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median cutaneous nerve of the forearm along the groove between
the anterior border of the basilic vein and the brachial artery, and
through the opening in the deep fascia to the bend of the elbow.
It gives off several branches before it pierces the deep fascia (p. 69).
Now clean the basilic vein, displace it forwards and follow the
ulnar nerve, which descends, along the posterior angle between
the brachial artery and the basilic vein, to the middle of the arm.
Then, at the level of the insertion of the coraco-brachialis, it
passes backwards, accompanied by the superior ulnar collateral
branch of the brachial artery, pierces the medial intermuscular
septum, and enters the posterior compartment of the arm, where
it will be dissected at a later period. The median nerve should
next be cleaned. Follow it along the lateral margin of the
proximal part of the brachial artery to the middle of the arm,
there it crosses anterior to the artery and then descends, on its
medial side, to the cubital fossa ; note that the nerve gives off
no branches till the cubital fossa is reached. After the median
nerve has been cleaned, clean the vense comites of the artery.
Note that they anastomose across the artery frequently, and that
at the lower border of the subscapularis they end in the axillary
vein. Now displace the proximal part of the brachial artery
forwards and follow the radial (museum-spiral) nerve behind it,
to the proximal end of the sulcus for the radial nerve at the
back of the humerus. The radial nerve is accompanied by the
profunda branch of the brachial artery. Clean the branches
which pass from the lateral side of the artery to the biceps,



THE FRONT OF THE ARM 101

coraco-brachialis, and brachialis. A little distal to the middle
of the arm, on the medial side of the artery, seek for its nutrient
branch to the humerus. Clean the superior profunda branch,
which accompanies the radial nerve, and the superior ulnar
collateral branch which accompanies the ulnar nerve. About
two inches proximal to the elbow, find the inferior ulnar
collateral branch, follow it towards the medial intermuscular
septum, and note its division into two branches, an anterior
which descends in the front of the medial epicondyle to anasto-
mose with the volar ulnar recurrent, and a posterior which
pierces the medial intermuscular septum. Lastly, clean the
brachial artery itself.

Nervus Medianus. The median nerve arises in the axilla
by two heads, one from the medial and one from the lateral
cord of the brachial plexus. The medial head crosses the
front of the axillary artery to unite with the lateral head.
The nerve thus formed descends, along the lateral side of
the distal part of the axillary artery and the proximal half of
the brachial artery, to the level of the insertion of the coraco-
brachialis; there it crosses in front of the brachial artery
(sometimes behind) and descends along its medial side to
the bend of the elbow. It gives off no branches either in
the axilla or in the arm.

Nervus Ulnaris. The ulnar nerve is the largest branch
of the medial cord of the brachial plexus. It descends, along
the medial sides of the third part of the axillary artery and
of the proximal half of the brachial artery, to the insertion of
the coraco-brachialis ; then it leaves the brachial artery and,
accompanied by the superior ulnar collateral artery, passes
distally and backwards through the medial intermuscular
septum, into the posterior compartment. In the posterior
compartment it descends, along the medial head of the triceps,
to the back of the medial epicondyle. Do not follow it into
the posterior compartment at present ; it will be dissected
there at a later period. Like the median nerve it gives
off no branches whilst it is in the axilla and the arm.
Accompanying the ulnar nerve will be found the ulnar
collateral branch of the radial nerve which descends to
the distal part of the medial head of the triceps.

Arteria Brachialis. The brachial artery is the direct con-
tinuation of the axillary artery; it begins, therefore, at the lower
border of the teres major, and it passes, distally and slightly
laterally, to the cubital fossa, where, at the level of the neck of
the radius, it divides into its two terminal branches the radial

i-7 &



IO2



THE SUPERIOR EXTREMITY



and the ulnar arteries. In the proximal part of the arm it lies
to the medial side of the humerus, but as it approaches the
elbow it passes to the front of the humerus.

This change of position must be borne in mind when
pressure is applied to the vessel with the view of controlling
the flow of blood through it. In the proximal part of the arm
the pressure must be directed laterally and backwards, and in
the distal part directly backwards.



Brachial
artery

Median nerve

Medial
cutaneous
nerve of the -
forearm

Basilic vein .
Medial inter- ;
muscular, 4^
septum
Ulnar '
nerve




, Cephalic vein

Musculo-cutaneous nerve



Profunda artery
r of the arm

- -Radial nerve

~-L^_. Brachio-radialis
muscle



-',_ Lateral intermuscular
septum



FIG. 42. Transverse section through the Distal Third of the
Right Arm.

