HISTOCHEMICAL ASPECTS OF
LIMB MORPHOGENESIS IN VERTEBRATES
J. MILAIREf
Laboratoire d
f Anatomie et d
1 Embryologie humaines de la Faculto de Midecine
Universito de Bruxelles, Belgium
I. Introduction
183
II. Experimental Data
184
I I I . Histoehemical and Morphological Data
185
A. Methods
186
B. Observations
186
IV. Conclusions
204
References
208
I. Introduction
Our knowledge of the morphogenetic processes involved in the development of limbs of tetrapod vertebrates has considerably increased
during the last twenty years, chiefly as the result of great advances in
experimental embryology. Hamburger (1938) was the first embryologist
to apply microsurgical techniques to the limb buds of chick embryos,
and he found that the axial relationships of a limb bud are already
established from the stage of 25 somites onwards. He also studied the
development of nerveless limb buds and found that nervous connections
are not essential for normal growth (Hamburger, 1939). But an important question still remained unanswered: what are the relative roles of
the mesoderm and the ectoderm in the development of a limb? During
the last thirteen years much work has been done on the chick embryo,
and to a lesser extent on the urodele embryo, to find a solution to this
problem. It is now generally accepted that the development of the limb,
especially the genesis of each of its skeletal segments, depends on the
interactions between the mesoderm and a thickened zone of the marginal ectoderm, the apical ectodermal ridge. The experimental data on
limb morphogenesis have been exhaustively reviewed by Zwilling (1961),
who has also attempted to estimate to what extent the data support the
hypothesis mentioned above.
However, nothing was done about the histoehemical aspects of limb
f Fellow of the National Foundation for Scientifical Research of Belgium
183
LIMB MORPHOGENESIS IN VERTEBRATES
J. MILAIREf
Laboratoire d
f Anatomie et d
1 Embryologie humaines de la Faculto de Midecine
Universito de Bruxelles, Belgium
I. Introduction
183
II. Experimental Data
184
I I I . Histoehemical and Morphological Data
185
A. Methods
186
B. Observations
186
IV. Conclusions
204
References
208
I. Introduction
Our knowledge of the morphogenetic processes involved in the development of limbs of tetrapod vertebrates has considerably increased
during the last twenty years, chiefly as the result of great advances in
experimental embryology. Hamburger (1938) was the first embryologist
to apply microsurgical techniques to the limb buds of chick embryos,
and he found that the axial relationships of a limb bud are already
established from the stage of 25 somites onwards. He also studied the
development of nerveless limb buds and found that nervous connections
are not essential for normal growth (Hamburger, 1939). But an important question still remained unanswered: what are the relative roles of
the mesoderm and the ectoderm in the development of a limb? During
the last thirteen years much work has been done on the chick embryo,
and to a lesser extent on the urodele embryo, to find a solution to this
problem. It is now generally accepted that the development of the limb,
especially the genesis of each of its skeletal segments, depends on the
interactions between the mesoderm and a thickened zone of the marginal ectoderm, the apical ectodermal ridge. The experimental data on
limb morphogenesis have been exhaustively reviewed by Zwilling (1961),
who has also attempted to estimate to what extent the data support the
hypothesis mentioned above.
However, nothing was done about the histoehemical aspects of limb
f Fellow of the National Foundation for Scientifical Research of Belgium
183