FIG. 8.—View of the under side of the brain. B, basis of the crura; P, pons; Mo, medulla
oblongata; Ce, cerebellum; Sc, spinal cord.The Cerebrum.—The cerebrum occupies all the upper part of the skull from the
front to the rear. It is divided symmetrically into two hemispheres, the right and
the left. These hemispheres are connected with each other by a small bridge of
fibers called the corpus callosum. Each hemisphere is furrowed and ridged with
convolutions, an arrangement which allows greater surface for the distribution of
the gray cellular matter over it. Besides these irregularities of surface, each
hemisphere is marked also by two deep clefts or fissures—the fissure of
Rolando, extending from the middle upper part of the hemisphere downward and
forward, passing a little in front of the ear and stopping on a level with the upper
part of it; and the fissure of Sylvius, beginning at the base of the brain somewhat
in front of the ear and extending upward and backward at an acute angle with the
base of the hemisphere.