Relations. The brachial artery is superficial in the
whole of its length. To expose it, therefore, it is necessary
to reflect only the skin and the fascia ; but it is overlapped,
from the lateral side, by the medial margins of the coraco-
brachialis and biceps brachii (see Figs. 10, 41). At the bend
of the elbow it is crossed superficially by the lacertus fibrosus,
which intervenes between it and the median cubital vein.

The basilic vein lies to the medial side of the artery and
on a somewhat posterior plane. In the distal part of the
arm it is separated from the artery by the deep fascia ; but
in the proximal part, after the vein has pierced the fascia,
it comes into closer relationship with the artery. The two
vense comites are closely applied to the sides of the artery,



THE FRONT OF THE ARM



103



and the numerous connecting branches which pass between
them, both in front of and behind the artery, make Ihe
relationship still more intimate.

Behind the brachial artery there are four muscles.
Proximo-distally, they are (i) the long head of the triceps,
which is separated from the artery by the radial nerve and the
profunda vessels; (2) the medial head of the triceps; (3) the
insertion of the coraco-brachialis ; (4) in the remainder of
its course the brachialis forms the posterior relation.



N. musculo-
cutaneus *

N. medianus,

N. cut. antib.

med. T
A. brachialis '

V. basilica J
N. ulnaris -'-'



M. coraco-
brachialis




I "..Sept. inter-
r* muse. lat.

- Brs. of A. prof,
brachii

F7-N. radialis
(musculo-spiral)



' Dorsal cutaneous nerve of arm (O.T.
external cutan. of musculo-spiral)

FIG. 43. Transverse section through Middle of the Arm.

With the exception of the musculo-cutaneous nerve, all
the terminal branches of the brachial plexus lie in relation to
the brachial artery. The median nerve lies on the lateral side
and somewhat anteriorly in the proximal half of the arm ; it
crosses anterior to the artery at the level of the insertion of
the coraco-brachialis, and in the distal half of the arm and
in the cubital fossa it is to the medial side of the artery. The
ulnar nerve and the medial cutaneous nerve of the forearm
lie close to the medial side of the artery as far as the
insertion of the coraco-brachialis ; then they leave it. The
ulnar nerve inclines backwards, pierces the medial inter-



104 THE SUPERIOR EXTREMITY

muscular septum, and, passing behind the medial epicondyle,
enters the forearm. The medial cutaneous nerve of the
forearm inclines forwards and medially, pierces the fascia
brachii and becomes superficial. The radial nerve is
behind the proximal part of the artery, but it soon leaves it
by passing distally and laterally into the sulcus for the
radial nerve, between the medial and the lateral heads of the
triceps.

Branches of the Brachial Artery. Several branches arise
from the brachial artery. Those which arise from its lateral
aspect are irregular in number, origin, and size. They are
termed the lateral branches, and are distributed to the muscles
and integument on the front of the arm. The series of
medial branches which proceed from the medial and posterior
aspect of the parent trunk are named as follows as they arise
proximo-distally :

I. A. profunda brachii. 3. A. nutricia humeri.

2 A. collateralis ulnaris superior. 4. A. collateralis ulnaris inferior.

The profunda artery (O.T. superior profunda) is the
largest of the branches which spring from the brachial trunk.
It takes origin about 25 mm. (one inch) or so distal to the
lower margin of the teres major, and associates itself with the
radial (musculo-spiral) nerve, which it accompanies to the
back of the arm. Consequently, only a short part of the
vessel is seen in the present dissection. It soon disappears
from view between the long and medial heads of the triceps.

The superior ulnar collateral artery (O.T. inferior profunda)
is a long slender artery, which can be recognised from the
fact that it follows closely the course pursued by the ulnar
nerve. Its origin is somewhat variable. As a general rule, it
issues from the brachial artery opposite the insertion of the
coraco-brachialis, but very frequently it arises in common
with the profunda brachii. It pierces the medial inter-
muscular septum, with the ulnar nerve, and descends behind
that fascial partition to the interval between the olecranon
and the medial epicondyle of the humerus.

The nutrient artery may arise directly from the brachial
trunk, or take origin from the superior ulnar collateral
artery. It should be sought for at the distal border of
the insertion of the coraco-brachialis, and the dissector
should not be satisfied until he has traced it into the



THE FRONT OF THE ARM



I0 5



nutrient foramen of the bone. When the nutrient artery
is not seen in its usual position it will probably be found in
the dissection of the back of the arm, taking origin from the
profunda artery.

