ON MUSCLE REGENERATION IN THE 

 LIMBS OF PLETHEDON. 



ELIZABETH W. TOWLE. 



SPALLANZANI (1768) and Bonnet (1777) showed that a 

 salamander whose limbs have been cut off has the power to 

 regenerate new ones. This discovery has been confirmed by 

 later writers, and although some histological work has been 

 done, yet the method of regeneration of the muscle bundles 

 has not been worked out. There are several possibilities : 

 first, the old fibers might break clown at the cut ends and the 

 new ones develop from the indifferent tissue so formed, each 

 old muscle thus completing itself independently. Or, the 

 cut muscles might degenerate along their entire length, and 

 new ones take their place ; or some of the old muscles might 

 degenerate, new ones being formed from this tissue, while some 

 fibers might break up into smaller new fibers. An attempt 

 has been made in this work, not so much to follow the origin 

 of the cells in detail as to discover the general processes 

 taking place in the leg that lead to the formation of the new 

 muscles. The regenerating limbs of Plethedon cinercns were 

 used. They were studied by means of serial sections. 



In addition to this histological study, I have also experimented 

 on a number of American urocleles in order to see in which ones 

 regeneration of the limbs takes place. For this purpose a 

 number of the commoner forms have been studied, and in 

 connection with these results a statement is given of the 

 previous observations on European forms. 



I. 



MetJiod.--Q\-\o. of the anterior limbs of Plethedon cinercns 

 was removed halfway between elbow and hand. The regen- 

 erating limbs were put up at intervals varying from four days 



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