l.'N 



T1IK AUTICULATI 



with rcganl to those articulations, as it will IK- found sulliciciit to oall to mind 

 tho topographical description of each pieco entering into their formation. 



4. Temporo-iiKt. rill <ir// ArtiritlntUm. 



(Preparation. Reiuovt* tho mus-sottr muBcIoninl tin- puiotiil gliuul. Saw through the 

 liriul uljout tlic nii.MIr Jims. OIHMI the articulation externully to rxhihit tin- intrr- 



Tho lower jaw, in its union with the cranium, constitutes a double 

 coudyloid articulation. 



Articular surfaces. With tho temporal bone, these are tho condylc, tin- 

 glenoid cavity, and tho supracondyloid process which exists at the base of 

 the zygouiatic process. The gleuoid cavity is not lined by cartilage, :unl 

 appears to be merely covered by synovial membrane. With the maxillary 

 bone there is the oblong condylo situated in front of tho coronoid process. 

 Interarticular fibro-cartilage. The articular surfaces just named are 

 far from fitting each other accurately ; this is 

 only accomplished by tho interposition of a 

 fibro-cartilaginous disc between the temporal 

 and maxillary bones. This disc is a kind of 

 irregular plate, flattened above and below, 

 thicker before than behind, and moulded on 

 each of tho diarthrodial surfaces it separates. 

 Its superior face, therefore, presents : in front, 

 a cavity to receive the condylo of tho temporal 

 bone; behind, a boss which is lodged in the 

 glenoid cavity. The inferior face is hollomd 

 by an oblong fossa in which the maxillary con- 

 dyle is lodged. 



Mode of union. A fibrous envelope a true 

 capsular ligament surrounds the articulation, 

 and is attached by its borders to the margin of 

 the articular surfaces it unites. Formed, out- 

 wardly, by a thick fasciculus of white vertical 

 ligament. A, Base of fibreg / Fig< 8 2, 2), this ligament becomes grey- 

 the coronoid process; it, Neck i -i j a % L* * > a m 



of the maxillary condylc; c, jsh-colourcd and elastic for the remainder of 

 Mastoid process; D, External its extent, and greatly diminishes in thickness, 

 auditory hiatus. especially in front. Its inner face is lined by 



the synovial capsules, and adheres to tho cir- 

 cumference of the interarticular fibro-cartilage. Its external face responds, 

 in front, to the temporal arid masscter muscles; behind, to tho parotid 

 gland ; inwardly, to tho external pterygoid muscle ; and outwardly, to a 

 fibrous expansion which separates it from the skin. (Leyh mentions a 

 lateral external and a posterior ligament for this articulation, but Chauveau 

 and Rigot evidently look upon these as portions of tho capsular.) 



Synovial membranes.- This articulation has two synovial sacs, one above 

 the other, which are separated by tho fibro-cartilaginous disc. 



Movements. Tho temporo-maxillary articulation is the centre of all tho 

 movements performed by the lower jaw. These are: depression, eleixtti<>n, 

 lateral motion, and horizontal gliding. 



The lower jaw is depressed when it separates from the superior one, and 

 is elevated when it approaches this. These two opposite movements are 

 executed by a mechanism of such great simplicity that it need not be 



TEMl-OUO-XAXlLLAltY AKT1CU- 

 LAT1ON. 



, Interarticular fibro-cartilage ; 

 2, External fasciculus of the 



