ME. J. L. CLAEKE ON THE INTIMATE STEUCTUEE OF THE BEAIN. 
267 
viduals in Man, than in mammalia of the same species ; but the general arrangement of 
the parts is nevertheless the same in all. Fig. 11, Plate IX. represents the posterior 
aspect of the medulla oblongata of a healthy middle-aged man who died in consequence 
of an accident: a is the cut surface of the lower end of the medulla, near the level of 
the points of the anterior pyramids. Adjoining the median sulcus, on each side, is the 
posterior pyramid (5), which, as it ascends to the point of the calamus scriptorius, ex- 
pands into a thick bulbous mass ( b '), and then diverges as a flattened band. External 
to the pyramid is the restiform body (c), which also enlarges as it ascends to the same 
level. Between this and the posterior edge of the antero-lateral column ( d ) is a super- 
ficial tract of grey substance (e), consisting of the expansion of the caput cornu, or 
dilated extremity of the posterior horn, and known as the grey tubercle of Bolando. 
(9) At the point of the calamus scriptorius, on each side of the median line, is an 
oval or pyriform mass of ganglionic substance (g), of a bluish or pearly hue, constituting 
the superficial part of the nucleus of the vagus nerve, seen in section at g , fig. 9, Plate 
VIII. ; and the small tract ( t ') between this and the median fissure is the upper part of 
the nucleus of the hypoglossal nerve, seen in section in fig. 10, Plate VIII. ; its lower 
end being covered in by the spinal-accessory nucleus and the posterior pyramids ( t , b\ 
figs. 6, 7 & 8, Plate VIII.). In the angle between the outer side of this vagal nucleus 
( g , fig. 11, Plate IX.) and the upper divergent end of the posterior pyramid (5'), is the 
commencement of another and larger mass of grey substance (i), which is seen in section 
in fig. 10, Plate VIII., and forms the posterior nucleus of the auditory nerve, covered by 
epithelium. 
(10) If the posterior pyramid b V {on the left side ) be carefully dissected from the 
restiform body (c), from below upwards, and he thrown forward, as shown in fig. 12, 
Plate IX., the exposed surface of the medulla will present the appearances delineated 
at the lower half of this figure ; t is the downward continuation of the vagal nucleus or 
tract, constituting the nucleus of the spinal-accessory nerve, and previously covered in 
by the bulb of the posterior pyramid (b 1 ), as shown at t, fig. 7, Plate VIII. in a trans- 
verse section. The oval mass g, marked off by the dotted line, is the inner and posterior 
portion of the vagal nucleus exposed at the point of the calamus scriptorius by the 
divergence of the posterior pyramid ; l is its inner and more anterior portion, covered , 
like the spinal-accessory nucleus t, lower down, by the posterior pyramid, as seen in 
transverse sections, figs. 8 & 9, Plate VIII. Its upper point ( m ) forms the principal 
nucleus of the glossopharyngeal nerve. Along the outer and anterior part of this grey 
tract is a slender, longitudinal white column (n), which it lodges, as it were, in a groove 
(see n, fig. 9, Plate VIII.), and which tapers to a point as it descends obliquely inward 
along the base of the posterior pyramid to the mesial line (see n, fig. 12). In its course 
upward it ascends along the inner edge of the pyramid, and joins those fibres of the 
latter which pass into the anterior or outer auditory nucleus (see n, fig. 42, Plate XII., 
and fig. 58, Plate XIV.). On the outer side of this slender white column is a some- 
what fusiform mass of grey substance, o (fig. 12, and oo', fig. 24, Plate X.), imbedded 
