y; they assist the corpus callosum in
maintaining a close connection between the right and left hemispheres.

[Illustration]

Behind the thalami we see the quadrigemina, the posterior pair of
which is labelled _testes_, and resting upon them we have the pineal
gland, a centre of spiritual influx. Behind the thalami, the posterior
lobes are cut away that we may look down to the cerebellum, and the
middle of the cerebellum is also removed so that we may see the back
of the medulla oblongata and its fibres, called restiform bodies,
which give origin to the cerebellum. The fibres from the cerebellum to
the quadrigemina are shown, and the space at the back of the medulla,
called the fourth ventricle.

As the fibres of the medulla pass up through the pons to the great
inferior ganglion, and the fibres of the corpus striatum pass outward
and upward to form the cerebrum, this procession of the fibres is
shown in the annexed engraving, in which we see the restiform bodies
passing up to form the cerebellum, and the remainder of the medulla
fibres passing through the pons, and then, under the name crus cerebri
or thigh of the cerebrum, passing through the thalamus and striatum to
expand in the left hemisphere of the cerebrum. We see the quadrigemina
on the back of the ascending fibres and their connection by fibres
with the cerebellum behind, as they connect with the thalami in front.
This is as complete a statement of the structure of the brain as is
necessary, and further anatomical details would only embarrass the
memory.

[Illustration]

The engraving above represents not an actual dissection, but the plan
of the fibres as understood by the anatomist. The intricacy of the
cerebral structure is so great that it would require a vast number of
skilful dissections and engravings to make a correct portrait.
Fortunately, this is not necessary for the general reader, who
requires only to understand the position of the organs in the head,
and the direction of their growth, which is in all cases directly
outward from the central region or ventricles, so as to cause a
prominence of the cranium--not a "bump," but a general fulness of
contour. Bumps belong to the growth of bone--not that of the brain.

Let us next consider the genesis of the brain, which will give us a
more perfect understanding of its structure, by showing its origin,
the correct method of estimating its development.

CHAPTER III.--GENESIS OF THE BRAIN