ARTICULATIONS OF Till. III.'AI'. 



137 



2. Ocdptto-a&oid Aiiicnlalinn. 



(/'re/xir.///./;i. Dksoot away nil the soft parts that pass from the neck to the hood 



iiiul erner tin- articulation, and more partiVularly the llexor, 



ti, ainl tlit 1 .-mall nhliijiie muscle* ut' the In ail. To fjj gj 



tin- syimvial membranes, open the sides of the ea|nlar 



ligament.) 



This is a condyloid articulation. 



Articular surfaces. In the atlas, the two cavities 

 which replace the anterior articular processes and 

 the lu -juls of the other vertebra} ; in the occipital 

 In >iic, the two coiulyles flanking the sides of the occi- 

 pital fonimen. 



Mode of union. A single capsular ligament en- 

 velopes the entire articulation ; it is attached by its 

 anterior border to the margin of the occipital con- 

 <ly h s, ami by its posterior to the anterior contour of the 

 atlas. Thin and slightly elastic in its inferior half, 

 this ligament presents, superiorly, four reinforcing 

 uli : two middle, which intercross in X from 

 \\lieiice tin- name " cruciform," sometimes given to this 

 ligament (Fig. 81, 1, 1) ; and two lateral, which pass 

 from the sides of the atlas to the base of the styloid 

 processes (Fig. 81, 2, 2). It is lined within by the 

 synovial membranes, and is enveloped externally by a 

 large number of muscles, which protect the articu- 

 lation and greatly strengthen it every where. Among 

 these may be particularly noticed the straight muscles 

 of the head, the small oblique, and the great coin- 

 plexus. There is also the cord of the cervical liga- 

 ment. 



Synovial membranes. These membranes are two 

 in number, one for each condyle and corresponding 

 atloid cavity. Sustained above, below, and outwardly 

 by the capsular ligament, they are related inwardly 

 to the dura mater and to the fibrous tractus which, 

 from the odontoid ligament, is carried to the in- 

 ternal face of the occipital condyles. 



Movements. Extension, flejcion, lateral inclination, 

 and rin-HiiiiJiirtion, are the possible movements of the 

 ocdpito-atloid articulation. 



In the /'/'./. I toy, and Cat this articulation, (strengthened 



M.- it i- liv the e:i|iular and odontoido-occipitol ligaim nts 

 already mentioned, has only <me synovia! ca|.suli . 



3. Arlifitlnti'iins of the Bones of the Head. 



If we except the articulation which unites tho 



inferior jaw to the cranium the temporo-maxillary 

 and the hyoid'-al articulations, it will be found that 

 all the I'ones of the cranium and face are united to 

 each other by synarthrosis, forming the iliHen-nt 

 kinds of sutures already generally ih M-I il d (l>agc 128^. 

 to IMJ gained by entering into more detail 



ATLO-OXOID AND OCCIPI- 

 TO-ATU)ID ARTH I I \- 

 iniNs. The UJ>IH.T arch 

 of the atlas has been 

 removed to show the 

 odontoid ligament. 



1, 1, Middle access 

 ciculi ; 2. 



i':iM-iriili of the cajisular . 

 ligament of the ocd|>iu>- 

 atloid articulation ; .",, 

 <>iloutoid ligament; 4, 



uniting the scoml ;\ml 

 thinl vertehra- <>f the 

 ii'-fk ; .">, Kiln-oils i-:i|i>ule 

 uniting the artimlar 



-A, Anterior in- 

 tornal foraiiu-n of tlu- 

 atlas converted into a 

 groove by the sect in of 

 the bone ; 



I'l-.il fi>r:iuiio;i of tin- 

 atlas . 



iv|ilai-iiij thr aiitc 

 ijiitch.-.- ..f tin. i 



