No. 6.] THE LIMBS Ol- PLETHEDOX. 297 



SUMMARY. 



The main changes that take place in the muscles of Flcthcdon 

 cincrcus during the process of regeneration are as follows : 



i (a] In the cut muscles the nuclei divide directly and in the 

 outer bundles the fibers disintegrate, leaving masses of nuclei 

 with a small amount of cytoplasm, (b) Some of the cells so 

 formed later divide mitotically, and by them new muscle sub- 

 stance is laid down, (r.) As the number of nuclei is, however, 

 far in excess of the normal number of muscle fibers, many nuclei 

 must degenerate or be transported. 



2. The fibers of the inner bundles do not disintegrate, but 

 split longitudinally, giving rise to smaller fibers, which are soon 

 indistinguishable from those formed as described in i. 



3. The arrangement into muscle bundles first becomes 

 clear at the end of about six weeks. 



4. There is no change in the muscles of the upper arm. 



II. 



The following is a brief summary of the main observations 

 that have been made on the power of regeneration of the limbs 

 in European species of salamanders. 



Spallanzani (8), in 1768, published a number of observations 

 on aquatic salamanders, presumably species of Triton. In these 

 he found that any or all of the limbs will regenerate, no matter 

 what the species, size, or age of the animal, the larger ones 

 regenerating more slowly than the smaller forms. Regenera- 

 tion will take place, he maintained, even when the limbs are 

 disarticulated. 



Bonnet, 1777 (2), confirmed Spallanzani's observations, finding 

 that in Triton cristatus the hands and fingers will regenerate. 



Von Siebold (7), in 1828, recorded abnormal regeneration of 

 the fingers of Triton cristatus. 



Higginbottom, in 1847 (4- P- 2 9)> observed that in Triton the 

 limbs will regenerate at a temperature of from 48 to 57 F. 



Philippeaux (6), in 1866, was the first to prove conclusively 

 that limbs when disarticulated will not regenerate. His experi- 

 ments were made on Triton cristatus and Axolotl. 



