572 
space. This nerve, where crossed by the external 
jugular vein, gives one or two minute twigs, 
which follow its direction toward the angle of 
the jaw. 
e supra-clavicular and super-acromial are 
the two superficial branches in which the 
plexus terminates: as they descend, they di- 
vide into a lash of twigs, which diverge in the 
oars triangle of the neck, and at various 
eights pierce its fascia, become subjacent to 
the platysma, and contribute to supply it. Their 
ultimate branching takes a very wide range: the 
inner filaments obliquely cross the clavicular 
origin of the sterno-mastoid ; the outer, the 
anterior fibres of the trapezius; the middle 
ones, the clavicle itself; and are dis- 
tributed, in their respective regions, to the in- 
teguments of the scapula, shoulder, chest, and 
sternum. 
The branch from the portio dura, which enters 
the neck, is the lower division of its cervico- 
facial part. From near the angle of the jaw, 
where it traverses the fascia, it passes toward 
the hyoid bone, and supplies the platysma 
from its deeper side. Some of these twigs, 
approaching the cutaneous surface of the 
muscle in the anterior triangle of the neck, 
communicate with filaments of the anterior cer- 
vical nerve. 
1. Mesial region of the neck.—This presents 
different relations, as considered above or below 
the level of the os hyoides. 
Above the os hyoides, and extending from 
the body of that bone to the symphysis of the 
lower jaw, is the narrow space which separates 
the anterior bellies of the digastric muscles. It 
is an elongated triangle, broadest below—where 
the tendons of the digastrics are kept apart by 
the body of the hyoid bone—having its apex 
above, where these, having expanded into the 
fleshy anterior bellies, are infixed side by side 
at the median line of the jaw. The platysmata 
in their cellular sheath cover this space, and 
sometimes decussate across it with each other. 
The cervical aponeurosis likewise extends over 
it, adhering to its bony limits, and strength- 
ened by the tendinous slip, which is derived 
from the digastric. Deeper than the digastrics 
are seen the fibres of the mylo-hyoid muscles, 
meeting in the median raphe, which runs along 
the space. The natural direction of this raphe 
is almost antero-posterior, and that of the fibres 
which meet in it almost horizontally transverse : 
but when (as in any operation on this part of 
the neck) the head is thrown back and the chin 
elevated, the raphe presents a considerable 
downward slope, and the fibres of the mylo- 
hyoid have a corresponding obliquity. The 
same observation applies to the deeper fibres 
which course from the tubercles within the sym- 
physis to the body of the hyoid bone—those, 
namely, of the genio-hyoid and genio-hyo-glos- 
sal muscles. This little region can hardly be 
said to have any special surgical relations; it 
contains neither vessels nor nerves of size ;its 
injuries only assume importance when taey 
extend beyond it into the adjoining digastric 
space; its diseases derive a0 peculiarities from 
their situation, and for the most part belong to 
NECK. 
the integuments, which are vascular, 
folliculated, and in the male densely beardes 
sycosis often extends to them, and they are 
frequent seat of sebaceous tumours. es 
Below the os hyoides, the anatomy, ¥ 
involves the surgical relations of the laryn: 
trachea, becomes of extreme importance. — 
tween the two layers of the fascia superfi 
the platysma no longer intervenes; they 
cordingly lie together and are blended. ' 
vaginal processes of cervical fascia, which | 
isolated the sub-hyoid muscles, become wi 
into a strong and single raphe along the mi 
line, from above to within a short distane 
the sternal notch; but here the layers rem 
distinct, a superficial one fixing itself 
notch and to the interclavicular ligame at, W 
the deeper one descends with the muscles ii 
the mediastinum. The interval contains” 
cellular tissue, and sometimes (as Burns 
ticed) an absorbent gland. Accordingly, in 
very median line, an operator may expose t 
larynx, trachea, or thyroid body without 
ding or displacing any portion of muscle ; 
a lateral deviation from this imaginary 
would imply an exposure of the 
muscles on one side or on the other. 
the muscles so nearly approach to the lit 
question, and constitute in their lamin: 
rangement so useful a guide to the subje 
parts, that the bare possibility of avoiding 
is wisely neglected, and the surgeon | 
from them his nearness to the organs 4 
they cover. = 
In tracing, from the hyoid bone dowm 
the irregular profile of the air-tube, the 
may distinguish through the integume 
following changes of outline. 1. A horiz 
semicircular notch, limited below by the 
minent angle of the thyroid cartilage, am 
responding, in the interval of the mu: 
the thyro-hyoid membrane ; the lateral p 
this give passage, as we shall presently. 
the laryngeal artery and nerve, but its 1 
art, with which alone we are now oct 
1as only a small twig from the thyro 
rainifying over it: the membrane is thie 
composed of strong vertical fibres in the 
line ; it becomes weaker and of laxer 1 
pene backward. Its deep aspei 
utes to the skeleton of the pharynx, 
responds to the epiglottis, from the 
portion of which it is separated onl 
lular tissue and the epiglottidean glan 
above, the mucous membrane, in bein 
forward to the epiglottis, intervenes bi 
and the membrane. This notch is fre 
invaded by the knife of the suicide; an 
is perhaps no part of the neck on whi 
may be inflicted with less serious ijt 
large vessels are far removed, and tl 
lies below the blade, which may, if mi 
hyoid bone, enter the pharynx 
glottidean fold of mucous mem 
the epigicttis unhurt, or, if more m 
proached to the thyroid border 
may partly or entirely sever that 
its inferior attachments. No sp 
operation belongs to the space; if inc 
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