68 JOURNAL OF COMPARATIVE NEUROLOGY. 
of which was only about 24% to be quite numerous. I think, 
therefore, that the smallest medullated fibers are included in 
my count. 
In Tables II-X XXII are to be found the number of nerve 
fibers for each fascicle, and in Table I° is found the totals for 
each root. 
3. Comparison of Stilling’s Estimate with the author's Enu- 
meration. On comparing the determination of the number of 
nerve fibers in the dorsal roots of the spinal nerves made by 
STILLING with those of the author a wide difference is manifest. 
According to his estimate there are only 262,919 fibers in 
these roots on one side, while according to my count there are 
653,627. In other words, STILLING’s result is 39.9%, or in 
round numbers 40%, of my results. In searching for the 
source of this difference I found two significant statements by 
STILLING (1859). First, that he finds no nerve fibers of so 
small a diameter as 2.7—4.5, and second, that the nerve fibers 
range, in diameter, from 7—22y. It thus seems evident that 
for the most part STILLING failed to see nerve fibers the diame- 
ters of which were much less than 7y, and in this lies the chief 
source of the difference between our results. I find, as we 
have seen, that STILLING’s results are about 40% of mine, or in 
other words, my total, in round numbers, is 60% greater than 
the results of Stititinc. It therefore remains to be determined 
whether this 60% of difference can be explained by the fibers 
the diameter of which is less than 74—these being the fibers 
smaller than STILL1NG’s lowest limit. 
In searching for data to determine this point I find that 
RosENTHAL (1845)‘, BrnpER and VoLKMaANN (1842), KOLLIKER 
(1850), and DucHENE (1864)", estimate the small fibers in the 
dorsal roots of the spinal nerves of various vertebrates to range 
from 4%—¥% of their entire number. 
SIEMERLING (1886-1887)”-, counted in each dorsal root, 
mostly on the left side, the nerve fibers seen in 9 mm.’ of the 
ocular micrometer. He found that 670 of the nerve fibers so 
counted were less than 5 in diameter, and 536 between 5. 3— 
23.94—that is, 55% % are small and 44% % large fibers. In 
