DEGENERATION AND REGENERATION OF NERVE FIBERS 511 
the remainder of the peripheral stretch. These changes have 
been described by Perroncito (’05), Poscharissky (’07), and 
Cajal (08), with whose observations our own are in full accord. 
These changes begin very early. One day after operation 
they are already well adanced in both the medullated and non- 
medullated fibers. In the millimeter nearest the cut surface 
the non-medullated fibers possess lateral branches, and the 
fibers as well as their branches end in bulbs (figs. 8 and 9). The 
mode of formation of these branches is the same as the mode 
of formation of the similar branches seen in the immediate 
neighborhood of the lesion in the proximal stump; but, since 
the successive stages are more clearly seen there, we will describe 
their formation when describing the central stump. The side 
branches are usually as large as the parent stem. The end 
bulbs are very characteristic, differing markedly from those 
seen on the ends of fibers taking part in the ultimate regener- 
ative changes. These bulbs have a darkly staining core with 
a neurofibrillar network, and a peripheral lightly staining zone, 
which is often of considerable thickness and shows no visible 
neurofibrils. These side branches are so numerous and _ their 
end bulbs so large that they separate widely the original fibers 
of a bundle. The last 0.5 mm. of the stump assumes a charac- 
teristic appearance under low magnification due to the replace- 
ment of the parallel bundles by a network, the individual fibers 
of which are separated by large end bulbs. It seems probable 
that the outer lightly staining zone of these end bulbs represents 
ap. excessive accumulation of interfibrillar substanee. 
The growth of lateral branches and the formation of end 
bulbs does not progress much, if any, after the first day, but 
remains stationary during the second, third and fourth days. 
We have unfortunately no intermediate stages between the 
fourth and eighth days, and during this time the products of 
this abortive regeneration have almost entirely disappeared. 
There are to be seen after eight days shadowy outlines of the 
bulbs and a somewhat more definite indication of the branched 
fibers. A few of the fibers and end bulbs are still clearly stained. 
After fourteen days there are still a few scattered fibers show- 
