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and inferior part of the vocal cord (Klein) (fig. 177, c).

Taguchi gives the following data for the determination of the position of

r~\






Fig. 175. ANTERIOR ASPECT OF THYROID CARTILAGE TO SHOW POINTS OPPOSITE WHICH THE TRUE

AND FALSE VOCAL CORDS ARE ATTACHED. (Taguchi.)

a, bottom of thyroid notch ; c and d, opposite attachment of false vocal cords ; b, opposite attach-
ment of true vocal cords.

Fig. 176. HORIZONTAL SECTION OF THE LARYNX AND LARYNGEAL PART OF PHARYNX. (J. S.) 1

'1, thyroid cartilage ; 2, thyro-arytenoid muscle ; 3, lateral crico-arytenoid muscle ; 4, arytenoid
cartilage ; 5, rima glottidis ; 6, arytenoid muscle ; 7, cavity of laryngeal part of pharynx ; 8, inferior
constrictor of pharynx.



156 ORGANS OF RESPIRATION AND VOICE.

the true and false vocal cords in the undissected body. The true vocal cords are
attached to the thyroid cartilage, close to one another, in the male 8'5 mm. and in
the female G'5 below the bottom of the median notch on the upper border of
the thyroid cartilage. The false vocal cords are 4 mm. apart at their anterior
attachment, and 2'5 mm. higher than the true cords (see fig. 175).

The rima glottidis, an elongated aperture, situated, anteriorly, between the
inferior or true vocal cords (pars vocalis), and, posteriorly, between the bases of the
arytenoid cartilages {pars respiratoria}, forms a long narrow slit, slightly wider in
the centre when nearly closed, as in the production of the voice, and opening
out to a triangular form in the pars respiratoria (fig. 173, A'). When moderately
open, as in easy respiration, its shape is that of a long triangle, the pointed
extremity being directed forwards, and the base being behind, between the arytenoid
cartilages (fig. 173, B') ; in its fully dilated condition it is lozenge-shaped (the
posterior sides being formed by the inner sides of the bases of the arytenoid
cartilages), while the posterior angle is truncated (c'). The rima glottidis is
the narrowest part of the interior of the larynx ; in the adult male it measures about
23 mm., or nearly an inch, in an antero-posterior direction, and 6 or 8 mm. across at
its widest part, which may be dilated to nearly 12 mm. In the female, and
in males before the age of puberty, its dimensions are less, its antero-posterior
diameter being about 17 mm., and its transverse diameter about 4 mm. The vocal
cords are about 15 mm. long in the adult male and 11 mm. in the female.

The ventricles or sinuses of the larynx (fig. 171, s, and fig. 174, &') are
narrower at their orifice than in their interior. The outer surface of each is
covered by the upper fibres of the corresponding thyro-arytenoid muscle.

The small recesses named the laryngeal pouches (fig. 171, s'), lead from the
anterior part of the ventricles upwards, for the space of half an inch, between the
superior vocal cords inside and the thyroid cartilage outside, reaching as high as the
upper border of that cartilage, and nearly to the level of the aryteno-epiglottic
folds. The pouch, which is of variable size, is conical in shape, and curved slightly
backwards. Its opening into the ventricle is narrow, and is generally marked by
two folds of the lining mucous membrane. Numerous small mucous glands, sixty or
seventy in number, open into its interior, and it is surrounded by a quantity of fat.
Externally to the fat, this little pouch receives a fibrous investment, which is
continuous below with the superior vocal cord. Over its laryngeal side and upper
end is a thin layer of muscular fibres (compressor sacculi laryngis, arytceno-
epiglottideus inferior, Hilton) connected above with those found in the aryteno-
epiglottic folds. The upper fibres of the thyro-arytenoid muscles pass over the
outer side of the pouch, a few being attached to its lower part. The laryngeal
pouch is supplied abundantly with nerves, derived from the superior laryngeal.

THE MUCOUS MEMBRANE AND VESSELS OF THE LARYNX.

