208
J. M I L A I R E
development is assumed by different and successively more restricted
ectodermal areas as the limb bud grows. The whole ventral ectoderm is
first involved in promoting mesodermal proliferation in its proximal part
and inducing regional mesodermal properties in its distal part. These
two different ectodermal properties later become confined to two more
restricted areas: the former in the proximo-axillary zone, the latter in
the whole cephalo-caudal length of the marginal ectoderm. While the
proximal zone continues for some time to stimulate the differentiation
of mesoderm in the limb bud stump, the a.e.r. differentiates in the
marginal ectoderm and induces the presumptive autopodium.
As in many other embryonic structures, the formation of limbs is
governed by reciprocal inductive mechanisms: the mesoderm provides
its ectodermal covering with special inductive properties and then itself
becomes subjected to the new ectodermal influence. Such a mechanism
was reported for the first time by Bodenstein (1952) in the formation of
the dorsal fin in amphibian larvae. It was later demonstrated in the
development of several structures which form from mesodermal and
ectodermal components during late stages of embryonic development—
metanephros and sub-maxillary gland in the mouse embryo (Grobstein,
1953, 1955) and the early rudiments of the feathers in the chick embryo
(Sengel, 1957). In its main modalities, the development of limbs is thus
in complete agreement with the modern conceptions of organogenesis,
and, moreover, it may be regarded as one of the best examples of how
two embryonic anlagen, initially provided with poor morphogenetic
properties, come to form a remarkably specialized organ by exerting
on each other a series of subtle reciprocal interactions.
References
Amprino, R. and Camosso, M. (1955). C. R. Ass. Anat. 42, 197-203.
Amprino, R. and Camosso, M. (1959). Arch. Anat. micr. Morph. exp. 48, 261-305.
Balinsky, B. I. (1931). Roux Arch. EntwMech. Organ. 123, 565-648.
Bell, E., Kaighn, M. E. and Fessenden, L. M. (1959). Bevel. Biol. 1, 101-124.
Bodenstein, D. (1952). J. exp. Zool. 120, 213-247.
Braus, H. (1906). In 'Handbuch der Entwicklungslehre der Wirbeltiere von
O.Hertwig'3, 166-338.
Chaube, S. (1959). J. exp. Zool. 140, 29-77.
Coming, H. K. (1899). Morph. J. 28, 28-104.
Dalcq, A. (1956). G. R. Ass. Anat. 43, 254-258.
Filatow, D. (1928). Roux Arch. EntwMech. Organ. 113, 240-244.
Forsthoefel, P. F. (1959). J. Morph. 104, 89-142.
Grobstein, C. (1953). Science 118, 52-55.
Grobstein, C. (1955). J. exp. Zool. 130, 319-340.
Hamburger, V. (1938). J. exp. Zool. 77, 379-400.
Hamburger, V. (1939). J. exp. Zool. 80, 347-385.
J. M I L A I R E
development is assumed by different and successively more restricted
ectodermal areas as the limb bud grows. The whole ventral ectoderm is
first involved in promoting mesodermal proliferation in its proximal part
and inducing regional mesodermal properties in its distal part. These
two different ectodermal properties later become confined to two more
restricted areas: the former in the proximo-axillary zone, the latter in
the whole cephalo-caudal length of the marginal ectoderm. While the
proximal zone continues for some time to stimulate the differentiation
of mesoderm in the limb bud stump, the a.e.r. differentiates in the
marginal ectoderm and induces the presumptive autopodium.
As in many other embryonic structures, the formation of limbs is
governed by reciprocal inductive mechanisms: the mesoderm provides
its ectodermal covering with special inductive properties and then itself
becomes subjected to the new ectodermal influence. Such a mechanism
was reported for the first time by Bodenstein (1952) in the formation of
the dorsal fin in amphibian larvae. It was later demonstrated in the
development of several structures which form from mesodermal and
ectodermal components during late stages of embryonic development—
metanephros and sub-maxillary gland in the mouse embryo (Grobstein,
1953, 1955) and the early rudiments of the feathers in the chick embryo
(Sengel, 1957). In its main modalities, the development of limbs is thus
in complete agreement with the modern conceptions of organogenesis,
and, moreover, it may be regarded as one of the best examples of how
two embryonic anlagen, initially provided with poor morphogenetic
properties, come to form a remarkably specialized organ by exerting
on each other a series of subtle reciprocal interactions.
References
Amprino, R. and Camosso, M. (1955). C. R. Ass. Anat. 42, 197-203.
Amprino, R. and Camosso, M. (1959). Arch. Anat. micr. Morph. exp. 48, 261-305.
Balinsky, B. I. (1931). Roux Arch. EntwMech. Organ. 123, 565-648.
Bell, E., Kaighn, M. E. and Fessenden, L. M. (1959). Bevel. Biol. 1, 101-124.
Bodenstein, D. (1952). J. exp. Zool. 120, 213-247.
Braus, H. (1906). In 'Handbuch der Entwicklungslehre der Wirbeltiere von
O.Hertwig'3, 166-338.
Chaube, S. (1959). J. exp. Zool. 140, 29-77.
Coming, H. K. (1899). Morph. J. 28, 28-104.
Dalcq, A. (1956). G. R. Ass. Anat. 43, 254-258.
Filatow, D. (1928). Roux Arch. EntwMech. Organ. 113, 240-244.
Forsthoefel, P. F. (1959). J. Morph. 104, 89-142.
Grobstein, C. (1953). Science 118, 52-55.
Grobstein, C. (1955). J. exp. Zool. 130, 319-340.
Hamburger, V. (1938). J. exp. Zool. 77, 379-400.
Hamburger, V. (1939). J. exp. Zool. 80, 347-385.