64 A Reconstruction of the Nuclear Masses in 



8abin in the new-born medulla, but it differs from her reconstruction in the 

 fact that the cephalic cell-mass is connected with the middle mass, and in 

 the fact that the constriction between the caudal and middle lobes is not as 

 marked in the adult as in the reconstruction of the new-born. 



Dorsal to the caudo-dorsal portion of the inferior olivary nucleus, and 

 lateral and somewhat dorsal to the lower part of the main cell-mass of the 

 mesial accessory olive, is a short and small, regular column of cells, belonging 

 to the mesial accessory olive. This lies very closely related to the inferior 

 portion of the caudal lobe. It probably corresponds to the cell-collection 

 lying dorsal to the caudal column of cells as described by Miss Sabin. At 

 the dorsal border of the hilum, on a level with the secondary transverse 

 dorsal fissure and with the cephalic portion of the medial accessory olive, 

 is another cell-mass, rather shorter but broader and thicker than the one 

 described as lying dorsal to the caudal cell-mass. This mass undoubtedly 

 corresponds to the small collection of cells found dorsal to the superior column 

 in the new-born. Ventrally and somewhat laterally, the cephalic portion 

 of the main cell-mass in the adult is continued into two irregularly shaped 

 collections of cells, the lateral and larger of which lies behind the other on 

 mesial view. Just cephalic to the superior ventral angle of the middle cell- 

 mass of the mesial accessory olive there lies laterally a rather larger and quite 

 regular cell-mass, whose cells resemble those of the mesial olive and should 

 undoubtedly be considered as belonging to the same complex. 



No cell-masses, corresponding to the two collections lying dorsal to the 

 middle column of cells in the new-born, were modeled in the adult (figure 4). 

 The two dorsal spurs, the inferior arising from the superior dorsal angle of 

 the caudal division and the superior from the middle of the dorsal border of 

 the middle division, may perhaps be the analogies of these two dorsal cell- 

 masses. Such a view has considerable support in the great range of varia- 

 tions seen in the divisions of nuclear material efTected by the nerve fibers. 



Lying along the middle three-fifths of the ventral border of the main 

 cell-sheet of the mesial accessory olive, is an irregular cell-column (figure 4) . 

 This column also lies ujion the pyramids. Histologically, there is more 

 correspondence to the structure of the arcuate nuclei than to the mesial 

 olive, but its relation to the mesial accessory complex may be assumed by 

 virtue of its position (figure 11). The caudal portion of this arcuate-olivary 

 column is attached to the cephalic portion of the caudal division of the main 

 cell-sheet, but no other connection with the mesial olive is made out. This 

 column shows a gradual dorsal prolongation just inferior to its middle portion 

 and a small but prominent ventro-lateral spur above its middle. It ends 

 just caudal to the cephalic ending of the middle division of the main cell- 

 mass, projecting somewhat mesially in its more superior part. This cell- 

 mass is easily made out in figure 1. 



The right medial accessory olive, as modeled and fixed in position to 

 show constantly its relationships, shows, as far as can be made out, the same 