The laryngeal mucous membrane is thin and of a pale colour. In some
situations it adheres intimately to the subjacent parts, especially on the epiglottis,
and still more in passing over the true vocal cords, on which it is very thin and most
closely adherent. About the upper part of the larynx, above the glottis, it is
extremely sensitive. In and near the aryteno-epiglottic folds it covers a quantity
of loose areolar tissue, which is liable in disease to infiltration, constituting oedema
of the glottis. Like the mucous membrane in the rest of the air-passages, that of
the larynx is covered in the greater part of its extent with a columnar ciliated
epithelium, by the vibratory action of which the mucus is urged upwards. The
cilia are found higher up in front than on each side and behind, reaching in the
former direction as high as the widest portion of the epiglottis, and in the other



MUCOUS MKMBRANE OF THE LARYNX.



157



directions only to a line or two above the superior vocal cords : above these points
the epithelium loses its cilia, and assumes a stratified squamous form, like that of
the pharynx and mouth. Upon the true vocal cords also the~epitheliuni is
squamous, although both above and below them it is columnar and ciliated. Patches
of stratified squamous epithelium are found also dotted here and there in the ciliated
tract above the glottis, especially on the under (posterior) surface of the epiglottis, the
inner surface of the arytenoid cartilages, and at the free border of the superior vocal
cord. Bodies which are to all appearance similar to the taste-buds which occur in
connection with the mucous membrane of the tongue (Vol. III., Pt. 3) are here and
there found imbedded in this stratified epithelium (but not over the vocal cords).

The lining membrane of the larynx is provided with numerous glands, which
secrete an abundant mucus, and the orifices of which may be seen almost everywhere




a.



m




Fig. 177. VERTICAL SECTION THROUGH THE VENTRICLE OF THE LARYNX OF A CHILD. (Klein.)

0, stratified epithelium over true vocal cord ; b, ciliated epithelium over false vocal cord ; c, nodule
of elastic cartilage (cartilage of Luschka) ; d, ventricle ; I, lymphoid tissue ; m, bundles of thyro-
arytenoid muscle, cut across.

Fig. 178. POSTERIOR VIEW OF THE NERVES OF THE LARYNX. (Sappey.)

1 , superior laryngeal nerve ; 2, its external branch ; 3, 4, 5, branches to the mucous membrane of
the larynx ; (5, filaments uniting the left superior and inferior laryngeal nerves ; 7, the same on the
right side, cut ; 8, 8. inferior laryngeal nerves ; 9, branch to the posterior crico-arytenoid muscles ;
10, branch to the arytenoid ; 11, 12, branches passing to the lateral crico-arytenoid and the thyro-
arytenoid muscles.

excepting upon and near the true vocal cords. They abound particularly upon the
epiglottis, in the substance of which are found upwards of fifty small compound glands,
some of them perforating the cartilage. Between the anterior surface of the epiglottis,
the hyoid bone, and the root of the tongue is a mass of yellowish fat, erroneously
named the epiglottic gland, in or upon which some small glands may exist. Another
collection of glands is placed within the fold of mucous membrane in front of each
arytenoid cartilage, from which a series may be traced forwards, along the corre-
sponding superior vocal cord. The glands of the laryngeal pouches have already
been noticed.

Vessels and Nerves of the Larynx. The arteries of the larynx are derived
from the superior thyroid, a branch of the external carotid, and from the inferior



158



ORGANS OF RESPIRATION AND VOICE.



thyroid, a branch of the subclavian. The veins join the superior, middle, find
inferior thyroid veins. The lymphatics are divisible into two sets, upper and lower.
The upper pierce the tbyro-hyoid membrane and join glands near the bifurcation
of the common carotid artery ; the lower pass through the crico-thyroid membrane,
and end either in one or two small glands often found in front of that membrane,
or in some inferior laryngeal glands at the side of the lower part of the
larynx. Their mode of distribution resembles that in the trachea. The nerves
are supplied from the superior laryngeal and inferior or recurrent laryngeal branches
of the pneumo-gastric nerves, joined by branches of the sympathetic. The superior
laryngeal nerves supply the mucous membrane and the crico-thyroid muscles, and
also, in part, the arytenoid muscle. The inferior laryngeal nerves supply, in part,
the arytenoid muscle, and all the other muscles, excepting the crico-thyroid.

