498 7 S. WALTER. RANSON 
be essentially different from that occurring when the two ends 
are in apposition, but with the idea that the process would be 
easier to analyze, and that in this way evidence would be obtained 
which could be applied in the analysis of the more complex 
conditions obtaining in the divided and reunited nerve. 
Fortunately we now have in the method of Cajal a technique 
giving a sharp stain of the finest branchings of axons and 
enabling the investigator to see clearly the complicated changes 
going on near the cut surfaces and to correctly understand the 
mechanism of nerve regeneration. With the solution of the 
problem, which is given by this new method of staining, there 
ceases to be any reason for an attempt to secure an isolated 
stump for study, since it would be highly improbable that there 
would occur in an isolated stump a process which was essentially 
different from that which occurs in the peripheral stump when 
in connection with the central nervous system. 
A number of observers have made use of Cajal’s method for 
the study of degenerative and regenerative changes in nerve 
fibers. Perroncito (05) and Cajal (08) have obtained brilliant 
results. Marinesco (’05, ’06), Poscharissky (07) and Tello (’07) 
have also made use of this method. As we proceed with the 
discussion of our own results we will point out in what ways 
our results differ from those of others who have used this method. 
TECHNIQUE 
The experiments were made on the sciatic nerve of adult 
dogs. With strict aseptic precautions the nerve was exposed 
in the upper part of the thigh and cut with a sharp scalpel or 
scissors. The ends were in some cases allowed to retract; in 
others a stretch of 1 cm. was removed and retraction allowed; 
and in still others, without resection of any of the nerve, the 
two ends were approximated with sterile silk or catgut sutures. 
The dogs were allowed to live for a period of from one to thirty- 
five days and at the autopsy a short stretch of the proximal 
stump and a longer stretch of the distal stump together with 
the intervening scar were removed and subjected to histological 
analysis. Since we deal only with the early stages of regenera- 
