XIV THE MUSCULAR SYSTEM 257 



extending from near the anterior angle of the jaw to the 

 thyroid and posterior lateral processes of the hyoid. It 

 draws the hyoid forward and upward. In connection with 

 sternohyoid it lowers the jaw. 



The sternohyoid, attached posteriorly to the dorsal surface 

 of the sternum and coracoids, where it joins the rectus 

 abdominis, of which it may be regarded as an extension. 

 Anteriorly it is inserted into the lower surfece of the hyoid 

 and its thyroid processes. It draws the hyoid backward 

 and lowers it, thus enlarging the buccal cavity. 



The ojnohyoid, extending from the scapula to the lateral 

 portion of the ventral surface of the hyoid. It draws the 

 hyoid backward. 



The petrohyoids, a series of four slender muscles arising 

 from the outer portion of the prootic bone and inserted into 

 the hyoid. The anterior muscle is the largest, and is attached 

 ventrally to the lateral margin or the body of the hyoid near 

 the middle. The three posterior petrohyoids diverge ven- 

 trally to be inserted upon the thyroid process of the hyoid. 

 The petrohyoids raise the hyoid apparatus and pull it 

 forward. 



The hyog/ossus arises from the thyroid processes and 

 ventral surface of the body of the hyoid. The two halves 

 of this muscle converge toward the middle line as they 

 pass forward. Anteriorly the single muscle thus formed 

 bends backward around the concave anterior margin of the 

 tongue, where it breaks up into numerous branches. 



