234 



THE NERVOUS SYSTEM 



Cranial nerves. From the under side, or base, of the 

 brain are given off twelve pairs of nerves, which supply 

 the two sides of the face and its various organs and mus- 

 cles, such as the nose, ears, eyes, mouth, teeth, tongue, 

 pharynx and the muscles which control them. Two 

 of them also aid in supplying and controlling the organs 



FIG. 129. Diagram illustrating the course of nerve fibres within Ihe brain. (After 

 Starr.) A, track of nerve fibres running from the frontal convolutions to the 

 pons and thence to the cerebellum ; B, motor tract ; C, sensory tract for touch; 

 D, visual tract; E, auditory tract; F. G, H, tracts to cerebellum. Numerals 

 indicate the cranial nerves. Dotted areas represent the cellular, or gray, matter. 



of the chest, and the stomach and liver. Since they are 

 entirely within the skull, or cranium, they are called 

 the cranial nerves. Each pair of cranial nerves is named 

 according to its function, as, for example, the pair which 

 supply the nose are called olfactory; those which go to 

 the ears are auditory; those to the eyes are optic; and 

 those to the tongue, gustatory. Some of the cranial 

 nerves are purely sensory, others purely motor, and still 



