NINTH PAIR OF NERVES. 
NINTIT PAIR OF NERVES (Nervi 
hypoglossi, vel gustatorii, Winslow; Lingualis, 
Vie d’Azyr; Ninth nerve of Willis; Twelfth of 
Semmering.) The ninth pair of nerves take 
their origin from the side of the medulla ob- 
longata, commencing by a variable number of 
small radicles in the fissure which separates 
_ the corpus olivare from the pyramidale. 
__ The superior of these radicles are attached 
about the centre of this fissure, and the infe- , 
rior a little below its termination; they are 
laced on a line one below the other, which 
ine describes a slight curve looking upwards 
_ and backwards, following the curved form of 
_ the olivary body. 
___The origin of this nerve is superior to that 
_ of the first cervical, to which also it lies ona 
_ plane a little anterior ; it is separated from the 
_ origins of the par vagum by the olivary body, 
_ and has lying immediately in front the corpus 
_ pyramidale and the vertebral artery. 
_ The radicles which form the origin of this 
“nerve vary in number from five to ten or 
twelve ; and if any of these radicles be ex- 
amined closely, they will be found to consist of 
fee, or more minor filaments, so that it is very 
‘difficult to say exactly by how many roots or 
Origins the ninth nerve is attached to the me- 
_dulla spinalis.* 
__ These filaments in general unite into two 
fasciculi, which pass in a direction downwards, 
forwards, and outwards to the anterior condy- 
~ loid foramen, through which the nerve escapes 
rom the cavity of the cranium. 
It rarely happens that these fasciculi unite 
in the cavity of the cranium; in general, they 
‘pass on separately until they reach the foramen, 
' where in passing through the dura mater they 
yecome united into one trunk, which is here 
invested with a strong neurilemma, derived 
from the dura mater. 
__ The ninth pair of nerves, on emerging from 
the anterior condyloid foramen, is in close re- 
-Tation to the eighth pair of nerves, the internal 
rotid artery, internal jugular vein, and with 
@ superior cervical ganglion of the sympa- 
etic. » 
Here the nerve lies external to the vagus. 
onnected to it by a dense cellular tissue, for a 
about the eighth of an inch, it passes 
hind the internal carotid artery immediately 
fore that vessel enters the carotid canal, and 
ties in front of the jugular vein; here also the 
‘herve is connected to the anterior and superior 
‘Part of the superior cervical ganglion, in a 
‘Manner to be presently described. 
__ In this situation the ninth nerve lies deep in 
neck, being covered by the origins of the 
Styloid muscles, the posterior belly of the di- 
gastric, the sterno-mastoid, the skin, platysma, 
and fascia 
"The trunk of the nerve then passes down- 
wards, outwards, and slightly forwards, escapes 
from beneath the posterior belly of the digas- 
* Quarum incertus numerus causa est, cura a 
Variis varie descripte et delineate exstent. Alii 
enim quatuor, alii octo componi fasciculis dixe- 
rar = ppteete Basi encephali et originibus 
nervorum, page 168, 
VOL. IIL. 
72t 
tric and anterior edge of the sterno-mastoid, 
becomes more superficial, is crossed in -this 
part of its course by the occipital artery, and 
at a point in the neck corresponding to the 
level of the third cervical vertebra,* and 
opposite the angle of the jaw,t the nerve 
turns forwards and upwards, forming an 
arch, the convexity of which looks downwards 
and backwards; here the nerve is covered only 
by the skin, platysma, and fascia, crosses and 
lies in front of the origin of the occipital 
artery, the internal jugular vein, external ca- 
rotid artery, and vagus nerve ; passing still in- 
wards and upwards towards the posterior edge 
of the hyoglossus muscle, the nerve is crossed 
by the tendon of the digastric, lying here su- 
perior to the lingual artery. 
Itthen passes between the mylo-hyoid and the 
hyo-glossus, and having reached the anterior edge 
of the last-named muscle, it enters and passes 
through the fibres of the genio-hyoglossus, in 
the substance of which muscle it divides into 
its terminating branches, the connections and 
distribution of which shall be examined after 
we have considered the connections of this 
nerve and the branches which it gives off and 
receives in its course through the neck. 
The ninth nerve, on escaping from the an- 
terior condyloid foramen, is connected to the 
par vagum, as was before noticed, by dense cel- 
lular tissue, but also by a nervous filament; 
further on, as the ninth nerve approaches the 
transverse process of the atlas, it receives a 
twig from the first cervical nerve, or from the 
nervous loop formed round the transverse 
process of the atlas by the communicating 
branches of the first and second cervical 
nerves.{ 
In this situation, also, the ninth is connected 
by a small nerve with the superior cervical gan- 
glion. 
Ramus cervicalis descendens, seu descendens 
noni.—The next regular branch given off by 
this nerve is immediately before it turns in front 
of the jugular vein and carotid artery, when it 
gives off a large and regular branch called cer- 
vicalis descendens,. or descendens noni. 
The point at which the ninth nerve gives off 
this branch is immediately below the angle of 
the jaw, and where it escapes from under the 
edge of the sterno-mastoid muscle. The de- 
scendens noni from this passes downwards and 
forwards to the inferior part of the neck; at 
its origin this nerve frequently receives a twig 
from the par vagum ; it passes down the neck 
in front of the jugular vein and carotid artery, 
crossing these vessels obliquely, being in this 
course superficial to the cellular investment de- 
rived from the cervical fascia which constitutes 
the sheath of these vessels. 
Omo-hyoid branch.—About the centre of the 
neck, the cervicalis descendens gives off a con- 
siderable branch, which, passing in a direction 
upwards and inwards, enters the interior belly 
* See Meckel, Manuel d’Anatomie, vol. iii. 
page 53. - 
+ See Boyer, Traité d’Anatomie, vol. ili. p. 359. 
t See Traité d’Anatomie, Boyer, vol. iii. p. 359, 
3A 
