104 
costal, and to the first and third of the neck ; 
then has a large branch that comes out at the 
exterior edge of the sterno-mastoideus muscle, 
where it joins with the accessorius of the eighth 
pair ; and is afterwards distributed to the pla- 
tysmA my o ides, teguments of the side oi hie 
neck and head, parotid gland, and external 
ear, being connected to the portio dura of the 
auditory nerve, and to the first cervical. 
The remainder of this second cervical is spent 
on the levator scapulae and the extensors of 
the neck and head. Generally a large branch 
is here sent off to join the accessorius of the 
eighth pair, near the superior angle of the 
scapula. From the irritation of the brandies 
of this nerve it probably is, that in an inflam- 
mation of the parotid gland, the neck is pained 
so far down as the clavicle, the head is drawn 
towards the shoulder of the affected side, 
and the chin is turned to the other side. 
The third pair of the neck passes out be- 
tween the third and fourth cervical verte- 
bra" ; having immediately a communication 
with tiie second, and sending down a branch, 
which, being joined by a branch from the 
fourth cervical, forms the phrenic nerve. 1 his 
descending enters the thorax between the 
subclavian vein and artery ; and then be- 
ing received into a groove formed by it m 
the pericardium, it has its course along the 
caps' ila of the heart, till it is lost in the middle 
part of the diaphragm- 1 he right phrenic 
has a straight course ; but the left one is ob- 
liged to make a considerable turn outwards, 
to go over the prominent part of the pericar- 
dium, where the point of the heart is lodged. 
Hence in violent palpitations ot the heart, 
a pungent acute pain is felt near the left ori- 
fice of the stomach. The middle of the dia- 
phragm scarce could have been supplied by 
any other nerve which could have had such a 
straight course as the phrenic has. 
The other branches of the third cervical 
nerve are distributed to the muscles and te- 
guments at the lower part of the neck and 
lop of the shoulder. No wonder then that 
an inflammation of the liver or spleen, an ab- 
scess in the lungs adhering to the diaphragm, 
or any other cause capable of irritating the 
diaphragm, should be attended with a sharp 
pain on the top of the shoulder, as well as 
wounds, ulcers, &c. of the muscle itself. If 
the irritation of the muscle is very violent, 
it may occasion that convulsive contraction 
of the diaphragm which is called an hic- 
cough. 
The fourth cervical nerve, after sending off 
that branch which joins with the third to form 
the phrenic, and bestowing twigs in the mus- 
cles and glands of the neck, runs to the arm- 
pit, where it meets with the fifth, sixth, and 
seventh cervical?, and first dorsal, that escape 
in the interstices of the musculiscalcnitocome 
at the armpit, where they join,, separate, and 
rejoin, in a way scarcely to be rightly express- 
ed in words; and, after giving several consi- 
derable nerves to the muscles and teguments 
which cover the thorax, they divide into se- 
veral branches, to be distributed to all the 
parts of the superior extremity. Several of 
these branches we shall describe under parti- 
cular names. 
1. Scapularis runs straight to the cavitas 
semilunata of the upper coats of the scapula, 
which is a hole in the recent subject, by a li- 
gament being extended from one angle of 
the bone to the other; giving nerves, m its 
ANATOMY. 
way, to the muscles of the scapula. When it 
has passed this hole it supplies the supraspi- 
natus muscle, and then descending at the an- 
terior of the spme of the scapula, it is lost in 
the other musclesthat lie on the dorsum of that 
bone. 
2. Articularis sinks downwards at the ax- 
illa, to get below the neck of the head ot the 
os humeri, and to mount again at the back part 
of it ; so that it almost surrounds the articula- 
tion, and is described in the muscles that 
draw the arm back, and to those that raise it 
up. 
3. Cutaneus runs down the fore part ot 
the arm, near the skin, to which it gives off 
branches ; and then divides on the inside of 
the fore-arm into several nerves which supply 
the teguments there, and on the palm of the 
hand. In opening the basilic vein of the arm, 
at the usual place, the same symptoms are 
sometimes produced as in opening the exter- 
nal jugular vein, and from a like cause ; to 
wit, from hurting a branch ot this cutaneous 
nerve with the lancet. 
4. M usculo-cutaneus, or perforans casseri, 
passes through the coraco-brachialis muscle , 
and after supplying the biceps, flexor cubiti, 
and brachialis internus, passes behind the 
tendon of the biceps, and over the cephalic 
vein, to be bestowed on tiie teguments on 
the outside of the fore arm and back of the 
hand. This nerve is sometimes hurt in open- 
ing the cephalic vein, and causes pain and 
numbness tor a short time. 
