SPECIAL ANATOMY. 119 



illary bone is the buccal hrancJi of the inferior maxillarij 

 division of the fifth cranial nerve; it sends some large fibres 

 to the buccal glands, and runs onwards to supply buc- 

 cinator and caninus as far forwards as the angle of the 

 mouth. The facial hranch of the same nerve winds round 

 the posterior margin of the lower jaw just below the con- 

 dyle, combines with the seventh nerve or portio dura, and 

 proceeds over the cheek on the external surface of masseter 

 externus. One of its portions runs with the temporal 

 artery, the inferior branch passes to the lower lip, and 

 there unites with that portion of the dental branch of the 

 inferior maxillary nerve, which passes out of foramen 

 nienti (or the anterior maxillary foramen). The middle 

 and largest branch proceeds over the cheek, and sends 

 communicating fibres to the nerve which passes out of the 

 infra-orbital foramen; these pass in a curved manner 

 around the origin of retractor labii superioris, but the 

 greater number of the fibres blend with the infra-orbital 

 fibres, and run to the nostril and upper lip. Some small 

 muscles on the muzzle remain yet to be noticed. 



Dilator naris inferior arises from the superior process 

 of the anterior maxillary bone, winds round its smooth 

 superior margin, and becomes inserted into the cartilagi- 

 nous anterior extremity of the inferior turbinated bone 

 into the skin of the false nostril. From the superior ex- 

 tremity of the false nostril a small muscle running to the 

 superior maxillary hone just above the termination of the 

 zygomatic ridge may frequently he found. 



Depressor labii superioris arises from the external sur- 

 face of the body of the anterior maxilla around the alveolae 

 of the incisors, and extending back to the canines : it 

 becomes inserted into the mucous membrane lining the 

 upper lip, and may be exposed by removing this mem- 

 brane and the labial glands. It will be found to blend 

 centrally with its fellow. In the lower lip we find a 

 corresponding muscle, levator labii inferioris. Internally 

 to these muscles is a layer of salivary glandular substance 

 from which run numerous ducts which pierce the mucous 

 membrane of the lips, by inversion of which their openings 

 may be rendered visible to the naked eye. The structure 

 of the lower lip is completed by a mass of fatty matter 

 throughout which many muscular fibres are interspersed. 

 The lips, therefore, consistof skin, muscle, glandular struc- 



