566 
separated by a distinct cellular interspace, cor- 
responding to the sterno-clavicular articulation : 
1. from the anterior surface of the first bone 
of the sternum close to its clavicular joint, by 
a very strong flat tendon which is directed up- 
ward and backward for the space of more than 
an inch, before terminating in fleshy fibres ; 
2. from the upper edge of the inner third of 
the clavicle by a thin origin composed of pa- 
rallel aponeurotic fibres, which directly be- 
come fleshy, and take a nearly vertical course. 
As these two bundles ascend, the sternal, more 
oblique in its course, seems to overlap the 
other, and, both by difference of direction and 
by a line of cellular separation, can often be 
distinguished from it in the lower two-thirds of 
the neck ; but in approaching the mastoid pro- 
cess they are indistinguishably fused together. 
The insertion is, 1. by a strong and rounded 
tendon into the mastoid process, of which it 
seems to embrace the tip and anterior border ; 
2. by a thin aponeurosis along the posterior 
edge of the process, and about a third of the 
superior semicircular line, which is continued 
into it. 
This muscle, to which I shall have abun- 
dant occasion to refer in speaking of the sur- 
gical anatomy of the neck, has very important 
relations: the space between its heads corres- 
ponds to the bifurcation of the arteria inno- 
minata; and the broad band-like muscle, as 
it ascends, crosses in succession the subclavian 
and carotid arteries, the jugular and subclavian 
veins, the hypo-glossal, ppeumogastric, phrenic, 
sympathetic, spinal accessory nerves, and a 
rtion of the cervical plexus; the sterno- 
fyoid, sterno-thyroid, omo-hyoid, scaleni, le- 
vator anguli scapule, splenius, and digastric 
muscles, besides many lymphatic glands and 
branches from several of the nervous and vas- 
cular trunks which have been enumerated. Its 
superficial aspect corresponds to the integu- 
ments and platysma, to the external jugular 
vein and superficial branches of the cervical 
plexus; its thick anterior edge bounds the 
anterior triangle of the neck, receives branches 
from the external carotid artery or from its 
thyroid branch, and corresponds above to the 
parotid gland and posterior aural artery ; its 
thin posterior edge limits the other great trian- 
gle of the neck, is pierced by the pit acces- 
sory nerve, corresponds to a chain of lymphatic 
glands, and is wound round by the nerves and 
vein which lie on the surface of the muscle. 
The two sterno-mastoid muscles acting toge- 
ther directly bend the head on the chest, and 
their joint action is well illustrated in an en- 
deavour to raise the head from the supine 
ition. But when the head is thrown far 
k, a predominance is given to the posterior 
fibres of the muscle, which being attached 
behind the line of the jt, sre arti- 
culation, become then capable of increasing 
this direction of the head. The sterno-mastoid 
of one side, acting singly, rotates the head and 
flexes it with a lateral inclination to its own 
side, so as to bring the side of the head nearer 
to the shoulder, and to turn the face in the op- 
posite direction. 
NECK. 
The platysma myoides (latissimus colli of 
Albinus) is a broad, thin, membraniform mus- 
cle, which covers the side of the neck and 
lower part of the face, and is in its whole 
course subcutaneous. It arises scattered — 
fibres in the superficial fascia below the clavicle, 
and covers by its origin the upper of 
toralis major and deltoid, as also the spa 
atween those muscles, which corresponds to— 
the coracoid process, This origin does not 
extend within an inch or two of the median 
line, but reaches as far outwardly as the acro- 
mial process. The fibres become more closely 
aggregated as they ascend, and the muscle 
accordingly narrows. Its direction is obliquely 
upward and to the median line; it ver 
the base of the lower jaw, and its fibres again 
spread to their insertion: those which are pos- 
terior lose themselves in the skin covering the 
parotid gland and masseter muscle; others 
from this neighbourhood bend forward toward 
the angle of the mouth, and in some subject 
constitute a very distinct horizontal acto 
anguli oris, which is generally known as th 
risorius Santorini: some fibres from the midd 
of the muscle obtain a more fixed insertion 
about the base of the jaw and into the 
covering it; while the anterior portion ¢ 
muscle, which is most constant in its i 
is inserted into the lower lip by blending 
fibres with those of the depressor labii i 
rioris, and by decussating toward the boi 
of the lip and ia the substance of the « 
with the mesial fibres of its fellow. 
This muscle is subcutaneous in its w 
extent, and by its extremities intimately 
tached to the deep surface of the skin w 
covers it. In approximating its extreme atte 
ments, it wrinkles the skin in a directio 
verse to that of its fleshy fibres. It is. 
and partial relique in the human — ubjec ' 
that general muscular investment, which fu 
various functions in different orders of Mi 
malia, as an appendage of the tegumen 
system: rolling the hedge-hog in a ball » € 
ing the quills of the porcupine, and the br 
of the ten, or dislodging insects from 
hide of grazing cattle. Its relations to 
deeper parts in the neck will be detailed hi 
after: between it and the cervical apor 
rosis lie chiefly, cutaneous nerves and ye 
branches from the cervical division of | 
portio dura are distributed to its upper po 
reaching the deep surface just below the ar 
of the jaw, and branches from the cer 
plexus crossing the sterno-mastoid p: 
ply the platysma, partly pierce it in their co 
to the skin; the gi aaa > pectoral b 
lie beneath it till they reach the clavicle 
external jugular vein lies immediately bet 
this muscle, and runs nearly parallel to 
fibres, crossing transversely those of the st 
mastoideus. oe! 
: 
bn 
we 
- 
IIl.—Fasci# OF THE NECK. 
Pa >- 
1. The superficial fuscia, or subcutanec 
| 
areolar tissue, presents characters in com 
with the same structure in other parts of | 
body, and is universally continuous with tha 
