cerebrum is when fully developed in man has already been
shown; what it is in the fishy stage of development, when it is the
smaller portion of the brain, may be understood by a dissection given
in Serres "Anatomie Comparee du Cerveau," representing the brain of
the codfish dissected or opened from above. In this figure H is the
spinal cord, E the cerebellum, C the optic lobes divided, and B the
cerebrum divided, showing the radiating fibres of the corpus striatum,
m, from which the cerebrum begins its development.

When animal life reaches a high development, the functions which are
diffused become concentrated into special organs. Intelligence or
psychic life is concentrated in the cerebrum, and entirely removed
from the spinal cord. The physiological energy apart from the psychic,
is concentrated in the cerebellum, and thus the intermediate
psycho-physiological organ, the optic lobes or quadrigemina, being no
longer important, dwindles to become the smallest part of the brain.

[Illustration: EXPLANATION.--In the codfish, roach, and flounder, II
is the cerebellum, n the optic lobes, in front of which is the
cerebrum, from which the olfactory nerve extends forward. Behind the
cerebellum is the superior end of the spinal cord. The letter c is
placed on the restiform bodies or posterior part of the medulla
oblongata of the cod. The engravings show the upper surfaces of the
brains, as we look down upon them.]

If the reader will look at the sketch of the brains of the codfish,
flounder, and roach, as figured by Spurzheim, he will see in each a
very small cerebrum, a larger cerebellum, and still larger middle
brain or optic lobes. This is the model on which the human brain is
first developed, when in the second month it becomes possible to study
it with the microscope. It presents to view in the third month three
vesicles of soft neurine, the one which is to form the cerebellum
being larger than that which is to become the cerebrum.

These are three brains of different grades, formed alike on the same
vesicular plan. The resemblance of the optic lobes to the cerebrum is
very striking, and when we open them we see what corresponds to the
lateral ventricles of the cerebrum, with a structure at the bottom
corresponding in position and character with the inferior ganglion of
the cerebrum. The subdivision of function is similar to that of the
cerebrum, the anterior portion of these lobes being of an
intellectual, percepti