That cartilage in the larynx which lies immediately next the windpipe, resembles a ring with its protuber ance on the sternal part of the neck, where it may easily be felt below the sharp ridge. This is called the cricoid or annular cartilage, see Fig. 6. It constitutes the most solid part of the larynx, and forms the sacral boundary of that cavity. On the dorsal side next the gullet, it is considerably enlarged, nearly of a quadrilateral form, with a projecting angle in the mesial line. Its central surface is concave, narrow on the sternal, and broad on the dorsal aspect. At its atlantal part there is a broad and roundish sloping surface, for the attachment of membranes. On its sacral surface it presents a waving appearance, being convex sternad and dorsad, and a lit tle concave in the middle of each side. It is connected to the most atlantal ring of the windpipe, on the dorsal aspect, by a fibrous membrane, similar to those which connect the rings of the windpipe to each other.
Above the cricoid cartilage, is another, composed of two broad, lateral portions, obliquely angular, with seve ral projecting processes, uniting at their sternal edges, so as to form a sharp ridge, a little above the sternal jnotuberauce of the cricoid cartilage. This angular ridge may be readily felt in the fore pail of the neck, a little below the chin, and forms what has been called ponnilli edam), or Adam's apple. Sec AnAmi pomum. rs called the thyroid or seutiform cartilage, because it pro tects the sternal and lateral parts of the laryngeal cal fly as with a shield. A perspective view of it is given at B 1),i), Fig. 5. Considered as one piece, it has a cleft immediately above the sternal projecting angle, from which it proceeds laterally in a waving direction, till it terminates in its most atlantal part on each side, in a long narrow process. These two processes are called the horns of the thyroid cartilage, and arc connected by ligament (/),e,) to the horns of the os hyohlc•. Two short processes extend from the dorsal edge sacred, and are connected by ligaments and muscles to the cricoid carti lage. Considered on its central surface, the thyroid cartilage presents an angular hollow, corresponding to its sternal ridge. Immediately within the angle are fixed the principal ligaments of the glottis, and the muscles that connect this cartilage with those which we are about to describe. On the central surface of its lateral parts there is a quantity of fat, separating them from the neighbouring muscles and ligaments.
Attached to the atlantal and lateral parts, towards the dorsal side of the cricoid cartilage, are two other carti lages of a triangular form, broadest at their attachment to the cricoid, obtusely pointed at their atlantal extremi ties, which approach each other, and are bent obliquely backwards, so as to make the dorsal side of each cartilage hollow, while the sternal side is rounded. These carti lages are called arytenoid. Their pointed extremities are called their horns, and the whole cartilages arc so connected to each other, by membranes and muscles, as to be susceptible of considerable separation or approxi mation. They are also connected with the neighbour ing cartilages by muscles and ligaments.
The epiglottis, or that oval convexo-concave cartilage, which is attached to the root of the tongue, may be con sidered as belonging to the larynx, as during deglutition it is pushed back over the aperture into this cavity, so as to prevent the food or drink from entering the windpipe.
See Figs. 5, and 6. E. The concave surface of the epi glottis is next the aperture of the larynx ; while its con vex surface, in its natural position, as represented in Fig. 5. points to the palate. It is connected with the atlantal part of the thyroid cartilage, being fixed in its middle notch by a broad short ligament. It is also con nected with the arytenoid cartilages by two lateral liga ments, and is fixed to the Os hyoffit• and tongue by a membrane called its frenum or bridle.
All these cartilages ace thick and solid, extremely elastic, not of a shining appearance, like the cartilages that are attached to the articulating surfaces of the bones, but of a dull grayish colour. The epiglottis differs from the rest in being partly of a fibrous, and partly of a carti laginous texture, and in being rather more pliable than the other cartilages.
Besides the membranes that connect the several carti lages of the larynx with each other, and with the neigh bouring parts, the peripheral surface of this organ is covered with a fibrous membrane, resembling the perios teum. On its central surface it is also invested with a membrane that is reflected into various bands and dou blings, that form some of the principal parts of the or gans of voice. Two of these faceted membranes, in the lorm of fibrous bands, run hots the side of ( ach of the tenoid c artilages to the internal angle of the thy roid c tilages, 'ahem they meet each other, leas fug, next the :try timers, a space wnn h, by the motion of these Lute r cartilage s, admits of an almost infinite s ante ty of contractions coil dilat ctiuus. mutg between these two membranous hands is usually c ailed the glottis, or chink of the glottis g iida.) Sac rad of tin se hands there are two other ligamentous membranes, aris ing from the roots of the avytc. noid cat tilages, and also attach( d belOre to the thy void cartilage. These arc larger, and usually more distinct than the former, and arc generally called the proper ligaments of the glottis. Between the upper and lower ligaments on each side, there is a reflection from the inner membrane of the limning a small cavity, communicating with the central part of the larynx by a fissure. These lateral membranous (Las ities are called the ventric les of the glottis. Though we have. described these membranes as distinct from each other, they may properly be consi dered as continuations of the general investing mem brane of the larynx, reflected in different directions, so as to produce bands and cavities. The investing mem brane is furnished with numerous mucous glands, which secrete the fluid with which the whole interior cavity is moistened. Among these glands, two are more conspi cuous than the rest, and are situated in small depres sions at the roots of the arytenoid cartilages. They are hence called arytenoid glands, and appear to have been first discovered and described by Another glandular body is placed at the root of the epiglottis, and appears to secrete a fatty matter.