ME. J. L. CLAEKE ON THE INTIMATE STEUCTUEE OE THE BEAIN. 
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crossing the fan-shaped set of commissural fibres and reaching as far as the scattered 
cells intervening between it and the spinal-accessory nucleus. The lateral roots com- 
pletely inclose the group of cells, those on the outer side curving inward, and those on 
the inner side taking an opposite course. The latter often approach the raphe at L' so 
closely that they might easily be supposed to cross it ; hut they may always be traced 
outward and backward as far as a separate but small group of cells (K7) lying nearer 
the side and lower border of the canal. This little group or column contains numerous 
longitudinal fibres, and is composed of much smaller cells than those of the hypoglossal 
nucleus. At this level of the medulla it is in some sections scarcely perceptible, but it 
increases in size as it ascends, and is a structure of great importance ; for I shall pre- 
sently show that it forms the lower end of the column of cells and fibres which consti- 
tute the fasciculus teres, and part of the nucleus of the facial nerve. We have here, 
then, a most interesting communication between the facial nerve and even the lower 
roots of the hypoglossal. Still further back and nearer the canal is another very small 
group of nuclei, the use of which I have not ascertained. 
(20) For some distance around the canal there is a dense layer of exceedingly fine 
nucleated fibres, which decussate each other both behind and in front (L/), and run down 
the raphe towards F. Further out from the side of the canal they are joined by similar 
fibres which proceed from the oval group of the spinal-accessory nucleus (H), and from 
the little group (K') belonging to the facial nucleus. In the Ox, Sheep, Rabbit, &c., 
all these fibres are more conspicuous than in Man. They are crossed at right angles by 
a multitude of longitudinal fibres of a similar nature, which form a layer that is denser 
in proportion as it approaches the border of the canal. 
(21) I have already stated that fine fibres run between the hypoglossal and spinal- 
accessory nuclei. At a higher level of the medulla I discovered a still more intimate 
and a most important connexion between these parts. It can only be properly seen in a 
longitudinal and horizontal section made at the point of the calamus scriptorius and 
carried up through the middle of the hypoglossal and spinal-accessory nuclei ; for 
the fibres arch upward, and are therefore more or less divided in a transverse section. 
Fig. 31, Plate X. represents such a longitudinal section; and fig. 32, Plate XI. a trans- 
verse section of the parts of these nuclei left after the longitudinal section was made, so 
that the line of section J, PI, H' corresponds to the lower edge J, H, IT of fig. 31, Plate X. ; 
where J is the hypoglossal nucleus, and PI the group of cells forming the anterior pro- 
jecting horn of the spinal-accessory and vagus nucleus, on the inner side of the slender 
column n, where the nerve r enters. In the hypoglossal nucleus (J', J", fig. 31, Plate X.) 
a number of cells send their processes laterally outward in an arched direction to the 
inner or anterior horn (H) of the spinal-accessory nucleus ; and from this, hi return, 
elongated cells send their processes inward to the hypoglossal nucleus (J"). The majority 
of the cells of the anterior horn (PI) of the spinal-accessory nucleus are elongated longi- 
tudinally with a multitude of fibres, and some of the transverse fibres coming from 
the hypoglossal nucleus (J") cross these to the outer part of the spinal-accessory nucleus 
(H'), and thence to the slender column n. 
mdccclxviii. 2 E 
