The Face. 469 



temporal ridge; the soft tissues are cut through down to 

 the bone, the latter is chiselled along the line of the skin 

 incision ; the flap, composed of the bone and soft parts, is 

 laid back, the dura mater and the temporal lobe of the 

 brain raised up, the trunk of the fifth nerve identified and 

 followed back to the apex of the petrous bone on which 

 the ganglion is situated, the dura mater is then incised and 

 the ganglion scraped away, avoiding the cavernous sinus. 



Fracture of the lower jaw. In the great major- 

 ity of instances, the fracture involves the body of the bone, 

 especially in the neighborhood of the mental foramen, since 

 this is the weakest part of the bone. The deformity that 

 results is, generally, as follows: The anterior portion is 

 displaced downwards, partly from gravity, and partly 

 from the depressing action of the muscles that connect 

 the lower jaw with the hyoid bone. The posterior frag- 

 ment is drawn upwards by the action of the temporal, 

 masseter and the internal pterygoid muscles ; slightly for- 

 wards by the external pterygoid, and outwards by the 

 masseter muscle. 



Dislocation of the lower jaw is generally 

 the result of a sudden contraction of the external 

 pterygoid muscle drawing the jaw forwards, when, 

 at the same time, the condyles have already been advanced 

 by widely opening the mouth. This sudden action of the 

 external pterygoid occurs, for instance, in yawning, or in 

 vomiting, etc. When dislocation occurs, the condyles and 

 cartilages are drawn upwards, beneath the zygoma, by the 

 action of the masseter and internal pterygoid muscles, and 

 in its reduction, the thumbs, placed upon the lower molar 

 teeth, press the posterior portion of the jaw, downwards 

 and backwards, so as to disengage the condyles from be- 

 neath the zygoma, when the tense elevator muscles will 

 close the teeth with a snap, thus indicating reduction of 

 the dislocation. 



