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ATURALIST [Vol. XLII 



able to cut off a longer piece of the stump than will he 

 required, and then to cut this in half, putting either half 

 back into the pocket, which being incompletely filled, 

 allows the skin to be drawn more readily over the end. 

 The hind-limb being larger was used. The implanted 

 piece, reversed in orientation, consists of bones, muscles, 

 nerves, etc. The skin covering these parts is the old skin 

 with normal orientation. Therefore, at least one ele- 

 ment in the complex is not reversed. 



In some respects this method of grafting proved un- 

 satisfactory, because the cut end of the stump is so near 

 to the graft that the new material from the stump and 

 that from the graft may easily become mixed, so that 

 the results would be complicated. The shortness of the 

 grafted piece is another source of difficulty, since the 

 short piece may become displaced during the healing of 

 the end. To overcome these difficulties I devised another 

 method, in which however only a single organ has its 

 orientation reversed. The hind leg was cut off at the 

 knee, and the femur removed from the stump for nearly 

 its entire length. It is then shortened by cutting off 

 part of one end, and pushed back into its original posi- 

 tion, but with its orientation reversed. Owing to the 

 slightly bent shape of the femur, and its much enlarged 

 knee-end, no chance for a mistake in its orientation is 

 possible. This procedure proved superior to the first, 

 although the problem involved is somewhat different. 



At first the large salamander, Spelerpes ruber, was 

 used. This is a terrestrial form. Later the somewhat 

 smaller Diemyctylus viridescens was used. Both species 

 withstand the operation well and regenerate readily. 

 Serial sections were made of the limbs at different stages 

 of their regeneration. 



Regeneration from the Proximal End of a 

 Reversed Piece 



which a cross-section of the 1 limb°was° implanted in a 



