Bauhaus-Universität Weimar

Titel:
The Cyclopaedia of Anatomy and Physiology, vol. 4: Pla [corr.: Ple] - Wri
Person:
Todd, Robert Bentley
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit29465/757/
SPINAL ACCESSORY NERVE. 747 
the posterior and anterior spinal nerves at 
their origin. 
The spinal accessory in its course within 
the spinal canal frequently forms communi¬ 
cations with the posterior root of the first 
cervical, and much more seldom with the 
posterior root of the second cervical nerve.* 
When these communicating filaments come 
from the second cervical, they are generally 
few in number. This communication between 
the spinal accessory and the posterior root of 
the first cervical is, according to Lobstein, 
more frequently present than absent.f When 
the posterior root of the first cervical joins 
itself, either in whole or in part, to the spinal 
accessory, a branch of equal size generally leaves 
the accessory, either at the point where it is 
joined by the posterior root of the first cervi¬ 
cal, as figured and described by Asch J, or a 
little above this junction, as figured by Hu¬ 
ber^ and described by Bellingeri. |] This 
branch, after leaving the accessory, proceeds 
outwards, approaches the anterior root of 
the first cervical, and takes the place of the 
posterior root of that nerve.®!! When the 
posterior root comes from the accessory, 
it generally presents a ganglion in the usual 
position. Sometimes, however, though rarely, 
this ganglion is found on the accessory where 
the posterior root of the first cervical leaves 
it to join itself to the anterior root. This 
ganglion was first pointed out by Huber ; its 
existence has been denied by Lobstein, Asch, 
Haller, and Scarpa, and it has again been 
described by Bellingeri. I have seen this gan¬ 
glion twice, and it was present on one side 
only. It becomes an interesting question in 
a physiological point of view to know, whether 
or not the whole of the filaments of the pos¬ 
terior roots of the spinal nerves which join 
themselves to the accessory, again leave it 
to form the posterior root of the first cervical. 
Bellingeri answers this question in the affirm¬ 
ative. “ The filaments,” he says, “ coming 
from the posterior roots to the accessory are 
not intermixed, but only approximated, so that 
they can be separated by slight traction.”** 
* Scarpa states (opus cit. p. 395.) that in a great 
number of bodies he examined with a special refer¬ 
ence to this point, he found a communication be¬ 
tween the accessory and the posterior root of the 
second cervical only in two instances. 
f Circa harum radicularum, quæ pro radicibus 
posticis primi paris habenter, communicationem 
illud notamus, quod sæpius accessorium subire, quam 
eundem intactum relinquere observenter. Opus cit. 
p. 223. 
J De Primo Pare Nervorum Medullæ Spinalis, 
tab. x. fig. 2. ; et explicatio, p. 335. Ludwig Scrip. 
Nevr. Min. Sei. tom. i. 
§ Opus cit. 
|| Opus cit. p. 80. Monro secundus has also given 
a representation of this communication between the 
accessory and posterior root of the first cervical. 
Observations on the Structure and Functions of the 
Nervous System, tab. x. fig. 2. 1783. 
Bischoff states (opus cit. pp. 34. 82.) that in 
none of the numerous instances in which he dis¬ 
sected the accessory in the lower animals, did he 
ever observe any filaments of the posterior roots of 
the spinal nerves join themselves to it. 
** Opus cit. p. 81. 
And in another place he says, “ I believe that 
the filaments from the posterior roots, which 
join the accessory, leave it again to proceed 
to the posterior root of the first cervical.”* 
From this he concludes that the accessory 
contains no sensiferous filaments. Miiller, on 
the other hand, has adduced some unusual 
anatomical arrangements in this nerve, which 
may be regarded as favouring the opinion that 
it contains sensiferous filaments independant 
of those which it may receive from the pos¬ 
terior roots of the spinal nerves. He men¬ 
tions an instance f, which he elsewhere J 
describes at considerable length, where the 
posterior root of the first cervical nerve on 
the right side was not present, and where its 
place was supplied by two bundles of fila¬ 
ments from the superior part of the spinal 
accessory. The upper of these bundles, at 
least, came from the medulla oblongata. 
Upon the posterior root of the first cervical 
thus constituted, a ganglion was formed while 
it was still within the theca vertebralis. The 
upper fibres of the posterior root of the 
second cervical of this sidelined themselves 
to the accessory, but no nervous filaments 
were attached to the spinal chord in the usual 
position of the posterior root of the first 
cervical. On the left side, the posterior 
root of the first cervical presented its usual 
appearance, and was connected to the spinal 
accessory by some filaments of communi¬ 
cation. The filaments of the accessory arising 
from the medulla oblongata did not, as on the 
right side, divide themselves into two parts, 
one of these becoming the substitute of the 
posterior root of the first cervical : but the 
whole ran upwards into the accessory nerve.|| 
Miiller also states that Hyrtl has often seen 
a ganglion upon the accessory nerve opposite 
the entrance of the vertebral artery into the in¬ 
terior of the cranium ; and that Remak showed 
him an instance of a ganglion upon the spinal 
accessory at its passage through the foramen 
lacerum. “ I do not, however, affirm,” Miil¬ 
ler remarks in reasoning from these cases, 
“ that the spinal accessory always contains 
originally sensiferous filaments, but leave it 
doubtful.” “ But in the case,” he continues, 
“ where the nervus accessorius forms an inti¬ 
mate connection with the posterior root of 
the first cervical, or any other nerve, we may 
suppose an interchange; and this, in the same 
degree, will render probable the idea of Monro, 
* Ibid, p. 79. 
f Archiv, für Anat. und Physiol. 1834, p. 12. 
j Idem opus, 1837, pp. 279—281. 
§ Arnold (Bemerkungen über den Bau des Hirns 
und Bückenmarks, &c., S. 181—183 ; Zürich, 1838) 
has published remarks upon this anomalous instance 
in the origin of the posterior root of the first cervical 
from the accessory, the object of which is to en¬ 
deavour to show that Müller had misinterpreted 
the facts observed. Among other things urged 
with this view, is the circumstance that the pos¬ 
terior root of the first cervical does not arise usually 
in the same line with the posterior roots of the 
other spinal nerves, but somewhat anterior to these. 
We cannot, however, believe that so experienced 
and accurate an anatomist as Müller is, could fall 
into any such mistake as is here insinuated.
        

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