The superior and inferior laryngeal nerves of each side communicate with each
other in two places, viz., at the back of the larynx, beneath the pharyngeal mucous
membrane, and on the side of the larynx, under the ala of the thyroid cartilage.
Numerous ganglion-cells are found on the branches, both on those which enter the




Fig. 179. INTKAEPITHELIAL NERVE-TERMINATIONS IN THE LARYNX. (Gr. Retzius.)

Silver-chromate preparation.
The section is taken at a place where the ciliated epithelium passes into stratified.

muscles, and also underneath the mucous membrane. End-bulbs are also described
in the mucous membrane which covers the posterior or laryngeal surface of the
epiglottis (Lindemann). Other nerve-bundles enter the epithelium, within which
they end in arborisations of fine fibrils (fig. 179).

The further details of the distribution of the vessels and lymphatics will be
found in Vol. II., Pt. 2, and of the nerves in Vol. III., Ft. 2.

MUSCLES OF THE LARYNX.

Besides certain extrinsic muscles elsewhere described viz., the sterno-hyoid,
omo-hyoid, sterno-thyroid, and thyro-hyoid muscles, together with the muscles
of the supra-hyoid region, the middle and inferior constrictors of the pharynx, and
the stylo-pharyngeus and palato-pharyngeus, all of which act more or less upon the
entire larynx there are other muscles which move the different cartilages upon one
another, and modify the size of the apertures and the state of tension of the vocal
cords. These intrinsic muscles are the crico-thyroid, the posterior crico-anjtenoid,
the lateral crico-artjtenoid, the thyro-arytenoid, the arytenoid, and the art/teno-
epiglottic, together with certain other slender muscular fasciculi. All these muscles,
except the arytenoid which crosses the middle line, are in pairs.

The crico-thyroid muscle (fig. 180, A, 14) is a short, thick, triangular muscle
seen on the front of the larynx. Its attachment below, to the cricoid cartilage,
extends from the median line a considerable way backwards, and its fibres passing
upwards and outwards, diverging slightly, are fixed above to the inferior border of
the thyroid cartilage, and to the anterior border of its lower cornu. The latter
portion of the muscle, the fibres of which are nearly horizontal, is usually distinct
from the rest. Some of the superficial fibres are almost always continuous with the
inferior constrictor of the pharynx. The muscles of the two sides are somewhat



MUSCLES OF THE LARYNX.



159



separate from one another in the middle line in front, leaving an interval which is
triangular, with the base upwards. The crico-thyroid membrane is here exposed,

Action. The anterior part of the muscle contracting 1 will approximate the cricoid and
thyroid cartilages in front. In this action the thyroid is fixed by the extrinsic muscles, and
the anterior part of the cricoid rotating on the axis which unites the articulations between
the cricoid and the lower cornua of the thyroid is drawn upwards, and the part behind
the crico-thyroid joints is depressed, and with it the arytenoid cartilages, so that the vocal
cords are thus put on the stretch. This stretching of the vocal cords is still further assisted
by the action of the oblique fibres, which, acting from the cornu of the fixed thyroid, draw
the cricoid cartilage backwards. It is found, also, that with electric excitation of this muscle
the anterior part of the cricoid is raised towards the thyroid. Paralysis of these muscles is
accompanied by inability to produce high tones of the voice.

The posterior crico-arytenoid muscle (fig. 180, B, 1), situated behind, arises
from the broad depression on the corresponding half of the posterior surface of the
cricoid cartilage, and its fibres, converging upwards and outwards, are inserted into





Fig. 180. MUSCLES OF THE LARYNX. (Sappey.)
A, as shown in a view of the larynx from the right side.

