236
LEO LEME2
present on the 1st postembryonic day are replaced in about 7 to 9
days by new, postembryonically produced erythrocytes.
III. Autodifferentiation of Embryonic Blood-forming Tissues
Chick embryo blood corpuscles and blood-forming tissues have been
explanted or cultivated in vitro by many authors. The blood or whole
blastoderm has been kept in vitro for up to 24 hours in an 'acute' expiant
under conditions of mere survival and has been examined in recent years
by phase contrast microscopy or microcinematography in order to
extend observations done on blood smears and to trace various cytological processes like mitosis, cellular movements, etc. (Sabin, 1920,
1928; Sugiyama, 1926; Muller, 1930; Dawson, 1936; Fennell, 1947;
O'Connor, 1951; Perri et al., 1951a, b, c, 1953; Borghese et al., 1954a, b,
1955; Rondanelli et al., 1955a, b, 1956, 1957; Rondanelli and Strosselli,
1957). Results have been reviewed in the previous section. Borghese
et al. (1954b) have described various degenerative changes in 60 to 70hour-old primitive red blood cells due to explantation up to 24 hours.
A. Autodifferentiation in vitro
Tissue cultures in vitro were made of the early blastoderm before the
appearance of the first blood islands in order to analyse its blood-forming
potential (in most cases that of red blood cells) (Shipley, 1916; Tagaki,
1931; Murray, 1932; Rudnick, 1938a, b; Settle, 1949, 1954). Sabin
(1921), Silberberg and Orzechowski (1928), Murray (1932, 1933), and
Rudnick (1952) also studied the autodifferentiation of blood cells other
than the erythrocytes.
1. Prospective Erythrocyte-forming
Areas
Shipley (1916) cultivated for 3-4 days the area opaca from 18-hourold blastoderms and obtained differentiation of erythrocytes from
amoeboid cells. The erythrocytes were, however, muchsmaller, spherical,
and only 4 μ in diameter. Degenerative changes, pycnoses, and nuclear
fragmentation were abundant. Murray (1932) showed that erythrocytes
may be formed from any part of the posterior three-quarters of the
primitive streak. Rudnick (1938a, b) cultivated for 2-6 days in vitro
V-shaped pieces of blastoderms with short primitive streaks, and transverse strips (fourths or fifths) of definitive primitive streak and headprocess blastoderms. She found that the part of the blastoderm
containing the posterior half of the streak in all instances produces large
masses of erythroblasts. It was evident that the prospective area
involved in blood formation was migrating towards the streak to be
invaginated. Settle (1949, 1954) published a detailed study on changes
LEO LEME2
present on the 1st postembryonic day are replaced in about 7 to 9
days by new, postembryonically produced erythrocytes.
III. Autodifferentiation of Embryonic Blood-forming Tissues
Chick embryo blood corpuscles and blood-forming tissues have been
explanted or cultivated in vitro by many authors. The blood or whole
blastoderm has been kept in vitro for up to 24 hours in an 'acute' expiant
under conditions of mere survival and has been examined in recent years
by phase contrast microscopy or microcinematography in order to
extend observations done on blood smears and to trace various cytological processes like mitosis, cellular movements, etc. (Sabin, 1920,
1928; Sugiyama, 1926; Muller, 1930; Dawson, 1936; Fennell, 1947;
O'Connor, 1951; Perri et al., 1951a, b, c, 1953; Borghese et al., 1954a, b,
1955; Rondanelli et al., 1955a, b, 1956, 1957; Rondanelli and Strosselli,
1957). Results have been reviewed in the previous section. Borghese
et al. (1954b) have described various degenerative changes in 60 to 70hour-old primitive red blood cells due to explantation up to 24 hours.
A. Autodifferentiation in vitro
Tissue cultures in vitro were made of the early blastoderm before the
appearance of the first blood islands in order to analyse its blood-forming
potential (in most cases that of red blood cells) (Shipley, 1916; Tagaki,
1931; Murray, 1932; Rudnick, 1938a, b; Settle, 1949, 1954). Sabin
(1921), Silberberg and Orzechowski (1928), Murray (1932, 1933), and
Rudnick (1952) also studied the autodifferentiation of blood cells other
than the erythrocytes.
1. Prospective Erythrocyte-forming
Areas
Shipley (1916) cultivated for 3-4 days the area opaca from 18-hourold blastoderms and obtained differentiation of erythrocytes from
amoeboid cells. The erythrocytes were, however, muchsmaller, spherical,
and only 4 μ in diameter. Degenerative changes, pycnoses, and nuclear
fragmentation were abundant. Murray (1932) showed that erythrocytes
may be formed from any part of the posterior three-quarters of the
primitive streak. Rudnick (1938a, b) cultivated for 2-6 days in vitro
V-shaped pieces of blastoderms with short primitive streaks, and transverse strips (fourths or fifths) of definitive primitive streak and headprocess blastoderms. She found that the part of the blastoderm
containing the posterior half of the streak in all instances produces large
masses of erythroblasts. It was evident that the prospective area
involved in blood formation was migrating towards the streak to be
invaginated. Settle (1949, 1954) published a detailed study on changes