THE STRUCTURE OF THE SPINAL GANGLIA 167 
markedly from the latter because of the bundles of fine black fibers 
which it contains. One can see this contrast in a striking way 
where the bundles from the two roots decussate as fibers from the 
ventral root run into the dorsal ramus (d) and others from the 
dorsal root into the ventral ramus (c). Fig. 18 represents a por- 
tion of this decussation under higher magnification. In the 
center is a pure bundle of medullated fibers derived from the 
ventral root, while the fibers taking the other direction are derived 
from the dorsal root, and of these some are medullated but more 
are non-medullated. 
It has not been possible to show that no non-medullated fibers 
run into the nerve from the ventral root, but if present they are 
in very small number. The majority of such fibers seen in the 
nerve can be directly traced into the spinal ganglion. Nor has 
the contribution of the ramus communicans to the non-medul- 
lated fibers of the nerve been investigated, but even this must be 
small compared to the enormous numbers coming through the 
dorsal root. 
As to what ultimately becomes of these fibers, there are as yet 
no observations. That the central branches of the non-medul- 
lated axons enter the spinal cord, there can be no doubt, but their 
distribution within it has not yet been investigated. That their 
peripheral branches run for long distances in the nerve has been 
shown in a previous paper. They have been demonstrated in 
the sciatic nerve of man, dogs, cats, rabbits and rats (Ranson, 
11). Figs. 14 and 15 have been drawn with the aid of a camera 
lucida from adjacent sections of the same human sciatic nerve, 
the one (fig. 14) prepared according to the Pal-Weigert technique 
and the other (fig. 15) by the Cajal silver method. The magnifi- 
cation is the same in both instances. Great care was exercised 
not to decolorize any medullated fibers in differentiating the Pal- 
Weigert preparations and the field from which fig. 14 was drawn 
was chosen because it exhibited the maximum number of small 
medullated fibers. In the Cajal preparation (fig. 15) the color- 
less rings represent the myelin sheaths, within which are lightly 
stained axons. In the interspaces between these medullated fibers 
are enormous numbers of small black axons directly imbedded 
