294 ACTIVE OKGANS OF MASTICATION. 



like elevations. At tlie point of junction of the lateral and 

 transverse ridges, another ridge is spoken of as branching 

 off, which has a tooth, and also three and sometimes five 

 sharp, hooked, and small pointed elevations. 



The hooked teeth are represented as seizing the food and 

 carrying it between the teeth with flattened crowns. 



Insects and worms cannot be said to have any organs 

 which can be compared to teeth. The stomachs of some of 

 them seem to be furnished with " scales or horny hooks," 

 which are supposed to be intended for a kind of mastication. 



SECTION VI. 



ACTIVE ORGANS OF MASTICATION, CONSISTING OF MUSCLES. 



1. Masseter Muscle. The same dissection made for the 

 muscles of prehension will exhibit this muscle. 



FIG. 82. The masseter (fuuHtuofUM, I 



chew) is a superficial, thick, 

 and strong muscle, situated at 

 the side and back part of the 

 face, and extended between the 

 zygoma and angle of the lower 

 jaw. It consists of two portions, 

 an anterior and posterior, or 

 superficial and deep, which de- 

 cussate. The anterior is the 

 larger, and arises tendinous from the inferior edge of 

 the malar bone, and from the point where it unites 

 with the maxillary. The posterior arises fleshy from the 

 zygomatic arch as far back as the glenoid cavity. The 

 fibres of the anterior portion pass backwards and down- 

 wards; of those of the posterior, some descend obliquely 



FIG. 82 Lateral view of the Muscles of the face, cranium, and external 

 ear. 1 Occipito-frontalis, 2 Orbicularis palpebrarum, 3 Pyramidalis nasi, 4 

 Compressor nasi, 5 6 Levator labii superioris alseque nasi, 7 Zygomaticus mi- 

 nor, 8 Zygomaticus major, 9 Masseter muscle, 10 Buccinator, 11 Depressor 

 anguli, or triangularis orisj 12 Depressor labii inferioris, 13 Orbicularis oris, 

 14 Anterior auris, 15 Superior auris, 16 Posterior auris, 17 External lateral 

 ligament, 18 Deep-seated portion of masseter, 19 Fascia temporalis. 



