REGENERATION AFTER EXARTICULATION 111 
determine whether the new part exactly resembles the old both 
in size and gross structure. In addition fifteen amputations 
were made through the distal end of the femur for comparison 
with the exarticulation experiments. 
Descriptive. Wendelstadt (’04) and Glaeser (’10) have given 
very detailed accounts of regeneration in the limbs based chiefly 
on species of the European salamander Triton and on the Axolotl. 
In Diemyctylus the process is quite similar to that observed in 
Triton. A study of the specimens in which amputation was 
made through the distal end of the femur, i.e., an operation 
corresponding to those of Wendelstadt and Glaeser, showed that 
the descriptions given by these writers for Triton, apply almost 
equally as well to Diemyctylus. It is true there is some slight 
discrepancy in their accounts but this can be discussed more 
conveniently when comparing the exarticulation experiments 
with those previously made. 
The earlier changes which take place in the stump may be 
passed over briefly here. They are concerned chiefly with the 
over-growth of the integument, the breaking down of the soft 
parts, notably the muscle and the formation of a dense mass or 
bud of small cells with round, deeply staining nuclei over the 
distal end of the bone (femur). This mass lengthens out and 
forms a projection when seen externally but does not always lie 
in the axis of the limb. The origin of these cells could not be 
determined with exactness. Wendelstadt (’04) encountered 
the same difficulty. Towle (’01) however, states that the 
accummulation of ‘nuclei’ in the bud is due to rapid (direct) 
division of nuclei in the old muscle fibers and the disintegration 
of these fibers.t Undoubtedly the degeneration of muscle- 
fibers is largely responsible for the accumulation, but whether 
exclusively so or not, is difficult to decide. Connective tissue 
elements may also contribute something. 
Turning now to the changes in the bone and cartilage with 
which this paper is chiefly concerned, it is here that an essential 
difference appears between regeneration after exarticulation and 
4 Towle’s experiments are concerned almost entirely with the regeneration of 
muscle. 
