Chap. VII] 



MUSCULAR TISSUE 



99 



In most cases the movements of the eye are somewhat complex 

 and more than one muscle is involved. 



Levator palpebrae superioris (lifter of the upper lid). — It 

 arises from the sphenoid bone, passes forward, and is inserted into 

 the tarsal cartilage of the upper lid. 



Action. — It elevates the upper lid and opens the eye. 



Fig. 71. — Pterygoid Muscles. Viewed from behind, the back portion of the 

 skull having been removed. (Gerrish.) 



Muscles of mastication. — They are: (1) the masseter (chew- 

 ing muscle), (2) the temporal (temple muscle), (3) the internal 

 pterygoid, and (4) the external pterygoid. These muscles can 

 be located on the illustrations. They have their origin in one or 

 more of the immovable bones of the skull, and are inserted into 

 the movable lower jaw. 



Action. — The muscles of mastication generally act in con- 

 cert, bringing the lower teeth forcibly into contact with the 



