DISSECTION OF THE BRAIN. Th 
Carlie TERNAL CHLARACTERS OF THE BRATN. 
1. The Dorsal Surface of the Brain. 
a. THE CEREBRAL HEMISPHERES occupy the greater 
portion of the dorsal surface. They show a number of 
well-marked fissures and convolutions (sulciand gyri). 
The two hemispheresare connected by a broad white 
commissure, the corpus callosum, which may be seen 
by gently separating the two hemispheres and tearing 
or cutting away the pia mater which stretches across 
from one to the other. The corpus lies well toward 
the ventral surface of the hemispheres. 
b. THE OLractory Lopes are a pair of large flat 
tened triangular lobes projecting from the ventral sur- 
face of the brain, but visible in a dorsal view. 
c. THE CoRPORA QUADRIGEMINA may be exposed 
by pressing apart the cerebellum and the cerebrum, and 
tearing away the intervening pia mater. They consist 
of two pairs of rounded elevations, of which the pos- 
terior pair are the larger. 
d. THE CEREBELLUM. The whole surface is marked 
with narrow folds which run both in a transverse and 
a longitudinal direction. ‘They are seen better if the 
pia mater is stripped off. The cerebellum is divided 
into a large median lobe, the vermzs, in which the 
folds run transversely, and two lateral lobes or /em- 
spheres in which the folds have a general longitudinal 
direction. On the outer and under sides of the hemi- 
spheres the loose floccular lobes will be seen if the brain 
has been carefully removed. 
Weth a parr of forceps tear away carefully the pra 
mater beneath and posterior to the cerebellum to bring 
ento view the medulla oblongata. 
e. THE MeEpuLLta Oxstoncata lies beneath and 
