578
E T I E N N E
W O L F F
opment, an embryonic axis possessing a primitive streak, head process,
and mesoblastic plates. He also observed the appearance of small
trophoblastic villi.
Various attempts were made at culture in vitro by Maximow (1925),
Celestino da Costa and Pires Soares (1932), and Waddington and
Waterman (1933). Then Nicholas and Rudnick (1931, 1933) tried
to cultivate in vivo 8-day-old eggs of rat on the membranes of the chick
embryo, using the method of chorioallantoic grafts. In 1934, these same
authors cultivated in vitro eggs removed at the stage of first somite
formation in a medium of heparinized rat plasma to which was added
embryo extract of rat. Within 24-36 h they obtained the development
of an embryonic axis with a nervous system, heart, blood, ocular and
auditory vesicles, and numerous somites. Maximum development was
obtained in 48 h. In 1938, Nicholas succeeded in cultivating the rat egg
in a circulating liquid medium made up of complex and heterologous
mixtures such as: heparinized plasma of rat or cat, plus Tyrode's
solution, plus amniotic fluid of pig. In these conditions, embryonic
survival could be pushed forward to 96 h.
In 1936 and 1938 Jolly and Lieure used a method similar to that of
Nicholas and Rudnick to cultivate guinea-pig and rat eggs in fresh
plasma, rendered incoagulable, to which was added a small quantity
of decidual extract, at a temperature of 38°C for rat and 39°C for
guinea-pig. Out of 196 rat eggs removed at the primitive streak stage
(9-10-day-old embryos), 106 developed, 34 gave rise to an embryonic
axis, 55 to an embryo with a heart beating rhythmically, and 17 to an
embryo with a circulation of blood in the vitelline area. Culture,
continued for 24-48 h, made it possible to allow the embryo to pass
an essential stage of embryogenesis: the stage which corresponds to the
evolution of the primitive streak and the head process; the formation
ofthe chord, the neural axis, the somites, and the tail-bud; the development of the brain, the sense organs and the marrow; the formation of
heart, vessels, blood and haemoglobin; the appearance of vitelline
circulation; and the development of the allantoic and the umbilical
vessels.
By observing embryos in culture, Jolly and Lieure (1938) were able
to describe many points of normal development which could not be
resolved by ordinary histological methods. Thus it was established
that heart-beats precede the establishment of the circulation and that
haemoglobin appears in the red blood corpuscles before this stage.
Jolly especially attempted to resolve by observation and by experiments with eggs in culture problems relating to the circulatory system.
A pertinent question was to know whether, amongst mammals, the
vascular buds ofthe membranes are formed by pressure from the vessels
E T I E N N E
W O L F F
opment, an embryonic axis possessing a primitive streak, head process,
and mesoblastic plates. He also observed the appearance of small
trophoblastic villi.
Various attempts were made at culture in vitro by Maximow (1925),
Celestino da Costa and Pires Soares (1932), and Waddington and
Waterman (1933). Then Nicholas and Rudnick (1931, 1933) tried
to cultivate in vivo 8-day-old eggs of rat on the membranes of the chick
embryo, using the method of chorioallantoic grafts. In 1934, these same
authors cultivated in vitro eggs removed at the stage of first somite
formation in a medium of heparinized rat plasma to which was added
embryo extract of rat. Within 24-36 h they obtained the development
of an embryonic axis with a nervous system, heart, blood, ocular and
auditory vesicles, and numerous somites. Maximum development was
obtained in 48 h. In 1938, Nicholas succeeded in cultivating the rat egg
in a circulating liquid medium made up of complex and heterologous
mixtures such as: heparinized plasma of rat or cat, plus Tyrode's
solution, plus amniotic fluid of pig. In these conditions, embryonic
survival could be pushed forward to 96 h.
In 1936 and 1938 Jolly and Lieure used a method similar to that of
Nicholas and Rudnick to cultivate guinea-pig and rat eggs in fresh
plasma, rendered incoagulable, to which was added a small quantity
of decidual extract, at a temperature of 38°C for rat and 39°C for
guinea-pig. Out of 196 rat eggs removed at the primitive streak stage
(9-10-day-old embryos), 106 developed, 34 gave rise to an embryonic
axis, 55 to an embryo with a heart beating rhythmically, and 17 to an
embryo with a circulation of blood in the vitelline area. Culture,
continued for 24-48 h, made it possible to allow the embryo to pass
an essential stage of embryogenesis: the stage which corresponds to the
evolution of the primitive streak and the head process; the formation
ofthe chord, the neural axis, the somites, and the tail-bud; the development of the brain, the sense organs and the marrow; the formation of
heart, vessels, blood and haemoglobin; the appearance of vitelline
circulation; and the development of the allantoic and the umbilical
vessels.
By observing embryos in culture, Jolly and Lieure (1938) were able
to describe many points of normal development which could not be
resolved by ordinary histological methods. Thus it was established
that heart-beats precede the establishment of the circulation and that
haemoglobin appears in the red blood corpuscles before this stage.
Jolly especially attempted to resolve by observation and by experiments with eggs in culture problems relating to the circulatory system.
A pertinent question was to know whether, amongst mammals, the
vascular buds ofthe membranes are formed by pressure from the vessels