THE CRANIAL NERVES AND THEIR NUCLEI 171 



fibers, which innervate the striated musculature derived from the myotomes. 

 This group of nuclei is indicated in red in Fig. 120 and by small circles in Figs. 

 121 and 122. 



The nucleus of the oculomotor nerve is an elongated mass of cells in the cen- 

 tral gray matter ventral to the cerebral aqueduct at the level of the superior 

 colliculus (Figs. 121, 122). Even a superficial examination shows that it is 

 divided into a lateral paired and a medial unpaired portion (Fig. 116). The 



Nuc. Ill E-W. 

 Nuc. Ill lat. 



Nuc. Ill med. 

 Nuc. IV 



Velum medul- 

 lare superiua 



Nuc. mot. V 



Nuc. VI 



Nuc. mot. VII 



Nuc. sal. sup. 



Nuc. sal. inf. 



Ala cinerea 



Nuc. dorsal. X 



Nuc. ambiguua 



Nuc. XII 



Colliculus sup. 

 Corp. genicula- 

 tum mediale 



Nuc. com. 

 Cajal 



Fig. 121. Dorsal view of the human brain stem with the positions of the cranial nerve nuclei 

 projected upon the surface. Sensory nuclei on the right side, motor nuclei on the left. Circles 

 indicate somatic efferent nuclei; small dots, general visceral efferent nuclei; large dots, special 

 visceral efferent nuclei; horizontal lines, general somatic sensory nuclei; cross-hatching, visceral 

 sensory nuclei; stipple, special somatic sensory nuclei. (Herrick.) 



lateral groups of cells spreads out upon the surface of the medial longitudinal 

 bundle, extends throughout the entire length of the nucleus, and may be divided 

 into ventral and dorsal portions (Fig. 123). The medial group of cells is placed 

 exactly in the median plane and is found only in the rostral half of the nucleus. 

 Dorsolateral from this median group, and restricted to the most rostral part of 

 the nucleus, is a collection of small cells which form the nucleus of Edinger- 

 Westphal. This is a visceromotor nucleus and will be considered elsewhere. 



