THE MEDULLA OBLONGATA AND TEGMENTUM OF THE PONS. 207 



from the vaplie ; these pass upward and decussate very near the 

 floor of the rhomboidal fossa. They are here gathered into 

 bundles, which run across this floor. These, the striae acusticae, 

 which pursue a course analogous to that of the central sensory 

 tract, pass from above downward into the dorsal nucleus; then, 

 skirting along the border of the restiform body, are continued on 

 to the ventral nucleus of the acoustic nerve (Figs. 121 and 



Monakow states that these striae atrophied after he had 

 divided the opposite lemniscus high up near the corpora quad- 

 rm-cmina. This, and their situation in the lower animals, lead 



o 3 * 



to the conclusion that they are the central sensory tract of the 

 acoustic. 



At this level no new nucleus has appeared, only that of the 

 facial nerve has increased in size. Fibres from the ascending 

 root of the trigeminus are given off to the root of the last-named 

 nerve. This is important, for we know that from just this por- 

 tion of the trigeminus come the sensory fibres of the face. 



Somewhat farther forward (Fig. 125) the fibres of the facial 

 have been gathered together into a nerve-trunk. This, however, 

 does not pass at once to the surface, but runs cephalad for a 

 short distance, and then turns in the direction of the basis. In 

 this way it makes two turns, one in the horizontal and one in 

 the descending part of its course. Just in the bend between 

 these two turns is situated the nucleus of the abduccns (Fig. 124). 



The root-fibres of the abducens, gathered into several 

 bundles, run a straight course through the tegmentum and pons, 

 and emerge laterally on the ventral surface of the latter. The 

 nucleus is connected internally with the posterior longitudinal 

 fasciculus. It has been stated, but I think without sufficient 

 foundation, that these fibres enter the opposite oculo-motor 

 nucleus higher up. On the other hand, there is certainly a 

 remarkable connection between the nucleus of the abducens and 

 the superior olivary body. This tract, which you see running 

 parallel to the root of the facial nerve in Fig. 125, must connect 



