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into two terminal branches, the a. circumflexa scapulae, and
the a. thoraco-dorsalis. The circumflex scapular branch turns
round the axillary border of the scapula on its way to the
infraspinous fossa of that bone, where it anastomoses with
branches of the transverse cervical and transverse scapular
arteries. It gives numerous branches to the adjacent
muscles. The thoraco-dorsal branch descends along the lower
border of the subscapularis to the inferior angle of the
scapula. It gives branches to the adjacent muscles and
anastomoses with the lateral thoracic artery and with
branches from the intercostal arteries. It sends branches
also into the subscapular fossa which anastomose with twigs
of the transverse and circumflex scapular arteries, and
with branches of the descending branch of the transverse
cervical artery.

Aa. Circumflexae Humeri, Anterior et Posterior (O.T.
Anterior and Posterior Circumflex Arteries). The anterior
and the posterior humeral circumflex arteries both arise from
the axillary at the same level, a short distance distal to the
origin of the subscapular artery. The posterior humeral cir-
cumflex artery is much the larger of the two. Only a small
portion of it can be seen at the present stage. It springs
from the posterior aspect of the axillary artery, and at once
passes backwards, with the axillary nerve, in the interval
between the subscapularis and teres major muscles on the
medial side of the surgical neck of the humerus. The
smaller anterior humeral circumflex artery takes origin from the
lateral aspect of the axillary artery, and runs laterally, in front
of the surgical neck of the humerus, under cover of the
coraco - brachialis and short head of the biceps brachii.
Reaching the intertubercular sulcus, it divides into two
branches. One of the two is directed proximally, along the
long head of the biceps brachii, to the shoulder-joint ; the
other passes laterally, to the deep surface of the deltoid, and



AXILLARY SPACE 37

finally anastomoses with some of the terminal twigs of the
posterior circumflex artery of the humerus.

Vena Axillaris. The axillary vein has the same extent
as the artery. It begins at the lower border of the teres
major, as the proximal continuation of the basilic vein of the
arm, and it becomes the subclavian vein at the outer margin
of the first rib. At the lower margin of the subscapularis
it receives the two vtncz comites of the brachial artery, and
above the level of the pectoralis minor it is joined by the
cephalic vein. Its other tributaries correspond, more or
less closely, to the branches of the axillary artery.

M. Subclavius. The subclavius is a small muscle which
lies immediately below the clavicle, enclosed between the
two layers of the costo-coracoid membrane. It takes origin,
by a short rounded tendon, from the superior surface of
the first costal arch, at the junction of the bone with the
cartilage, and the fleshy belly is inserted into the shallow
groove on the inferior surface of the clavicle. The nerve of
supply is derived from the fifth and sixth cervical nerves and
enters the posterior surface of the muscle. When the muscle
contracts it depresses the clavicle and draws it slightly
forwards.

Dissection. When the subclavius has been examined it must
be divided horizontally, and when that has been done the costo-
clavicular ligament will be found behind the medial end of the
muscle.

At this stage, with the assistance of the dissector of the head
and neck, the clavicular part of the sterno-cleido-mastoid muscle
must be detached from the superior border of the clavicle and
the sternal part of the muscle must be pulled towards the median
plane.

Articulatio Sternoclavicularis. The sterno-clavicular joint
is a diarthrodial joint, formed by the sternal end of the
clavicle, the lateral part of the superior border of the
manubrium sterni, and the superior surface of the sternal
end of the cartilage of the first rib. It helps to increase
the range of the forward, backward, and upward movements
of the arm. The clavicle is attached to the sternum and the
first rib by a strong fibrous capsule. Within the capsule is an
articular disc which separates the joint cavity into two parts.
It is attached to the superior border of the sternal end of the
clavicle, to the superior surface of the first costal cartilage, and
to the anterior and posterior parts of the capsule. On the



THE SUPERIOR EXTREMITY



lateral aspect of the capsule there is a strong accessory
ligament, the costo-clavicular ligament, which lies behind the
origin of the subclavius muscle and passes upwards, back-
wards, and laterally from the first rib to the costal tubercle on
the lower surface of the clavicle. In the capsule itself there
are three thickened bands, an anterior, a posterior, and a
superior, and as some of the fibres of the latter pass from
one clavicle to the other, it is called the interclavicular
ligament.



Joint capsule
Joint cavity



Interarticular
ligament




Joint cavity

FIG. 1 8. Sterno-clavicular and Costo-sternal Joints.



