no THE MUSCLES. 



Insertion into the external coronoid fossa. 



Relations. — Outer surface with the following, beginning at 

 the caudal border: the external ear, the parotid gland (Fig. 

 65, 1), the platysma, the submentalis, the zygomaticus (major), 

 the zygomaticus minor. Ventral border with a lymph gland 

 caudad of the angle of the mouth (Fig. 65, 3), and the digastric 

 muscle {U). Inner surface with the bones. 



Action. — A very powerful elevator of the lower jaw. 



M. temporalis (Fig. 63, ;/). — The temporal muscle is the 

 great mass taking origin from the temporal fossa and having 

 its insertion on both surfaces and both borders of the coronoid 

 process of the mandible. It may be divided into two layers, 

 deep and superficial. 



The superficial layer. The temporal fascia stretches over 

 the temporal fossa, being attached to its borders; that is, to the 

 sagittal and lambdoidal crests, to the curved ridge which con- 

 nects the sagittal crest with the zygomatic process of the frontal 

 bone, to the caudal border of this process, to the caudal border 

 of the malar bone, to the caudal border of the ligament con- 

 necting the malar bone and the zygomatic process of the 

 frontal, and to the dorsal border of the zygomatic process of 

 the temporal bone and its dorsal root. The craniolateral part 

 of this fascia is much stronger than the remainder. 



The muscle-fibres take origin from the strong craniolateral 

 part of the inner surface of the temporal fascia, from the groove 

 on the temporal bone dorsad of the dorsal root of its zygomatic 

 process, from the whole inner surface of this process and of the 

 zygomatic process of the malar bone, and sometimes also from 

 that part of the frontal bone which lies within the temporal 

 fossa. 



Insertion.- — The outer surface of the coronoid process of the 

 mandible dorsad of the coronoid fossa, and both borders of the 

 coronoid process. The cranial fibres may be inserted craniad 

 of the coronoid process onto the aponeurosis covering the deep 

 portion of the muscle. The caudal part of this portion is more 

 or less distinct and is sometimes described as a separate head. 



The deep portion. 



Origin by fleshy fibres from the whole surface of the tem- 



