578 
thorax, at which during life the pleura bul- 
gingly rises, deriving considerable support 
from the horizontal infixion of the cervico- 
thoracic fascial septum. Externally to the curve 
of the rib, (with the coracoid process bounding 
it outwardly, the clavicle in front, and the su- 
perior costa of the scapula behind,) is the space 
through which vessels and nerves connect the 
cervical and axillary regions; to the borders of 
which, deep layers of aponeuroses are so fixed 
that-the regions only communicate in the line 
of the vessels, within the infundibulum of pre- 
vertebral fascia. Its anterior or covering wall 
presents, in addition to the platysma and sub- 
cutaneous areolar tissue, which in all direc- 
tions extend beyond its margins, the cervical 
fascia, as a single layer (except where it splits 
at the trapezius and sterno-mastoid) fixed to the 
clavicle below, and enclosing the omo-hyoid 
above. From the higher part of its posterior 
wall, originating at the anterior tubercles of 
the transverse processes, descends the scalenus 
anticus to fix itself in the floor of the space, 
on the upper surface of the rib, anteriorly. It 
intercepts, like a flying buttress, a space be- 
tween itself and the posterior wall, occupied 
by the brachial plexus and subclavian artery, 
round a!] which, as also round the subclavian 
vein, which lies in front of the scalenus, the 
prevertebral aponeurosis is folded and prolongs 
itself as a funnel; it is from this, that the slip 
of fascia is derived, which passes to the cla- 
vicle, in the manner described above, as a ho- 
rizontal process, dividing the axilla from the 
neck. 
As the distributive anatomy of the vessels 
and nerves will be detailed in a future article, 
(vide Spinat Nerves, SuscLavian ARTERY), 
their arrangement will now be only sketched, 
in its regard to surgical relations. The many 
important points of distinction between the 
right and left sides of the body in this region 
will presently be considered, the description 
meanwhile applying to both indifferently. The 
subclavian artery, from the sterno-clavicular 
joint outward, over-arches the floor of this 
region, presenting upwards a convexity in the 
interspace of the scaleni, downwards a con- 
cavity, which adapts itself to the pleura and to 
the rib. It gives off, as from an axis, branches 
from the four cardinal points of its cireum- 
ference: 1. downwards the internal mammary, 
which, crossed at its origin by the phrenic 
nerve, descends within the cartilages of the 
ribs; 2. upwards the vertebral, which, after a 
course of an inch between the scalenus anticus 
and longus colli, enters the canal of the trans- 
verse processes, usually at the sixth; 3. for- 
wards the thyroid axis, a short trunk giving 
origin to the inferior thyroid branch (already 
seen obliquely ascending behind the carotid 
sheath), the ascending cervical, which mounts 
beside the phrenic nerve, along the scalenus 
anticus, two transverse branches, which 
direct themselves outwardly, crossing that mus- 
cle,—the transversalis humeri along the clavicle, 
the transversalis colli higher, amid the branches 
of the brachial plexus and winding round the 
sealenus posticus to gain the inner edge of the 
NECK. 
scapula; lastly, 4. backwards an artery, which, — 
directing itself to the neck of the rib, sub 
divides there into two branches, one of which 
descends across the rib to the thorax, the supe- 
rior intercostal, while the other continues, = 
tween the neck of the rib and the seventh cer= 
vical transverse process, the backward dif 
tion of the common trunk, and then ascends 
among the deep muscles of the dorsal region— 
the arteria cervicalis profunda. The course of 
the subclavian artery is conveniently di 
into three stages ; a last or distal one, in whiel 
after having behind the scalenus anticus, 
it has, behind it, the scalenus posticus, below 
it the groove of the rib, above it (exter 
likewise a little behind) the brachial plexus — 
nerves, in front of it the coverings of the space 
we are considering, a familiar knowledge of 
which is here especially needed, since it is in 
this portion of its course that the artery is 
usually tied for axillary aneurism: a second 
stage, in which it lies between the scaleni, itt 
convexity toward their origin from which th 
brachial plexus divides it, its concavity re 
posing ou the pleura; and a first or trachea 
portion of its course, differently related on th 
two sides of the body, but thus far alike? 
both, that from it the branches originate, t 
its concavity is to the pleura and its convexit 
almost at right angles to the direction of t 
carotid, looks upward; that it is ed, b 
hind, to the sympathetic and to the last cervic 
transverse process,—in front, to the vagus ¢ 
phrenic nerves and to the jugular and si 
clavian veins,—inwardly to the carotid ar 
The circumstances of difference are ' 
to the fact, that, while on the right side a ea 
mon brachio-cephalic trunk exists—the art 
innominata,—which lies at no great dept 
the sternum, so that its branches di 
their respective destinations from a compa 
tively superficial and single point, behind @ 
sterno-clavicular joint ; on left side, « 
trarily, the carotid and subclavian arise 
rately from the arch, the latter, ata ' 
from the surface, actually beside the 
with the exception of having a thoracic ¢ 
mencement (nearly corresponding to the 
cheal Aalf of the arteria innominata), th 
carotid can scarcely be said to differ i 
tantly from the right, at least in virtue 
own course; it is somewhat deeper, hi 
front of the esophagus from the inel 
of that tube, has the thoracic duct 
at its outer side, and is, as will be 
directly, overlapped by the jugular 
lower part of the neck. The subclaviat 
on the right side passes from its ori 
transversely to the scalene space, COV 
the muscles which have been enw 
crossed at right angles by the 
pneumo-gastric nerves and by the jugular 
the left subclavian, on the other hand, 1 
the groove on the rib after a v ep a 
very oblique course ; it can | 
have any transverse direction, but gra 
by an inclination outwards and forward 
proaches the rib during its ascent, sO” 
traced toward its origin from the trach 
maint’ 
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4 
“Ft 
