face. This is the plan in the cerebrum
and cerebellum, and here are found devices for increasing the surface: the
cerebrum having convolutions, the cerebellum transverse ridges.

2. _That of collections of cell-bodies into rounded masses._ Such masses
are found in the bulb, the pons, the midbrain, and the base of the
cerebrum.

3. _That of arrangement in a continuous column._ This is the plan in the
spinal cord. It matters not at what place the spinal cord be cut, a
central area of gray matter, resembling in form the capital letter H, is
always found.

The fibers connecting with the cell-bodies in the brain and spinal cord
are gathered into bundles or tracts, and these pass through different
parts somewhat as follows:

1. _In the cerebrum_ they extend in three general directions, forming
three classes of fibers. The first connect different localities in the
same hemisphere, and are known as _association_ fibers (_A_, Fig. 134).
The second make connection between the two hemispheres, and form the
corpus callosum. These are known as _commissural_ fibers (_C_, Fig. 134).
The third connect the cerebrum with the parts of the nervous system below,
and are called _projection_ fibers (_P_, Fig. 134).

2. _In the cerebellum_ both association and commissural fibers are found.
Bands of fibers, passing upward toward the cerebrum and downward toward
the cord, connect this part of the brain with other parts of the nervous
system.

[Fig. 134]

Fig. 134--*Semi-diagrammatic representation of a section through the right
cerebral hemisphere*, showing fiber tracts. _A._ Association fibers. _C._
Commissural fibers. _P._ Projection fibers. The cell-bodies with which the
fiber bundles connect are in the surface layer or cortex.

3. _In the midbrain, bulb, and spinal cord_ fibers are found: first, that
connect these parts with the cerebrum(101) and cerebellum above; second,
that pass into and become a part of the nerves of the body; and third,
that connect the opposite sides of these parts together.

*The Peripheral Division.*--The peripheral division of the nervous system
includes all the nervous structures found outside of the brain and spinal
cord. These consist of the cranial, spinal, and sympathetic nerves, and of
various small ganglia, all of which are closely connected with the central
system.

*Spinal Nerves and Dorsal-root Ganglia.*--The spinal nerves comprise a
group of thirty-o