1, hyoid bone ; 2, 3, its cornua ; 4, right ala of thyroid cartilage; 5, posterior part of the same
separated by oblique line from anterior part ; 6, 7, superior anil inferior tubercles at ends of oblique
line ; 8, upper cornu of thyroid ; 9, thyro-hyoid ligament ; 10, cartilago triticea ; 11, lower cornu of
thyroid, articulating with the cricoid ; 12, anterior part of cricoid ; 13, crico-thyroid membrane ;
14, crico-thyroid muscle ; 15, posterior crico-arytenoid muscle, partly hidden by thyroid cartilage.

B, as seen in a view of the larynx from behind.

1, posterior crico-arytenoid ; 2, arytenoid muscle ; 3, 4, oblique fibres passing around the edge of the
arytenoid cartilage to join the thyro-arytenoid, and to form the aryteno-epiglottic, 5.

the outer angle of the base of the arytenoid cartilage, behind the attachment of the
lateral crico-arytenoid muscle. The upper fibres are short, and almost horizontal ;
the middle are tlie longest and run obliquely ; whilst the lower or external fibres are
nearly vertical. Near their insertion the upper fibres are blended with the lower
fibres of the arytenoideus.

Action. The posterior crico-arytenoid muscles draw the outer angles of the arytenoid carti-
lages backwards and inwards, and thus rotate the anterior or vocal processes outwards, and widen
the rima glottidis. Acting- with the lateral crico-arytenoid muscles, they approximate the
vocal cords (Kanthack). They may also draw the arytenoid cartilages apart. They come into



160



ORGANS OF RESPIRATION AND VOICE.



action during deep inspiration. If paralysed, the lips of the glottis approach the middle line,
and come in contact during each inspiration, so that severe dyspnoea may be produced.
Expiratory efforts, however, are not impeded, and vocalization is unaffected.

Variety. In connection with the posterior crico-arytenoid muscle may be mentioned an
occasional small slip in contact with its lower border, viz., the kerato-cricoid muscle
of Merkel. It is a short and slender bundle, arising from the cricoid cartilage near its lower
border, a little behind the inferior cornu of the thyroid cartilage, and passing obliquely
outwards and upwards to be inserted into that process. It usually exists on one side only.
Turner found it in seven out of thirty-two bodies. It is not known to be of any physiological
significance. (Merkel, Anat. und Phys. des menschl. Stimm-und Sprach-organs, Leipzig, 1857 :
Turner in Month. Med. Journal, Feb. 1860.)

The lateral crico-arytenoid muscle (fig. 182, cr.ar.lat.), smaller than the
posterior, is in a great measure hidden by the ala of the thyroid cartilage It lies
along the sloping upper border of the
cricoid cartilage, from which it arises,
its origin extending as far back as the
articular surface for the arytenoid. Its





cth/



Fig. 181. OUTLINE OF THE RIGHT HALF OF THE CARTILAGES OF THE LARYNX AS SEKN FROM THE

INSIDE, WITH THE THYRO-ARYTENOID LIGAMENT, TO ILLUSTRATE THE ACTION OF THE CRICO-THYROID

MUSCLE. (Allen Thomson. )

t, thyroid cartilage ; c, cricoid cartilage ; a, right arytenoid cartilage ; a', its vocal process ;
s, corniculum ; c v, the thyro-arytenoicl ligament ; the position of the lower cornu of the thyroid
cartilage on the outside of the cricoid is indicated by a dotted outline, and r indicates the point or axis
of rotation of the cricoid cartilage on the cornu of the thyroid ; ct.h, a line in the principal direction of
action of the crico-thyroid muscle ; cap, the same of the posterior crico-arytenoid muscle.

Fig. 182. SIDE VIEW OF THE LARYNX AFTER REMOVAL OF THE RIGHT ALA OF THE THYROID CARTILAGE.

