THE THORAX OR CHEST 



189 



A 



the face. It carries six molar teeth, or grinders, on each side, and six 

 incisor teeth in front. In addition, it also gives lodgment to two canine 

 teeth or tusks in the male. Above it forms a hinge joint on either side, 

 where its rounded prominences or condyles are fitted to corresponding 

 depressions in the temporal bones by the interposition of a disc of cartilage. 

 In front of the condyles are two long, thin, and flattened bony pro- 

 minences, the " coronoid processes", which give attachment to muscles 

 of mastication. On the inner sides above, and on the outer sides below, 

 are two openings com- 

 municating with a long 

 canal, through which 

 pass an artery and a 

 nerve to supply the teeth 

 with blood and sensation. 



Os Hyoides or 

 Tongue Bone. This 

 bone is situated in the 

 region of the throat, and 

 is composed of five dis- 

 tinct pieces. One is 

 formed like a spur, hav- 

 ing a short, pointed pro- 

 cess projecting forward, 

 and embedded in the 

 root of the tongue, and 



- like branches A Superior or Long Cornu of Os Hyoides. B, Inferior or Short 



directed backwards tO Cornu. c, Thyroid or Heel-like Process. D, Spur Process. 



. , E, Epiglottis. F, Glottis, o, Cricoid Cartilage. H, Thyroid Cartilage, 



be Connected With the i, First Ring of Trachea. j, Arytamoid Cartilage. 



larynx or upper part of 



the windpipe. The others, two flat slender pieces on either side (superior 

 and inferior cornua), are united together and attached above to the 

 petrous temporal bone at the base of the cranium by means of a short 

 rod of cartilage. The several parts composing the bone are joined to- 

 gether by articulations, some of which form free-moving joints, to which 

 the extreme mobility of the tongue is due. 



Fig. 291. The Hyoid Bone and the Larynx 



THE THORAX OR CHEST 



The bony framework of this cavity is formed by the dorsal vertebrae 

 above, which we have already referred to, the sternum below, and the 

 ribs which form the sides and part of the roof. 



