266 HEAD AND NECK 



which extends downwards to the angle, and upwards so as to 

 include the lateral aspect of the coronoid process. 



Dissection. To display the temporal muscle, and at the same time 

 expose^the nerve and artery of supply to the masseter, make the following 

 dissection. Divide the deep part of the temporal fascia along the upper 

 border of the zygomatic arch and remove it. The middle temporal artery 

 and the zygomatico-temporal nerve, which pierce it, must be disengaged 

 from it and preserved. The zygomatic arch, with the attached masseter, 

 must next be thrown down by dividing the bony arch anterior and posterior 

 to the origin of the muscle. First make use of the saw, and then complete 

 the division by means of the bone forceps. The posterior cut should be 

 made immediately anterior to the mandibular (O.T. glenoid) fossa and 

 the head of the lower jaw ; the anterior cut must extend obliquely through 

 the zygomatic bone, from the extreme anterior end of the upper margin of 

 the arch, downwards and anteriorly to the point where the lower margin 

 meets the zygomatic process of the maxilla. When the division is com- 

 pleted, and the nerve and artery to the masseter are divided, the whole 

 arch and the attached masseter may be readily thrown downwards towards 

 the angle of the mandible. The fleshy origin of the deep portion of 

 the masseter from the medial surface of the zygomatic arch can now be 

 seen. The dissection is frequently complicated by a number of fibres from 

 the temporal muscle joining this part of the masseter. In turning the 

 masseter down, its nerve and artery of supply must first be cleaned as 

 they pass laterally through the incisura mandibulse (O.T. sigrnoid notch), 

 posterior to the tendon of the temporal muscle. Leave the masseter 

 attached to the angle of the jaw and clean the temporal muscle. 



Musculus Temporalis. The temporal muscle is fan-shaped. 

 It arises from the whole extent of the temporal fossa, from the 

 lower of the two lines which constitute the temporal ridge to 

 the infratemporal crest on the great wing of the sphenoid. 

 It receives additional fibres also from the deep surface of 

 the temporal fascia. From this broad origin the fasciculi 

 converge towards the coronoid process of the mandible. 

 The anterior fibres descend vertically, the posterior fibres at 

 first pursue a nearly horizontal course, whilst the intermediate 

 fasciculi proceed with varying degrees of obliquity. As it 

 approaches its insertion, a tendon is developed upon its 

 superficial aspect, and this is inserted into the summit and 

 anterior edge of the coronoid process. The deep part of the 

 muscle remains fleshy, and gains insertion to the medial 

 surface of the same bony prominence by an attachment which 

 reaches as low down as the point where the anterior margin of 

 the ramus merges into the body of the mandible. The inser- 

 tion cannot be fully examined at present ; it will be dealt with 

 later. 



Dissection. Detach the coronoid process from the mandible, and turn 

 it upwards with the attached temporal muscle. A very oblique cut is 



