ce and inspect the bottom,
we observe at the back the cerebellum, which dips into the neck, the
middle lobe, which is over the ears and the side face, and the front
lobe, which rests over the eyes.

We observe posteriorly the medulla oblongata, on the face of which we
may observe the crossing of the fibres, and on the side of which we
observe the origins of many nerves. Above the medulla we observe the
pons Varolii, just above which we observe the fibres ascending to each
hemisphere under the name of _crus cerebri_, or thigh of the cerebrum.
Next we see the optic nerves crossing on the median line, the
olfactory nerve, running under the front lobe, which is separated by
the fissure of Sylvius from the middle lobe. There is also a glimpse
of the corpus callosum at its anterior end, obtained by pulling the
front lobes apart at the median line.

[Illustration]

Let us next cut through the head exactly on the median line, dividing
the right and left hemispheres, and look at the inner face of the
right hemisphere. We observe that it has convolutions, just like the
exterior surface, which do not join across the median line, but are
separated from those of the left hemisphere by a firm membrane (an
extension of the dura mater or principal investing membrane) called
the falx, which is removed, leaving the convolutions in view.

The reader will observe that it is only in the lower portion of the
engraving that he sees any surfaces produced by cutting to separate
the right and left halves of the brain. It is by these structures
which are here divided that the right and left halves are connected,
so that the whole brain is adapted to acting in a unitary manner.

The first section we encounter as we pass down is that of the _corpus
callosum_, a body of white fibre firmer than the external surface of
the brain, and therefore called the corpus callosum or callous body,
which consists of white nerve fibres gathered in from nearly all parts
of the brain on each side and crossing the median line. We may regard
it as a mass of representative fibres rooted in the soft substance of
the convolutions or gray matter of the brain generally, and thus
connecting across the median line the corresponding parts of the right
and left brain.

[Illustration]

It must be borne in mind that the brain like the body is double, and
that every organ is fully developed in each brain, so that no amount
of injury or paralysis of organs would deprive u