166 A STUDY OF THE SUPERIOR OLIVE. 



the latter approaching the median line. The shifting in position of the successive 

 sections, confirmed by careful measurements, involves changes in two directions 

 the rapid, dorso-lateral inclination, which in toto attains a considerable degree, the 

 topmost section being at an angle of 45 degrees with the perpendicular of the most 

 caudal section, and a twisting upon its caudal pole to such an extent that the 

 extremities of the bar swing around a quarter of a circle, the long diameter of the 

 individual section extending almost transversely. The entire mass forms a robust 

 cell-column of irregular, wavy outline in a cephalo-caudal direction, more marked 

 upon the convex ventro-mesial surface. The dorso-lateral surface is concave, 

 conforming to the adjacent medially directed surfaces of the lateral masses and 

 overhanging the upper lateral mass to a certain extent above. 



The lateral mass is much less developed in man and consists of two portions, 

 one just above the other. The lower, slightly larger portion, begins 19 sections 

 above the caudal limit of the medial bar and extends somewhat above the mid- 

 point of this bar, where it ends in a pointed extremity. The second mass begins 

 5 sections cephalad to the former and ends in a blunt pole 21 sections below the 

 cerebral limit of the medial bar. These lateral portions are simply irregular cell- 

 masses presenting no hila and no definite modeling comparable to the beautiful 

 S-shaped structure found in other animals. Both masses are channeled by blood- 

 vessels, and are situated very close to the medial bar, almost in contact with its 

 dorsally directed margin; whereas the point of continuity in the dog and that of 

 closest proximity in the cat are with the ventral margins of the two portions. 



CELL STUDY. 



The superior olivary nucleus presents an enormous number of nerve-cells 

 which have been variously described by different authors, the majority of whom, 

 however, are perhaps agreed that the cells in the superior and inferior olives are 

 alike. This is well demonstrated in Barker's summary, which is to the effect that 

 Held, Kolliker, and Cajal describe their results in a general way as follows: The 

 cell bodies in the superior olivary nucleus markedly resemble in type those found 

 in the inferior olive and the dentate nucleus; they possess numerous, much branched 

 dendrites which are turned toward the interior of the nucleus, the axons in the 

 main being directed toward the periphery of the nucleus. Still others describe 

 these cells as being spindle-shaped or club-shaped. One reason for this diversity 

 of opinion, perhaps, is the fact that prior to complete development and differentia- 

 tion the great majority of nerve cells resemble each other rather closely, since all 

 are of the embryonic type; and in studying a given cell-mass in an embryo, even 

 one comparatively well advanced in other respects, one is liable to be led into error 

 as to the definite morphology of a given type of cell unless one studies the same cell 

 area through several successive stages of development. It is even more satisfactory 

 to study the fully differentiated adult stage as well . A much more complete picture of 

 a given cell group can be obtained by comparative study in a number of animals. 



In a comparative study of the inferior olive (unpublished) it was found that 

 there was a striking uniformity in shape, size, and structure of the cell peculiar to 



