ON THE SKELETON OF REGENERATED ANTERIOR 



LIMBS IN THE FROG. 



ESTHER F. BYRNES. 



While the skeletal structures of regenerated posterior limbs 

 in the Anura have been found to be capable of almost complete 

 restoration, I know of no similar studies on the anterior limbs. 

 As the anterior limbs of Anurous batrachians appear relatively 

 late in the life of the larvae, some interest attaches to the power 

 of regeneration possessed by these organs. 



That the lost regions of the anterior limbs may be restored 

 more or less completely has already been proven, 1 but how com- 

 pletely the skeleton can be restored within the various limb- 

 regions it is the purpose of this article to show. The many less 

 complete instances of regeneration which are of frequent occur- 

 rence after amputation of the anterior limb have been omitted 

 from consideration. 



A comparison of the regenerated skeletons seen in Figs. 2 

 and 3 with the normal skeleton figured in I shows that the skel- 

 etal structures are often less completely regenerated than might 

 be expected from the outward appearance of the limb. In both 

 cases there is a tendency not only to reduction in the number of 

 digits in the regenerated hands, 'but also to a reduction in the 

 number of phalanges in each digit. 



The relatively greater length of the middle digit in both 2 

 and 3 marks it as undoubtedly the fourth digit, though in 

 each case but three phalanges are present, while in the normal 

 limb there are four. A similar reduction of parts likewise 

 occurs in the fifth digit of both 2 and 3 which normally is also 

 composed of four phalanges. In the case of the remaining digit 

 in the regenerated hands, I am unable to determine whether it is 

 the third or the second digit that has regenerated. In Fig. 2 

 the digit contains the normal number of phalanges, whether it be 



1 Byrnes, E. F., " Regeneration of the Anterior Limbs in the Tadpoles of Frogs." 

 Archiv fiir Entwickelungsmechanik der organistnen. Bd. XVIII. , 2 Heft, 1904. 



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