms on the 2nd day of incubation the formation of histiocytes
(macrophages) which, however, were not considered to be true blood
cells. Cells appearing on the 5th day, called lymphocytes, are, according
to the illustration, undoubtedly definitive basophilic erythroblasts
(Ε II). Murray (1932) cultivated, for up to 4 days in vitro, fragments of
blastoderms from the well-developed primitive streak stage to the
advanced head process and head fold but pre-somite stage. He observed
primitive erythrocytes and their various immature forms including
proerythroblasts or haemocytoblasts (large lymphocytes, which Murray
does not identify with the true lymphocytes occurring later). Various
types of degeneration of red cells were also observed, especially
vacuolization of the cytoplasm. A great many phagocytosing histiocytes
were present, as well as some endodermal cells. Young eosinophils (i.e.,
neutrophils) were found with certainty in one culture and probably in
three others. No lymphocytes and thrombocytes were observed, though
they were looked for. So far the study presents the most thorough
analysis of autodifferentiation of various chick embryo blood corpuscles
in vitro. The eventual self-differentiation of definitive erythrocytes was
not followed. Further experiments using various media to elucidate the
problem of self-differentiation of white blood corpuscles were unsuccessful (Murray, 1933).
More highly differentiated haemopoietic organs, such as spleen and
bone marrow (Thomson, 1914; Delorenzi, 1935), spleen (Rioch, 1923;
Fazzari, 1926 ; Fischer and Dolschansky, 1929) have also been studied in
tissue cultures. Katzenstein (1925) observed development of blood
237
in the localization of erythrocyte-forming areas in the early chick
blastoderm based on in vitro cultivation ranging from the beginning of
incubation to 9 somite stages. He summarized in 11 successive diagrams
the localization of regions of potential haemopoiesis in the blastoderm
from the late prestreak to the 4-6 somite stages. Establishment of
haemoglobin-forming potentiality occurs before the appearance of the
embryonic shield in the preprimitive streak blastoderm and is relatively
uninfluenced by the course of the subsequent movement of the tissue
through the primitive streak to its definitive site.
2. Autodifferentiation
of Various Gell Types
Sabin (1921) studied chick blastoderms in vitro. The endothelial cells
during the 2nd day gave rise to red blood cells, while during the 3rd
day they gave rise to monocytes intravascularly and to histiocytes
(macrophages, clasmatocytes) extravascularly. On the 3rd day also, the
granulocytes (neutrophils) developed extravascularly from mesenchymal
cells. Silberberg and Orzechowski (1928) found in young explanted
blastoderms on the 2nd day of incubation the formation of histiocytes
(macrophages) which, however, were not considered to be true blood
cells. Cells appearing on the 5th day, called lymphocytes, are, according
to the illustration, undoubtedly definitive basophilic erythroblasts
(Ε II). Murray (1932) cultivated, for up to 4 days in vitro, fragments of
blastoderms from the well-developed primitive streak stage to the
advanced head process and head fold but pre-somite stage. He observed
primitive erythrocytes and their various immature forms including
proerythroblasts or haemocytoblasts (large lymphocytes, which Murray
does not identify with the true lymphocytes occurring later). Various
types of degeneration of red cells were also observed, especially
vacuolization of the cytoplasm. A great many phagocytosing histiocytes
were present, as well as some endodermal cells. Young eosinophils (i.e.,
neutrophils) were found with certainty in one culture and probably in
three others. No lymphocytes and thrombocytes were observed, though
they were looked for. So far the study presents the most thorough
analysis of autodifferentiation of various chick embryo blood corpuscles
in vitro. The eventual self-differentiation of definitive erythrocytes was
not followed. Further experiments using various media to elucidate the
problem of self-differentiation of white blood corpuscles were unsuccessful (Murray, 1933).
More highly differentiated haemopoietic organs, such as spleen and
bone marrow (Thomson, 1914; Delorenzi, 1935), spleen (Rioch, 1923;
Fazzari, 1926 ; Fischer and Dolschansky, 1929) have also been studied in
tissue cultures. Katzenstein (1925) observed development of blood