ANATOMY, 
103 
again at the side of the oesophagus, to which, 
they give branches, are lost at last in the la- 
rynx. These are called the recurrent nerves. 
The muscles of the larynx being in a good 
measure supplied with nerves from the re- 
current, it is to be expected that the cutting 
of them will greatly weaken the voice, though 
it will not entirely be lost so long as the su- 
perior branches of the eighth pair are entire. 
Why the recurrent nerves rise so low from 
the eighth pair, to go round a large artery, 
and to have such a long course upward, we 
know not. 
The eighth pair above, and at or near the 
place where the recurrent nerves gooff from 
it, or frequently the recurrents themselves, 
send off small nerves to the pericardium, 
and to join with the branches or the inter- 
costal that are distributed to the heart; but 
their size and situation are uncertain. 
After these branches are sent off, the par 
vagum on each side descends behind me 
great branch of the trachea, and gives nu- 
merous filaments to the lungs, and some to 
the heart, in going to the oesophagus. The 
one of the left side running on the fore part 
of the oesophagus, communicates by several 
branches with tire right one in its descent to 
be distributed to the stomach ; the right one 
goes behind the oesophagus, where it splits 
and rejoins several tunes before it arrives at 
the stomach, to which it sends nerves ; and 
then being joined by one or more branches 
from the left trunk, they run toward the c ce- 
liac artery, there to join into the great semilu- 
nar ganglion formed by the two intercostals. 
From" the distribution of the par vagum 
we may learn how tickling the fauces with a 
feather, or any such substance, excites a nau- 
sea and inclination to vomit ; why coughing 
occasions vomiting, or vomiting raises a 
cough ; why an attempt to vomit is some- 
times in danger of suffocating asthmatic peo- 
ple ; why the superior oriiice of the stomach 
is so sensible as to be looked on as the seat 
of the soul by some; why people subject to 
distensions of the stomach have so often the 
sensation of balls in their breast and throat ; 
why the globus hystericus is so often attended 
with a violent strangulation of the glottis. 
The ninth pair of nerves comes from the 
inferior part of the corpora pyramidalia, to go 
out of the skull at their proper holes of the 
occipital bone. After their egress they ad- 
here for some way to the eighth and inter- 
costal ; and then sending a branch that, in 
many subjects, is joined with branches ot the 
lirst and second cervical nerves, to be diffri- 
buted to the thyroid gland and muscles on 
the fore part of the trachea arteria, the ninth 
is lost in the muscles and substance of the 
tongue. Some have thought this nerve, and 
others have esteemed the third branch of the 
fifth pair of nerves, to be the proper gustatory 
nerve. We know no observation or experi- 
ments to prove either opinion, or to assure us 
that both nerves do not serve for tasting and 
for the motion of the tongue. May not the 
distribution of. this nerve to the muscles be- 
low as well as above the os hvoides, contri- 
bute to their acting more uniformly in de- 
pressing the lower jaw or head ? 
The tenth pair rises in separate threads i 
from the sides of the spinal marrow, to go i 
out between the os occipitis and lirst vertebra ' 
of the neck. After each of them has given s 
branches to the great ganglion of the inter- t 
costal, eighth, ninth, and firff cervical 
nerves-, it is distributed to the straight, ob- 
lique, and some of the extensor muscle ol 
the head. \\ hether the name of the tenth 
of the head, or of the lirst vertebral, ought to 
be given to this pair of nerves, is of no such 
consequence as to deserve a debate, though it 
has some of the mark of spinal nerves ; to w it, 
its being formed of lilaments, proceeding from 
both the fore and back part of the medulla; 
and a little ganglion being formed where these 
ldaments meet. 
In the description of the sixth pair we' fol- 
lowed the usual way ot speaking among ana- 
tomists, and called that the beginning of the 
intercostal nerve which comes out of the 
skull ; and shall therefore here subjoin a cur- 
sory description ot this nerve, notwithstanding 
its much larger part is composed of nerves 
coming out from the spinal marrow. There 
is no greater incongruity in point of method 
to say, that the nerve we are describing re- 
ceives additions from others that have not 
been described, than it is to repeat in the 
description of a great many nerves, that 
each of them gives branches to form a nerve 
which we are ignorant of; which is all the 
difference between describing the intercostal 
before or after the spinal nerves. 