(S. G. Shattock.)

h, body of hyoid bone, cut ; e, epiglottis ; tk, cut surface of right ala of thyroid cartilage ; cr, front
of cricoid cartilage, the articular facet for the inferior cornu of the thyroid is seen posteriorly ; th.ar,
th.ar, fibres of the thyro-arytenoid (outer portion) passing from the thyroid in front to the arytenoid
behind ; th.ar', others arising from the crico-thyroid membrane ; another considerable mass of fibres is
seen arising from the same parts, and passing at first obliquely and afterwards nearly vertically upwards
as the thyro-epiglottic muscles, th.ep. ; th.ar.m, small thyro-arytenoid ; th.ar. m', a small slip of the
same muscle passing into the false vocal cord ; cr.ar.lat. lateral crico-arytenoid'; cr.ar.p, posterior
crico-arytenoid ; r.ar.tp, right aryteno-epiglottic muscle near its origin ; l.ar.ep, left aryteno-
epiglottic near its insertion ; l.ar.ep' ', portion of the same inserted into the corniculum ; /, fat ;
, saccule covered by mucous glands.

fibres pass backwards and upwards, the anterior or upper ones being necessarily
the longest, and are attached to the muscular process of the arytenoid cartilage
and to the adjacent part of its anterior surface.



MUSCLES OF THE LARYNX. 161

This muscle is covered internally by the lateral part of the crico-thyroid
membrane, and externally at its anterior part by the upper part of the_crico-thyroid
muscle. The upper part is in close contact, and, indeed, is always more or
less blended with the thyro-arytenoid, and a few of its fibres are continuous round
the outer side of the arytenoid cartilage with the arytenoideus muscle.

Action. These muscles, drawing the muscular procasses of the arytenoids forwards and
downwards, rotate the vocal processes inwards, and approximate the vocal cords. They thus
act antagonistically to the posterior crico-arytenoids.

If both posterior and lateral crico-aryfcenoids be thrown into action simultaneously, the
arytenoids will not undergo rotation, but will be drawn inwards, and the glottis will thus be
narrowed.

The thyro-arytenoid muscle consists of two portions, one external situated
immediately within the ala of the thyroid cartilage, and one internal lying in close
contact with the vocal cord. Sometimes these are described as distinct muscles
under the names external and internal thyro-arytenoid (Henle), but the separation
between them has to be effected by artificial means. The inner portion of the
muscle is triangular in section corresponding with the vocal fold which it occupies ;
the outer is laterally compressed and extends both above and below the inner
portion. Each contains both antero-posterior and oblique fibres.

Inner portion. The antero-posterior fibres of the internal portion arise
in the lower half of the angle formed by the alee of the thyroid cartilage,
a few even from a nodule of firmer tissue (cartilage of Luschka) in the
anterior part of the vocal cord itself ; and, passing backwards in a slight curve
with the concavity inwards, are attached behind to the vocal process along
its whole length, and to the adjacent part of the outer surface of the arytenoid
cartilage. They are joined internally by short fibres, which are attached in front to
the vocal cord, and behind to the vocal process of the arytenoid (portio ary-vocalis
of Ludwig) ; and externally they are contiguous with the antero-posterior fibres of
the external portion. The oblique fibres of the internal portion pass from the
sloping portion of the crico-thyroid membrane below the vocal cord proper (in its
anterior third), upwards, outwards, and somewhat backwards, passing between the
antero-posterior fibres, and over the ventricle of Morgagni, to end in the tissue of the
false vocal fold.

Outer portion (fig. 182). The fibres of the external portion arise in front from
the thyroid cartilage, close to the origin of the internal portion, and from the
crico-thyroid membrane ; from here they in part pass backwards to be inserted into
the lateral border and muscular process of the arytenoid cartilage, in part
obliquely upwards towards the aryteno-epiglottidean fold, some which are more
vertical in direction passing in a thin layer around the ventricle of Morgagni and
the sacculus, to end in the false vocal fold. The portion of this muscle which
extends towards the epiglottis is often described as a separate muscle under the name
of thyro-epiglottidean (fig. 182, th.ep). It resembles the crico-arytenoideus
lateralis in having some of its fibres continuous with those of the arytenoideus.

