74 
MAMMALIAN ANATOMY 
to the surface of the bone. Take care not to saw too deeply and 
thus injure the surface of the brain which lies just beneath the 
bone. After sawing along the lines marked out, gently pry at 
various points with a chisel to determine if there are any regions 
which the saw has not completely separated, and, if such regions 
are found, cautiously chisel through them by light taps of the 
wooden mallet. Finally remove the bony roof by prying it up 
and detaching the adherent regions of the dura mater from its 
inner surface. This will expose the brain in situ covered by the 
dura mater. If there are portions of the roof which overhang 
the brain laterally, carefully chip these away with the bone 
forceps. 
From the exposed surface of the brain remove the dura mater 
including the falx cerebri, that thickening of the dura which dips 
into the longitudinal fissure between the two cerebral hemispheres, 
and the tentorium which lies in the transverse fissure between the 
cerebrum and the cerebellum. Beneath the dura mater may be 
seen the pia mater with its plexus of blood vessels. The arachnoid 
layer which lies between is too poorly defined to appear as a 
distinct membrane. 
To remove the brain from the cranial cavity, gently loosen it 
from the dura mater on all sides by means of the wet flat handle 
of a scalpel. Make sure that the tentorium is wholly removed. 
Lift the anterior end of the brain with care and, reaching in to the 
extreme anterior region of the floor of the cranial cavity with the 
wet scalpel handle, detach the olfactory lobes from the cribriform 
plate of the ethmoid upon each side. The anterior region of the 
brain may now be lifted up from the floor of the cavity. Then 
reach still farther back beneath the brain and, with a very sharp 
scalpel or with scissors, cut the optic nerves as far as possible from the 
ventral surface of the brain. If the head is now held in a vertical 
position with the nose pointed upward, gravitation will cause the 
brain to drop backward sufficiently to enable one to look in at the 
anterior end between the ventral surface of the brain and the floor 
of the cavity and see the stalk of the hypophysis, the carotid 
arteries, and the various pairs of cranial nerves which must be 
severed successively. As the process continues, the brain will 
fall farther and farther back and its weight should be supported 