1 lie branch rellected from the sixth pair, 
joined possibly by some lilaments of the oph- 
thalmic branch of the lifth, runs along with 
the internal carotid artery, through the 
crooked canal formed for it in the temporal 
bone, where the little nerve is very sott and 
pappy, and in several subjects divides and 
unites again, and is joined by one or more 
branches from the tilth, particularly of its 
superior maxillary branch, before it comes 
out ol the skull. May not the compression of 
this nerve by the carotid artery, when 
stretched during the systole, contribute to 
the diastole ot the heart ? As soon as the 
nerve escapes out of the bony canal, it is con- 
nected a lutle way with the eighth and ninth ; 
then separating from these, after seeming to 
receive additi onal nerves from them, it forms 
a large ganglion, into which branches from 
the te nth of the head, and from the lirst and 
second cervical, enter. From the ganglion 
the nerves come out again small, to run down 
the neck along with the carotid artery, 
communicating by branches with the cervi- 
cal nerves, and giving nerves to the muscles 
that ->end the head and neck. As the inter- 
costal is about to enter the thorax it forms 
another ganglion, from which nerves are sent 
to the trachea and to the heart ; those de- 
signed for the heart, joining with the branches 
of the eighth, and most of them passing be- 
tween the two great arteries and the auricles, 
as the substance of that muscle. The inter- 
costal alter this consisting of two branches, 
one going behind, and the other running over, 
the fore part of the subclavian artery, forms a 
new ganglion where the two brandies unite 
below the artery ; and then descending along 
the sides of the vertebrae of the thorax, re- 
ceives branches from each of the dorsal 
nerves; which branches appearing to come out 
between the ribs, have given the name of in- 
tercostal to the whole nerve. Where the 
addition is made to it from the lifth dorsal 
nerve, a branch goes off obliquely forward ; 
which being joined by such branches from the 
sixth, seventh, eighth, and ninth dorsal, the 
anterior trunk is formed, and passes between 
the fibres of the appendix rouficulosa of the 
diaphragm to them, along with the other 
intercostal and the branches of the eighth, 
pair, a large semilunar ganglion, situated be- 
tween the cellular and superior mesenteric 
arteries ; the roots of which are as it jjvere 
involved in a sort of nervous net-work of tins 
ganglion, from which a great number of very 
email nervous threads run out to be extended 
on the surface of all the branches of those two 
arteries, so as to he easily seen when any of 
the arteries are stretched, but not to be raised 
trom them by dissection; and thus the liver, 
gall-bladder, duodenum, pancreas, spleen, je- 
junum, ilium, and a large share of the colon, 
have their nerves sent from this great solar 
ganglion or plexus. May not the peristaltic 
motion of the intestines depend, in some mea- 
sure, on the passage of the intercostal nerves 
through tire diaphragm ? 
Several fibres ot this ganglion, running 
down upon the aorta, meet with other nerves, 
sent trom the posterior trunk of the intercos- 
tal, which continues its course along the sides 
of the vertebra: : they supply the glandular re- 
nales, kidneys, and testes in men, or ovaria in 
women ; and then they form a net-work on the 
inferior mesenteric artery, where the nerves of 
the two sides meet, and accompany the branch- 
es of this artery to the part of the colon that lies 
in the left side of the belly, and to the rec- 
tum, as far down as the lower part of the 
pelvis. 
r l he intercostal continuing down by. the 
sides of the vertebra: of the loins, is joined bv. 
nerves coming from between these vertebra:, 
and sends nerves to the organs of gene- 
ration, and others to the pelvis, being even 
joined with those that are sent to the inferior 
extremities. 
r i he spinal nerves rise generally by. a num- 
ber of disgregated fibres from both the fore 
and back part of the medulla spinalis ; . and 
soon after form a little knot or ganglion, . where 
they acquire strong coats, and are extended 
into firm cords ; but the ganglion is entirely 
formed by the posterior bundle. They are 
distinguished by numbers, according to the 
vertebra' from between which they come out ; 
(he superior of the two bones forming the hole 
through which they pass, being the one from 
which the number is applied to each nerve.. 
I here are generally said to be thirty pair of 
them; seven of which come out between the ■ 
vertebra of the neck, twelve between those 
of the back, five between those of the loins,, 
and six from the false vertebra. 
I he first cervical pair of nerves comes out 
between the first and second vertebra of the 
neck ; and having given branches to join with 
the tenth pair of the head, the second cer- 
vical, and intercostal, and to serve the mus- 
cles that bend the neck, it sends its largest 
branches backwards to the extensor muscles of 
the head and neck; some of which piercing 
through these muscles, run up on the occiput 
to be lost in the teguments here ; and many 
fibres of it advance, so far forward as to be 
connected with the fibrils of the first branch 
of the fifth pair of the head, and of the portio 
dura of the auditory nerve. Hence possibly 
it is, that a clavus hystericus changes suddenly 
sometimes, from the forehead to a violent pain ■ 
and spasm in the back part of the head and 
neck. 
The second cervical is soon joined by some 
branches to the ninth of the head and inter- 
