110 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 (4). 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- 
