ME. J. L. CLAEKE ON THE INTIMATE STEHCTUEE OF THE BEAIN. 
275 
the spinal-accessory nerve, and carried downward through the parts of the medulla 
represented by figs. 7, 6, 5. From such a longitudinal section fig. 27, Plate X. was 
drawn. The lower edge (L t) of the figure corresponds to the line L t of fig. 5, Plate 
VIII. d is the superficial white substance of the lateral column, to the depth of the 
angle formed by the lines L O, fig. 5, Plate VIII. It consists of coarse longitudinal 
nerve-fibres, irregularly interlaced and crossed at right angles by some finer transverse 
fibres, d' is the posterior part of the network which reappears after the bundles in its 
meshes have ceased to supply the anterior pyramid, and corresponds to that part of the 
line L t in fig. 5, Plate VIII., which lies between O and n. It consists of finer fibres 
than those of the preceding or superficial white layer. These fibres are moreover 
collected into neat longitudinal bundles, which are very close together and parallel, but 
communicate with each other by very oblique lateral offsets, so as to enclose a multitude 
of fusiform, and often exceedingly elongated meshes, which are filled with groups and 
streaks of nucleated cells and nuclei, of a corresponding shape and size. Some of the 
processes of the cells extend along the longitudinal bundles, while others project across 
them in the plane of the section and in the direction of numerous fibres issuing from 
the spinal-accessory nucleus ( t t). 
As they ascend the medulla, the deepest longitudinal bundles (W, fig. 27, Plate X.) of 
this layer diverge inwards, and become much more widely separated from each other, 
but still communicate by lateral offsets. At the upper border of the figure this portion 
of the layer (n m ) in the longitudinal section, occupies the part between N and n ; and 
in a transverse section of the medulla at this level (fig. 8, Plate VIII.) it occupies that 
portion of the line L which also extends between N and n. Several of the innermost 
fibres, in ascending from n! (fig. 27, Plate X.), unite into bundles to form the slender 
longitudinal column n, which increases in thickness and curves inward and backward as 
it approaches the upper border of the figure. In fig. 8, Plate VIII., this little column 
{n) is seen in transverse section. In the transverse section (fig. 5, Plate VIII.), which 
corresponds to the lower border of the longitudinal section (fig. 27, Plate X.), it is at 
first separated from the spinal-accessory nucleus (t) by the numerous bundles of transverse 
fibres which sweep round from behind forward to decussate into the anterior pyramid. 
In the longitudinal section (fig. 27, Plate X.), the cut ends of these transverse bundles 
are represented at the lower border of the figure by the dark dots at n ". . They are con- 
tained in the transversely elongated meshes of a network composed chiefly of fibres pro- 
ceeding from the spinal-accessory nucleus (t), and connected with numerous nerve-cells. 
As the slender longitudinal column ascends the medulla to n, fig. 27, the transverse 
bundles ( n ", dark dots) diminish in number until they are reduced to a comparatively 
few fibres, which are seen in the transverse section (fig. 25, M, Plate X.), arching round 
the inner border of n. But in proportion as these transverse bundles diminish on the 
inner side of the slender column, the fibres proceeding from the posterior portion (AA, 
fig. 25, Plate X.) of the spinal-accessory nucleus sweep forward round it on its outer 
side, in company with other fibres coming from the posterior pyramid. In fig. 8, Plate 