The inferior ulnar collateral artery (O.T. anastomotica)




Radial nerve ,



Anterior branch

of profunda

artery

Lateral inter-
muscular septum



Inferior ulnar

collateral artery.

(O.T. ana-

stomotic)




Radial nerve
(O.T. musculo-spiral)



Profunda artery
(O.T. superior profunda)-



Ulnar nerve
Superior ulnar
"collateral artery



Ulnar nerve
Superior ulnar....
collateral artery
Nerve to medial
head of triceps"

Medial intermuscular
septum



Inferior ulnar
collateral artery"



Triceps
' (lat. head)

( Nerve to lateral
'head of triceps
Nerve to long

"head of triceps
Posterior

"cutaneous nerve
of arm (O.T.
int. cutan. of
musculo-spiral)

Dorsal cu-
taneous nerves
of forearm
I (O.T. ext.
v ! cutan. of
> musculo-
spiral)

| Posterior
4 branch of pro-
\ funda artery

fl Lateral inter-
*i- muscular
B septum



Nerve to anconseus

FIG. 44. Diagram to show relation of Radial, Nerve (O.T. Musculo-spiral)
to the Humerus, and of Vessels and Nerves to the Intermuscular Septa.



arises about 50 mm. (two inches) proximal to the bend of the
elbow, and runs medially upon the brachialis. It soon divides
into a small anterior and a larger posterior branch. The
anterior branch is carried distally in front of the medial
epicondyle of the humerus, in the interval between the
brachialis and the pronator teres. It anastomoses with the



106 THE SUPERIOR EXTREMITY

volar ulnar recurrent artery. The posterior branch pierces
the medial intermuscular septum, and will be seen, at a later
stage, in the posterior compartment of the arm.

Dissection. Clean the biceps brachii. Clean the coraco-
brachialis; separate it carefully from the short head of the
biceps, and find the musculo-cutaneous nerve as it leaves the
lateral surface of the coraco-brachialis. Follow the musculo-
cutaneous nerve, between the biceps and the brachialis, to the
point where it emerges at the lateral border of the tendon of the
biceps and becomes the lateral cutaneous nerve of the forearm.
Clean the brachialis as far as the bend of the elbow, but do not
injure the lacertus fibrosus.

Nervus Musculocutaneus. The musculo-cutaneous nerve
arises from the lateral cord of the brachial plexus, at the
lower border of the pectoralis minor. Inclining laterally,
it perforates the coraco-brachialis, and passes between the
biceps brachii and the brachialis. It proceeds obliquely
distally, between those muscles, until it reaches the bend
of the elbow, where it comes to the surface at the lateral
border of the tendon of the biceps brachii. From that
point onwards it has already been traced as the lateral
cutaneous nerve of the forearm (p. 69).

In the arm the musculo-cutaneous nerve supplies branches
to three muscles of the region. The branch to the coraco-
brachialis is given off before the parent trunk enters the
substance of the muscle ; the branches to the biceps brachii
and brachialis issue from it as it lies between them.

M. Coracobrachialis. The coraco-brachialis is an elongated
muscle, which takes origin from the tip of the coracoid
process, in conjunction with the short head of the biceps
brachii. It proceeds distally, along the medial margin of the
biceps brachii, and obtains insertion into a linear ridge
situated upon the medial aspect of the body of the humerus,
about its middle.

M. Biceps Brachii. The biceps brachii muscle arises
from the scapula by two distinct heads of origin. The short
or medial head springs from the tip of the coracoid process in
conjunction with the coraco-brachialis (Fig. 24, p. 46). The
long or lateral head is a rounded tendon, which occupies the
intertubercular sulcus of the humerus. Its origin cannot be
studied at this stage of the dissection, because it is placed with-
in the capsule of the shoulder-joint, where it arises from an
impression on the scapula immediately above the glenoid cavity.



THE FRONT OF THE ARM



107



Supraspinatus



Subscapularis



... Crest of the
lesser tubercle



Pectoralis major
^- Teres major



Deltoid



"~ Coraco-brachialis



Both heads swell out into
elongated fleshy bellies,
which, at first, are merely
closely applied to each
other, but afterwards are
united in the distal third
of the arm. Towards the
bend of the elbow the
fleshy fibres converge upon
a stout, short tendon, which
is inserted into the dorsal
part of the tuberosity of
the radius. The insertion
will be more fully examined
at a later period, but it
may be noticed, in the
meantime, that the tendon
is twisted so as to present
its margins to the front
and dorsal aspect of the
limb, and, further, that a
bursa mucosa is interposed
between it and the smooth,
volar part of the radial
tuberosity.

