CH. XLIV.] 



CRANIAL NERVES 



631 



the nuclei of the eighth nerve (only one of which, Vlllm., is seen in the 

 diagram), and the glossopharyngeal and vagal portions of a long 

 strand of nerve-cells called the combined nucleus of the ninth, tenth, 

 and eleventh nerves. The remaining nuclei (coloured blue) are 

 efferent, and may be principally arranged into two groups : (1) the 

 nuclei of the third, fourth, sixth, and twelfth nerves, which are close 

 to the middle line ; and (2) the motor nucleus of the fifth, the nucleus 

 of the seventh, and the nucleus ambiguus (motor nucleus of the ninth 

 and tenth nerves) which form a line more lateral in position. 



It should be added that van Gehuchten has shown that, except 

 a few fibres of the third, and the whole of the fourth nerves, none 



SUP. PED. OF CEREBELIA 



MIDDLE 



INF. 



CEREBELLAR 



4 

 HEMISPHERE 



FIG. 460. Diagrammatic representation of dorsal aspect of medulla, pons, and mid-brain. 



of the fibres of the cranial nerves cross to the opposite side. 



The first two pairs of cranial nerves, the olfactory and the optic, 

 will be studied in connection with smell and vision later on. 



We can now pass to the consideration of transverse sections of 

 this part of the central nervous system. We will limit ourselves to 

 seven, the level of which is indicated in the above diagram (fig. 460). 

 The cerebellum has been bisected into two halves and turned out- 

 wards, its upper peduncles having been cut through to render the 



