32 ^4 Rec()iislni(ii()ii of (he Nuclcdr Alasses in 



cell can be made out in the sections, but these cells have not been included, 

 the model being onl^' of those cells which show a characteristic grouping. 



The superior cell-column in the nucleus ambiguus (figure 4) begins 

 caudalh' as a verj- small column of cells, which rapidly widens into an oval 

 cell-mass with the long, transverse diameter antcro-posteriorly, but with 

 the dorsal end slightly drawn toward the mesial line. Directly above this 

 is a marked constriction, superior to which begins the main division of the 

 cell-column. This is oval on cross-section, the long axis coinciding with the 

 long diameter of the lower cell-mass. This main division progresses upward, 

 widening somewhat at first, but soon gradually narrowing into a second 

 constriction. Cephalic to this constriction is a small dilatation of the 

 nuclear column, above which a third constriction occurs. The cells in the 

 constriction increase in number and in distribution as one goes cephalad, 

 the result being a slightly increased size of the column. This gradually 

 narrows and tapers off into the cephalic termination of the column of cells. 

 The cephalic ending concerns only a small column of cells, but is well defined. 



NUCLEUS NERVI COCHLE/E. 



In the new-born medulla Dr. 8abin found that the nucleus of the coch- 

 lear nerve was rectangular in outline, with a thick ventral portion and a 

 thin dorsal layer lying against the surface of the corjius restiforme. 



The cochlear nucleus in the adult shows most of its characteristics on 

 lateral view (figure 2). Lying lateral and, in j^art, ventral to the corpus 

 restiforme, the nucleus contributes in part to the wall of the lateral recess 

 of the fourth ventricle. Dorsal and mesial to the nucleus lies the corpus 

 ponto-bulbare (Essick). 



The lateral view (figure 2) of the cochlear nucleus reveals a large ventral 

 parallelogram, from the spinal end of which the dorsal nucleus projects 

 around the corpus restiforme. The ventral border is irregularly notched: 

 the most cephalic of the notches corresponds to the entering root fibers. 

 Below this notch the ventral border slopes caudalwards and dorsally to 

 turn abruptly, at the inferior limit of the nucleus, into a fairly straight dorso- 

 ventral border. This straight caudal border, bending in the direction of the 

 lateral limit of the corpus restiforme, curves cephalad to form the dorsal 

 and mesial limit of the dorsal nucleus. The cephalic border is fairly straight 

 in its dorsal half, with a general dorso-ventral direction, but with the ventral 

 end slightly cephalad to the dorsal. About the middle of this cephalic border 

 there occurs an abrupt turn cephalad, then a right-angled defiection ven- 

 trally, resumed in a general cephalic direction, parallel to the ventral border. 

 The ventral broader and larger portion is further separated by a right-angled 

 elevation of the dorsal portion continuing the dorso-ventral line from the 

 middle of the cephalic border. This gives the a]ipearance as if the ventral 

 nucleus were inserted into the dorsal portion. \\\\]\ some histological proof 

 and the peculiar morphologically suggestive separation, the segregation of 



