THE NERVOUS SYSTEM. 



which pass directly to the mid-brain (fasciculus vestibulomesencephalicus), chiefly t 

 the oculomotor and trochlear nuclei (Fig. 524, p. 590). 



Central Connexions of the Cochlear Nerve. The cochlear nuclei are brough 

 into connexion with the inferior colliculus and the medial geniculate body of the opposit 

 side by the fibres of the corpus trapezoideurn and the lateral lemniscus. 



The fibres of the cochlear nerve end in the ventral cochlear nucleus and in the dorsg 

 cochlear nucleus (tuberculum acusticum). From the cells of these nuclei two tract 

 arise, viz., a ventral tract, composed of the fibres of the corpus trapezoideum, and 

 dorsal tract, which is represented by the strise medullares. 



The corpus trapezoideum (Figs. 531 and 532) is formed of the axons of the cells of th 

 ventral cochlear nucleus, as well as certain of the axons of the cells of the dors? 

 nucleus. In the midst of the corpus trapezoideum are lodged large cells which are know 

 as the nucleus trapezoideus, and these give off axons which join the strand with whic 

 they are associated. Many of the fibres of the corpus trapezoideum end in a large mass ( 

 gray matter called the nucleus olivaris superior, which is placed immediately behind th 



12 



FIG. 536. SECTION THROUGH THE PONS OF THE ORANG. 

 The left side of the drawing is taken from a section at a level slightly inferior to the section 



from which the right side is taken. 



A B 



1 Ascendin^ part of facial nerve. 1. Ascending part of facial nerve. 



2. Medial longitudinal bundle. 2. Emergent portion of facial nerve. 



3. Descending root of vestibular nerve. 3. Restiform body. 



4 Radicular fibres of facial nerve. 4. Nucleus of abducens nerve. 



5. Restiform body. 5. Abducens nerve. 



6 Facial nucleus. 6. Emergent part of facial nerve. 



7. Spinal tract of trigeminal nerve. 7. Peduncle of superior olive. 



8. Vestibular nerve. 8. Superior olive. 



9 Superior olive. 9. Corpus trapezoideum. 



10. Lemniscus medialis. 10. Facial nerve. 



11. Pyramidal tract. 11. Abducens nerve. 



12. Transverse fibres of pons. 12. Pyramidal tract. 



13. Transverse fibres of pons. 



trapezoid body. The trapezial fibres cross the median plane and decussate with th 

 corresponding fibres of the opposite side. Reaching the opposite superior olivar 

 nucleus, more fibres leave the trapezoid body, and almost immediately after this tt 

 strand bends upwards and forms the lemniscus lateralis (Figs. 535, p. 605 ; 537, p. 607 

 But still another nucleus is interposed in its path, viz., the nucleus lemnisci lateral! 

 Here some fibres are dropped, whilst from the nuclear cells others are acquired, an 

 the lateral lemniscus then proceeds upwards until it reaches the inferior collicuh 

 and the medial geniculate body, in which its fibres end. 



Other fibres arise from the cells of the dorsal cochlear nucleus, and arrange themselv- 

 in the conspicuous bundles which sweep round the dorsal aspect of the restiform hoc 

 and proceed medially across the floor of the fourth ventricle, often immediate 

 beneath the ependyma (Fig. 482, p. 550). Reaching the median plane they dip forwar- 

 into the substance of the pons, and, crossing the median plane, they join the later 