Anterior chondro-
sternal ligament



Dissection. Pull the sternal head of the sterno-cleido-
mastoid muscle towards the median plane. Cut through the
anterior part of the capsule of the joint close to the sternum.
Pass the knife behind the capsule, avoiding the anterior jugular
vein, which runs laterally behind the upper border of the joint,
and detach the fibres of origin of the sterno-hyoid muscle which
spring from the back of the capsule. Cut through the posterior
ligament and pull the clavicle laterally. The articular disc is
now exposed. Detach it from the first rib ; then carry the knife
laterally below the clavicle and cut through the lower part of
the capsule and the costo-clavicular ligament. The clavicle
can now be displaced sufficiently upwards and laterally to bring
the whole of the brachial plexus into view. Before studying
the plexus, the dissector should note that behind the sterno-



AXILLARY SPACE



39



clavicular joint there are the lower fibres of the sterno-hyoid
and sterno-thyreoid muscles which intervene, on the right side,
between the capsule of the joint and the bifurcation of the
innominate artery into its right common carotid and subclavian
branches, and, on the left side, between the joint and the left
common carotid artery.

Plexus Brachialis (Brachial Plexus). This important




Subscapular nerve j
Ulnar nerve



Lateral cutaneous nerve
| Lateral cutaneous nerve
j Intercosto-brachial nerve

| Medial cutaneous nerve of arm
Medial cutaneous nerve of forearm



FIG. 19. Diagram of Brachial Plexus and its Branches.

plexus is formed by the anterior rami of the lower four
cervical nerves and the greater part of the anterior
ramus of the first thoracic nerve. The plexus is further
reinforced, above, by a small twig of communication which
passes from the fourth to the fifth cervical nerve, whilst, below,
a similar connecting twig not infrequently passes upwards, in
front of the neck of the second rib, from the second to



THE SUPERIOR EXTREMITY



the first thoracic nerve. The manner in which the nerves
join to form the plexus is very constant. The fifth and sixth
cervical nerves unite to form an upper trunk ; the seventh remains
single and proceeds distally as a middle trunk ; whilst the



Upper trunk




Scalenus anterior and longus colli
Scalenus medius and posterior

Phrenic nerve

Seal, anterior and longus colli
Seal, medius and posterior
Middle trunk



Seal, anterior and longus colli
Seal, medius and posterior



Scalenus anterior and longus colli
Scalenus medius and posterior



Lower trunk



T2



ANTERIOR

N.INTE.RCOSTAUS



FIG. 20. Diagram of the Brachial Plexus. (After Paterson.)

eighth and first thoracic nerves join, to constitute a third or
lower trunk. A short distance above the clavicle each of the
three trunks splits into an anterior and a posterior division.
When the three anterior divisions are raised on the handle
of a knife, the three posterior divisions will be seen uniting to
form the posterior cord of the plexus. It should be noted that
the lowest or most medial of the posterior divisions is much



AXILLARY SPACE 41

smaller than the other two. Of the three anterior divisions
the two upper join to constitute the lateral cord, whilst the
lower passes distally by itself, as the medial cord of the plexus.
From the three cords of the plexus the branches are given
off which supply the superior extremity (Figs. 19, 20, 22).

From the above description it will be seen that the plexus
may be divided into four stages :

First Stage . . Five separate nerves (viz. , lower four cervical and first

thoracic).

Second Stage . Three nerve-trunks (viz., an upper, middle, and lower).
Third Stage . Three anterior divisions and three posterior divisions.
Fourth Stage . Three nerve -cords (viz., a lateral, a medial, and a

posterior).

The plexus extends from the lateral border of the scalenus
anterior to the lower border of the pectoralis minor, and it
lies in the lower and medial part of the posterior triangle of
the neck, behind the middle third of the clavicle, and in the
axilla. As a rule, the first two stages are in the neck, the
third stage is behind the clavicle, and the last stage is in the
axilla (Figs. 21, 22).

It has been customary to divide the branches of the
plexus into supraclavicular and infraclavicular groups, but
such a division is neither scientifically accurate nor of practical
importance. The branches of the plexus spring either from
its roots, or its trunks, or its cords.

The parts of the plexus above the clavicle, and the branches given off in
the supraclavicular region, must be found and cleaned by the dissector of
the head and neck ; the remaining parts of the plexus and its branches
should be displayed by the dissector of the upper extremity, but the two
dissectors must combine to examine thoroughly the general relations and
the branches of the plexus.

The Relations of the Plexus. Superficial to the cervical
part of the plexus lie the skin, the superficial fascia, the
platysma, the deep fascia, the external jugular vein, the trans-
verse cervical and transverse scapular veins, the posterior
belly of the omo-hyoid muscle, and the transverse cervical
artery. Behind it is the scalenus medius muscle (Fig. 21).

