122
R. J.
GOSS
That skeletal parts are essential neither for the occurrence of limb
regeneration nor for the development of cartilaginous elements in such
regenerates has been conclusively demonstrated in numerous extirpation
experiments. When the fibula is removed from the hind limb, as shown
by Reed (1903) and Morrill (1918), a new fibula is nevertheless formed in
subsequent leg regenerates. Similarly, Goss (1956a), Goss and Nalbandian
(1954) and Rieck and Rudich (1956) have reported that the ulna is not
necessary for the replacement of its counterpart in the regenerating
fore-limb. Moreover, total bone ablation likewise does not preclude the
formation of normal limb regenerates including skeletal parts. Following
removal of the humerus and amputation through the boneless region,
normal skeletal regeneration occurs (Fritsch, 1911; Weiss, 1922, 1925a;
Bischler, 1923; Bischler and Guyénot, 1925a, 1926; Swett and Parsons,
1929; Thornton, 1938), and lower arms, lacking their bones, also give
rise to qualitatively complete regenerates, as described by Bischler
(1925) and Goss (1956a) in urodeles, and Goss (1953) in anurans.
Experiments involving extirpation of femurs from hindlimbs have
yielded similar results (Weiss, 1925a; Bischler and Guyénot, 1926), and
Kurz (1912) showed that in the absence of the pelvic girdle, a new limb
can develop from the body wall. Even when parts of limbs without
skeletal elements are transplanted to other regions of the body, regeneration can occur normally (Liosner, Woronzowa, and Kosmina, 1936;
Umanski, 1938b). Thus it is abundantly evident that in the regeneration
of an amphibian limb, the presence of skeletal structures in the stump is
not essential for the differentiation of new cartilage. It is concluded that
such a deficiency can be regulated by other tissues in the stump.
Yet the role of bone in affecting the differentiation of the regenerating
blastema in urodele extremities is not so passive as the results of
extirpation experiments might indicate. A number of experimenters, in
accordance with the theory that if bone does influence morphogenesis
the replacement of one skeletal part by another should result in the
production of regenerates at least partly altered by the presence of the
substituted bone, have exchanged limb bones in amphibians and
studied the regenerates produced. When tarsals were substituted for the
femur (Bischler and Guyénot, 1925b; Juge, 1940), or humeri (Liosner,
1939) or femurs (Umanski, 1939) put in place of the tibia and fibula, or
the humerus replaced by the carpáis (Juge, 1940), the resulting regenerates exhibited structural alterations in accordance with the origins of
the transplanted skeletal elements. When proximal bones were transplanted distally, the regenerated limbs frequently showed indications
of at least partly formed extra segments, while distal bones in proximal
positions tended to result in shortened regenerates commensurate with
the derivations of the implanted skeletal structures.
R. J.
GOSS
That skeletal parts are essential neither for the occurrence of limb
regeneration nor for the development of cartilaginous elements in such
regenerates has been conclusively demonstrated in numerous extirpation
experiments. When the fibula is removed from the hind limb, as shown
by Reed (1903) and Morrill (1918), a new fibula is nevertheless formed in
subsequent leg regenerates. Similarly, Goss (1956a), Goss and Nalbandian
(1954) and Rieck and Rudich (1956) have reported that the ulna is not
necessary for the replacement of its counterpart in the regenerating
fore-limb. Moreover, total bone ablation likewise does not preclude the
formation of normal limb regenerates including skeletal parts. Following
removal of the humerus and amputation through the boneless region,
normal skeletal regeneration occurs (Fritsch, 1911; Weiss, 1922, 1925a;
Bischler, 1923; Bischler and Guyénot, 1925a, 1926; Swett and Parsons,
1929; Thornton, 1938), and lower arms, lacking their bones, also give
rise to qualitatively complete regenerates, as described by Bischler
(1925) and Goss (1956a) in urodeles, and Goss (1953) in anurans.
Experiments involving extirpation of femurs from hindlimbs have
yielded similar results (Weiss, 1925a; Bischler and Guyénot, 1926), and
Kurz (1912) showed that in the absence of the pelvic girdle, a new limb
can develop from the body wall. Even when parts of limbs without
skeletal elements are transplanted to other regions of the body, regeneration can occur normally (Liosner, Woronzowa, and Kosmina, 1936;
Umanski, 1938b). Thus it is abundantly evident that in the regeneration
of an amphibian limb, the presence of skeletal structures in the stump is
not essential for the differentiation of new cartilage. It is concluded that
such a deficiency can be regulated by other tissues in the stump.
Yet the role of bone in affecting the differentiation of the regenerating
blastema in urodele extremities is not so passive as the results of
extirpation experiments might indicate. A number of experimenters, in
accordance with the theory that if bone does influence morphogenesis
the replacement of one skeletal part by another should result in the
production of regenerates at least partly altered by the presence of the
substituted bone, have exchanged limb bones in amphibians and
studied the regenerates produced. When tarsals were substituted for the
femur (Bischler and Guyénot, 1925b; Juge, 1940), or humeri (Liosner,
1939) or femurs (Umanski, 1939) put in place of the tibia and fibula, or
the humerus replaced by the carpáis (Juge, 1940), the resulting regenerates exhibited structural alterations in accordance with the origins of
the transplanted skeletal elements. When proximal bones were transplanted distally, the regenerated limbs frequently showed indications
of at least partly formed extra segments, while distal bones in proximal
positions tended to result in shortened regenerates commensurate with
the derivations of the implanted skeletal structures.