The dissector has al-
ready taken notice of the
lacertus fibrosus, and has
separated it, artificially,
from the deep fascia of the
arm, and of the forearm.
Observe now that it springs
from the anterior margin
of the tendon of the biceps
brachii, and also from the
short head of the muscle.
It is supplied by the mus-
culo-cutaneous nerve and
is a supinator of the fore-
arm and a flexor of the

elbow-joint. FlG ' J 5- -Anterior aspect of Humerus with

_ J _ _ _ Muscular Attachments mapped out.

M. Brachialis (O.T.



Brachio-radialis



Extensor carpi
\- radialis
jongus



Extensors



Pronator teres
and flexors



io8 THE SUPERIOR EXTREMITY

Brachialis Anticus). The brachialis arises from the entire
width of the anterior aspect of the distal half of the body of
the humerus, from the medial intermuscular septum, and from
a small part of the lateral intermuscular septum proximal to
the brachio-radialis. The origin from the bone is prolonged
proximally in two slips which partially embrace the insertion
of the deltoid. The fibres converge to be inserted into the
base of the coronoid process of the ulna by a short, thick
tendon. The muscle lies partly under cover of the biceps
brachii, but projects beyond it on each side. It is over-
lapped on its medial side by the pronator teres, and on the
lateral side by the brachio-radialis and extensor carpi radialis
longus. Its deep surface is closely connected to the anterior
part of the capsule of the elbow-joint. Its chief nerve of
supply, from the musculo-cutaneous^ has already been secured,
but it receives also one or two small twigs from the radial
(musculo-sptrat) nerve which are given off under cover of the
brachio-radialis. It is a flexor of the elbow-joint.

Dissection.- Separate the brachio-radialis from the brachialis
muscle, and dissect out the radial nerve, with the anterior
terminal branch of the profunda brachii artery, which lie deeply
in the interval between the muscles. There also, in a well-
injected subject, the anastomosis between the profunda brachii
artery and the radial recurrent artery may be made out ; and
the twigs which are given by the radial nerve to the brachialis,
the brachio-radialis, and the extensor carpi radialis longus, should
be looked for.

Fossa Cubitalis. The cubital fossa is the hollow in
front of the elbow. It is triangular in outline and it
corresponds generally with the popliteal fossa at the back
of the knee.

It possesses a roof or superficial boundary ; a floor or
deep boundary ; medial and lateral boundaries ; a base and
an apex.

The roof is formed by the deep fascia in which lies
the thickened band called the lacertus fibrosus. It is
pierced by a communication from the deep veins of the
forearm to the median cubital vein. It is covered by the
skin and superficial fascia, and upon it, in the superficial
fascia, lie a portion of the cephalic vein, a portion of the
basilic vein, the median cubital vein, the volar branch of
the medial cutaneous nerve of the forearm, and the lateral
cutaneous nerve of the forearm.



THE FRONT OF THE ARM



109



The " base " is an imaginary line drawn between the
two epicondyles of the humerus. The medial border,
formed by the lateral margin of the pronator teres muscle




Lateral end of clavicle
^__ Margin of acromion

Pectoralis major
Cephalic vein

Deltoid



Cutaneous branches of Axillary
nerve piercing deltoid

Lateral brachial cutaneous branch
of axillary (O.T. circumflex) nerve



Biceps brachii
Lateral head of triceps

Brachialis

Proximal branch of dorsal
cutaneous nerve of forearm

Cephalic vein

Distal branch of dorsal cutaneous
nerve of forearm

Brachio-radialis
Tendon of triceps



Olecranon
Extensor carpi radialis longus



FIG. 46. The Deltoid Muscle and the lateral aspect of the Arm.

descending from the medial epicondyle, and the lateral
border, formed by the medial margin of the brachio-radialis,
as it descends from the lateral supra - epicondylar ridge,
meet distally at the apex where the brachio-radialis overlaps



I 10



THE SUPERIOR EXTREMITY



the pronator teres. The floor is formed by the distal part
of the brachialis muscle and the anterior part of the supinator.
Within the fossa are the termination of the brachial artery,
and the proximal parts of the radial and ulnar arteries, into
which it divides. To the lateral side of the main vessel