In the interval between the neck and the axilla, the clavicle
and the transverse scapular artery and vein are in front of
it ; and the third part of the subclavian artery is anterior to
its lowest trunk. The scalenus medius is still behind it.

In the axilla it has in front of it the integument, the fasciae,



THE SUPERIOR EXTREMITY



the platysma, the pectoralis major, the pectoralis minor, the
costo-coracoid membrane, the cephalic vein, and the axillary
artery; behind it lie the upper serration of the serratus
anterior, the fascia -filled interval between the medial and
posterior walls of the axilla, and the subscapularis muscle

(Fig. 22).

The Branches of the Plexus. The branches from the
roots of. the plexus are: (i) Branches to the scalenus
anterior, the longus colli, the scalenus medius, and the
scalenus posterior (from C. v., vi., VIL, vin.). (2) A com-
munication to the phrenic nerve (from C. v., or v. and vi.).




Levator scapulae



Dorsal scapular nerve
External jugular ve



Scalenus mediu
Transverse cervical artery



Omo-hyoid muscle
Brachial plexus



Suprascapular
nerve



Sterno-hyoid muscle



Sterno-mastoid
muscle



Transverse
scapular artery
Scalenus anterior
Subclavian artery
Subclavian



FIG. 21. Dissection of the lower part of the Posterior Triangle of the Neck,
showing the Supraclavicular Part of the Brachial Plexus.

(3) The dorsalis scapulae nerve, which supplies the rhomboid
muscles (from C. v.). (4) The long thoracic nerve, which
supplies the serratus anterior (from C. v., vi., VIL).

The branches from the trunks of the plexus are: (i) The
nerve to the subclavius, from the upper trunk (from C. v., vi.).
It has already been seen piercing the posterior surface of the
costo-coracoid membrane and entering the posterior aspect
of the subclavius (p. 37). (2) The suprascapular nerve,
from the upper trunk (from C. v., vi.). It will be found
crossing the lower part of the posterior triangle, deep to
the posterior belly of the omo-hyoid muscle, and disappear-
ing through the scapular notch on its way to the dorsum
scapulae (Fig. 22).



AXILLARY SPACE 43

The branches from the cords are
From the lateral cord :

Nervus thoracalis anterior lateralis (O.T. External Anterior

Thoracic) (from C. v., vi., vn.).
N. musculocutaneus (from C. v., vi., vn.).
N. medianus, caput lateralis (O.T. Outer Head of Median) (from

C. v., vi., vn.).
From the medial cord :

N. thoracalis anterior medialis (O.T. Internal Anterior Thoracic)

(from C. viii., T. I.).
N. cutaneus antibrachii medialis (O.T. Internal Cutaneous) (from

C. viii., T. i.).
N. cutaneus brachii medialis (O.T. Lesser Internal Cutaneous)

(from T. I.).
N. medianus, caput medialis (O.T. Inner Head of Median) (from

C. viii., T. i.).

N. ulnaris (from C. viii., T. i.).
From the posterior cord :

Nn. subscapulares (O.T. Upper and Lower) (from C. v., vi.).

N. thoracodorsalis (O.T. Long Subscapular) (from C. vi., vn.,

VIII.).

N. axillaris (O.T. Circumflex) (from C. v., vi.).

N. radialis (O.T. Musculospiral) (from C. v., vi., vn., viii., T. i).

In the above table the different spinal nerves from which the fibres
of the several branches are derived are indicated.

Nn. Thoracales Anteriores. The anterior thoracic nerves
supply the pectoral muscles. They are two in number, the
lateral and the medial. The lateral anterior thoracic nerve
springs from the lateral cord of the plexus, passes forwards
across the lateral side of the first part of the axillary artery,
communicates, in front of the artery, with the medial nerve,
pierces the costo-coracoid membrane, and breaks up into
branches which end in the pectoralis major. The medial
anterior thoracic nerve is smaller than the lateral. It springs
from the medial cord of the plexus, passes forwards between
the axillary artery and vein, communicates, in front of the
artery, with the lateral nerve, gives twigs of supply to the
pectoralis minor, then pierces that muscle and ends in the
pectoralis major, which it supplies. The pectoralis major is,
therefore, supplied by both anterior thoracic nerves, the
pectoralis minor by the medial nerve alone.

Nn. Subscapulares. The subscapular nerves are two in
number the upper and the lower. They spring from the
posterior cord of the plexus. After a very short course the
upper nerve sinks into and supplies the upper and posterior
part of the subscapularis. The lower subscapular nerve



44



THE SUPERIOR EXTREMITY



passes downwards and laterally, gives branches to the lower
part of the subscapularis, then passes through the angle




FIG. 16. Dissection to show the General Relations of the Brachial Plexus.



