PRACTICAL CONSIDERATIONS: THE FACE. 



247 



Fig. 26 



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process may readily be defined. In dislocation this is unnaturally prominent. Be- 

 tween its base and the last molar tooth there is often a space through which liquid food 

 or other fluids can be conveyed by a tube to the pharynx in cases in which fracture- 

 dressing, or trismus, or ankylosis renders the lower jaw immovable. Along the lower 

 border externally, just in advance of the anterior edge of the masseter, the groove 

 for the facial artery may be felt, and in the middle line the ridge which indicates the 

 thickening at the symphysis. • 



On the inner surface of the jaw may be recognized the genial tubercles, some- 

 times in two distinct pairs, indicating 

 the attachments of the genio-hyo- 

 glossi and genio-hyoidei. The sub- 

 lingual fossae may be located, and just 

 external to them, and at their lower 

 border, the faint beginning of the 

 mylo-hyoid ridge, which runs upward 

 and backward, becoming more evident 

 opposite the last two molars. 



Above this line the bone is cov- 

 ered by the mucous membrane of the 

 mouth ; hence diseases of this portion 

 find their expression in the oral cavity, 

 while those of the lower portion of the 



bone are more apt to involve the soft parts and glands of the neck (Fig. 267). 

 The fossae for the submaxillary glands cannot be felt through the mouth, but, as they 

 lie below the ridge, while the sublingual fossae lie above it, the well-known clinical 

 relations of the former glands to the neck and of the latter to the mouth are explained. 



The familiar change in the shape of the lower jaw in edentulous old persons is 

 due to absorption of the alveolar process. 



(Most of the landmarks of the face are of more importance in relation to the 

 soft parts, the nerves, and the contents of the cavities of the orbit, nose, and mouth 

 than in connection with the bones themselves. They will, therefore, be further con- 

 sidered in those connections.) 



Inner surface of lower jaw, showing various areas. 



