nnection
with different parts of the body. Several of them have to do with the
special senses, and are for this reason very important. They connect the
brain with the different parts of the head, neck, and trunk, as follows:

1. The first pair (_olfactory_ nerves; nerves of smell; afferent) connect
with the mucous membrane of the nostrils (Fig. 136).

2. The second pair (_optic_ nerves; nerves of sight; afferent) connect
with the retina of the eyes.

3. The third, fourth, and sixth pairs (_motores oculi;_ control muscles of
the eyes; efferent) connect with the internal and external muscles of the
eyeballs (Fig. 136).

[Fig. 136]

Fig. 136--*Diagram suggesting the distribution and functions of the cranial
nerves* (Colton). See also Fig. 132.

4. The fifth pair (_trigeminal_ nerves; nerves of feeling to the face, of
taste to the front of the tongue, and of control of muscles of
mastication; afferent and efferent) connect with the skin of the face, the
mucous membrane of the mouth, the teeth, and the muscles of mastication.

5. The seventh pair (_facial_ nerves; control muscles that give the facial
expressions; efferent) connect with the muscles just beneath the skin of
the face.

6. The eighth pair (_auditory_ nerves; nerves of hearing; afferent)
connect with the internal ear.

7. The ninth pair (_glossopharyngeal_ nerves; nerves of taste to back of
tongue and of muscular control of pharynx; afferent and efferent) connect
with the back surface of the tongue and with the muscles of the pharynx.

8. The tenth pair (_vagus_, or pneumogastric, nerves; nerves of feeling
and of muscular control; afferent and efferent) connect with the heart,
larynx, lungs, and stomach. They have the widest distribution of any of
the cranial nerves.

9. The eleventh pair (_spinal accessory_ nerves; control muscles of neck;
efferent) connect with the muscles of the neck.

10. The twelfth pair (_hypoglossal_ nerves; control muscles of the tongue;
efferent) connect with the muscles of the tongue.

*Sympathetic Ganglia and Nerves.*--The sympathetic ganglia are found in
different parts of the body, and vary in size from those which are half an
inch in diameter to those that are smaller than the heads of pins. The
largest and most important ones are found in two chains which lie in
front, and a little to either side, of the spinal column, and extend from
the neck to the region of th