Mammalia: Skin, Muscles, Skeleton 007 



highly variable. They may ossify to form, on each side, a chain of small 

 elongated bones (four in the cat), the lower end of the chain being 

 attached to one end of the median hyoid (basihyal, "body," or 

 copula) and the upper end attached to the otic region of the skull 

 (Fig. 468A). These chains thus support the ventral hyoid bone and the 

 larynx. In man a dorsal region of the embryonic arch ossified to pro- 

 duce, on each side, a long spike of bone whose upper end becomes 

 immovably fused to the temporal bone to form its characteristic 

 styloid process (Fig. 468B). The region of the arch between the styloid 

 process and the ventral hyoid bone is transformed into a stylohyoid 

 ligament. These ligaments serve to swing the ventral hyoid and 

 laryngeal structures from the base of the skull. The third visceral 

 arch, corresponding to the first branchial of fishes, is commonly 

 represented by a pair of small ossifications, each of which may articu- 

 late with an end of the median hyoid and extend backward to assist in 

 supporting the larynx, or may become immovably fused to the hyoid 

 body (as in man: Fig. 468B), forming the posterior cornu (horn). The 

 pair of shorter anterior cornua of the human hyoid are products of 

 the hyoid arch and serve for attachment of the stylohyoid ligaments. 

 Remnants of embryonic visceral arches posterior to the third appear 

 in a highly modified way in the cartilaginous skeleton of the larynx 

 (p. 612). * 



