A STUDY OP THE SUPERIOR OLIVE. 161 



pontis. Hence in these types the olive is much nearer the ventral surface of the pons. 

 It was found to be more superficially placed in the cat than in the dog. 



This area of the pons is very vascular, comparatively large vessels cutting into 

 and between the portions of the nuclear complex. In the medulla the vagus and 

 hypoglossal nerves embrace the inferior olive, the latter nerve cutting the nucleus 

 and partially separating the so-called accessory from the main nucleus. In the pons 

 we find the same arrangement to some degree, with the abducent and facial-nerves 

 embracing the superior olive. In the cat and man, however, the abducens runs well 

 medial to the superior olive ; whereas in the dog it comes in contact with the medial 

 margin of the nucleus, even cutting through it in one specimen examined (fig. 5). 

 In man the emerging facial fibers run closer to the olive than do the abducent. 



Functionally, the superior olive is to be classed with the cell masses which are 

 developed in relation to the special sense organs. That this nucleus is a way- 

 station in the auditory pathway is borne out by a study of its fiber relations, which 

 will be discussed later on, and by pathological conditions produced experimentally. 

 Baginsky claims that destruction of the cochlea in a new-born animal is followed 

 by atrophy and disappearance of the superior olive of the same side; and von 

 Monakow found that sectioning of the lateral lemniscus in one of the lower animals 

 (cat or dog) was followed by atrophy and disappearance of the dorsal portion of the 

 superior olive of the same side. He assumes from this that only a portion of the 

 cells of this nucleus stands in relation to the lateral lemniscus. Other studies have 

 established the fact that fibers, axons of the cells of the ventral cochlear nucleus, 

 run transversely across the pons, forming the corpus trapezoideum, and that a 

 portion of them, at least, terminate among the cells in the superior olivary nucleus. 

 Flechsig suggested that the superior olivary nucleus might be concerned with the 

 innervation of the muscles of the ear, as it is considerably larger in animals with large, 

 very movable ears. This contention is successfully disposed of by Spitzka, who 

 states that he has found this nucleus highly developed in the cetaceans. 



The superior olivary nuclei in all of the animals studied present a sufficient 

 degree of similarity in gross morphology, histologic constituents, and relations to 

 enable us to establish a definite type of nuclear mass as a standard which can be used 

 as a basis for further study and comparison. The conformity to type presented by 

 this nucleus in each of the animals is as close as is to be found in comparative 

 studies of any other structure common to all of the individuals in this group. While 

 it is admitted that a certain amount of variation is to be found in the nuclei in the 

 various forms of animal life, and even on the two sides of the same animal, these 

 variations, in normal tissue, were found to be confined within fairly narrow limits. 



With these facts in view, therefore, we would expect to find, and do find, the 

 inferior olive presenting one definite and constant type both in its gross and minute 

 structure, while the superior olive presents quite another type. While they may be 

 said to possess some general features in common, just as is true of any two nuclear 

 masses, they nevertheless differ so widely in form, degree of complexity, folding, 

 size, relations, cell and fiber-content, that they can be classed only as separate and 

 distinct entities. In comparing the two in the different species an interesting feature 



