298 
ME. J. L. CLAEKE ON THE INTIMATE STEUCTUEE OE THE BEAIN. 
inward in the direction of the line m\ m", fig. 51, Plate XIII. (examining by means of a 
lens the cut surface of the medulla after each section), until I found that I had exposed 
the outer fibres of the nerve. The remaining portion of the nerve, in its course inward 
to the “ fasciculus teres,” was then exposed by carefully taking off a succession of similar 
sections in planes inclining more and more horizontally inward as the “ fasciculus teres ? 
was approached, the last sections being quite horizontal, from l' to l ", fig. 56, Plate 
XIII.., and therefore including the posterior portion of the longitudinal column (T") 
lying at the side of the median furrow ( h When this process was completed, it was 
found that the nerve, on reaching the fasciculus teres, bent longitudinally down the 
medulla, and after a very short course, again bent transversely forward, to form a loop 
along the side of the median furrow, as shown at q" in the Sheep (fig. 53, Plate XIII.) 
and in Man (fig. 54). The summit of this curve constitutes the longitudinal bundle of 
fibres of which the oval cut-end in transverse sections is seen at T", figs. 51, 52, & 56. 
In the Sheep the course of the nerve q", fig. 53, through the medulla on its way to the 
“fasciculus teres” is nearly straight, and nearly at a right angle to the axis of the 
medulla; while in Man (fig. 54) its course through the medulla is not only rather ser- 
pentine or wavy, but inclines somewhat upward. Hence the differences of appearance 
between transverse sections in Man and those in animals. The loop which it forms 
reaches close up to the edge of the median furrow ( h "), and encloses its nucleus (Q"), 
which together with it forms the oval swelling (r") seen on the surface of the fasciculus 
teres of the opposite side. The lower arm of the loop in its course forward divides 
like a brush into separate fibres which plunge into the motor nucleus of the fifth nerve, 
and into the superior olivary body ( s Pig. 55, Plate XIII., represents a thin section 
of this loop, made in the plane of its course, from Man, magnified about 100 dia- 
meters, and viewed as from the side of the medulla, g'" g'" is the superficial grey layer 
on the surface of th e fasciculus teres , and seen in transverse section at l" g” g"', fig. 56, 
Plate XIII. The root of the facial nerve (v'" q”, fig. 55), just before it curves down- 
ward along the side of the median furrow, beneath the superficial grey layer, is divided 
into separate bundles by long but very narrow streaks of longitudinal fibres, represented 
by the perpendicular, dotted lines. Its uppermost fibres (at v'") run directly backward 
and slightly upward to a collection of small .cells and nuclei ( v ") lying beneath the super- 
ficial grey layer of the ventricle, which is here composed of fine longitudinal fibres and 
numerous oval cells. The rest of the nerve divides into two portions, composing a 
superficial and a deep stratum of fibres. Its superficial stratum, on reaching the grey 
layer, curves downward , — that is, to the right, and in the plane of the paper, as seen in 
fig. 55, — to form the loop already mentioned. Its deep stratum of fibres bends forward, 
that is, perpendicular to the plane of the paper, and not to the right, in looking at fig. 
55. For the most part they directly enter the nucleus Q", as shown at <f Q", fig. 56. 
The course of these two strata of fibres may be better understood, perhaps, by supposing 
fig. 56 to be turned halfway round to the right with its plane perpendicular instead of 
parallel to the plane of fig. 55, and so that its nerve c[' shall coincide with the nerve q" 
