102 
ANATOMY. 
dura of the seventh pair as it passes through 
the os petrosum, is sent into the nose by the 
hole common to the palate and sphenoidal 
bone ; and the remaining part of this nerve 
runs in the palate-maxillary canal, giving off 
branches to the temples and pterygoid mus- 
cles, and comes at last into the palate to be 
lost. Hence the ache in the teeth in the up- 
per jaw occasions a growing pain deep-seated 
in the bones of the face, with swelling in the 
eye-lids, cheek, nose, and under lip ; and, on 
the other hand, an inflammation in these 
parts is often attended with sharp pain in the 
teeth. 
The third or maxillaris inferior branch of 
the fifth pair, going out of the oval hole of 
the sphenoid bone, serves the muscles of the 
lower jaw, and the muscles situated between 
the os hyoides and jaw. All the salivary 
glands, the amygdales, and the external ear, 
have branches from it: it has a large branch 
lost in the tongue, and sends another through 
the canal, in the substance of the lower jaw, to 
serve all the teeth there, and to come out at 
the hole in the fore part of the jaw, to be lost 
in the chin and under lip. Hence a convul- 
sive contraction of the muscles of the lower 
jaw, or the mouth’s being involuntarily shut, a 
great flow of spittle or salivation, a pain in the 
car, especially in deglutition, and a swelling 
all about the throat, are natural consequences 
of a violent irritation of the nerves of the 
lower teeth in the tooth-ache ; and pain in 
the teeth and ear is as natural a consequence 
ot angina. Perhaps the sympathy of the or- 
gans of tasting and smelling may, in some 
measure, depend on their both receiving 
nerves from the fifth pair. 
The sixth pair, which is the smallest ex- 
cept the fourth, rises from the fore part of the 
-corpora pyramidalia: and each entering the 
dura mater some way behind the posterior 
clinoid process of the sphenoid bone, has a 
long course below that membrane, and with- 
in the receptaculum at the side of the sella 
Turcica, where it is immersed in the blood of 
the receptacle. It afterwards goes out at 
the foramen lacerum into the orbit, to serve 
the abductor muscle of the eye. In the 
passage of this nerve below the dura mater, it 
lies very contiguous to the internal carotid ar- 
tery, and to the ophthalmic branch of the 
-fifth pair of nerves. At the place where the 
■sixth pair is contiguous to the carotid, a nerve 
either goes from each of them in an uncom- 
mon way, to wit, with the -angle beyond 
where it rises obtuse to descend with the ar- 
tery, and to form the beginning of the inter- 
costal nerve, according to the common de- 
scription ; or, according to other authors, 
this nerve co nes up from the great ganglion 
of the intercostal to he joined t.> the. sixth 
here. 
The arguments for this latter opinion are, 
that, according to the common doctrine, this 
beginning of the intercostal nerve, as it is 
called, would rise in a manner not ordi- 
nary iii nerves. In the next place, it is ob- 
served, that the sixth pair is larger nearer to 
the other than it is before it comes to the 
place where this nerve is said to go off ; and 
therefore it is said to be more probable that ii 
receives an addition there, rather than gives 
-off a branch. Lastly, it is found that, upon 
cutting the intercostal nerves of living ani- 
mals, the eyes were plainly affected ; they 
lost their bright water; the gum or gore, as 
we call it, was separated in greater quantity ; 
the pupil was more contracted ; the cartila- 
ginous membrane, at the internal ca'nthus, 
came more over the eye ; and the eye-ball it- 
self was diminished. 
To this it is answered, in defence of the 
more common doctrine, 1st. That other 
branches of nerves go off in a reflected way, 
as well as this does, supposing it to be the be- 
ginning of the intercostal ; and that the re- 
flection would rather be greater, if it is 
thought to come up from the intercostal to 
the sixth. 2d. It is denied that this nerve is 
in ordinary thicker at its fore than at its back 
part ; and if it was to be the thickest nearest to 
the orbit, the conclusion made above could 
not be drawn from this appearance, because 
other nerves enlarge sometimes where there 
is no addition made to them, as in the in- 
stance already mentioned of the trunk of the 
fifth pair, while below the dura mater. 3dly. 
The experiments on living animals show, in- 
deed, that the eyes are alfected upon cutting 
the intercostal nerve ; but not in the way 
which might have been expected, if the in- 
tercostal had furnished such a share of the 
nerve that goes to the abductor muscle of the 
eye: for it might have been thought that this 
muscle would have been so much weakened 
immediately upon cutting the intercostal, 
that its antagonist, the adductor, would have 
greatly prevailed over it, and have turned 
the eye strongly in toward the nose ; which 
is not said to be a consequence of this experi- 
ment : so that the arguments are still equi- 
vocal ; and more observations and experi- 
ments must be made before it can be deter- 
mined with certainty whether the sixth pair 
gives or receives a branch here. In the mean 
time, we shall continue to speak about the 
origin of the intercostal with the generality of 
anatomists. 
