MR, J. L. CLARKE OK THE INTIMATE STRUCTURE; OF THE BRAIN. 293 
•(f ), gives origin to the small or motor root (G') of the fifth nerve, which is separated 
from the large root(C") by the smaller division (A') of the triangular space, transmitting 
a small bundle of the middle peduncle coming from the pons Varolii. The larger root 
of the fifth nerve (C") is separated from the anterior auditory nerve (P") by the larger 
division (B') of the triangular space, transmitting a corresponding portion of the middle 
peduncle, ascending also from the pons. At E' the superior peduncle of the cerebellum 
is rolled forward, exposing a thick and broad tract of grey substance (D") which extends 
obliquely upward beneath it from the conical nucleus (I)') of the fifth nerve. On the 
inner side of the auditory nucleus (*)■ is an oval mass (F) imbedded in the substance of 
the fasciculus teres, and connected with the facial nerve. 
(42) In Mammalia generally the auditory nuclei and nerves present nearly the same 
appearances as those which I have described in Man ; but in all those animals there are 
one or two points of difference, and in some there are certain peculiarities which deserve 
notice. In all the larger Mammalia, as the Ox, Sheep, &c., the nerve-cells of the outer 
nucleus which gives origin to the anterior or lower root of the auditory nerve, are much, 
superior in size to those of the human medulla. Moreover the anterior root on enter- 
ing the nucleus is generally somewhat more divergent than in Man, as may be seen at 
P", fig. 48, Plate XII., which represents the left lateral half of the medulla and part of 
the inferior vermiform process of the cerebellum in the Rabbit. Amongst the divergent 
roots are many longitudinal fibres, which are especially numerous at the bottom (d 1 !) of the 
grey tubercle ( e ). In the same animal the 'posterior root of the nerve is very large, and 
is especially remarkable for the enormous convex enlargement, or ganglion on its sur- 
face, at the side of the fourth ventricle just before it enters the inner nucleus. In the 
Cat this remarkable ganglion is absent ; but as the nerve proceeds outward it gradually 
swells into a large club-shaped ganglionic mass (PP', fig. 49, Plate XIIL), which is 
crowded with nerve-cells. The inner nucleus (d 6) is largely developed, and its con- 
nexion with the inner layer (P m ) of the nerve, which consists chiefly of white fibres, is 
very distinct. Below the inner nucleus (do) is the descending trigeminal root (e"), which 
here forms a broad and compact layer of fibres on the outer side of the grey tubercle (e). 
On the inner side of this tubercle is the large round antero-lateral nucleus (s), which is 
connected on the one hand with the arciform fibres sweeping round from the restiform 
body ( p',p "), and on the other hand, with its opposite fellow, by means of a broad band 
of commissural fibres which decussate across the raphe with those of the opposite side*. 
(43) Just above the posterior root of the auditory nerve the auditory nucleus becomes 
closely connected with the flocculus ; and at the level of the anterior root (P", fig. 48, 
Plate XII.) the nuclei (d o and i) stretch backward and inward to join the side of the 
inferior vermiform process (I' I"). At this part the plexus of bundles from the outer 
* In the Rabbit the glossopharyngeal nucleus is very large, and the fibres which cross it from the inner 
auditory nucleus (see t", fig. 24, Plate X.) are unusually numerous. On a former occasion (Phil. Trans. 1859) 
I pointed out the very large size of the caput cornu and grey tubercle in all the Rodentia. The grey tubercle 
in the Rabbit is seen at e, fig. 48‘, Plate XII., surrounded by the descending root of the fifth nerve (e"). 
