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GOSS
of bones grafted to irradiated limbs. Transplanted humeri cause limblike outgrowths, tail vertebrae produce tail regenerates, and mandibles
do not promote regeneration (Trampusch, 1958a).
The paradox arising from the facts that skeletal regeneration occurs
not only in the absence of old bones in the limb, but also as a result of
influences emanating from accessory bones implanted into the stump,
must be resolved on the basis of two complementary hypotheses. Limb
regenerates can, in the course of their development, regulate for the
absence of skeletal parts in the stump, but not for the presence of excess
structures. Unable to resist whatever influences are exerted by extra
bones, the blastema does not, under these conditions, develop normally,
since it possesses supernumerary skeletal parts. In view of these data, it
can only be concluded that bone does, indeed, participate in the
induction of regenerated skeletal tissues, but that other limb tissues, in
the absence of bone, can likewise effect skeletal regeneration. This kind
of double assurance accounts for the regulation attending deficiencies in
the regenerating limb and its lack in the presence of superabundant
structures.
3. Muscle
Numerous experiments have been directed toward the effects of
musculature on the development of the regenerate. Transplantation of
muscle from the hand or lower limb to proximal segments of extremities
from which the muscle had previously been removed, gives rise to
regenerates commensurate with the source of the muscle (Woronzowa,
1937a). Ichikawa and Okada (1954) substituted thigh muscle for that of
the upper arm and claimed that 20 such arms regenerated hind limbs
and 34 gave rise to forelimbs. However, since the criterion for diagnosing
the kind of extremity produced was the number of digits, which tends
to be variable even in normal regenerates, these results cannot be
considered entirely valid. Thigh musculature transplanted to the lower
segments of hind limbs has been shown by Savchuk (1938) to regenerate
extremities with both upper and lower segments. Replacement of inner
tissues of the thigh by shoulder musculature results in the regeneration
of shoulder girdle skeleton in the foreign location (Woronzowa, 1938).
However, when body musculature is added to limbs, Woronzowa (1937b)
reported the regeneration of a normal or slightly atypical limb, indicating
little or no morphogenetic effects by muscles from nonregenerating
regions of the body. Umanski (1938b) substituted dorsal musculature
for the hind limb mesoderm and obtained either no regeneration, or the
production only of fin-like structures.
Other experiments have involved the transplantation of tail muscles
to limbs and observations of the effects on the morphogenesis of sub-
R. J.
GOSS
of bones grafted to irradiated limbs. Transplanted humeri cause limblike outgrowths, tail vertebrae produce tail regenerates, and mandibles
do not promote regeneration (Trampusch, 1958a).
The paradox arising from the facts that skeletal regeneration occurs
not only in the absence of old bones in the limb, but also as a result of
influences emanating from accessory bones implanted into the stump,
must be resolved on the basis of two complementary hypotheses. Limb
regenerates can, in the course of their development, regulate for the
absence of skeletal parts in the stump, but not for the presence of excess
structures. Unable to resist whatever influences are exerted by extra
bones, the blastema does not, under these conditions, develop normally,
since it possesses supernumerary skeletal parts. In view of these data, it
can only be concluded that bone does, indeed, participate in the
induction of regenerated skeletal tissues, but that other limb tissues, in
the absence of bone, can likewise effect skeletal regeneration. This kind
of double assurance accounts for the regulation attending deficiencies in
the regenerating limb and its lack in the presence of superabundant
structures.
3. Muscle
Numerous experiments have been directed toward the effects of
musculature on the development of the regenerate. Transplantation of
muscle from the hand or lower limb to proximal segments of extremities
from which the muscle had previously been removed, gives rise to
regenerates commensurate with the source of the muscle (Woronzowa,
1937a). Ichikawa and Okada (1954) substituted thigh muscle for that of
the upper arm and claimed that 20 such arms regenerated hind limbs
and 34 gave rise to forelimbs. However, since the criterion for diagnosing
the kind of extremity produced was the number of digits, which tends
to be variable even in normal regenerates, these results cannot be
considered entirely valid. Thigh musculature transplanted to the lower
segments of hind limbs has been shown by Savchuk (1938) to regenerate
extremities with both upper and lower segments. Replacement of inner
tissues of the thigh by shoulder musculature results in the regeneration
of shoulder girdle skeleton in the foreign location (Woronzowa, 1938).
However, when body musculature is added to limbs, Woronzowa (1937b)
reported the regeneration of a normal or slightly atypical limb, indicating
little or no morphogenetic effects by muscles from nonregenerating
regions of the body. Umanski (1938b) substituted dorsal musculature
for the hind limb mesoderm and obtained either no regeneration, or the
production only of fin-like structures.
Other experiments have involved the transplantation of tail muscles
to limbs and observations of the effects on the morphogenesis of sub-