500 S. WALTER RANSON 
are then placed in the dark for three days at 35°C. in a 2 per 
cent aqueous solution of silver nitrate, then rinsed in distilled 
water and placed for one or two days in a 4 per cent solution of 
pyrogallic acid in 5 per cent formalin. Sections are made in 
paraffin and after mounting are ready for examination. This 
modification has many advantages over the original Cajal method 
when applied to the peripheral nervous system. It is only occa- 
sionally that one obtains with the older method a satisfactory 
stain of the non-medullated fibers, while when pyridine is used 
these fibers stand out with great clearness, not only in their 
normal state but also in the early stages of degeneration. The 
various regenerative phenomena in these fibers also stand out 
with great clearness. Cajal was able with his method to observe 
some of these changes in the non-medullated fibers but seems to 
have seen relatively few of these fibers showing that his method 
was not especially suited for their study. Perroncito (’09), who 
used the original method, states that ‘“‘the first phenomenon 
which is noticed in the peripheral stump of a divided nerve is 
a clearer differentiation of bundles of non-medullated fibers 
which run between the medullated fibers.” The old Cajal 
method in the hands of the writer has, only rarely, given a clear 
differentiation of the non-medullated fibers, and one gathers 
from the statements of Perroncito and Cajal that it has only 
been in injured nerves that they have seen them clearly, and 
even then with less distinctness than that with which they 
appear in the pyridine-silver preparations. They consider that 
these fibers are of sympathetic origin and fail entirely to appre- 
ciate their great number. As a result of the inadequacy of the 
old Cajal method many of the most important steps in the degen- 
eration and regeneration of these fibers also escaped their atten- 
tion. It is evident, however, from their figures and descriptions 
that when they use the term ‘non-medullated fibers’ they refer 
to the same structures which are designated by that name in 
the present paper. 
Another objection to the old Cajal method, as applied to the 
study of regenerating nerves, is that by this method it is diffi- 
cult to get both the old and the new axons to stain in the same 
