as that represented by 30 mm. of water. Such is a general conception of the mechanism of voice.
The cartilages form the framework of the larynx. They consist
of three single pieces (the thyroid, the cricoid and the cartilage of
Fig. 3.—Right Half of the
Larynx, from a vertical
and slightly oblique
section; abt. two-thirds
nat. size. 1, epiglottis;
2, arytenoid cartilage;
3, processus vocalis of
arytenoid; 4, cricoid
cartilage; 5, capsular
thyro-hyoid ligament;
6, lateral crico-thyroid
ligament; 7, posterior
crico-thyroid ligament;
8 inferior thyro-arytn
oid ligament, or true
vocal cord; 9, thyroid
cartilage; 10, superior
thyro-arytenoid
ligament, or false vocal
chord; 11,
thyro-ary-epiglottideus muscle;
12, middle thyro-hyoid
ligament; 13, hyo-epiglottic
ligament; 14,
body of hyoid bone; 15,
smaller cornu of hyoid
bone. (From Krause.)
the epiglottis) and of three pairs (two
arytenoids, two cornicula laryngis or
cartilages of Santorini, and two cuneiform
cartilages or cartilages of Wrisberg),
see figs. 1 and 2. The epiglottis,
the cornicula laryngis, the cuneiform
cartilages and the apices of the arytenoids
are composed of yellow or elastic
fibro-cartilage, whilst the cartilage of
all the others is of the hyaline variety,
resembling that of the costal or rib
cartilages. These cartilages are bound
together by ligaments, some of which are
seen in figs. 1 and 2, whilst the remainder
are represented in fig. 3. The
ligaments specially concerned in the
production of voice are the inferior
thyro-arytenoid ligaments, or true vocal cords.
These are composed of fine elastic fibres
attached behind to the anterior
projection of the base of the arytenoid
cartilages, processus vocalis, 3 in fig. 3,
and in front to the middle of the angle
between the wings or laminae of the
thyroid cartilage. They are practically
continuous with the lateral crico-thyroid
ligaments, 6 in fig. 3.
The cavity of the larynx is divided into
an upper and lower portion by the
narrow aperture of the glottis or chink
between the edges of the true vocal
chords, the rima glottidis. Immediately
above the true vocal cords, between
these and the false vocal chords, there
is on each side a recess or pouch
termed the ventricle of Morgani, and
opening from each ventricle there is a
still smaller recess, the laryngeal pouch,
which passes for the space of half an inch
between the superior vocal chords
inside and the thryoid cartilage outside,
reaching as high as the upper border of
that cartilage at the side of the
epiglottis. The ventricles no doubt permit
a free vibration of the true vocal cords.
The upper aperture of the glottis is
triangular, wide in front and narrow
behind; and, when seen from above by
means of the laryngoscope, it presents
the view represented in fig. 4. The aperture is bounded in front
by the epiglottis, e, behind by the summits of the arytenoid
Fig. 4.—Laryngoscopic View
of the Glottis. t, tongue;
e, epiglottis; pe,
pharyngo-epiglottis fold; g,
pharyngo-laryngeal groove;
ae, aryteno-epiglottis fold;
c, cuneiform cartilage, or
cartilage of Wrisberg;
ar, arytenoid cartilage;
r, inter-arytenoid fold;
o, glottis; v, ventricle;
ti, inferior or true vocal
cord; ts, superior or false
vocal cord. (From Mandl.)
cartilages, ar, and on the sides by two
folds of mucous membrane, the
aryteno-epiglottis folds, ae. The
rounded elevations corresponding to
the cornicula laryngis and cuneiform
cartilages, c, and also the cushion
of the epiglottis, e, are readily seen
in the laryngoscopic picture. The
glottis, o, is seen in the form of a
long narrow fissure, bounded by the
true vocal cords, ti, whilst above
them we have the false vocal cords,
ts, and between the true and false
cords the opening of the ventricle, v.
The rima glottidis, between the true
vocal cords, in the adult male
measures about 23 mm., or nearly an
inch from before backwards, and
from 6 to 12 mm. across its widest
part, according to the degree of
dilatation. In females and in males
before puberty the antero-posterior
diameter is about 17 mm. and its
transverse diameter about 4 mm.
The vocal cords of the adult male
are in length about 15 mm., and
of the adult female about 11 mm.
The larynx is lined with a layer of
epithelium, which is closely adherent
to underlying structures, more especially over the true vocal
cords. The cells of the epithelium, in the greater portion of the
larynx, are of the columnar ciliated variety, and by the vibratory
action of the cilia mucus is driven upwards, but over the true
vocal cords the epithelium is squamous. Patches of squamous
epithelium are also found in the ciliated tract above the glottis,
on the under surface of the epiglottis, on the inner surface of the
arytenoid cartilages, and on the free border of the upper or false
cords. Numerous mucous glands exist in the lining membrane of
the larynx, more especially in the epiglottis. In each laryngeal
pouch there are sixty to seventy such glands, surrounded by fat.
