THE NERVES AND THEIR FUNCTIONS. 147 



general law is kept, viz., that a ganglion is formed in the 

 sensific nerves, before they become associated with the fila- 

 ments of motion. 



8. (The sixth pair arise near the last, and also enter the 

 orbitj^jhere they are entirely expended upon the muscle 

 which turns the eye towards the temple. Where this nerve 

 has been injured or lost its power, the eye is permanently 

 turned in towards the nose ; and such a person is said to be 

 cross-eyedt 



9< The ninth pair arise from the pyramidal bodies, and 

 passing through holes in the occipital bone, proceed forwards 

 towards the angle of the jaw, by the side of the hyoid bone 

 of the tongue, and are distributed upon the muscles between 

 the lower jaw, hyoid bone, and tongue, the motions of which 

 it regulate^ 



10. THIRD ORDER. This division embraces what Sir 

 Charles Bell calls thefyespirato7-y nerves) These are not only 

 connected with the function of respiration, but contribute also 

 to the expression of the passions and emotions of the mind. 

 They consist of the fourth ; the portio dura ; of the seventh, 

 or facial ; the eighth, or par wgum ; the phrenic ; and the 

 external respiratory. As the medulla oblongata, consists of 

 three columns ; the nerves of motion arise from the anterior, 

 those of sensation from the posterior ; while the respiratory 

 nerves, already mentioned, spring from the middle portion, 

 and all nearly on the same horizontal plane. 



1 1 . (The fourth nerve supplies the superior oblique muscle 

 of the eye, which rising from the bottom of the orbit, runs 

 along the roof of that cavity, till it comes close to its brim, 

 where it terminates in a small tendon, which passes through 

 a loop or pulley, then turns back, and is inserted into the 

 posterior part of the ball, so that its contraction turns the 

 eye in towards the nose.) When the will ceases to control 

 the, movements of the eye, it comes under the action of the 

 superior oblique muscle. We see this, in acute bodily 

 pain, and at the point of death, when the voluntary muscles 



