THE SKULL AS A WHOLE 



65 



lingual process, and the thyroid processes are fused together, and may be compared 

 to a spur or a fork with a very short handle. 



The lingual process (Processus lingualis) projects forward medially from the 

 body, and is embedded in the root of the tongue during life. It is compressed 

 laterally and has a l)Iunt-pointed free end. The lateral surfaces are slightly con- 

 cave. The upper border is narrow, the lower thick and irregular. 



The thyroid comua or thyrohyoids (Cornua laryngea)' extend backward and 

 upward from the lateral parts of the body. They are compressed laterally (except 

 at their junction Avith the body), and their posterior ends are connected with the 

 anterior cornua of the thyroid cartilage of the larynx. 



The small comua or keratohyoids (Cornua minora) are short rods which are 

 directed upward and forward from either end of the upper surface of the body. 

 Each is somewhat constricted in its middle part and has slightly enlarged ends. 

 The lower end has a small concave facet which articulates with the body. The 

 upper end articulates with the great cornu. or with the middle cornu when present. 



The great comua or stylohyoids are much the largest parts of the bone. They 

 are directed upward and backward, 

 and are connected above with the 

 base of the i)etrous temporal bones. 

 Each is a thin plate, seven or eight 

 inches (ca. 18 to 20 cm.) long, which 

 is slightly curved in its length, so 

 that the external surface is concave 

 and smooth. The internal surface 

 is convex and smooth. The borders 

 are thin. The upper extremity is 

 large and forms two angles; the 

 upper angle is connected by a rod 

 of cartilage with the h^'oid process 

 of the petrous temporal bone; the 

 lower angle is somewhat thickened 

 and rough for muscular attachment. 

 The lower extremity is small, and 

 articulates with the small or the 

 middle cornu. 



The middle comua or epihyoids 

 are small wedge-shaped pieces or 

 nodules interposed between the 



small and great cornua. They are usually transitory, and unite with the great 

 cornua in the adult. 



Development. — The hyoid ossifies in the cartilages of the second and third 

 visceral arches. Each part has a separate center, except the lingual process, which 

 ossifies by extension from the body. The latter has primarih' two centers (Martin). 



Fig. 32. — Hyoid Bone of Horse, Viewed from the Side 



AND SOMEWH.VT FROM IN FrONT. 



a, Body; b, lingual proces.s; c, thyroid cornu; c', car- 

 tilage of c; d, .small cornu; e, middle cornu; /, great cornu; 

 /'. mu.scular angle of great cornu; g, cartilage of great cornu. 

 (Ellenberger-Baum, Anat. d. Haustiere.) 



THE SKULL AS A WHOLE 



The skull of the horse has the form of a long four-sided pyramid, the base of 

 which is posterior. It is convenient to exclude the mandil^le and hyoid from present 

 consideration. The division between the cranium (Cranium cerebrale) and the face 

 (Cranium viscerale) may be indicated approximately by a transverse plane through 

 the anterior margins of the or])its. 



The superior or frontal surface (Norma frontalis) is formed by the upper part 

 of the occipital, the interparietal, parietal, frontal, and nasal bones. It may be 

 ^ These correspond to the great cornua of man. 



