170 A STUDY OF THE SUPERIOR OLIVE. 



so intricate as to render their study a very difficult task. Much work has been 

 done in an effort to determine the fiber relations of this portion of the brain-stem, 

 and certain facts have been fairly definitely established; among others, the manner 

 in which the fiber element of the superior olive is related to the corpus trapezoideum, 

 the lemniscus lateralis, and the tractus olivo-nucleus abducentis, and through 

 these indirectly to the various parts with which these tracts are connected. While 

 it is impossible at this time to give a complete study of these fiber elements and 

 their relations to other parts of the central nervous system, a few of the more perti- 

 nent facts may be recorded. 



The fibers that are distinguishable in relation to the superior olive may be 

 roughly grouped into three classes: (1) Those that can be traced from the olive to 

 the nucleus of .the abducent nerve, the olivary peduncle (shown in figs. 7 and 10, 

 plate 2). These fibers are quite fine and are grouped in small bundles which can 

 be traced vertically from the dorsal surfaces of both medial and lateral masses of 

 the superior olive, from a point near its middle portion to the nucleus nervi abdu- 

 centis. The bundles run parallel to the emergent portion of the nervus facialis. 

 The olivary peduncle forms a connecting link between the auditory pathway and 

 the nerve supply of the ocular muscles. Santee believes that a part of the fibers 

 from the olivary peduncle go to the nucleus abducentis, and part go by way of the 

 medial longitudinal bundle to the trochlear and oculo-motor nuclei, thus correlat- 

 ing all the nerve nuclei supplying the ocular group of muscles with the auditory 

 pathway. This may serve to explain some of the results of Ferrier's experiments 

 upon monkeys. This observer claims that the animals will, when anesthetized, 

 turn the eye in the direction from which a sound is perceived, a similar movement 

 being observed when the cortical center for hearing is stimulated. This action 

 will necessarily call into play the lateral rectus muscle through stimulation of the 

 nervus abducentis. 



(2) This group would include all those fibers which extend between the ven- 

 trally situated corpus trapezoideum and the ventral surfaces of both parts of the 

 nuclear mass of the superior olive. These vary in length; some can be traced for 

 only a short distance, others extend well out toward the periphery of the section. 

 All are better developed in adult tissue. Some of the fibers are terminal, but the 

 major part is undoubtedly collateral. In the trapezium they can be seen to branch, 

 T-shaped, one collateral passing dorsalward toward the olive. The olive rests in 

 a bay in the dorsal surface of the corpus trapezoideum, the fibers of which curve 

 around ventral to the nucleus. The strands of trapezial fibers are observed to 

 occupy a much greater antero-posterior extent in the interval between the olives 

 of the two sides (fig. 5), but curve sharply forward at the medial margin of the 

 nucleus to decussate in the median line with those from the opposite side, none of 

 them apparently entering the nuclear mass. Indeed, one commonly finds the 

 collaterals, not the terminal fibers, entering the nucleus, though the fibers of these 

 strands appear to give off no collaterals in this region. Kolliker claimed to have 

 found, in a study of frontal sections, fibers coming from the direction of the median 

 raphe to end about the cells in the dorsal part of the olive. Barker suggests that 



