ME. J. L. CLAEKE ON THE INTIMATE STEUCTUEE OF THE BEAIN. 
303 
curve first slightly downward, then upward, and again downward as they reach the floor 
of the ventricle ( b , c). In consequence of this peculiar course, we find that in transverse 
sections of the pons, at this level, the roots of the abducens nerve are always cut into 
portions of variable length. Moreover, in transverse sections it is found that they are 
also somewhat tortuous from side to side , and that, unlike the roots of the other cerebral 
nerves, they curve outward instead of inward towards the raphe, as may be seen in 
figs. 51 and 56, V, Plate XIII., from the adult brain, and fig. 65, Plate XIV., from 
the brain of a child five years old. 
(60) The lower bundles of the roots (V', fig. 51, Plate XIII.), as they approach the 
fasciculus teres, give off some lateral branches or tufts of fibres which curve outward to 
the column lying immediately below, or in front of, the great nucleus ( Q "), and containing 
branched nerve-cells, with numerous longitudinal and transverse fibres, the latter of 
which might easily be mistaken for these branches. They then taper into a kind of 
narrow band, composed of the remaining fibres, which curves backward and outward 
round the inner side of the great nucleus (Q"), and along the outer margin of the longi- 
tudinal portion (T") of the loop of the facial nerve. Amongst this band are numerous 
cells of considerable size and of different shapes,- but for the most part oval, and elon- 
gated with their processes in the direction of the fibres. They appear to form part of 
the great nucleus (Q"). Some of the fibres curve outward into the middle of this nucleus ; 
others curve outward round its posterior border, where they meet fibres coming in an 
opposite direction from the facial nerve (q"), the two sets together forming a kind of 
loop, interspersed with nerve-cells and some longitudinal bundles. The remaining 
fibres run directly backwards, and crossing the facial roots between the nucleus (Q") and 
the longitudinal column (T") of the facial nerve, diverge into the superficial grey layer 
of the fasciculus teres, at rj". Some of them run more or less directly backward towards 
the surface ; some turn outward over the convex surface of the facial nerve, amongst 
nerve-cells of considerable size lying at the bottom of the grey layer ; while the rest 
turn inward around the posterior border of the longitudinal column (T"). 
(61) As it ascends beneath the floor of the fourth ventricle the common nucleus (Q", 
fig. 56, Plate XIII.) becomes gradually smaller. Its outer portion, or that which is in 
connexion with the roots of the facial nerve {(f), consists, as it does lower down, of nume- 
rous large multipolar cells and many longitudinal bundles ; but in its inner portion, or 
that which is more immediately connected with the roots of the abducens nerve (V'), the 
cells are for the most part smaller, less numerous, and elongated in different directions, 
or crescentic ; while the longitudinal bundles (represented by the dark masses), which 
are often embraced by the cells, and of which many are exceedingly thick, have in- 
creased considerably in number and are enclosed in the meshes of a network formed by 
the rootlets of the abducens nerve, exactly as represented in fig. 56. These rootlets 
unite rather abruptly, like the roots of a plant, to form four or five bundles (V'), which 
lean against each other at the point of junction, and then separate or diverge slightly 
as they traverse the pons Varolii outward. Many of the fibres, however, that con- 
mdccclxviii. 2 u 
