UNILATERAL CEREBELLAR AGENESIA 367 
principal nucleus while the right dorsal accessory olivary nucleus 
is almost entirely absent, only the barest vestige being discernible 
in a few of the sections. The right olivary nuclei appear some- 
what different microscopically, in the Weigert-Pal preparations, 
from the left. They contain fewer coarse fibers, apparently 
more fine fibers, especially at the periphery, and apparently 
fewer nerve-cells. They contain, however, nerve-cells of normal 
appearance. These appear to be very few in number in the 
cephalic, most reduced, part of the principal nucleus. A com- 
parison of the transverse fibers of the two sides is interesting. 
On the right are seen dorsally the fibers passing principally 
from the nucleus cuneatus to the opposite fillet, ventrally are 
seen numerous fibers from the left side which pass through or 
dorsal to the right olivary nuclei and thence dorso-laterally, 
through.or around the gelatinous substance of Rolando and 
spinal root of the trigeminus to the right restiform body. These 
latter, olivo-cerebellar, fibers are practically absent entirely 
on the left and the course of the fillet fibers is rendered especially 
clear. It will be noted that there are lateral external arcuate 
fibers to the restiform body on both sides and that the right 
restiform body is already decidedly larger than the left. At- 
tention has already been called to the aberrant pyramidal fibers 
(p. 366). 
The lateral reticular nuclei are present on both sides. Owing 
to their lack of clear outlines, it is not easy to detect any slight 
inequality but if there be such it is not very great. 
In sections at the level of the emergence of the glosso-pharyn- 
geus and cochlear portion of the acusticus (fig. 9), the great 
disparity in size between the left and right restiform bodies and 
the inequality of the olives are still more marked and are the 
most striking features. The left restiform body is, however, 
nearly three times the size of the left dorsal spino-cerebellar 
tract in the cervical cord. This accession of fibers would be 
from the external arcuate fibers and the small right olive. The 
great disparity in size between the two restiform bodies is obvi- 
ously due entirely or almost entirely to the enormously greater 
number of olivo-cerebellar fibers received by the right restiform 
