THE HEAD AND NECK. 



97 



EMINENTIA ARTICULARIS 



Interarticular flbro- 

 cartilage 



MANOIBULAR CONDYLE 



FIG. 59. SCHEMATIC. TEMPORO-MANDIBULAR ARTICULATION. 



This is assumed to represent relation of condyle and cartilage to eminentia articularis when the mouth is 

 open. Here both condyle and cartilage slide forward on to the eminentia articularis ; the former 

 by action of the lower, the latter by action of the upper, head. 



EMINENTIA ARTICULARIS 



Upper head of external 

 pterygoid 



Lower head of external 

 pterygoid 



GLENOID SYNOVIAL CAVITY 



CONDYLE UNATTENDED BY THE CARTILAGE ON 

 THE EMINENTIA ARTICULARIS 



FIG. 60. SCHEMATIC. TEMPORO-MANDIBULAR ARTICULATION. 



This is assumed to' represent abnormal relation of condyle and cartilage to eminentia articularis in those 

 cases where the nerve-twig that supplies the upper head of the external pterygoid muscle is paralyzed. 

 A cracking noise on opening the mouth is a symptom. Here the cartilage remains back in the 

 glenoid, there being nothing to pull it forward. The condyle slips over the thick margin and pro- 

 duces the noise. 



