162 A STUDY OF THE SUPERIOR OLIVE. 



develops. The simplest type of the superior olive was found in man, the most com- 

 plex in the cat and rabbit. In the inferior olive these conditions are reversed, the 

 most complex nucleus being found in man, the simpler types in the lower animals. 



The pontine olive in most animals consists of two portions; a smaller, medially 

 placed, bar-shaped mass, and a larger, laterally placed, S-shaped portion. The 

 surfaces of these cell collections, seen en masse, are only slightly irregular, lacking 

 entirely the crinkled, tortuous outline which is so marked in the larger, bulbar 

 olive. The nucleus is entirely surrounded by a very rich network of fine nerve 

 fibers, which is in close relationship with the transverse fibers of the corpus trape- 

 zoideum, but there is no demonstrable intranuclear commissure between the olives 

 of the two sides, such as is found so well developed in the medulla the interolivary 

 decussation. There seem to be no cross fibers aside from those to be identified with 

 the corpus trapezoideum. The individual sections of both the medial and lateral 

 portions of the superior olive are much broader and more robust than is the shell 

 of the inferior nucleus, and show a much more densely packed mass of cells. 



Kolliker, in his embryology, gives the most complete and accurate description 

 of the superior olive extant. He states: 



"One can get a better understanding of the relations of this olive from the lower mam- 

 malia, where this organ is better developed than in man Whether this olive appears 



simpler or more complex, it always possesses essentially the same structure in man and the 

 lower animals, as Golgi's slides of young animals show." 



With both of these statements my own findings are in entire accord, though 

 Kolliker gives no results other than those obtained from a study of individual sections, 

 and hence leaves much to be desired as to the gross morphology of this important 

 nucleus. 



A detailed study of the models of the upper olive in the three subjects chosen 

 as the basis for this paper shows the general similarity of outline, as stated above; 

 that of the cat being the most complex, the human the simplest, and the dog con- 

 stituting an intermediate. The nucleus of the adult cat presents a medially situated, 

 bar-shaped mass which is separate and distinct from a laterally placed S-shaped mass. 

 The latter is considerably less extensive vertically than is the former, being overlapped 

 from above by the outward-leaning medial mass. Both portions of the nucleus are 

 smooth in outline, rather comparable to the accessory mass of the inferior olive, 

 and not at all resembling the wavy, crumpled outline of the major nucleus. 



The medial mass in individual sections begins about 16 sections farther caudal- 

 ward than does the lateral mass. It is rather club-shaped, curving somewhat like 

 an italic letter /, its extremity pointing ventro-laterally and dorso-medially, the 

 dorsally directed pole being slightly broader than the other. The highest level 

 reached by this medial portion is 38 sections farther cerebralward than the highest 

 point of the lateral mass. The medial bar trends gradually lateralward, farther 

 from the median raphe, and becomes thicker and more robust as we ascend the 

 stem. The model of this medial portion is a long, band-like column occupying 

 about the lower half of the pons. It is somewhat irregular, presenting a wavy 

 outline from above downward, with a decided lateral inclination, so marked above 