We are now in a position to understand the action of the muscles
of the larynx by which the vocal cords, forming the rima glottidis,
Fig. 5.— Muscles of the left
side of the larynx, seen
from within; abt.
two-thirds nat. size. 1,
hyo-epiglottic ligament, seen
in profile; 2, epiglottis;
3, aryteno-epiglottis
muscle; 4, Santorini's
cartilage; 5, oblique
arytenoid muscle; 6, transverse
arytenoid muscle,
seen in profile; 7,
posterior crico-arytenoid;
8, lateral crico-arytenoid;
9, lower cornu of thyroid
cartilage cut through;
10, insertion of posterior
portion of crico-thyroid
muscle; 11, left lamina
of thyroid cartilage cut
through; 12, long
thyro-epiglottic
muscle (a variety);
13, inferior
thyro-arytenoid; 14,
thyro-epiglottic; 15, superior
thyro-arytenoid; 16,
median thyro-hyoid ligament.
(From Krause.)
can be tightened or relaxed, and by
which they can be approximated or
separated. Besides certain extrinsic
muscles—sterno-hyoid, omohyoid,
sterno-thyroid and thyro-hyoid—which
move the larynx as a whole, there
are intrinsic muscles which move the
cartilages on each other. Some of
these are seen in fig. 5. These muscles
are (a) the crico-thyroid, (b) the
posterior crico-arytenoid, (c) the lateral
crico-arytenoid, (d) the thyro-arytenoid,
(e) the arytenoid, and (f) the
aryteno-epiglottidean. Their actions will be
readily understood with the aid of the
diagrams in fig. 6. (1) The crico-thyroid
is a short thick triangular muscle, its
fibres passing from the cricoid cartilage
obliquely upwards and outwards to be
inserted into the lower border of the
thyroid cartilage and to the outer
border of its lower horn. When the
muscle contracts, the cricoid and thy
roid cartilages are approximated. In
this action, however, it is not the thyroid
that is depressed on the cricoid,
as is generally stated, but, the thyroid
being fixed in position by the action
of the extrinsic muscles, the anterior
border of the cricoid is drawn upwards,
whilst its posterior border, in consequence
of a revolution around the axis
uniting the articulations between the
lower cornua of the cricoid and the
thyroid, is depressed, carrying the
arytenoid cartilages along with it. Thus
the vocal cords are stretched. (2) The
thyro-arytenoid has been divided by
anatomists into two parts—one, the
internal, lying close to the true vocal
cord, and the other, external, immediately
within the ala of the thyroid
cartilage. Many of the fibres of the
anterior portion pass from the thyroid
cartilage with a slight curve (concavity
inwards) to the processus vocalis at the
base of the arytenoid cartilage. They
are thus parallel with the true vocal
cord, and when they contract the
arytenoids are drawn forwards, carrying
with them the posterior part of the cricoid and relaxing the vocal
cords. Thus the thyro-arytenoids are the antagonists of the
crico-thyroids. K. F. W. Ludwig has pointed out that certain fibres
(portioary-vocalis) arise from the side of the cord itself and pass obliquely back
to the processus vocalis. These will tighten the parts of the cord in
front and relax the parts behind their points of attachment. Some
of the fibres of the outer portion run obliquely upwards from the side
of the crico-thyroid membrane, pass through the antero-posterior
fibres of the inner portion of the muscle, and finally end in the tissue
of the false cord. These fibres have been supposed to render the
edge of the cord more prominent. Other fibres inserted into the
processus vocalis will rotate slightly the arytenoid outwards, whilst
a few passing up into the aryteno-epiglottidean folds may assist
in depressing the epiglottis (Quain). (3) The posterior and lateral
crico-arytenoid muscles have antagonistic actions, and may be
considered together. The posterior arise from the posterior surface of
the cricoid cartilage, and passing upwards and outwards are attached
to the outer angle of the base of the arytenoid. On the other hand,
the lateral arise from the upper border of the cricoid as far back as the
articular surface for the arytenoid, pass backwards and upwards,
and are also inserted into the outer angle of the base of the arytenoid
before the attachment of the posterior crico-arytenoid. Imagine
the pyramidal form of the arytenoid cartilages. To the inner angle
of the triangular base are attached, as already described, the true
vocal cords; and to the outer angle the two muscles in question.
The posterior crico-arytenoids draw the outer angles backwards and
inwards, thus rotating the inner angles, or processus vocalis,
outwards, and, when the two muscles act, widening the rima glottidis.
This action is opposed by the lateral crico-thyroids, which draw the
outer angle forwards and outwards, rotate the inner angles inwards,
