TEMPORAL AND INFRATEMPORAL REGIONS 169 



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. Divide the zygomatic arch, behind and in front 

 of the masseter, and throw the arch, with the attached masseter, 

 downwards. As that is being done cut the artery and nerve of 

 supply out of the masseter muscle, leaving a small portion of 

 the muscular substance attached to them so that they may be 

 identified at later stages of the dissection. 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 articular tubercle which lies in front of the mandibular 

 (O.T. glenoid) fossa and the head of the mandible ; the anterior 

 cut must extend obliquely through the zygomatic bone, from the 

 extreme anterior end of the upper margin of the arch, down- 

 wards and forwards to the point where the lower margin meets 

 the zygomatic process of the maxilla. When the division is 

 completed, and the nerve and artery to the masseter are detached, 

 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 then be seen. The dissection 

 is frequently complicated by a number of fibres from the temporal 

 muscle joining the deep part of the masseter. Leave the masseter 

 attached to the angle of the mandible, 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 temporal line 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 their 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. A tendon is developed upon its superficial aspect, 

 near its insertion, and the tendon 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 coronoid process 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 insertion 

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

 later. The temporal muscle raises the mandible and retracts 

 it. It is supplied by a branch of the mandibular division of 

 the trigeminal nerve. 



Dissection. Detach the coronoid .process from the mandible, 



