THE BRAIN. 519 
(tegmentum) to the optic thalamus of each side and onward 
to the temporo-sphenoidal lobes, forming the posterior commis- 
sure, 
3. Fibers connecting different parts of the cerebral convolu- 
tions on the same side. These are exceedingly numerous and 
are effected by such tracts as the “arcuate fibers,” passing from 
one gyrus to another ; “ collateral fibers,” forming distant convo- 
lutions; fibers of the fornix between the uncinate gyrus, hip- 
‘pocampus major, and optic thalamus; longitudinal fibers of the 
corpus callosum; fibers of the tenia semicircularis, uncinate 
fasciculus, etc. 
4, Fibers forming the cerebrum and the spinal cord. Ac- 
cording as they pass downward or upward do they converge or 
diverge, and the most important seem to pass through the in- 
ternal capsule; and while the majority do perhaps form some 
connection, either with the corpora striata and optic thalami, 
Fig. 379,—Diagrammatic representation of the course of some of the fibers in the cerebrum 
(after Le Bon). 
