166 S. WALTER RANSON 
TABLE I 
Ratio of spinal ganglion cells to dorsal root fibers 
YU 9 
NUMBER OF AMOR CO) 
AUTHOR ANIMAL | NERVE eel pti 
NERVE FIBERS 
Gaule and Lewin (’96)..°... Rabbit 1 Coe. 20,361 3,173 
laa (OZR tte Lk teeta oe White rat v1 C 12,200 4,227 
pth aly COZ ES. ae. ern oe eee White rat at Abs 9,442 1,644 
Ranson iOS) ssa yee se White rat ue (©; The 2,472 
showed that the small cells constitute about 60 per cent of the 
total number, while Warrington and Griffith (’04) working with 
the 1 C. spinal ganglion of the cat estimated the small cells as 
constituting 70 per cent of the total number. Now we have 
shown in a former paragraph that the axons of these small cells 
are non-medullated and it is therefore clear that they could not 
be taken into consideration in the enumeration of the afferent 
fibers represented in table 1 based as it was in every case upon a 
differential myelin sheath stain. It is to these non-medullated 
fibers, the axons of the small spinal ganglion cells, that we are to 
look for the explanation of the discrepancy between the number 
of spinal ganglion cells and medullated afferent fibers. If a count 
of the afferent axons were made, the number would probably 
closely approximate that of the spinal ganglion cells. 
We have shown in fig. 1 how these non-medullated fibers arise 
from the small cells, in fig. 2 how they divide dichotomously 
into a thin fiber directed toward the dorsal root and a slightly 
thicker one directed toward the nerve. These branches unite 
themselves into bundles of fine black fibers which course longi- 
tudinally through the ganglion—along with the medullated ‘fibers 
having an analogous origin from the large cells. These bundles 
of non-medullated fibers can be followed into the dorsal root to 
which they give an appearance wholly different from that of the 
ventral root. Similar bundles of non-medullated fibers can be 
followed into the nerve. Fig. 12 shows the point of union of the 
ventral and dorsal roots to form the mixed nerve. It cam be seen 
at a glance that the composition of the dorsal root (a), as it streams 
out of the spinal ganglion to unite with the ventral root (6b) differs 
