CARTILAGES OF THE LARYNX. 1065 



and dorsally in the form of a stout prominent angle or process, termed the processus 

 muscularis. Into the ventral side of this process is inserted the crico-arytaenoideus 

 lateralis muscle; whilst into its dorsal aspect the crico-arytsenoideus posterior 

 muscle is inserted. A small nodule of yellow elastic cartilage, called the 

 sesamoid cartilage, is frequently found on the lateral border of the arytsenoid 

 cartilage, where it is held in position by the investing perichondrium. The 

 ventral border of the arytaenoid is vertical, and at the base of the cartilage is 

 prolonged ventrally into a small sharp-pointed process called the processus 

 vocalis, which receives this name because it gives attachment to the vocal ligament 

 or supporting band of the vocal fold (O.T. true vocal cord). The base of the 

 arytrenoid cartilage presents on its inferior surface, particularly in the region 

 of the processus muscularis, an elongated concave facet for articulation with the 

 facet on the superior border of the lamina of the cricoid cartilage. 



Cartilaglnes Corniculatse (Santorini). The corniculate cartilages are two 

 minute conical nodules of yellow elastic cartilage which surmount the apices of the 

 arytasnoids, and prolong the upper curved ends of these cartilages in a dorso- 

 rnedial direction. Each corniculate cartilage is enclosed within the dorsal part of 

 the corresponding ary-epiglottic fold of mucous membrane. 



Cartilagines Cuneiformes ( Wrisbergi). The cuneiform cartilages are not always 

 present. They are two minute rod-shaped pieces of yellow elastic cartilage, each 

 of which occupies a place in the corresponding ary-epiglottic fold, immediately 

 ventral to the arytsenoid cartilage and the corniculate cartilage of Santorini. 

 On the superficial surface of each a collection of mucous glands is present, and 

 this tends to make the cartilage stand out in relief under the mucous membrane. 



Cartilago Epiglottica. The epiglottis is supported by a thin, leaf-like lamina of 

 yellow fibro-cartilage, the epiglottic cartilage, which is placed dorsal to the root of the 

 tongue and the body of the hyoid bone, and ventral to the aperture of the larynx. 

 When divested of the mucous membrane, which covers it dorsally and also to some 

 extent ventrally, the epiglottic cartilage is seen to present the outline of a bicycle- 

 saddle, and to be indented by pits and pierced by numerous perforations. In the 

 pits, glands are lodged, whilst through the foramina, blood-vessels and, in some cases, 

 nerves pass. The broad end of the epiglottic cartilage is directed upwards, and is 

 free. Its margins are, to a large extent, enclosed within the ary-epiglottic fold. The 

 ventral ^surface is free only in its upper part. This part is covered with mucous 

 membrane, and looks towards the pharyngeal part of the tongue. The dorsal 

 surface is covered throughout its whole extent with the lining mucous membrane of 

 the laryngeal cavity. The inferior pointed extremity is prolonged downwards in the 

 form of a strong fibrous band, termed the thyreo-epiglottic ligament. 



r Ossification of the Cartilages of the Larynx. The thyreoid and cricoid 

 cartilages and the greater part of the arytsenoid cartilages are composed of the hyaline 

 variety of cartilage. The apical parts, and also the vocal processes of the arytaenoid 

 cartilages, the corniculate cartilages of Santorini, the cuneiform cartilages, and the 

 epiglottis, are formed of yellow fibro-cartilage, and at no period of life do they exhibit 

 any tendency towards ossific change. The thyreoid, cricoid, and basal portions of the 

 arytaenoids, as life advances, become more or less completely transformed into bone. 

 In males over twenty years of age, and in females over twenty-two years of age, the 

 process will usually be found to have begun (Chievitz). It is impossible, however, by an 

 examination of the laryngeal cartilages, to form an estimate of the age of the individual, 

 although in old age it is usual to find the thyreoid, cricoid, and the hyaline parts of the 

 arytsenoids completely ossified. It would appear that the process is somewhat slower in 

 the female than in the male. The thyreoid is the first to show the change ; then, but 

 almost at the same time, the cricoid ; and lastly, a few years later, the arytsenoids. 



ARTICULATIONS, LIGAMENTS, AND MEMBRANES OF THE LARYNX. 



Crico-thyreoid Joints. These are diarthrodial joints, and are formed by 



5 apposition of the circular facets on the tips of the inferior cornua of 



the thyreoid cartilage with the elevated circular facets on the sides of the cricoid 



cartilage. An articular capsule surrounds each articulation, and this is lined with a 



