of
mucus, which irritates the passages and gives rise to efforts of hawking
and coughing to get rid of it.

350. The Larynx. The larynx, the essential organ of voice, forms
the box-like top of the windpipe. It is built of variously shaped
cartilages, connected by ligaments. It is clothed on the outside with
muscles; on the inside it is lined with mucous membrane, continuous with
that of the other air passages.

[Illustration: Fig. 148.--View of the Cartilages in front project and form
the lages and Ligaments of the "Adam's apple," plainly seen and Larynx.
(Anterior view.)

A, hyoid bone;
B, thyro-hyoid membrane;
C, thyroid cartilage;
D, erico-thyroid membrane;
E, cricoid cartilage, lateral ligaments seen on each side;
F, upper ring of the trachea.
("Adam's apple" is in the V-shaped groove on a line with B and C.)
]

The larynx has for a framework two cartilages, the thyroid and the
cricoid, one above the other. The larger of these, called the
thyroid, from a supposed resemblance to a shield, consists of two
extended wings which join in front, but are separated by a wide interval
behind. The united edges in front project and form the "Adam's apple"
plainly seen and easily felt on most people, especially on very lean men.

Above and from the sides rise two horns connected by bands to the hyoid
bone from which the larynx is suspended. This bone is attached by
muscles and ligaments to the skull. It lies at the base of the tongue, and
can be readily felt by the finger behind the chin at the angle of the jaw
and the neck (sec. 41 and Fig. 46). From the under side of the thyroid two
horns project downwards to become jointed to the cricoid. The thyroid thus
rests upon, and is movable on, the cricoid cartilage.

The cricoid cartilage, so called from its fancied resemblance to a
signet-ring, is smaller but thicker and stronger than the thyroid, and
forms the lower and back part of the cavity of the larynx. This cartilage
is quite sensitive to pressure from the fingers, and is the cause of the
sharp pain felt when we try to swallow a large and hard piece of food not
properly chewed.

[Illustration: Fig. 149.--Diagram of a Sectional of Nasal and Throat
Passages.

C, nasal cavities;
T, tongue;
L, lower jaw;
M, mouth;
U, uvula;
E, epiglottis;
G, larynx;
O, oesophagus.
]

On the upper edge of the cricoid cartilage are perched a pair of very
singular cartilages, pyramidal in shape, c