154 MAXILLARY GROUP. 



Dissection. The masscter has been already exposed by the pre- 

 ceding dissection. 



The masseter (fjuxtftfaojxai, to chew,) is a short and thick and some- 

 what quadrilateral muscle, composed of two planes of fibres, super- 

 ficial and deep. The superficial layer arises by a strong aponeuro- 

 sis from the tuberosity of the superior maxillary bone, and from the 

 lower border of the malar bone and zygoma, and passes backwards 

 to be inserted into the ramus and angle of the inferior maxilla. The 

 deep layer arises from the posterior part of the zygoma, and passes 

 forwards, to be inserted into the upper half of the ramus. This 

 muscle is tendinous and muscular in its structure. 



Relations. By its external surface with the zygomaticus major 

 and risorius Santorini muscle, the parotid gland and Stenon's duct, 

 the transverse facial artery, the pes anserinus and the integument. 

 By its internal surface with the temporal muscle, the buccinator, 

 from which it is separated by a large mass of fat, and with the 

 ramus of the lower jaw. By its posterior border with the parotid 

 gland ; and by the anterior border with the facial artery and vein. 



Dissection. Make an incision along the upper border of the 

 zygoma, for the purpose of separating the temporal fascia from its 

 attachment. Then saw through the zygomatic process of the malar 

 bone, and through the root of the zygoma, near to the meatus audi- 

 torius. Draw down the zygoma, and with it the origin of the mas- 

 seter, and dissect the latter muscle away from the ramus and angle 

 of the inferior maxilla. Now remove the temporal fascia from the 

 rest of its attachment, and the whole of the temporal muscle will be 

 exposed. 



The temporal is a broad and radiating muscle occupying a consi- 

 derable extent of the side of the head and filling the temporal fossa. 

 It is covered in by a very dense fascia (temporal fascia) which is 

 attached along the temporal ridge on the side of the skull, extending 

 from the external angular process of the frontal bone to the mastoid 

 portion of the temporal ; inferiorly, it is connected to the upper 

 border of the zygoma. The muscle arises by tendinous fibres from 

 the whole length of the temporal ridge and by muscular fibres from 

 the temporal fascia, and from the entire surface of the temporal 

 fossa. Its fibres converge to a strong and narrow tendon, which is 

 inserted into the apex of the coronoid process, and for some way 

 down upon its inner surface. 



Relations. By its external surface with the temporal fascia, 

 which separates it from the attollens and attrahens aurem muscle, 

 the temporal vessels and nerves : and with the zygoma and masseter. 

 By its internal surface with the bones forming the temporal fossa, 

 the external pterygoid muscle, a part of the buccinator, and the in- 

 ternal maxillary artery, with its deep temporal branches. 



By sawing through the coronoid process near to its base, and pull- 

 ing it upwards, together with the temporal muscle, which may be 

 dissected from the fossa, we obtain a view of the entire extent of the 

 buccinator and of the external pterygoid muscle. 



