of the brain continually leads us into grand philanthropic
conceptions by showing the splendid possibilities of humanity,--showing
how near we are to a nobler social state from which we are debarred by
ignorance, by moral apathy, by ignorant self sufficiency, by intolerant
bigotry, and by selfish animality,--qualities which, alas! pervade all
ranks to-day.

But returning from this digression to our study of the interior of the
brain: the great ventricles of which we have considered the position,
and which are called lateral ventricles, are interesting for another
reason, that they are the central region around which the cerebrum is
developed, as it folds over upon itself in its early growth, and
consequently must be borne in mind as its centre when we are studying
its comparative development in different heads. The basilar organs lie
below the ventricles and the coronal organs above.

If we have inserted a finger under the corpus callosum, the fibres of
which are above our finger, we may feel below, the structure which may
be called the bottom of the ventricle, and which is likewise the base
or trunk of the superincumbent parts from which they spring, as a tree
from its stump.

This structure is one mass, called anteriorly the corpus striatum, or
striated body, and posteriorly the optic thalamus or bed of the optic
nerve, though the optic nerve has its principal origin in another
part, called the optic lobes. The thalamus and corpus striatum are
called together, the _great inferior ganglion_ of the brain. They are
masses of gray substance, with white fibres from below passing through
them, and white fibres originating in them to ascend and spread, so
that their entire masses of fibres, ascending and spreading out like a
fan, constitute an extensive structure which folds together toward the
median line somewhat like a nervous sac, inclosing the cavity of the
ventricle and sending its representative fibres across the median
line,--which are called the corpus callosum. This will be more fully
explained when we consider the genesis of the brain as it grows in the
unborn infant.

As the reader now understands the principal parts around the
ventricles, let him look lower down to complete the survey and
understand the plan of the brain, though not its anatomical minutiae.
The optic thalamus is indicated in the engraving, but the corpus
striatum, being more exterior and anterior, does not appear.
Practically they may be r