Medial cutaneous nerve

of the forearm

Fascia of the arm

Basilic vein A



Brachial artery

Medial cutaneous
nerve of the forearm



Median nerve

Volar ulnar recurrent

artery

Nerve to pronat. teres

Ulnar artery
Lacertus fibrosus

Pronator teres, deep head



Flexor carpi radiali.s



Palmaris longus -



Medial cutaneous nerve
of the forearm
Basilic vein -




Lateral cutaneous nerve of
the forearm, volar branch
Cephalic vein

Brachialis

Lateral cutaneous nerve of
the forearm, dorsal branch



Radial nerve

Lacertus fibrosus
Radial nerve,
superficial branch

Radial nerve,

deep branch

Tendon of biceps brachii



Radial recurrent artery
Supinator muscle

Brachio-radialis muscle



-Radial artery



Lateral cutaneous
nerve of the forearm,
volar branch
Cephalic vein



Median vein
FIG. 47. Dissection of the Left Cubital Fossa.

is placed the tendon of the biceps brachii, and to its
medial side, the median nerve. A quantity of loose fat also
is present. The ulnar artery leaves the space by passing
under cover of the pronator teres ; the radial artery is con-
tinued distally beyond the apex of the fossa, overlapped by
the brachio-radialis. The median nerve disappears between
the two heads of the pronator teres, and the tendon of
the biceps brachii inclines posteriorly, between the two bones
of the forearm, to reach its insertion into the radial tuberosity.



THE FRONT OF THE ARM in

Other structures which are under cover of the boundaries
but are not strictly within the fossa are : the termination
of the radial nerve and parts of its deep and superficial
divisions; the anterior terminal branch of the profunda
artery; the radial recurrent artery; the volar and dorsal
ulnar recurrent arteries and twigs of the superior and inferior
ulnar collateral arteries.

Dissection. The fascial roof of the cubital fossa was partially
destroyed when the deep fascia of the front of the arm was
reflected, but the lacertus fibrosus is still in position. Now
cut across the lacertus near the biceps (Fig. 47), and reflect it
towards the medial border of the forearm, then proceed to clean
the contents of the fossa. Pull aside the medial and lateral
boundaries with hooks and then commence with the median
nerve. Follow it from above downwards to the point where it
disappears between the two heads of the pronator teres, and
secure the branches which spring from its medial side and pass
to the muscles which arise from the medial epicondyle of the
humerus.

Next clean the brachial artery, also from above downwards.
If its venae comites are in the way remove them. Follow the
artery to its division into its radial and ulnar branches, then
follow the radial artery to the apex of the fossa, and the ulnar
artery to the point where it disappears behind the deep head of
the pronator teres. Do not injure the radial recurrent branch
which springs from the lateral side of the radial artery, or the
volar and dorsal ulnar recurrent branches which arise from the
medial side of the ulnar artery. Now clean the tendon of the
biceps brachii and follow it to its insertion into the posterior part
of the tuberosity of the radius, and note that, as it passes to its
insertion, it twists so that its anterior surface becomes lateral,
and its posterior surface becomes medial. The tendon is
separated from the anterior part of the tuberosity by a small
bursa which may be opened with the point of the scalpel.

To facilitate the cleaning of the floor and to expose structures
which are not strictly contents of the fossa, but which lie close
to it, under cover of its medial and lateral boundaries, flex the
elbow slightly, and pull the medial and lateral boundaries of the
fossa still wider apart. Find the termination of the radial nerve,
and the anterior terminal branch of the profunda artery at the
level of the lateral epicondyle between the brachio-radialis and
the brachialis. Follow the deep and superficial terminal branches
of the nerve, downwards in front of the lateral part of the
capsule of the elbow- joint. The deep branch disappears into the
substance of the supinator. The superficial division descends
between the brachio-radialis and the supinator, either superficial
or deep to the branches of the radial recurrent artery. The
termination of the superficial division has already been dissected
on the dorsum of the hand where it supplies the lateral three-
and-a-half digits (see p. 71). Next follow the radial recurrent
artery to the lateral epicondyle, where it anastomoses with the
anterior terminal branch of the profunda artery. Then trace
the volar and dorsal recurrent branches of the ulnar artery to



ii2 THE SUPERIOR EXTREMITY

the medial epicondyle where they anastomose with the superior
and inferior ulnar collateral branches of the brachial artery.

After the relative positions of the contents of the cubital
fossa have been studied turn to the dissection of the back of
the arm.



DORSUM OF THE ARM.

In this region in addition to the cutaneous nerves the
following are the structures which must be studied :

1. The triceps muscle.

2. The profunda brachii artery, and the radial nerve.

3. The superior ulnar collateral artery, and the ulnar nerve.

4. The posterior branch of the inferior ulnar collateral artery.

5. The subanconaeus muscle.

The skin and the superficial fascia have already been



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