nsation on the inner
side of the cheek, on the teeth, and also on the scalp in front of the
ear. The motor branches supply the chewing muscles.

The seventh pair, the facial, proceed to the face, where they
spread over the facial muscles and control their movements. The
eighth pair are the auditory, or nerves of hearing, and are
distributed to the special organs of hearing.

The next three pairs of nerves all arise from the medulla, and escape
from the cavity of the skull through the same foramen. They are sometimes
described as one pair, namely, the eighth, but it is more convenient to
consider them separately.

The ninth pair, the glosso-pharyngeal, are partly sensory and
partly motor. Each nerve contains two roots: one a nerve of taste, which
spreads over the back part of the tongue; the other a motor nerve, which
controls the muscles engaged in swallowing.

The tenth pair, the pneumogastric, also known as the vagus
or wandering nerves, are the longest and most complex of all the cranial
nerves. They are both motor and sensory, and are some of the most
important nerves in the body. Passing from the medulla they descend near
the oesophagus to the stomach, sending off, on their way, branches to
the throat, the larynx, the lungs, and the heart. Some of their branches
restrain the movements of the heart, others convey impressions to the
brain, which result in quickening or slowing the movements of breathing.
Other branches pass to the stomach, and convey to the brain impressions
which inform us of the condition of that organ. These are the nerves by
which we experience the feelings of pain in the stomach, hunger, nausea,
and many other vague impressions which we often associate with that organ.

[Illustration: Fig. 117.--Anterior View of the Medulla Oblongata.

A, chiasm of the optic nerves;
B, optic tracts;
C, motor oculi communis;
D, fifth nerve;
E, motor oculi externus;
F, facial nerve;
H, auditory nerve;
I, glosso-pharyngeal nerve;
K, pneumogastric;
L, spinal accessory;
M, cervical nerves;
N, upper extremity of spinal cord;
O, decussation of the anterior pyramids;
R, anterior pyramids of the medulla oblongata;
S, pons Varolii.
]

The eleventh pair, the spinal accessory, are strictly motor, and
supply the muscles of the neck and the back.

The twelfth pair, the hypoglossal, are also motor, pass to the
muscles of the tongue, and help control the delicate movements in the