STRUCTURE OF THE PONS VAROLII. 



739 



already been divided along the line of the pyramid of the right side 

 (fig 263, p. 734) and turned outwards so as to denude the longitu- 

 dinal fibres (c) of that body ; and this set of longitudinal fibres, having 

 been cut across already in the medulla oblongata, may be raised as 

 far as the upper border of the pons. Beneath them will appear the 

 second or deep set of transverse fibres of the pons (fig. 264 /, p. 735). 

 The deep transverse fibres may next be cut through outside the 

 pyramidal tract (fig. 264), and the reticular formation will then be 



nvmo 



VH nVI 



pjr.t 



FIG. 267. TRANSVERSE SECTION OF THE LOWER PART OF THE PONS 

 (AFTER OBERSTEINER). 



ra. Raphe. 



ipc. Inferior peduncle of cere- 

 bellum. 



stf. Superficial transverse fibres. 



pyr.b. Pyramidal bundles. 



dtf. Deep transverse fibres. 



fi. Fillet. 



Son. Superior olivary nucleus. 



Va. Ascending root of fifth nerve. 



VI. Sixth nerve. 

 nVI. Its nucleus. 



VII. Seventh nerve. 

 n VII. Its nucleus. 



VIII. Upper root of auditory 

 nerve. 



nVIIIo. Outer auditory (dorsal 

 vestibular) nucleus. 



seen, in which deep longitudinal fibres ascend from the medulla 

 oblongata (d). 



The transverse fibres of the ventral portion of the pons pass into the Transverse 

 middle peduncle of the cerebellum. They are mostly collected into Centra? 

 two layers, superficial and deep (fig. 266), which enclose the longi- portion, 

 tudinal fibres of the pyramid ; but some transverse fibres pass 

 between the bundles of the pyramidal tract. The superficial fibres 

 are nearly horizontal in the lower part of the pons, but the upper 

 ones descend to join the cerebellar peduncle, and some are seen 

 on the surface crossing obliquely over the lower fibres. It will be 

 found, however, that the same bundles of transverse fibres cannot be 

 traced across in the pons from one side of the cerebellum to the 



3B 2 



