bular or elliptical in
shape, the transverse diameter being greatest. The body of the
cerebellum is composed of gray matter externally and of white matter in
the center. The cerebellum has the function of co-ordinating movements;
that is, of so associating them as to cause them to accomplish a
definite purpose. Injuries to the cerebellum cause disturbances of the
equilibrium but do not interfere with the will power or intelligence.

The cerebrum, or brain proper, occupies the anterior portion of the
cranial cavity. It is ovoid in shape, with an irregular, flattened base,
and consists of lateral halves or hemispheres. The greater part of the
cerebrum is composed of white matter. The hemispheres of the cerebrum
are usually said to be the seat of all psychical activities. Only when
they are intact are the process of feeling, thinking, and willing
possible. After they are destroyed the organism comes to be like a
complicated machine, and its activity is only the expression of the
internal and external stimuli which act upon it.

The spinal cord, or spinal marrow, is that part of the cerebrospinal
system which is contained in the spinal canal of the backbone, and
extends from the medulla oblongata to a short distance behind the loins.
It is an irregularly cylindrical structure, divided into two lateral,
symmetrical halves by fissures. The spinal cord terminates posteriorly
in a pointed extremity, which is continued by a mass of nerve
trunks--cauda equinae. A transverse section of the cord reveals that it
is composed of white matter externally and of gray matter internally.
The spinal cord does not fill the whole spinal canal. The latter
contains, besides, a large venous sinus, fatty matter, the membranes of
the cord, and the cerebrospinal fluid.

The spinal nerves, forty-two or forty-three in number, arise each by two
roots, a superior or sensory, and an inferior or motor. The nerves
originating from the brain are twenty-four in number, and arranged in
pairs, which are named first, second, third, etc., counting from before
backward. They also receive special names, according to their functions
or the parts to which they are distributed, viz:

1. Olfactory.
2. Optic.
3. Oculo-motor.
4. Pathetic.
5. Trifacial.
6. Abducens.
7. Facial.
8. Auditory.
9. Glossopharyngeal.
10. Pneumogastric.
11. Spinal accessory.
12. Hypoglossal.

Inflammation of the Brain and its Membra