THE STRUCTURE OF THE SPINAL GANGLIA 161 
of similar origin and appearance form bundles of fine black fibers 
which can be followed into the dorsal root on the one side and 
into the peripheral nerve on the other. These axons are devoid 
of a myelin sheath (or according to Dogiel, some of them may 
present a thin and interrupted coat of myelin similar to that 
which is seen on some sympathetic fibers). 
The axons in fig. 1 show about the average amount of coiling; 
but while in many cases they are almost straight, in a few the 
winding is as pronounced as that of the axon of any large cell. 
It is of interest to compare the bifurcation of these fibers with 
that of the medullated axons (fig. 2). These latter branch at a 
node of Ranvier and show a marked constriction both of the 
main stem and the two branches at the point of bifurcation. In 
none of the dividing non-medullated fibers is such a constriction 
to be seen. Instead there is a broad triangular area at the point 
of the bifurcation. These fibers differ then from the medullated 
in their small size, in the intensity with which they stain with 
silver, in the absence of a surrounding unstained ring of myelin, 
and in the manner of their bifurcation. 
The description which is here given of the small cells and their 
axons is in no sense new. JDogiel in 1897 gave a very satisfactory 
account of them, which was confirmed by Cajal (’07) and later 
again by Dogiel (’08, p. 33). Dogiel found on some of these 
fibers very fine myelin sheaths which disappeared and reappeared 
from stretch to stretch along the fiber. It is strange that neither 
author gave any further consideration to these axons, apparently 
overlooking the fact that they outnumber the medullated fibers 
by as much as the small cells outnumber the large. We will 
return to the significance of these observations in another part 
of this paper. 
2. Cells whose axons have collaterals ending in end bulbs. Do- 
giel’s type 11, Cajal’s type vi. The peculiarity of these cells lies 
in the fact that the axon gives off fine collaterals, which after 
a course usually of no great length, end in characteristic swellings, 
which according to their location may be divided into three sub- 
groups: (a) In the majority of the cases the collaterals are given 
off from the axon before it has left the connective tissue capsule 