At this place, where the intercostal begins, 
the fifth pair is contiguous, and adheres to the 
sixth ; and it is generally said, that the oph- 
thalmic branch of the fifth gives a branch or 
two to the beginning of the intercostal, or re- 
ceives such from it. Others deny any such 
communica.ion between them ; and those 
who affirm the communication confess that, 
in some subjects, they could not sec it. 
The seventh or auditory pair comes out 
from the lateral part of the annular process, 
behind where the medullary process of the 
cerebellum is joined to that tube; and each 
being accompanied with a larger artery than 
most other nerves, enters the internal meatus 
auditorius, where the two large bundles of 
fibres, of which it appeared to consist within 
the skull, soon separate from each other : 
one of them entering by several small holes 
into the vestibule, cochlea, and semicircular 
canal, is stretched on the inner camera of 
the ear in a very soft pulpy substance ; and 
being never seen in the form of a firm cord, 
such as the other parcel of this and most 
other nerves become, is called the portio 
mollis of the auditory nerve, 
The other part of the seventh pair passes 
through Galen’s foramen ccecuni, or Fallo- 
pius’s aqueduct, in its crooked passage by the 
side of the tympanum ; in which passage a 
nerve sent to the lingual branch of the infe- 
i' o; maxillary nerve along the outside of the 
tuba Eustachiana, and across the cavity of the 
tympanum, where it has the name of chorda 
tympani, is commonly said to be joined to 
if. The very acute angle which tlus nerve 
makes with the fifth, or the sudden violent 
reflection it would suffer on the supposition of 
its coming from the fifth to the seventh, ap- 
pears unusual ; whereas if we suppose that it 
comes from the seventh to the fifth, its course 
would be more in the ordinary way, and the 
chorda tympani would be esteemed a branch 
ot the seventh pair going to join the fifth, 
the size of which is increased by this acqui- 
sition. This smaller bundle of the seventh 
gives branches to the muscles of the mal- 
leus, and to the dura mater, while it passes 
tin ’ough the bony crooked canal ; and it last 
comes out in a firm chord, named portio du- 
ra, at the end of this canal, between the stv- 
loid and mastoid processes of the temporal 
bone, giving immediately filaments to the 
little oblique muscles of the head, and to those 
that rise trom the styloid process. It then 
pierces through the parotid gland, and di- 
vides into a great many branches, which are 
dispersed in the muscles and teguments that 
cover all the side of the upper part of the 
neck, the whole face and cranium, as far back 
as the temples, including a considerable part 
of the external ear. Its branches having 
thus a considerable connection with all the 
three branches of the fifth pair, and with the 
second cervical, occasions a considerable sym- 
pathy of those nerves with it. Hence in the 
tooth-ache the pain is occasioned very little 
in the affected tooth, compared to what it is 
all along the side of the head and in the ear. 
B y this communication or connection possi- 
bly too it is that a vibrating string held' be- 
tween one’s teeth, gives a strong idea of a 
sound to the person who holds it, which no- 
body else can perceive. Perhaps too the 
distribution of this nerve. occasions the head 
to be so quickly turned upon the impression 
of sound on our ears. 
The eighth pair of nerves or par vagum 
rise from the lateral bases of the corpora oli- 
varia in disgregated fibres, and as they are 
entering the anterior internal part of the 
holes common to the os occipitis and tempo- 
rum, each is joined by a nerve which ascends 
within the dura mater from the tenth of the 
head, the first, second, and inferior cervical 
nerves: this every body knows has the name 
of the nerves accessorius. When the two 
get off the skull, the accessorius separates 
from the eighth, and descending obliquely 
outward passes through the - sterno-mastoi- 
deus muscle, to which it gives branches, anil 
afterwards terminates in the trapezius muscle 
of the scapula. In this course it is generally, 
more or less, joined by the second cervical 
nerve. Why this nerve, and several others 
which are distributed to muscles, are made 
to pierce through muscles, which they might 
have only passed near to, we do not know. 
_ The large eighth pair, soon after its exit, 
gives nerves to the tongue, ■ larynx, pharynx, 
and ganglion, of the intercostal nerve ; and 
being disjoined from the ninth and intercos- 
tal, to which it adheres closely some way, 
runs straight down the neck behind the in- 
ternal jugular vein, and at the external side 
of the carotid artery. As it is about to enter 
the thorax, a large nerve goes off from the 
eighth of each side ; this branch of the right 
side turns round from the fore to the back 
part of the subclavian artery, while the branch 
of the left side turns round the great curve 
of the aorta ; and both of them mounting up 