5. Muscularis has a spinal course from t.ie 
axilla, under the os humeri, and backward to 
the external part of that bone ; supplying by 
the way the extensor muscles ot the fore- 
arm, to which it runs between the two bra- 
chial muscles, and within the supinator radii 
longus. At the upper part of the fore arm, 
it sends off a branch which accompanies tiie 
supinator longus, till it comes near the wrist ; 
where it passes obliquely over the radius, to 
be lost in the back ot the hand and fingers. 
The principal part of this nerve pierces 
through the supinator radii brevis, to serve 
the muscles that extend the hand and fin- 
gers, whose actions are not injured when the 
supinator acts. Part of this nerve seems to 
be lost upon the ligament ol tiie wrist. 
6. Ulnaris is extended along the inside of 
the arm, to give nerves to the muscles that ex- 
tend lire fore arm, and to the teguments 
of the elbow : toward the lower part of the 
arms it slants a little backward to come at 
the groove behind the internal condyle of the 
os humeri, through which it runs to the ulna. 
In its course along this bone it serves the 
neighbouring muscles and teguments; and 
as it comes near the wrist, it detaches a 
branch obliquely over the ulna to the back 
of the hand, to be lost in the convex part of 
the several fingers The larger part of the 
nerve goes forward to the internal side of the 
os pisiform e of the wrist ; where it sends oil a 
branch, which sinks under the large tendons 
in the palm to go across to the other side the 
wrist, serving the musculi lumbricales and 
intefossei, and at last terminating in the short 
muscles of the thumb and fore-ringer. VV hat 
remains of the ulnar nerve after supplying 
the short muscles of the little linger, divides 
into three branches : whereof two are ex- 
tended along the sides of the sheath of the 
tendons of the flexors of the little finger, to 
furnish the concave side of that finger ; the 
third branch is disposed in the same way 
upon the side of the ring-finger, next to the 
little finger. 
When we lean or press upon the internal 
condyle of the os humeri, the numbness and 
pricking we frequently feel, point out the 
course of this nerve. We have seen a weakness 
and strophy in the parts which we mentioned 
this nerve to be sent to, after a wound in the 
internal lower part of the arm. 
7. Radius accompanies the humeral artery, 
to the bending of the elbow, serving the flexor 
of the cubit in its way ; then passing through 
the pronator radii teres muscle, it gives 
nerves to the muscles on the fore part of the 
fore arm, and continues its course near to the 
radius, bestowing branches on the circum- 
jacent muscles. Near the wrist it sometimes 
gives off a nerve which is distributed to the 
back of the hand, and the convex part of 
the thumb, and several of the fingers, instead 
of the branch of the muscular. The large 
part of the nerve passing behind the annular 
ligament of the wrist, gives nerves to the 
short muscles of the thumb ; and afterwards 
sends a branch along each side of the sheath 
of the tendons of the flexors of the thumb, 
fore-finger, middle-finger, and one branch 
of the side of the ring-finger, next to the 
middle one, to be lost on the concave side 
of those lingers. 
Though the radial nerve passes through 
the pronator muscle, and the muscular nerve 
seems to be still more unfavourably placed 
within the supinator brevis; yet the action of 
these muscles does not seem to have any 
effect in hindering the influence of these 
neives; for the fingers or hand can be bent 
while pronation is performing vigorously, 
and they can be extended while supination 
is exercised. 
The manner of the going off of these 
nerves of the fingers, both from tiie ulnar 
and the radial, is, that a single branch is sent 
from the trunk to the side of the thumb and 
little finger farthest from the other fingers ; 
and all the rest are supplied by a trunk of a 
nerve, which splits into two in some way 
before it comes as far as the end of the meta- 
carpus, to run along the sides of the different 
fingers that are nearest to each other. 
It might have been observed, that in de- 
scribing the posterior branches of the ulnar 
and muscular nerve, we did not mention the 
particular fingers, to the convex part of 
which they are distributed. The reason for 
this omission is, the uncertainty of their distri- 
bution ; for though sometimes these pos- 
terior branches go to the same fingers, to the 
concave part of which the anterior branches 
of the ulnar and radial are sent, yet frequently 
they are distributed otherwise. 
The twelve dorsal nerves of each side, as 
soon as they escape from between the verte- 
bra, send a branch forward to join the inter- 
costal, by which a communication is made 
among them all ; and they soon likewise 
give branches backward to the muscles that 
raise the trunk of trie body, their principal 
trunk being extended outwards to come at 
the furrow in the lower edge of each rib ; in 
which they run toward the anterior part of 
the thorax, between the internal and external 
intercostal muscles, giving off branches in 
their course to the muscles and teguments 
of the thorax. 
The first dorsal, as was already observed 
