370 MUSCLES. 



> Temporally. 



The temporal muscle is placed on the side of the head, and 

 occupies its middle inferior region. It is covered externally 

 by the Fascia Temporalis, a thick, dense, tendinous membrane; 

 which arises by the semicircular ridge on the side of the cra- 

 nium, and is inserted into the upper margin of the zygoma. 



The temporal muscle arises from the inner face of this fas- 

 cia; from the whole length of the semicircular ridge on the 

 side of the os frontis and parietale; and from the surface of the 

 cranium between this ridge and the zygoma, including the part 

 contributed by the frontal bone, the parietal, the squamous por- 

 tion of the temporal, and the sphenoid. This muscle also re- 

 ceives an accession of fleshy fibres from the internal face of 

 the zygoma. 



From this extensive origin the fibres converge towards the 

 zygoma, and passing beneath it, are inserted tendinous into the 

 coronoid process of the lower jaw, so as to surround it on eve- 

 ry side; some of these tendinous fibres go down in front almost 

 to the last dens molaris. 



It pulls the lower jaw directly upwards* 



Pterygoideus Externus* 



The external pterygoid muscle, so called from its position, 

 arises fleshy from the outer side of the external pterygoid pro- 

 cess of the sphenoid bone, and from the adjoining surfaces of 

 the same bone by its spinous and temporal processes; also, 

 from the tuber of the upper maxillary. 



It passes outwards and backwards horizontally, and is in- 

 serted into the inner side of the neck of the inferior maxilla, 

 and into the capsular ligament of the articulation. 



When the muscles of the opposite sides act together, they 

 draw the lower jaw forwards, but if alternately, they give it a 

 grinding motion.* 



* Varieties. I have seen, in one case, this muscle continued into the inferior 

 margin of the temporal. 



