PRACTICAL CONSIDERATIONS : THE FACE. 



493 



Fig. 506. 



Upper joint-cavity 



Iiiterarticular 

 cartilage 



Tendon of- 

 ten! poral 

 muscle 



Coronoid 

 process 



Condyleof 

 jaw and 

 lower 

 joint- 

 cavity 



Ramus of 

 mandible 



" boule de Bichat, " "sucking cushion" — is believed to receive and distribute the 

 increased atmospheric pressure which follows the establishment of a partial vacuum 

 in the mouth during sucking. It thus aids in preventing the buccinator from being 

 carried in between the alveoli. .It is relatively smaller in adults than in infants and 

 in the latter does not much 

 diminish in size, even in the 

 presence of emaciation, when 

 the general subcutaneous fat 

 has largely disappeared 

 ( Ranke) . Sutton says, ' ' The 

 sucking cushions sometimes 

 enlarge in adults and simulate 

 more serious species of tu- 

 mors, and it is curious that in 

 some of the recorded cases 

 the enlargement has been as- 

 sociated with the impaction of 

 a salivary calculus in the duct 

 of the parotid gland." 



The importance of avoid- 

 ing conspicuous scars on the 

 face leads the surgeon to make 

 his incisions, whenever possi- 

 ble, either in or parallel with 

 the lines of the natural furrows due to the insertion of some of the facial muscles into 

 the skin itself, or in the shadow of overhanging parts, as beneath the upper brow 

 or the lower edge of the inferior maxilla. For a reason not understood, but possibly 

 associated with the difficulty in securing rest, combined with the large vascular sup- 

 ply, cicatricial overgrowth and true keloid are both relatively common after wounds 

 of the face. 



In fracture of the inferior maxilla the irregularity in the horizontal planes of the 

 two fragments (the anterior being the lower) is due to («) the weight of the chin and 



opposite side of the jaw ; 



Dissection showina: relations when mandible rests within glenoid 

 fossa ; outer part of capsular ligament has been cut away, exposing upper 

 and lower joint-cavities. 



Fig. 507. 



Articular eminence 



Upper joint-cavity 



Tendon of. 



temporal Lx 

 muscle / IP 

 Coronoid' — ' ' 

 process 



Interarticular 



cartilage, car- 



y ried forward 



.Condyle of 

 jaw and 

 lower joint- 

 cavity 



(S) the action on the an- 

 terior fragment of the di- 

 gastric and other depressors 

 of the chin ; and (<:) the 

 effect of the posterior fibres 

 of the temporal, the internal 

 pterygoid, and the super- 

 ficial fibres of the masseter 

 in elevating the posterior 

 fragment (Fig. 505). 



In fracture of the ramus 

 there is little displacement, 

 as the bone lies between the 

 two muscular planes of the 

 masseter and internal ptery- 

 goid and is splinted by 

 them. In fracture of the 

 neck of the condyle the 

 upper fragment is drawn 

 upward and forward by the 

 external pterygoid ; the re- 

 mainder of the jaw is some- 

 what elevated by the masseter, temporal, and internal pterygoid. The difficulty in 

 approximation of the fragments may result in excess of callus, which greatly interferes 

 with the subsequent movements of the temporo-maxillary articulation. 



The mechanism of dislocation of the lower jaw has already been described (page 



Ramus of 

 mandible 



Dissection showing relations when mandible is depressed and carried 

 forward upon articular eminence ; capsular ligament is stretched in con- 

 sequence. 



