188 



THE ARTICULATIONS. 



the head, the small oblique, and the complexus. There is also the cord of the 

 cervical ligament, 



Sijiiovial membranes. — These membranes are two in number — one for each 

 condyle and coiTesponding atloid cavity. Sustained above, below, and outwardly 

 by the capsular ligament, they are related inwardly to the dura mater and the 

 fibrous tractus which, from the odontoid ligament, is carried to the internal face 

 of the occipital condyles. 



Movements. — Extension, flexion, lateral inclination, and circumduction, are the 

 movements of the occipito-atloid articulation. 



In the Pig, Dog, and Cat, this articulation— strengthened, as it is, by the capsular and 

 odontoido-occipital ligaments already mentioned — has only one synovial capsule. 



3. Aeticulation of the Bones of the Head with each other. 

 If we except the articulation which unites the inferior jaw to the cranium — 

 the temporo-maxillary — and the hyoideal articulations, it will be found that all 

 the bones of the cranium and face are united to each other by synarthrosis, 

 forming the different kinds of sutures already generally described (p. 170). 

 Nothing is to be gained by entering into more detail with regard to these articu- 

 lations, as it will be found sufficient to call to mind the topographical description 

 of each bone entering into their formation. 



4. Temporo-maxillary Articulation (Fig. 125). 



{Preparation. — Remove the masseter muscle and the parotid gland. Saw through the 

 head about the middle liue. Open the articulation externally, to exhibit the interarticular 

 meniscus.) 



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

 articulation. 

 F'g 125. Articular surfaces. — With the temporal bone, 



these are the condyle, the glenoid cavity, and the 

 supra-condyloid process at the base of the zygomatic 

 process. The glenoid cavity is not lined by cartilage, 

 and appears to be merely covered by synovial mem- 

 brane. On the maxillary bone is the oljlong condyle 

 situated in front of the coronoid process. 



Interarticular fihro-cartilage. — The articular sur- 

 faces just named are far from fitting each other 

 accurately ; this is only accompUshed by the inter- 

 position 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 the 

 diarthrodial surfaces it separates. Its superior face, 

 therefore, presents : in front, a cavity to receive 

 the condyle of the temporal bone ; behind, a boss 

 which is lodged in the glenoid cavity. The inferior 

 face is hollowed by an oblong fossa, in which the 

 maxillary condyle is lodged (Fig. 125, 1). 



Mode of union. — A fibrous envelope — a true capsular ligament — surrounds the 

 articulation, aiid is attached by its borders to the margin of the articular surfaces 

 it unites. Formed, outwardly, by a thick fasciculus of white vertical fibres (Fig, 



TEMPORO-MAXILLARY ARTICU- 

 LATION . 



1, Interarticular fibro-cartilag;e ; 

 2, external fasciculus of the 

 capsular ligament. A, Base of 

 the coronoid process ; B, neck 

 of the maxillary condyle; C, 

 mastoid process ; D, external 

 auditory hiatus. 



