A STUDY OF THE SUPERIOR OLIVE. 171 



the olive also receives fibers from the formatio reticularis. It is entirely probable 

 that both collaterals and terminals pass in both directions between the superior 

 olive, a way-station in a specific tract, and that the cells in the formatio reticu- 

 laris constitute a part of the general association system. 



(3) This group includes the fine fibers surrounding the periphery of the nucleus 

 in well-defined bundles and filling the interval between the medial and lateral 

 masses, and also the hila of the lateral mass. Most of these fibers are probably 

 axons of the cells making up this nucleus. While fibers are seen to turn into the 

 substance of the cell-mass at all parts and levels, no bundles can be observed to 

 cut into and through the substance of the nuc'ear fold, which is so noticeable in the 

 fiber arrangement of the inferior olive; though in the cat the medial mass appears 

 at some points to have been separated from the lateral mass ventrally, and a still 

 greater tendency to group into bundles has been noted in the fibers of human tissue. 



Cajal describes the axons arising from the cells in the superior olive as passing 

 in three different directions: (1) The majority of them, after giving off collaterals 

 in the nucleus itself, pass to the dorsal surface of the nucleus, where either by 

 bending or bifurcating they turn to run vertically in a longitudinal bundle con- 

 tinuous with the lateral lemniscus of the same side. (2) A certain number of the 

 axons, much curved inside of the nucleus, leave the latter at its lateral border to 

 enter the trapezoid body, where they can be followed nearly as far as the ventral 

 cochlear nucleus. (Held describes these as actually terminating inside of this 

 nucleus.) (3) Other axons, arising from the cells of the superior olive, pass out at 

 the medial side of the nucleus, entering the plexus of the preolivary nucleus to 

 mingle there with the trapezial fibers. Held adds to these the group of axons which 

 make up the olivary peduncle described above. 



It is to be noted that the number of these fibers is greatly augmented in the 

 upper part of the nucleus. In the cat specimen, especially, great, dense whorls of 

 fibers are seen around and above the superior pole of the olive, where they form 

 the beginning of the lemniscus lateralis. In none of the tissues studied could any 

 connection be found between the cell-mass of the superior olive and the nucleus of 

 the lateral lemniscus, though such a condition is claimed by some investigators. 

 Bruce asserts (p. 48) that these two nuclei are continuous, and Cajal states that the 

 lower nucleus of the lateral lemniscus is anatomically continuous with the superior 

 olive. Nevertheless, it is to be sharply separated from the latter, for its constituent 

 cells are very different in shape and the axons are entirely different in distribution. 



The cell and fiber complex in the adult dog presents some features which are 

 altogether different from those observed in the other forms studied, there being a 

 disproportionately greater amount of fibrillar element as compared with the other 

 animals, the fine intranuclear fibrillar network making up the bulk of the nuclear 

 mass, the cells being widely scattered and enmeshed in the plexus. The extra- 

 nuclear fibers surrounding the nuclear mass are less abundant than in the cat. The 

 individual section of the superior olive of the dog is much coarser, presenting a 

 greater transverse measurement and a less sharply defined hilum. The adult cat 

 is the best subject for fiber study. Quite bulky strands of fine fibers can be seen 



