MUSCLES OF MASTICATION. 147 



Muscles of Mastication. 

 Muscles which depress the lower jaw. 

 Muscle. Attachments. 



Digastric. . . . , Mastoid process of the temporal bone 



Lower border of the inferior maxilla 

 near the symphysis ; with its central 

 tendon held to the side of the body 

 of the hyoid bone. 



Mylo-hyoid Body of the hyoid bone Mylo-hyoid 



ridge on the internal surface of the 

 inferior maxilla. 



Genio-hyoid Body of the hyoid bone Inferior gen- 

 ial tubercle on the inner surface of the 

 inferior maxilla near the symphysis. 



Platysma myoides Clavicle, acromion, and fascia Anterior 



half of the body of the inferior max- 

 illa near the inferior border. 



Muscles which elevate the lower jaw, and move it laterally and antero-pos- 



teriorly. 



Temporal Temporal fossa Coronoid process of 



the inferior maxilla. 



Masseter Malar process of the superior maxilla, 



lower border and internal surface of 

 the zygomatic arch Surface of the 

 ramus of the inferior maxilla. 



Internal Pterygoid Pterygoid fossa Inner side of the ra- 

 mus and angle of the inferior maxilla. 



External Pterygoid. Pterygoid ridge of the sphenoid, the 



surface between it and the pterygoid 

 process, external pterygoid plate, and 

 the tuberosity of the palate and the 

 superior maxillary bone Inner sur- 

 face of the neck of the condyle of 

 the inferior maxilla and the inter- 

 articular fibro-cartilage. 



Action of the Muscles which depress the Lower Jaw. The 

 most important of these muscles have for their fixed point of 

 action the hyoid Lone, which, under these circumstances, is 

 fixed by the muscles which extend from it to the upper part 

 of the chest. The central tendon of the digastric, as it per- 



