VIII.] 



THE MUSCLES, 



285 



The orbicularis oris is a muscle surrounding the aperture 

 of the mouth. 



The masseter passes from the malar down to the angle of 

 the lower jaw. 



The temporalis occupies the side of the skull within the 

 zygoma, and is inserted into the coronoid process of the 

 mandible. 



^}\Q pterygoideus interims passes from the pterygoid fossa 

 to the inner surface of the mandible just above its angle. 



The pterygoideus externus arises from the ali-sphenoid 

 (including the part called " external pterygoid process "), and 

 is inserted into the neck of the condyle of the lower jaw and 

 into the inter-articular fibre-cartilage. 



Inside the bony orbit, we have four slender, long, straight 

 muscles (or recti}, and two oblique muscles, all inserted into 

 the sclerotic, or outer coat of the globe of the eye. 



InfR. 



C.h. 



FIG. 263 THH MUSCLES OF THE EYEBALL, viewed from above and from the 

 outer side. 



S.R., the superior rectus ; Inf.R. the inferior rectus ; E.R., the external rectus ; 

 fn.R., the internal rectus ; S.Ob., the superior oblique; Inf. Ob., the inferior 

 oblique : Ch., the chiasma of the optic nerves (II. ) ; ///., the third nerve, 

 which supplies all the muscles except the superior oblique and the external 



The four recti all arise at the bottom of the orbit, about the 

 optic foramen, and are respectively inserted into the eyeball 

 above, within, below, and without, whence they are termed 

 superior, interims, inferior, and externus. 



The obliquus superior (a slender muscle, like each of the 

 recti) also arises near the optic foramen. At the inner margin 



