NECK, 
‘The siylo-glossus arises, as a round fleshy 
bundle, from the tip of the styloid process, 
and from the adjoining part of the stylo-maxil- 
lary ligament, becomes flattened into divergent 
parts, as it approaches the side of the tongue 
at the posterior border of the hyo-glossus, after 
a short course downward, forward, and inward, 
and is there inserted. A part is continued for 
Some distance along the hyo-glossus, crossing 
the direction of its fibres, and interwoven with 
them; other fibres seem to bend into the sub- 
Stance of the tongue, near its base and at right 
angles to its axis. Its surface corresponds to 
the parotid gland, external carotid aitery, in- 
ternal pterygoid muscle, and mucous mem- 
brane of the mouth ; deeply, it lies on the in- 
ternal carotid artery, the superior constrictor 
of the pharynx, the tonsil and hyo-glossus. 
The genio-hyo-glossus is a large, fan-shaped 
muscle, radiating from within the symphysis 
of the jaw to the entire length of the tongue, 
and constituting, with its fellow, the chief mus- 
cular bulk of that fleshy organ. It rises by a 
Strong square mass of short tendinous fibres 
from the upper genial tubercle, and the fleshy 
fibres, which succeed, immediately and widely 
diverge; the highest bend upward and some- 
what forward to the tip of the tongue; those, 
_ which next follow, occupy its entire remaining 
length, spreading with more or less obliquity 
into the substance of the organ, through which 
on a section they may be followed even to the 
dorsum: some of these may be traced beyond 
the posterior edge of the hyo-glossus, expand- 
ing on the side of the pharynx just above the 
hyoid attachment of the middle constrictor, 
and constituting the so-called lingual origin of 
the superior constrictor, (see Puarynx); the 
remaining fibres complete the semicircular 
spread of the muscle, by passing downward 
and backward, to be inserted into the upper 
border of the body of the os hyoides. This 
muscle is opposed by its entire mesial surface 
to its fellow: their tubercles of origin are 
almost blended on the symphysis, and their 
_ fleshy fibres are only to be distinguished by 
a thin intermediate layer of adipose tissue : 
their upper edges raise the mucous mem- 
_ brane of the mouth on either side of the 
 frenum; their lower edges extend to the 
__ hyoid bone in perfect parallelism to each other, 
and to the genio-hyoidei, which cover them ; 
their outer surfaces, partly covered by the hyo- 
glossi, form with these on each side the inner 
wall cf a triangular space (roofed by the mu- 
‘cous membrane and floored by the mylo-hyoid 
_ muscle) in which lie the terminal branches of 
the lingual and gustatory nerves, the lingual 
artery, the sublingual gland, and the excretory 
duct of the submaxillary. 
Close at the implantation of this muscle in 
the tongue, between its fibres and those of the 
hyo-glossus, and crossing the direction of both, 
is asmall bundle of fleshy fibres, which runs 
longitudinally from base to apex, and, since 
it has no fixed attachment, may most fitly 
be considered among the intrinsic muscles of 
the organ; it has been named Jingualis. (See 
Toncue.) 
565 
The genio-hyoideus is a strong cylindrical 
muscle intimately associated with the genio- 
hyo-glossus, and ordinarily co-operating with 
its posterior fibres. It rizes by a square tendon 
from the inferior genial tubercle, beside its 
fellow of the opposite side and just below the 
genio-hyo-glossus. From this origin it directs 
itself backward and downward, and is inserted 
into the upper surface of the body of the os 
hyoides. Its insertion is somewhat broader 
than its origin: its inner surface corresponds 
to that of the opposite side; its upper surface 
is parallel to the genio-hyo-glossus, which it 
supports; its under surface rests on the mylo- 
hyoid, beside its raphe; its outer surface has 
similar relations to that of the genio-hyo- 
glossus, contributing with it to form the inner 
wall of the sub-lingual space just described. 
The action of the extrinsic muscles of the 
tongue is modified and more nicely adapted to 
the delicate offices of speech by the co-opera- 
tion of other and intrinsic muscles. These 
will be described in a future article (see 
Toncue). Those already considered operate 
on the tongue en masse;—elevate, advance, 
depress or retract it, shift its volume to either 
side, and direct its extremity, by a kind of 
circumduction, over a wide range of surface. 
Thus, the stylo-glossus can elevate and retract, 
the hyo-glossus depress and lateralise; the 
anterior fibres of the genio-hyo-glossi, with the 
linguales, regulate the motions of the tip, while 
the genio-hyoid and adjunct fibres of the genio- 
hyo-glossi can cooperate in these movements by 
shifting the base of support in any direction. 
As the genio-hyo-glossus is of largest bulk, 
so is it of most various office in the tongue; 
by its posterior fibres it gives an elevation to 
the os hyoides by which the tongue is protruded 
from the mouth; or, half antagonizing this 
action by its middle fibres, it may so forcibly 
hollow the dorsum of the tongue as to direct 
its apex within the incisor teeth, and, with aid 
of the stylo-glossi, enable it to sweep the con- 
cavity of the palate; or, by this co-operating 
with either hyo-glossus and with the opposite 
lingualis and stylo-glossus, the tongue may be 
made, as it were, to probe with its eminently 
tactile extremity the entire length of the alve- 
olar arches, or by a yet more definite contraction 
to exert suction on any spot with which its 
dorsum can have contact. 
The third class includes the sterno-cleido- 
mastoideus and the platysma myoides. 
The sterno-cleido-mastoideus is a long and 
powerful muscle, obliquely crossing the side 
of the neck, from the neighbourhood of the 
sterno-clavicular joint to the mastoid process 
of the temporal bone. It is fleshy in almost 
its whole extent; flattened at the extremities, 
but rather prismatic in the intermediate portion ; 
and the anterior edge, which is more particu- 
larly continuous with the sternal origin of the 
muscle, and which, in certain positions of the 
neck, raises the integuments in a well-known 
diagonal relief, considerably exceeds the thick- 
ness of the posterior border. The name of 
the muscle is a summary of its attachments. 
It arises by two heads, which are usually 
