154 



THE NERVOUS SYSTEM 



the platysma and muscles of the face. These fibers emerge from the dorsal 

 surface of the nucleus and run dorsomedially toward the floor of the fourth 

 ventricle. Somewhat widely separated at first, they become united on the 

 medial side of the abducens nerve into a compact strand, which as the genu of 

 the facial nerve partly encircles this nucleus, and which then runs ventrolateraUy 

 between the spinal tract of the trigeminal nerve and its own nucleus toward 

 its exit from the brain (Figs. 108, 124). 



Anterior medullary velum 



Medial longitudinal fasckulus 

 Ventral spinocerebellar tract 



Trapezoid body: 

 Superior olive, 



Lateral lemniscus 

 Brachium pontis 



Fourth ventricle 



Brachium conjunctiwim 



Mesencephalic root of trigem- 



inal nerve 

 Motor nucleus of trigeminal 



nerve 



Sensory nucleus of trigem- 

 inal nerve 



Medial lemniscus 

 Superficial stratum of pons 



Trigeminal nerve 

 Corticospinal and corlico- 

 pontine tracts 



Nuclei pontis 



Fig. 110. Section through the pons of a child at the level of the motor nucleus of the trigeminal 



nerve. Pal-Weigert method. (X 4.) 



The nucleus of the abducens nerve along with the genu of the facial pro- 

 duces a rounded elevation in the rhomboid fossa, known as the facial colliculus 

 (Figs. 89, 108). It is a spheric mass of gray matter containing the cells of origin 

 of the fibers which innervate the lateral rectus. These emerge from the dorsal 

 and medial surfaces of the nucleus and run ventrally more or less parallel to the 

 median raphe toward their exit at the lower border of the pons. 



The Nuclei of the Trigeminal Nerve. In transverse section through approxi- 



