298 ORGANS OF INSAUVATION. 



masseter and the posterior fibres of the temporal can also as- 

 sist the pterygoid in the grinding process, while the buccina- 

 tor comes in to their aid by keeping the food under the teeth. 

 So that the whole are so adapted to each other as to act in 

 the utmost harmony for the most perfect performance of the 

 function of mastication. 



Blood-vessels, (Fig. 'TS.) The arteries supplying the 

 muscles of mastication come from the temporal, the external 

 and internal maxillary arteries, and are named according 

 to the muscles they supply, as the temporal, masseteric, and 

 pterygoid branches. The veins correspond to the arteries 

 and return the blood into the external jugular. 



Nerves, (Fig. 74.) The nerves supplying the muscles of 

 mastication come from the fifth and seventh pair. The 

 motor division of the inferior maxillary branch of the fifth, 

 seen in the zygomatic fossa, sends off five muscular branch- 

 es, i. e. the two deep temporal, masseteric, buccal and ptery- 

 goid, going to the muscles of the same name.* The portio 

 dura or facial nerve is a branch of the seventh, which 

 also supplies the muscles of mastication. It is situated in 

 the substance of the parotid gland, anastomoses freely with 

 the fifth, and is described more minutely under the head 

 of organs of expression, which see. 



SECTION VII. 

 ORGANS OF INSALIVATION, COMPRISING THE SALIVARY GLANDS. 



The salivary glands are six in number three on each 

 side of the face, i. e. the parotid, submaxillary , and sublin- 

 gual. These glands belong to the conglomerate order, 

 that is, they consist of numerous little follicles, (Fig. 85, B,) 

 averaging about the one-twelve-thousandth of an inch in 

 diameter, surrounded by a plexus of capillary blood-vessels, 

 and presenting the appearance of a multitude of small 

 granules each being a gland in miniature, and each, conse- 

 quently, having its own artery, vein, and excretory duct. 

 It is by the combination of these various little excre- 



*See inferior maxillary nerve, under the head of nerves supplying the teeth, 

 for a more minute account. 



