III.
REGENERATION OF VERTEBRATE APPENDAGES
127
The converse technique, namely, the transplantation of skinless limbs
to other regions of the body, accomplished essentially the same purpose
and has yielded much the same results as the above experiments,
although the incidence of regeneration under these circumstances was
generally less. Skinless hind limbs transplanted to the sides of animals
where their stumps healed with skin from that region, proved to be
capable of regenerating limbs (Ginzburg, 1947, 1952; Umanski and
Kudokotzev, 1949). When placed on the back, such transplants also
produced limb regenerates (Ginzburg, 1947). Limbs similarly grafted to
the head region likewise regenerated new extremities in many instances
(Ginzburg, 1947, 1948; Umanski and Kudokotzev, 1949). However, the
results were not so consistent when skinless limbs were transplanted to
tails. Although such implants yielded only limb regenerates in experiments on the axolotl (Belkin, 1934c, 1934d; Korobova, 1947; Umanski
and Kudokotzev, 1951), similar investigations on Rana temporaria
tadpoles by Ginzburg (1947) and Triturus cristatus by Umanski and
Kudokotzev (1951) resulted in the regeneration of limbs, tails, or taillimb chimerae. Indeed, Korobova (1947) obtained tail regenerates
exclusively when skinless T. cristatus limbs were grafted to tails, and
normally nonregenerating hind limbs of anuran tadpoles were observed
to stimulate the regeneration of accessory fin-like structures under the
same conditions (Polezhaev and Ginzburg, 1939; Polezhaev, 1947).
With the exception of the last group of experiments in which legs
transplanted to tails stimulated the regeneration of tail-like structures,
probably formed largely from tail mesoderm in the vicinity, the foregoing results reveal that limbs are able to regenerate normally despite
the participation of foreign skin. Collectively interpreted, this evidence
indicates that the epidermis, although necessary to promote regeneration, does not exert a morphogenetic effect on the developing regenerate.
Further elucidation of this problem has resulted from the combination of skin transplantation and selective irradiation techniques. When
the skin of X-rayed limbs was replaced by unirradiated limb skin,
the regeneration of limbs, frequently possessing less than the normal
number of digits, usually occurred (Umanski, 1937, 1939, 1946;
Umanski and Basina, 1948; Umanski, Tkatsch and Kudokotzev, 1951;
Pukhalskaia, 1940a, b; Sidorova, 1949; Trampusch, 1951, 1958a).
Unirradiated tail skin grafted to X-rayed hind limbs brought about the
regeneration of tails (Trampusch, 1958a). Experiments by Umanski
(1946) in which unirradiated tail skin was transplanted to X-rayed tails,
resulted in the development of tail regenerates. Also working on tails,
Luther (1948) and Trampusch (1958b), obtained no regeneration from
X-rayed tails whose skin had been replaced by body skin, but irradi-
REGENERATION OF VERTEBRATE APPENDAGES
127
The converse technique, namely, the transplantation of skinless limbs
to other regions of the body, accomplished essentially the same purpose
and has yielded much the same results as the above experiments,
although the incidence of regeneration under these circumstances was
generally less. Skinless hind limbs transplanted to the sides of animals
where their stumps healed with skin from that region, proved to be
capable of regenerating limbs (Ginzburg, 1947, 1952; Umanski and
Kudokotzev, 1949). When placed on the back, such transplants also
produced limb regenerates (Ginzburg, 1947). Limbs similarly grafted to
the head region likewise regenerated new extremities in many instances
(Ginzburg, 1947, 1948; Umanski and Kudokotzev, 1949). However, the
results were not so consistent when skinless limbs were transplanted to
tails. Although such implants yielded only limb regenerates in experiments on the axolotl (Belkin, 1934c, 1934d; Korobova, 1947; Umanski
and Kudokotzev, 1951), similar investigations on Rana temporaria
tadpoles by Ginzburg (1947) and Triturus cristatus by Umanski and
Kudokotzev (1951) resulted in the regeneration of limbs, tails, or taillimb chimerae. Indeed, Korobova (1947) obtained tail regenerates
exclusively when skinless T. cristatus limbs were grafted to tails, and
normally nonregenerating hind limbs of anuran tadpoles were observed
to stimulate the regeneration of accessory fin-like structures under the
same conditions (Polezhaev and Ginzburg, 1939; Polezhaev, 1947).
With the exception of the last group of experiments in which legs
transplanted to tails stimulated the regeneration of tail-like structures,
probably formed largely from tail mesoderm in the vicinity, the foregoing results reveal that limbs are able to regenerate normally despite
the participation of foreign skin. Collectively interpreted, this evidence
indicates that the epidermis, although necessary to promote regeneration, does not exert a morphogenetic effect on the developing regenerate.
Further elucidation of this problem has resulted from the combination of skin transplantation and selective irradiation techniques. When
the skin of X-rayed limbs was replaced by unirradiated limb skin,
the regeneration of limbs, frequently possessing less than the normal
number of digits, usually occurred (Umanski, 1937, 1939, 1946;
Umanski and Basina, 1948; Umanski, Tkatsch and Kudokotzev, 1951;
Pukhalskaia, 1940a, b; Sidorova, 1949; Trampusch, 1951, 1958a).
Unirradiated tail skin grafted to X-rayed hind limbs brought about the
regeneration of tails (Trampusch, 1958a). Experiments by Umanski
(1946) in which unirradiated tail skin was transplanted to X-rayed tails,
resulted in the development of tail regenerates. Also working on tails,
Luther (1948) and Trampusch (1958b), obtained no regeneration from
X-rayed tails whose skin had been replaced by body skin, but irradi-