UNILATERAL CEREBELLAR AGENESIA 373 
be ascertained whether it was completely absent or simply 
much reduced in size, but its absence contrasted with the large 
left nucleus is a striking feature in figures 19 and 20. Besides 
this and correlated changes in the field of Forel no other changes 
were noted at these higher levels. 
CONCLUSIONS 
1. The following structures were found to be markedly de- 
fective: The greater part of the left cerebellar hemisphere, 
possibly a part of the vermis and the left superior colliculus; 
the right inferior olivary nuclei, the right central tegmental 
tract and the left corpus restiforme; the left middle cerebellar 
peduncle, the right pons nuclei, the right pes and the right 
substantia nigra; the left nucleus dentatus, the left superior 
cerebellar peduncle and the right nucleus ruber. All ofthese 
findings are simply confirmatory, or illustrative, of the accepted 
views as to the cerebellar connections involved. It may be 
pointed out again that, while uncrossed olivo-cerebellar and 
ponto-cerebellar (from pontile nuclei) connections are not entirely 
excluded, they either do not exist or are relatively inconsiderable 
and that the great majority at least of the olivo-cerebellar fibers 
are distributed to the cerebellar hemispheres. 
2. The following structures usually supposed to be connected 
with the cerebellum were found to be, as far as could be ascer- 
tained, either normal or possibly slightly defective: The dorsal 
and ventral spino-cerebellar tracts (the dorsal slightly defective 
on left), the arcuate nuclei (defective on right possibly), the 
ventral and ventro-lateral external arcuate fibers (slightly de- 
fective on left possibly), the lateral reticular nuclei, the external 
nuclei of the column of Burdach and other nuclei of Goll and Bur- 
dach, the juxta-restiform bodies (vestibulo-vermis connections, 
possibly somewhat defective on left); the perpendicular pons 
(ponto-tegmental) fibers and certain tegmental nuclei. If these 
structures are connected with the cerebellum, we would be obliged 
logically to assume either that each is connected equally with both 
hemispheres of the cerebellum or they are mainly connected with 
