CARTILAGES OF LARYNX. 159 



to the thyroid cartilage, and the ligaments uniting one cartilage to another 

 on the left side, should not be destroyed. 



In the arytseno-epiglottidean fold of mucous membrane, a small carti- 

 laginous body (cuneiform) may be recognized ; an oblique whitish pro- 

 jection indicates its position. 



The hi/oid bone (os hyoides) (fig. 43) *'s situate between the larynx and 

 the root of the tongue. Resembling the letter U, placed horizontally and 

 with the legs turned backwards, it offers for examination a central part or 

 body, and two lateral pieces or cornua on each side. 



The body, c, is thin and flattened, and measures most in the transverse 

 direction. Convex in front, where it is marked by a tubercle, it presents 

 an uneven surface for the attachment of muscles ; whilst on the opposite 

 aspect it is concave. To the upper border the fibrous membrane (hyo- 

 glossal) fixing the tongue is attached. 



The cornua are two in number on each side (large and small). The 

 large cornu, H, continues the bone backwards, and is joined to the body 

 by an intervening piece of cartilage. The surfaces of this cornu look 

 somewhat upwards and downwards ; and the size decreases from before 

 backwards. It ends posteriorly in a tubercle. The small cornu, or ap- 

 pendix, j, is dissected upwards from the point of union of the great cornu 

 with the body, and is joined by the stylo-hyoid ligament: it is seldom 

 wholly ossified. 



CARTILAGES OF THE LARYNX (fig. 43). There are four large carti- 

 lages in the larynx, which are concerned in the production of the voice, 

 viz., the thyroid, the cricoid, and the two arytsenoid. In addition there 

 are some yellow fibre-cartilaginous structures, viz., the epiglottis, a capitu- 

 lum to each arytsenoid cartilage, and a small ovalish piece (cuneiform) in 

 each arytaeno-epiglottidean fold of mucous membrane. 



The thyroid cartilage, B, is the largest of all : it forms the front of the 

 larynx, and protects the vocal apparatus as with a shield. The upper 

 part of the cartilage is considerably wider than the lower, and in conse- 

 quence of this form the larynx is somewhat funnel-shaped. The anterior 

 surface is prominent in the middle line, forming the subcutaneous swelling 

 named pomum Adami ; but the cartilage is concave behind at the same 

 spot, and gives attachment to the epiglottis and the thyro-arytaenoid mus- 

 cles and ligaments. The upper border is notched in the centre. 



The cartilage consists of two square halves, which are united in the 

 middle line. Posteriorly each half of the cartilage has a thick border, 

 which terminates upwards and downwards in a rounded process or cornu 

 (E and F). Both cornua are bent slightly inwards: of the two, the upper, 

 E, is the longest ; but the lower one, F, is thicker than the other, and 

 articulates with the cricoid cartilage. The inner surface of each half is 

 smooth ; but the outer is marked by an oblique line for the attachment of 

 muscles, which extends from a tubercle near the root of the upper cornu, 

 almost to the middle of the lower border. 



The cricoid cartilage, D, is stronger though smaller than the thyroid, 

 and encircles the cavity of the larynx ; it is partly concealed by the shield- 

 like cartilage, below which it is placed. It is very unequal in depth be- 

 fore and behind, the posterior part being three times deeper than the 

 anterior, something like a signet ring. Its hollow is about as large as the 

 fore finger. 



The outer surface is rough, and gives attachment to muscles. At the 

 back of the cartilage there is a flat and rather square portion, which is 



