MR. J. L. CLARKE ON THE INTIMATE STRUCTURE OF THE BRAIN. 329 
tubercle of Rolando, having in front the cut ends of numerous bundles of de- 
scending root of trigeminus inclosed in a beautiful network of fibres containing 
nerve-cells. The tubercle is connected with the motor nucleus (U) of trige- 
minus by fibres ; i, upper part of inner auditory nucleus ; d o, outer auditory 
nucleus, extending backward to the cerebellum ; P", the anterior auditory 
nerve, entering this nucleus at d o, beneath the restiform body. Both the 
nucleus, and the root of the nerve P" are intimately connected with the outer 
side of the grey tubercle and with the network within it ; p\ radiating fibres of 
restiform body in the middle peduncle ; p", p'", arciform fibres from the same 
part extending round the olivary body ; J', corpus dentatum cerebelli. 
Fig. 47. Dissected portion of human fourth ventricle of left side : — c d, the restiform 
body or inferior peduncle of the cerebellum ; d", middle peduncle of cere- 
bellum ; C", large root of trigeminus ; D', its conical nucleus ; P", anterior 
division of auditory nerve; i, concavity left by removal of inner auditory 
nucleus beneath which P" enters the outer auditory nucleus. The anterior 
and under portion of the trigeminal nucleus D', connected with the point of 
the fillet ( f ), gives origin to the small or motor root (G') of the trigeminus, 
which is separated from the large root (C"j by a small bundle of the middle 
peduncle (A') coming from the pons. The larger root (C") is separated from 
the anterior auditory nerve (P") by a larger bundle of the middle peduncle 
coming from the pons ; E', superior peduncle rolled forward, exposing a thick 
and broad tract of grey substance (D") extending obliquely upward beneath it 
from the conical nucleus (D') of the trigeminus ; F, loop of the facial nerve. 
Fig. 48. Left lateral half of the medulla with part of the inferior vermiform process of 
the cerebellum from the Rabbit : — e, grey tubercle ; d', cut end of descending 
root of trigeminus in front of it ; P", anterior root of auditory nerve ; d", cut 
ends of longitudinal fibres at root of grey tubercle, in connexion with fibres of 
anterior auditory root ; d o, outer auditory nucleus giving origin to anterior 
root of auditory nerve ; i , upper part of inner auditory nucleus ; E' E", plexus 
of bundles, with intervening cells running through the lower part of superior 
peduncle to vermiform process (I' I"); T", longitudinal portion of loop of facial 
nerve ; s, antero-lateral nucleus. 
PLATE XIII. 
Fig. 49. Transverse section of left lateral half of medulla oblongata of Cat, at level of 
auditory nerve : — P w , under and whiter portion of nerve entering the outer 
auditory nucleus (d.o); P', bulbous portion crowded with nerve-cells; e", de- 
scending root of trigeminus ; s , antero-lateral nucleus connected with its oppo- 
site fellow of decussating fibres across the raphe. 
Fig. 50. Transverse section of the fourth ventricle in Man on left side: — g" g'", super** 
2 z 2 