1. Accessory nerve.

2. Nerve to levator scapulae.

3. Levator scapulae.

4. Dorsal scapular nerve.

5. Long thoracic nerve.

6. Scalenus medius.

7. Suprascapular nerve.

8. Serratus anterior.

9. Upper subscapular nerve.

10. Subscapularis.

11. Pectoralis minor.

12. Nerve to coraco-brachialis.

13. Axillary nerve.

14. Musculo-cutaneous nerve.

15. Radial nerve.

16. Median nerve.

17. Medial cutaneous nerve of forearm.



18. Medial cutaneous nerve of arm.

19. Intercosto-brachial nerve.

20. Latissimus dorsi.

21. Thoraco-dorsal nerve.

22. Long thoracic nerve.

23. Internal jugular vein.

24. Superior thyreoid artery.

25. Submaxillary gland.

26. External jugular vein.

27. Scalenus medius.

28. Upper trunk of brachial plexus.

29. Middle trunk of brachial plexus.

30. Kighth cervical nerve.

31. Omo-hyoid.

32. Nerve to subclavius.

33. Lateral anterior thoracic nerve.

34. Medial anterior thoracic nerve.



between the thoraco-dorsal and circumflex scapulae arteries
and ends in the teres major, which it supplies.



AXILLARY SPACE



45



N. Thoracodorsalis (O.T. Long Subscapular Nerve). The
thoraco-dorsal nerve springs from the posterior cord of the
plexus, passes obliquely downwards and laterally, through the
axilla, and joins the thoraco-dorsal artery near the lower part
of the lateral border of the subscapularis muscle. After cross-



Scalenus medius
Scalenus anterior



Upper part of Serratus
anterior



Middle portion of
Serratus anterior




Lower portion
of Serratus



FIG. 23. Serratus Anterior muscle and origin of the External Oblique
muscle ; the scapula is drawn away from the side of the chest.

ing in front of the artery it terminates in the latissimus dorsi,
which it supplies.

N. Thoracalis Longus (O.T. Posterior Thoracic or Ex-
ternal Respiratory Nerve of Bell). The long thoracic
nerve may now be studied in its whole length. It passes
downwards on the lateral surface of the serratus anterior, and
is the nerve of supply to that muscle. It arises, in the root of



46 THE SUPERIOR EXTREMITY

the neck, from the brachial plexus, by three roots. The upper
two roots (one from the fifth cervical and the other from the
sixth cervical nerve) pierce the scalenus medius, and, uniting



Coraco-
brachialis and
Biceps brachii
(short head) Pectoralis minor



Omo-hyoid



Triceps
(long head)




FIG. 24. Costal aspect of the Scapula with the Attachments
of Muscles mapped out.



into one stem, give off branches to the upper part of the
serratus anterior. The third root takes origin from the seventh
cervical nerve, passes in front of the scalenus medius, and runs
downwards for a considerable distance on the surface of



AXILLARY SPACE 47

the serratus anterior, before it unites with the other part of
the nerve. The entire nerve can be followed to the lower
part of the serratus anterior, giving twigs to each of its
digitations.

M. Serratus Anterior (O.T. Serratus Magnus). The
serratus anterior arises by fleshy digitations from the upper
eight ribs, about midway between their angles and cartilages.
The slips are arranged on the chest wall so as to present a
gentle curve convex forwards. The lower three interdigitate
with the external oblique muscle of the abdomen. The
serratus anterior is inserted into the entire length of the
anterior lip of the vertebral margin of the scapula, and it falls
naturally into three parts, (a) The upper part^ composed of
the large first digitation alone, arises from the first and second
ribs, and from a tendinous arch between them. The fibres
converge, to be inserted into a somewhat triangular surface on
the costal aspect of the medial angle of the scapula, (b) The
middle part consists of two digitations which take origin from
the second and third ribs. The upper slip is very broad, and
springs from the lower border of the second rib. The fibres
of the middle part diverge to form a thin muscular sheet,
which is inserted into the anterior lip of the vertebral margin
of the scapula, between the insertions of the upper and lower
portions. (c] The lower part is formed by the remaining
digitations of the muscle. They converge to form a thick
mass, which is inserted into a rough surface upon the costal
aspect of the inferior angle of the scapula. The deep surface
of the serratus anterior is in contact with the chest wall.
It is the most powerful protractor of the whole upper
extremity.



