THE SKULL. 49 



a semicylindrical transverse piece of bone attached to the 

 caudal margin of the coronoid process. It articulates with the 

 mandibular fossa of the temporal bone. 



Hyoid Bone. Os hyoideum (Fig. 38 and Fig. 104). 

 The hyoid bone forms the support for the tongue and gives 

 origin to muscles passing to the 

 tongue and larynx. It also 

 supports the thyroid cartilage 

 (Fig. 104, i). 



It consists of a transverse 

 bony bar, the body (Fig. 38, a) 

 and of two cornua or horns F 7 G . 3 8._H Y oiD BONE, DORSAL VIEW. 



attached to each end of the a, body; b, c, d, e, cranial cornu; /, 

 i j caudal cornu; b, ceratohyal; c, epihyal; 



d, stylohyal; e, tympanohyal ; /, thyro- 



The cranial cornu (lesser hyal. 



cornu of human anatomy) is the longer (Fig. 38, b-e}. Each 

 arises from the cranial face of the body at its lateral end, curves 

 laterad, and then caudodorsad. It consists of four bony pieces 

 movably united by cartilage. 



The terminal piece is the tympanohyal (e)\ it is imbedded 

 in the tympanic bulla just ventrad of the stylomastoid foramen. 

 It is not therefore seen attached to the cornu after the latter 

 has been separated from the skull. The other pieces become 

 successively shorter toward the body, and are called stylohyal 

 (d}, epihyal (c), and ceratohyal (b). 



The caudal cornua (/) (greater cornua of human anatomy) 

 arise from the ends of the body. Each consists of a single 

 piece of bone, the thyrohyal (_/"), which passes caudolaterad ; 

 its free end is united to a process of the thyroid cartilage (Fig. 

 104. 1). 



The Skull as a Whole. In the following description of the 

 skull as a whole the mandible, hyoid, and ear-bones are not 

 included. 



The skull forms a bony box which contains the brain and 

 is produced craniad into the facial portion which encloses the 

 nasal cavity and forms the framework of the face. 



In dorsal view (Fig. 39) the skull presents a smooth con- 

 vex surface, broadest caudad, with the two zygomatic arches 



