606 



THE BRAIN. 



nucleus or in nerve-cells lying dorsal to the accessory nucleus, and especially 

 in a group of cells giving rise to the tuberculum acusticum, which, small in 

 man, is conspicuous in some animals. Hence, the farther part of this dorsal 

 root, as it winds round the lateral and dorsal surface of the restiform body, 

 consists largely, if not wholly, of fibres which are derived not directly from 

 the trunk of the nerve, but indirectly through the relay of the accessory 

 nucleus or of other cells. Reaching the dorsal surface of the restiform body, 

 these fibres appear on the floor of the fourth ventricle as the strice acusticce 

 (Fig. 131, sr.), and end partly in the median nucleus, partly in other regions 

 of the bulb. The exact determination, however, of the endings of this root 



FIG. 134. 



Through the widest part of the Fourth Ventricle. (Sherrington.) Taken in the line 111, Fig. 

 131. Py., pyramidal fibres cut transversely ; tr. P., the superficial (ventral) transverse fibres of the 

 pons. The shaded part of the pons (gr. P.) indicates gray matter mingled with the deeper trans- 

 verse fibres. -F., the fillet ; Tp., the trapezium ; C. R., the restiform body or inferior peduncle of 

 the cerebellum, cut across obliquely : -S. P., the superior peduncles of the cerebellum ; r., raphe ; 

 s. o., superior olive ; C. D., corpus dentatum of the cerebellum ; Iff. n., the nucleus of the roof; 

 s. g. t tubercle of Rolando ; V. S., section through sulcus in the vermis superior of the cerebellum , 

 t., bundle from the olive to the lenticular nucleus VIII., the eighth or auditory nerve, its ventral 

 or vestibular root proceeding from VIII. ft. the front part of the lateral auditory nucleus ; VII. n., 

 the nucleus of the seventh or facial nerve ; VI., the nucleus of the sixth nerve ; VII. g., fibres of 

 the seventh nerve cut across as they sweep round the nucleus of the sixth before issuing from 

 the pons at VII.; 4th, the fourth ventricle, here roofed in by the cerebellum; the shading of 

 the central gray matter immediately surrounding the ventricle is, for the sake of simplicity 

 omitted. 



is a matter of considerable difficulty ; some observers regard the accessory 

 nucleus as homologous, not with the Gasserian and with the spinal ganglia, 