Action. The bundles of the thyro-arytenoid muscle, differing as they do in direction and
in points of attachment, must differ also in their action, if separately called into play. The
antero-posterior fibres will tend to draw forwards the arytenoid, and with it the posterior part
of the cricoid cartilage, rotating the latter upwards, and antagonising the action of the
crico-thyroid, the effect being to relax the vocal cords. But if the latter be kept stretched
and approximated by the action of other muscles, those fibres of the inner portion which are in
close contact with the vocal cord may serve to modify its elasticity and consistence, while the
fibres which constitute the portio ary-vocalis may serve, as Ludwig has pointed out, to tighten
the parts of the cord in front of their attachment, and to slacken the parts behind. The
vertical fibres of the muscle which extend from the sloping part of the crico-thyroid
membrane across the base of the vocal fold, and over the ventricle into the false vocal cord,
must, when they contract, render the free edge more prominent. Finally, the fibres which
are inserted into the muscular process and outer surface of the arytenoid will tend to draw

VOL. Ill,, PT 4. M



162 ORGANS OF RESPIRATION AND VOICE.

forwards and rotate inwards the arytenoid cartilage, and those which pass up into the
aryteno-epiglottidean folds may assist in depressing the epiglottis.

If the thyro-arytenoid muscles are paralysed, the lips of the glottis are no longer parallel,
but are curved with the concavity towards one another, and a much stronger blast of air is
required for the production of the voice.

Santorini described three thyro-arytenoid muscles, an -inferior, a middle, and a superior.
The latter is not always present. The inferior thyro-arytenoid muscle of Santorini comprises
most of the antero-posterior bundles ; the middle thyro-arytenoid, the oblique bundles of the
external portion. The fibres of the superior fasciculus, when present, arise nearest to
the notch of the thyroid cartilage, and are attached to the upper base of the arytenoid
cartilage (fig. 182, th.ar.m.'). This is named by Scemmering the small thyro-arytenoid. whilst
the two other portions of the muscle constitute the great thyro-arytenoid of that author.

Arytenoideus muscle. When the mucous membrane is removed from the
back of the arytenoid cartilages, a thick band of transverse fibres is laid bare
(fig. 180, B, 2), and on the dorsal surface of this are seen two slender decussating
oblique bundles (3, 4).

The transverse and oblique fibres are often described as separate muscles
(arytenoid and aryteno-epiglottic), but the two sets of fibres are intimately blended.
Most of the anterior or ventral fibres pass straight across between the arytenoid
cartilages, and are attached to about the outer half of the concave surface on the
back of each. The dorsal fibres can be traced into the lateral walls of the larynx,
the uppermost fibres to the cartilages of Santorini, the intermediate fibres run
partly independently and partly with the uppermost fibres of the thyro-arytenoidei
into the inner and outer walls of the saccules of the larynx, forming the so-called
aryteno-epiglottidean muscles, and the lowest fibres blend at the level of the true
vocal cords with the thyro-arytenoid and lateral crico-arytenoid muscles.

Action. The arytenoid muscle draws the arytenoid cartilages together, and, from the
structure of the crico-arytenoid joints, this approximation, when complete, is necessarily
accompanied with depression. If the muscle is paralysed, the intercartilaginous part of the
glottis remains patent, although the membranous lips can still be approximated.

The superior aperture of the larynx has been generally supposed to be closed during
the act of deglutition by the descent of the upper free end of the epiglottis as a lid over the
opening. From observations made by Stuart and McCormack (The position of tit e epiylottix in
swallowing, Jour. Anat. and Phys., vol. xxvi.), it has been shown that this is not the case, the



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