ME. J. L. CLAEKE ON THE INTIMATE STEUCTUEE OE THE BEAIN. 
311 
(76) Now some of the connexions which I have pointed out between the fibres of the 
anterior pyramids and certain other parts of the medulla oblongata, are exceedingly 
interesting in a physiological point of view*. I have shown, both now and on former 
occasions, that the spinal-accessory nerve may be traced to several different centres of 
origin. Its upper rootlets arise from a special nucleus or column of cells, which descends 
behind the canal to about the level of the lower end of the olivary body ; while its lower 
rootlets arise from the lateral grey substance, and from the anterior grey substance which 
gives origin to the lower roots of the hypoglossal nerve and to the anterior roots of the 
spinal nerves in the cervical region. According to Bendz and Claude Bernard, the 
upper roots — which I have shown to arise from the special nucleus behind the 
central canal — go to form the internal branch which joins the vagus and is distributed 
through it to the larynx, pharynx, and palate ; while the lower rootlets — which we have 
seen to arise from the antero-lateral grey substance of the cord and of the lower part of 
the medulla — are collected into the external branch, which supplies the trapezius and 
sternomastoid muscles employed in voluntary and forced efforts of respiration. Now it 
is particularly interesting to find, as I first showed in 1858, that decussating fibres of 
the anterior pyramid in their course downward from the cerebrum, turn obliquely 
backward to the point about which the special nucleus and upper roots cease to arise , 
and the lower roots begin. In fig. 5, Plate VIII., we see these bundles crossing each 
other from the opposite anterior pyramids (y y), then curving backward round the sides 
of the hypoglossal nuclei (t 1 ), and of the special spinal-accessory nuclei (if). Their outer 
bundles are connected at n, fig. 5, with the lateral grey substance where the lower roots 
of the spinal-accessory nerve r begin (fig. 28, Plate X.). In fig, 27, Plate X. we have 
an oblique transverse section of the left side of the medulla in the direction L, t, fig. 5, 
Plate VIII. In this section we see the transversely-cut ends of these decussating 
bundles (n") of the anterior pyramids, with fibres extending amongst them from the 
spinal-accessory nucleus ( t t). On their outer side we see the slender longitudinal 
column (n') ascending, from the point where the higher roots cease and the lower roots 
begin, to the side of the vagal nucleus, as already described (§ 15). Moreover, in 
descending the medulla oblongata and cervical region of the spinal cord, the decussating 
fibres of the anterior pyramids pass into and through the antero-lateral grey substance 
where the lowest roots continue to arise (see figs. 4, 3, 2, Plate VIII.). There appears, 
then, to be scarcely a doubt that these particular decussating bundles of the anterior 
pyramids are the channels through which the will influences the movements of respira- 
tion. It is very probable also that they are functionally related, in the same way, to 
the hypoglossal nuclei ( t '), or at least, that they are one of the channels through which 
the will acts on the hypoglossal nerves. 
(77) The functions of the olivary bodies have been the subject of much discussion 
amongst physiologists of different ages. Willis, I believe, was the first who considered 
them as the central organs of articulate speech f. Burdach and Betzius regarded them 
* The reperusal of the five last paragraphs of section 15 is here recommended. t Cerebri Anatome. 
MDCCCLXVIII. 2 X 
