Bauhaus-Universität Weimar

Titel:
The Cyclopaedia of Anatomy and Physiology, vol. 2: Dia-Ins
Person:
Todd, Robert Bentley
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit25760/562/
554 
ORGAN OF HEARING. 
Nerves of the accessory parts of the apparatus 
of hearing. 
Nerves of the tympanum.—The tympanum 
receives nerves from different sources—from 
the fifth, the seventh, eighth, and ninth pairs of 
cerebral nerves. Moreover, its nerves have 
communication with the sympathetic system. 
The facial nerve or portio dura of the seventh 
pair rises from the brain by two roots, which 
unite together in the meatus auditorius inter¬ 
nus, but before uniting, the smaller root sends 
off a delicate filament, which forms a commu¬ 
nication, as has been mentioned, with the au¬ 
ditory nerve. This communication, first pointed 
out by Swan, has recently been very fully in¬ 
vestigated by Arnold. According to the latter, 
in the middle or at the bottom of the internal 
auditory meatus, one or several delicate fila¬ 
ments go off from the smaller branch of the 
facial, and join the auditory nerve. After this 
the facial nerve enters the aqueduct of Fallo¬ 
pius, and issues from the cranium through the 
stylo-mastoid hole. In this course it receives, 
at the place where it forms the knee-like bend 
into the aqueduct of Fallopius, the superior 
branch of the Vidian or superficial petrosal 
nerve, nervus petrosus superficialis, s. major. 
The superficial petrosal nerve comes off, 
along with the inferior branch of the Vidian or 
deep petrosal nerve, from the posterior part of 
the spheno-palatine ganglion or ganglion of 
Meckel. Leaving the deep petrosal nerve at 
the posterior orifice of the Vidian canal, the 
superficial petrosal proceeds upwards through 
the cartilaginous substance in the foramen lace- 
rum medium, and then runs backwards in the 
groove on the anterior surface of the petrous 
bone leading to the hiatus of Fallopius. 
Having entered the latter, it joins the facial 
nerve, and forms, with its external fasciculi, a 
gangliform swelling, intumescentia ganglifor- 
mis nervi facialis, of a grayish appearance and 
soft consistence. 
From this swelling a filament arises by one 
or two roots, and runs backwards into the in¬ 
ternal auditory passage to join the upper por¬ 
tion of the auditory nerve, where the first fila¬ 
ment joined, and forms with it a small reddish 
gray elevation, known to and delineated by 
Scarpa. 
Another branch, which arises from the gan¬ 
glionic swelling, is the chorda tympani. The 
chorda tympani thus in reality derives its origin 
both from the facial and the superficial petrosal 
nerves. The chorda tympani accompanies the 
facial nerve along the aqueduct of Fallopius 
till within a little of the exit of the latter by the 
stylo-mastoid hole. The chorda tympani then 
leaves the facial nerve at an acute angle, and 
roceeds upwards in a proper canal in the 
one, enters the cavity of the tympanum by the 
opening just within the posterior part of the 
groove for the membrana tympani already de¬ 
scribed. From this opening it proceeds for¬ 
wards between the long process of the incus 
and the handle of the malleus, to the fissure of 
Glasser, through the canal beside which, already 
described, it makes its exit from the cavity of 
the tympanum. It then descends by the inner 
side of the ascending ramus of the lower jaw, 
and joins at an acute angle the lingual nerve. 
In its passage across the cavity of the tympa¬ 
num, the chorda tympani anastomoses by one 
or several filaments with the nerve which the 
fifth pair sends to the membrana tympani. 
Fig. 259. 
The membrana tympani from mithin, and the course 
of the chorda tympani across the tympanum, together 
with the connexions of the mallem and incm ( magni¬ 
fied). ( From Soemmerring). 
a. Membrana tympani ; b. handle of the malleus 
and tendon of the internus mallei cut near its in¬ 
sertion ; c, c. the chorda tympani. 
To return to the facial nerve. It gives off, 
a little below the pyramid, a branch to the sta¬ 
pedius muscle. 
The pneumogastric nerve, in its passage 
through the base of the skull, forms a small 
ganglion, from which springs a nerve which 
goes to the ear, ramus uuricularis nervi vagi. 
This nerve is joined by a filament from the 
petrous ganglion of the glosso-pharyngeal ; it 
then runs, according to Arnold, in a groove in 
the jugular fossa, and at last arrives at the 
aqueduct of Fallopius. Here it divides into 
three branches, the smallest of which runs up¬ 
wards in the aqueduct of Fallopius towards 
the origin of the facial nerve, and unites with 
it; the second branch, which is somewhat 
larger, runs downwards, and also anastomoses 
with the facial. The third and most considera¬ 
ble branch will be noticed along with the 
nerves of the auricle and auditory passage. 
The nervous anastomosis in the tympanum.— 
The principal nerve of this anastomosis is the 
nerve of Jacobson, or tympanic nerve of Arnold. 
The tympanic nerve, nervus tympanicus, ex¬ 
tends between the petrous ganglion of the glosso¬ 
pharyngeal nerve and the otic ganglion or gan¬ 
glion of Arnold. To follow it from the glosso¬ 
pharyngeal, we find it arises from the upper 
part of the petrous ganglion, along with another 
filament, which goes to communicate with the 
ganglion cervicale supremum, and also with the 
pneumogastric. The tympanic nerve enters, 
by the tympanic canal already described, the 
cavity of the tympanum. Here the nerve ap¬ 
pears near the anterior margin of the fenestra 
rotunda, traverses the groove on the promon¬ 
tory, arrives in front of the vestibular fenestra, 
then enters the proper osseous canal, into which 
the groove on the promontory is continued su-
        

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