Each of the fifth pair of nerves is in three branches, and proceeds mainly to the face.  They are called tri-facial, and are mixed nerves, partly sensory and partly motor.  The first branch is purely sensory, and gives sensibility to the eyeball.  The second gives sensibility to the nose, gums, and cheeks.  The third (mixed) gives the special sensation of taste on the front part of the tongue, and ordinary sensation 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 act of speech.