_ trachea in conjunction with the crico-thyroid 
muscle. The nature and position of the arti- 
bulation of the thyroid, with the cricoid, render 
he force of this ligament of great utility and 
pportance. 
The lateral crico-thyroid ligament, lig. crico- 
hyroid laterale, arises immediately at the side 
“of the crico-arytenoid articulation. Some fas- 
iculi, according to Cruveilhier and Lauth, are 
tiached to the bases of the arytenoids, others 
we reflected horizontally forwards to the in- 
srior margin of the cricoid. It is bounded 
sternally by the thyro-arytenoideus and crico- 
rytenoideus lateralis, and lined internally by 
é mucous membrane of the larynx. 
The crico-arytenoid articulation—The ob- 
ue articulating convex surface of the cricoid 
48 received in a corresponding channel or 
groove at the base of the arytenoid cartilage. 
‘The ligament arises from the cricoid, and ra- 
jates both anteriorly and posteriorly round the 
ase of the arytenoid cartilage; a fasciculus is 
reflected along the base of its anterior mem- 
brane behind the attachment of the thyro-ary- 
tenoid ligament. The crico-arytenoid liga- 
ment is thick and strong, yet sufficiently loose 
9 permit a diversity of motion. Some anato- 
mists divide the ligament into anterior and 
terior. The articulation is lined and lubri- 
ed by a synovial membrane. 
The thyro-arytenoid ligaments. Syn. Chor- 
de vocales, Ferrein. Stimmbander, Germ. 
| These ligaments, as their name implies, con- 
lect the thyroid with the arytenoid cartilages, 
ad are instrumental in the production of voice. 
There are on each side two vocal cords, a su- 
berior and an inferior; the cavities between these 
igaments are termed the ventricles of the 
wynx. The inferior thyro-arytenoid ligaments, 
r,as they are often denominated, “ the true 
igaments of the glottis,” are much thicker and 
stronger than the superior: they present the 
form of nearly rectangular parallelograms, 
and are stretched horizontally across the long 
axis of the larynx, from the anterior horizontal 
"tubercle of the arytenoids, to the angle formed 
by the junction of the wings of the thyroid (c, 
g. 27). On their outer side these ligaments 
@ connected with the thyro-arytenoid mus- 
les; their anterior extremities are inserted into 
the thyroid, the posterior to the arytenoid car- 
lages ; the internal margins are free to vibrate. 
On exposing them by the removal of the mu- 
ous membrane they are found less than their 
ipparent volume. Immediately after death 
hey are semi-transparent, very elastic, and 
‘Composed of parallel fibres. They are con- 
nected with, and form a continuation of the 
ligamentum crico-thyroideum lateralis (k, fig. 
24). The length of the vocal ligaments varies 
with the general dimensions of the larynx: in 
‘the adult male they are much longer than in 
the female. In infancy they are very short, 
and increase from that period to the age of 
puberty in an arithmetical ratio. Thus, if at 
} One year old their length in parts of an inch 
is 0,2500, at five years they will be 0,3333, 
at nine 0,4166, and at fourteen 0,4999: these 
close approximations. 
2 
Pa Si: 
NORMAL ANATOMY OF THE LARYNX. 
105 
The superior thyro-arytenoid ligaments or 
superior vocal cords are, in contra-distinction 
to the inferior, denominated (though incorrectly) 
the false ligaments: they are of less thickness 
and strength than the inferior ligaments, and 
are further removed from the axis of the larynx 
(4, fig. 24). They arise from the internal 
angle of the thyroid, and are inserted into the 
middle of the anterior superior prominence of 
the arytenoid cartilages (fig. £4); they are 
composed of a few slender fasciculi of elastic 
fibres, approaching less nearly the mesial 
plane than the inferior ligaments; they appear 
more prominent, in consequence of their form- 
ing the roof of the ventricles. They are in the 
same plane as the aryteno-epiglottic muscle, 
and are connected with the fibres of the lateral 
crico-thyroid ligefhents. 
According to M. Lauth there is a connexion 
between the crico-thyroid, the lateral crico- 
thyroid, and thyro-arytenoid ligaments by three 
—e one of which is vertical, one hori- 
zontal, and one ascending (yg, k, n . 24 
the first of these being the ee A at 
second the lateral ; the third connects the thyro- 
arytenoid with the superior thyro-arytenoid 
ligaments, and lines the bottom of the ventricles. 
M. Lauth considers also that the thyro-epi- 
glottic, the hyo-epiglottic, and glosso-epiglottic 
ligaments are composed of the same elastic 
tissue. Muller and Cruveilhier concur in these 
views. They certainly appear of the same 
colour and texture under the microscope, and 
undergo the same change by exposure to the 
atmosphere: they also possess the same cohe- 
sive elastic properties. The strength of the 
inferior thyro-arytenoid ligaments is so great 
that they will tear away the cartilage to which 
they are attached without being injured, and 
will support the force of many pounds weight. 
Muscles—The motions of the larynx are 
exceedingly complex, and are performed by 
two sets of muscles, which are divided into two 
classes :—1, the extrinsic; and, 2, the intrin- 
sic muscles. The muscles which elevate the 
larynx are the digastrici, stylo-hyoidei, mylo- 
hyoidei, genio-hyoidei, and hyo-glossi, and 
those pharyngeal muscles which are inserted 
into the cricoid and thyroid cartilages. The 
muscles which antagonize these and lower the 
larynx are the sterno-hyoidei, the omo-hyoidei, 
the sterno-thyroidei, and the thyro-hyoidei. The 
os hyoides is the centre of motion for the action 
of these muscles. (See Necx, Muscies or 
THE.) We shall here confine our description 
to the 
Intrinsic muscles of the larynx, Syn.; mus- 
cles intrinsiques, Cruveilhier—The muscles of 
this division comprise those acting exclusively 
on the larynx itself. There are four pairs and 
one single: 1, the crico-thyroidei; 2, the 
crico-arytenoidei postici; 3, crico-arytenvidei 
laterales ; 4, thyro-arytenoidei ; and, 5, aryte- 
noideus, which, from a difference in the direc- 
tion of certain of its fibres, is divided into the 
oblique and transverse. Independently of these, 
there are some muscular fasciculi, named the 
thyro-epiglottidei and the aryteno-epiglottidei. 
The crico-thyrvidei.—These are very short, 
