ANIMAL DENTISTRY. 129 



Omnivora: (i), the incisor teeth; (2), the canine 

 teeth; (3), the lips; (4), the tongue. 



(In sheep and goats the lips are very motile and serve to 

 gather attached food as in the horse.) 



MECHANISM OF MASTICATION. 



The organs of mastication comprise : The superior max- 

 illary, the inferior maxillary, the premaxilla, the molar teeth, 

 the tongue, the hard palate, the cheeks, and the masseter, 

 the internal pterygoid, the temporalis, the digastricus, the 

 external pterygoid, the stylo-maxillaris and the sterno- 

 maxillaris muscles. 



The superior maxillary is an immovable bone, closely 

 united by sutures to its contiguous facial and cranial bones, 

 and to its ieWow by a wide, flat process extending across the 

 mouth to form its bony roof. It receives into six deep cavi- 

 ties the imbedded portions of the superior molar arcade, and 

 with its fellow and premaxilla constitutes the upper jaw. 

 Its function is to hold taut the superior molars and to form 

 the roof of the mouth. 



The inferior maxillary is a movable bone articulating 

 with the squamous temporal by a diarthrosis having imper- 

 fect rotatory and perfect ginglymoid motion. It is a single 

 bone consisting of a small body anteriorly with two large 

 branches extending posteriorly to the temporo-maxillary 

 articulation. At the anterior extremity of the body it re- 

 ceives the six incisor teeth and along the superior margin of 

 each branch the six inferior molars. Its function in masti- 

 cation is to serve as a carriage for the inferior molars, a 

 medium for the attachment of the muscles which move it and 

 to assist in forming the bony boundary of the mouth. 



The premaxilla is an irregular bone, which, with its fel- 

 low completes the upper jaw anteriorly and contains the 



