NERVOUS SYSTEM 361 



(2) The optic nerves pass to the eyes. They are the nerves 

 of sight. 



(3) The oculo-motor nerves pass to certain muscles of the 

 eyes. They are the nerves that partly control the move- 

 ments of the eye-balls. 



(4) The paiheticus nerves go also to muscles of the eye. 



(5) The trigeminal nerve goes to different regions of the 

 face and the salivary glands. Figure 180 shows the general 

 plan of branching of the trigeminal nerve. 



(6) The abducent nerves, like the third and fourth, pass 

 also to certain muscles of the eye. 



(7) The facial nerves go to the muscles of the head and face. 



(8) The auditory nerves go to the ear. It is the nerve 

 of hearing. Its distribution is shown in figure 187. 



(9) The glosso-pharyngeal nerves pass to the tongue 

 and other parts of the mouth and throat. 



(10) The vagus or pneumo gastric nerves go to the 

 oesophagus, larynx, lungs, stomach, heart and intestines. 



(n) The spinal accessory nerves go to the neck and 

 shoulders. 



(12) The hypo glossal nerves go to the muscles of the 

 tongue. 



Each nerve consists of a mass of fibers surrounded by a 

 sheath of connective tissue. Each fiber is a fine thread-like 

 process continuous somewhere with a nerve cell. That is, it 

 is a branch of a nerve cell. Each of the hundreds and thou- 

 sands of nerve fibers within a single nerve functions in- 

 dependently of all the others. 



Internal structure of the brain. If the brain is sliced 

 through or sectioned, the solid part will be seen to be com- 

 posed of two kinds of matter, white and gray. The gray 

 matter follows the outer surface of the brain and the folds, 

 and is known as the cortex of the brain. The white mat- 

 ter forms the core of the brain. The cell bodies of the 

 brain lie in the cortex. The fibers, passing from a cell 



