858 NEUROLOGY 



of the fibers terminate in the superior olivary nucleus. The fibers of the striae 

 medullares are not always visible on the floor of the rhomboid fossa. From the 

 ventral portion of the cochlear nucleus axons pass into the trapezoid body, here 

 some of them end in the superior olivary nucleus of the same side, others cross the 

 midline and end in the superior olivary nucleus of the opposite side or pass by these 

 nuclei, giving off collaterals to them, and join the lateral lemniscus. Other fibers 

 either terminate in or give off collaterals to the nucleus of the trapezoid body of 

 the same or the opposite side. Other fibers from the ventral portion of the cochlear 

 nucleus pass dorsal to the inferior peduncle and then dip into the substance of the 

 pons to join the trapezoid body or the superior olivary nucleus of the same side. 

 From the superior olivary nucleus of the same and opposite sides axons join the 

 lateral lemniscus. Collaterals and probably terminals also pass from the lateral 

 lemniscus to other nuclei in its path and receive in turn axons from these nuclei. 

 They are the accessory nucleus, the medial preolivary nucleus, the lateral pre- 

 olivary or semilunar nucleus and the nucleus of the lateral lemniscus. 



The trapezoid body consists of horizontal fibers in the ventral part of the f ormatio 

 reticularis of the lower part of the pons behind its deep transverse fibers and the 

 pyramid bundles. The axons come from the dorsal and ventral portions of the 

 cochlear nucleus. After crossing the raphe, where they decussate with those from 

 the opposite side, they turn upward to form the lateral lemniscus. Fibers from the 

 striae medullares contribute to the trapezoid body, in addition it sends terminals 

 or collaterals to and receives axons from the superior olivary nucleus, the nucleus 

 of the trapezoid body, the lateral preolivary or semilunar nucleus and the mesial 

 preolivary nucleus. 



The cochlear nucleus, the terminal nucleus for the nerve of hearing, is usually 

 described as consisting of a larger dorsal nucleus on the dorsal and lateral aspect of 

 the inferior peduncle forming a prominent projection, the acoustic tubercle, and a 

 ventral or accessory cochlear nucleus more ventral to the inferior peduncle. The 

 two nuclei are continuous and are merely portions of one large nucleus. The axons 

 from cells of the spiral ganglion of the cochlear nerve on reaching the nucleus 

 divide into ascending and descending branches which enter the ventral and dorsal 

 nuclei respectively. Axons from the large fusiform cells of the dorsal nucleus pass 

 partly by way of the striae medullares to the trapezoid body and lateral lemniscus 

 and the nuclei associated with the former, and partly transversely beneath the 

 inferior peduncle and spinal tract of the trigeminal to the trapezoid body. Axons 

 from the ventral cochlear nucleus pass partly by the striae medullares but for the 

 most part horizontally to the trapezoid body. 



The superior olivary nucleus is a small mass of gray matter situated on the dorsal 

 surface of the lateral part of the trapezoid body. Some of its axons pass backward 

 to the abducent nucleus, this bundle is known as the peduncle of the superior 

 olivary nucleus. Other fibers from the nucleus join the posterior longitudinal 

 bundle and terminate in the nuclei of the trochlear and oculomotor nerves. The 

 majority of its axons, after giving off collaterals to the nucleus itself join the lateral 

 lemniscus of the same side, other axons pass in the trapezoid body toward the ven- 

 tral portion of the cochlear nucleus. 



The nucleus of the trapezoid body lies between the root fibers of the abducent nerve 

 and the superior olivary nucleus. Its cells lie among the fibers of the trapezoid 

 body. In it terminate fibers and collaterals of the trapezoid body which come 

 from the cochlear nucleus of the opposite and probably the same side and from the 

 opposite trapezoid nucleus. They terminate in the nucleus of the trapezoid body 

 in diffuse arborizations and peculiar end plaques or acoustic calyces of yellowish 

 color which fuse with the cell bodies. Its cells are round and of medium size; their 

 axons pass into the trapezoid body, cross the median line and probably join the 

 lateral fillet. 



