392 



MYOLOGY 





sometimes lined by a mucous sheath. A broad aponeurotic layer is given off 

 from the tendon of the Digastricus on either side, to be attached to the body 

 and greater cornu of the hyoid bone; this is termed the suprahyoid aponeurosis. 



Variations are numerous. The posterior belly may arise partly or entirely from the styloid 

 process, or be connected by a slip to the middle or inferior constrictor; the anterior belly may 

 be double or extra slips from this belly may pass to the jaw or Mylohyoideus or decussate with 

 a similar slip on opposite side; anterior belly may be absent and posterior belly inserted into the 

 middle of the jaw or hyoid bone. The tendon may pass in front, more rarely behind the Stylo- 

 hoideus. The Mentohyoideus muscle passes from the body of hyoid bone to chin . 



The Digastricus divides the anterior triangle of the neck into three smaller triangle (1) the 

 submaxillary triangle, bounded above by the lower border of the body of the mandible, and 

 a line drawn from its angle to the Sternocleidomastoideus, below by the posterior belly of the 

 Digastricus and the Stylohyoideus, in front by the anterior belly of the Digastricus; (2) the 

 carotid triangle, bounded above by the posterior belly of the Digastricus and Stylohyoideus, 

 behind by the Sternocleidomastoideus, below by the Omohyoideus; (3) the suprahyoid or sub- 

 mental triangle, bounded laterally by the anterior belly of the Digastricus, medially by the 

 middle line of the neck from the hyoid bone to the symphysis menti, and inferiorly by the body 

 of the hyoid bone. 



Sternum 



FIG. 386. Muscles of the neck. Anterior view. 



The Stylohyoideus (Stylohyoid muscle) is a slender muscle, lying in front of, and 

 above, the posterior belly of the Digastricus. It arises from the back and lateral 

 surface of the styloid process, near the base; and, passing downward and forward, 

 is inserted into the body of the hyoid bone, at its junction with the greater cornu, 

 and just above the Omohyoideus. It is perforated, near its insertion, by the tendon 

 of the Digastricus. 



Variations. It may be absent or doubled, lie beneath the carotid artery, or be inserted into 

 the Omohyoideus, Thyreohyoideus, or Mylohyoideus. 



The Stylohyoid Ligament (ligamentum Stylohyoideus). In connection with the 

 Stylohyoideus muscle a ligamentous band, the Stylohyoid ligament, may be 