DISSECTION OF THE BACK.

Dissection. At the end of the fifth day, after the dissector
has examined the serratus anterior and carefully revised the
contents of the axilla, he must replace the clavicle, pack the
axilla with tow or rags steeped with preservative solution and
fix the skin flaps to the wall of the thorax with a few stitches.
When he returns on the sixth day he will find that the body has
been placed upon its face, with blocks supporting the chest and
the pelvis. It will remain in that position for five days, and
during the first two of those the dissector of the upper extremity
must examine the structures which connect the limb with the
posterior aspect of the trunk.



48 THE SUPERIOR EXTREMITY

Surface Anatomy. In the median line of the back there



Mastoid proces

Spine of scapula
Acromion



Superior nuchal line
External occipital protuberance



V Spine of seventh cervical vertebra



Inferior angle of scapula



Posterior superior
spine of ilium *



Tip of coccyx %$JUL . '
Greater trochanter |
Tuberosity of ischium



Medial condyle of femur -44/_
Lateral condyle of femur _l7
Lateral condyle of tibia ~k*
Head of fibula -3




Styloid process of ulna
Styloid process of radius



\ I



Medial malleolus
Lateral malleolus



FIG. 25. Surface View showing Incisions and Bony Points.

is little difficulty in recognising the tips of the spinous processes



DISSECTION OF THE BACK 49

of the vertebrae (Fig. 25). They follow each other in con-
secutive order, and it may be noted, when the finger is passed
over them, that all of them do not lie in the median plane ;
some may be deflected, in a slight degree, to one side or the
other. The spines of the vertebras are the only parts of
the spinal column which come to the surface ; they alone
yield direct information, by touch, to the surgeon as to the
condition of the spine. At the lower end of the neck, the
spine of the seventh cervical vertebra (vertebra prominent)
makes a visible projection ; and the spines of the first
two thoracic vertebrae likewise are very prominent. As
a rule, the most evident of the three is that of the first
thoracic vertebra. At a lower level, in subjects of good
muscular development, a median furrow is produced by the
prominence of the sacrospinalis muscle on each side, and
the spines of the vertebrae may be felt at the bottom of
the groove. The furrow attains its greatest depth in the
upper part of the lumbar region, and it fades away, below,
at the level of the spine of the third sacral vertebra. The
finger should next be passed downwards from the third sacral
spine, between the buttocks, along the lower part of the tuber-
culated posterior surface of the sacrum, and along the posterior
surface of the coccyx to the tip of the coccyx, which is the
inferior extremity of the vertebral column. Afterwards the
finger should be carried along the crest of the ilium. It
commences at the posterior superior spine of the ilium which
can easily be detected because its position is indicated by
a small but distinct dimple which lies at the level of the
second sacral spine. From the posterior superior spine the
crest of the ilium pursues a sigmoid course, laterally and
forwards. The highest point it reaches is on a level with
the spine of the fourth lumbar vertebra, and it terminates
in front in a prominence called the anterior superior
spine.

The scapula, or shoulder blade, is, for the most part, thickly
covered by muscles ; but, in spite of that, its general outline
can be made out (Fig. 25). It covers a considerable area of
the upper portion of the posterior aspect of the thorax. With
the hand by the side its medial angle lies over the second
rib, the root of its spine is placed opposite the spine of the
third thoracic vertebra, whilst its inferior angle reaches
down as far as the seventh, or even the eighth, rib. The

VOL. i 4



50 THE SUPERIOR EXTREMITY

scapula is very mobile, and moves to a greater or less
degree with every movement of the limb. The spine and
acromion of the scapula are subcutaneous throughout.
Below the scapula the lower five ribs can be distinguished,
and the tip of the last rib can be felt at a point about two
inches or less above the iliac crest.

As the back is dissected the following are the parts which
must be examined :

1. The cutaneous vessels and nerves of the back. ]

2. The trapezius muscle. I ist day.

3. The latissimus dorsi muscle.

4. The rhomboid muscles and their nerve.

5. The levator scapulae muscle.

6. The accessory nerve and the nerves from the cervical plexus

which supply the trapezius. J>2nd day.

7. The transverse cervical artery and its two terminal branches.

8. The posterior belly of the omo-hyoid muscle.

9. The transverse scapular artery and the suprascapular nerve, j

This dissection must be completed in two days, in order that
the dissector of the head and neck may be enabled to con-
tinue the deeper dissection of the back. The first day's work
should comprise (i) the reflection of the skin ; (2) the
dissection of the cutaneous nerves and vessels ; and (3) the
cleaning of the latissimus dorsi and trapezius muscles. The



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