532
E T I E N N E W O L F F
study. The development of blastomeres isolated at the first stages of
segmentation could be considered within the province of this study,
but we shall refer only to those stages in which cells, grouped together as
coherent tissues, can be placed in special surroundings in order to
survive and develop.
What is the advantage of culturing an embryo in vitro? Such a culture
tries to provide the food requirements which in nature are supplied by
the maternal uterus of viviparous animals or the yolk of oviparous or
ovoviviparous animals. First it makes possible an analysis of nutritional
factors and, secondly, culture in vitro of whole embryos facilitates experiments of many types which it would be difficult or even impossible
to perform in the natural conditions of development. Such is the case
with all work on the embryos of Mammalia, and with certain experiments on the blastoderms of birds. Thus, much research on the embryogenesis of higher vertebrates has now been carried out by methods
similar to those which had already yielded so many results when used
on amphibian eggs.
I. C U L T U R E OF A M P H I B I A N E M B R Y O N I C A N L A G E
We shall first look at the results of culture of tissues from amphibian
embryos. This method has been frequently employed recently, in
conjunction with experiments on the whole embryo, in order to solve
problems of early development, with special reference to the nature
of inducing substances.
A. C U L T U R E S IN VIVO A N D IN
VITRO
Several authors (Diirken, 1926; Kusche, 1929; Bautzmann, 1929;
Holtfreter, 1929) tried, first of all, to study the potentialities of organ
rudiments by explanting them in vivo into a favourable milieu such as a
cavity in the body of the larva or the adult, e.g. the anterior chamber
of the eye, the peritoneal cavity, or the lymphatic spaces ofthe tadpole.
Unfortunately these surroundings are not without influence on the
differentiation of tissues, as has been shown by further research with
culture in vitro. Therefore, no valid conclusions could be drawn from
these investigations regarding the inherent potentialities of the organ
anlage isolated from the organism.
Holtfreter (1931) took a decisive step forward when he perfected a
medium which allowed the survival and differentiation in vitro of the
anlage of the gastrula of Triton. This medium, universally known as
Holtfreter's solution, is now widely used for investigations into the
E T I E N N E W O L F F
study. The development of blastomeres isolated at the first stages of
segmentation could be considered within the province of this study,
but we shall refer only to those stages in which cells, grouped together as
coherent tissues, can be placed in special surroundings in order to
survive and develop.
What is the advantage of culturing an embryo in vitro? Such a culture
tries to provide the food requirements which in nature are supplied by
the maternal uterus of viviparous animals or the yolk of oviparous or
ovoviviparous animals. First it makes possible an analysis of nutritional
factors and, secondly, culture in vitro of whole embryos facilitates experiments of many types which it would be difficult or even impossible
to perform in the natural conditions of development. Such is the case
with all work on the embryos of Mammalia, and with certain experiments on the blastoderms of birds. Thus, much research on the embryogenesis of higher vertebrates has now been carried out by methods
similar to those which had already yielded so many results when used
on amphibian eggs.
I. C U L T U R E OF A M P H I B I A N E M B R Y O N I C A N L A G E
We shall first look at the results of culture of tissues from amphibian
embryos. This method has been frequently employed recently, in
conjunction with experiments on the whole embryo, in order to solve
problems of early development, with special reference to the nature
of inducing substances.
A. C U L T U R E S IN VIVO A N D IN
VITRO
Several authors (Diirken, 1926; Kusche, 1929; Bautzmann, 1929;
Holtfreter, 1929) tried, first of all, to study the potentialities of organ
rudiments by explanting them in vivo into a favourable milieu such as a
cavity in the body of the larva or the adult, e.g. the anterior chamber
of the eye, the peritoneal cavity, or the lymphatic spaces ofthe tadpole.
Unfortunately these surroundings are not without influence on the
differentiation of tissues, as has been shown by further research with
culture in vitro. Therefore, no valid conclusions could be drawn from
these investigations regarding the inherent potentialities of the organ
anlage isolated from the organism.
Holtfreter (1931) took a decisive step forward when he perfected a
medium which allowed the survival and differentiation in vitro of the
anlage of the gastrula of Triton. This medium, universally known as
Holtfreter's solution, is now widely used for investigations into the