A RTIC ULA TIONS 3 



processes, often absent in the cervical, thin in the lumbar, 

 but round and well marked in the dorsal region. 



II. ARTICULATION OF ATLAS WITH AXIS. 



The atlo-axoid articulation consists of four joints (a) a 

 pivot joint consisting of two parts, (i.) between odontoid pro- 

 cess and anterior arch of atlas, and (ii.) between odontoid 

 process and transverse ligament ; (b) two arthrodial, between 

 the articular processes. 



The anterior atlo-axoid ligament consists of a superficial 

 and a deep part. The superficial part continues the anterior 

 common ligament. It is attached above to the anterior 

 tubercle of the atlas ; and below to the body of the axis and 

 base of the odontoid process. The deep part is broad, and 

 reaches from the lower border of the anterior arch of atlas to 

 the base of odontoid process and body of axis. 



The posterior atlo-axoid ligament : a thin layer, connected 

 above to the lower border of the posterior arch of atlas, and 

 below to the upper edge of laminas of axis, pierced by the 

 second cervical nerve. 



The transverse ligament keeps the odontoid process in its 

 place ; it is attached on each side to a tubercle on the inner 

 surface of the superior auricular process of the atlas. A thin 

 bundle of fibres passes upwards from the middle of the pos- 

 terior surface to the basilar process, and a like process down- 

 wards to the body of the axis. These two processes, together 

 with the transverse ligament, form the cruciform ligament. 



Capsular ligaments as in ordinary vertebrae, but supple- 

 mented at the posterior and inner part by an accessory liga- 

 ment passing downwards and inwards to the base of the 

 odontoid process (accessory atlo-axoid ligaments'). 



Synovial membranes : besides those of capsular ligaments, 

 two ; one in front and one behind the odontoid process, the 

 latter often communicating laterally with one of the occipito- 

 atloid joints. 



HI. ARTICULATION OF ATLAS WITH OCCIPITAL BONE. 



The anterior occipito-atloid ligament consists of a super- 

 ficial and a deep part. The superficial, rounded, pa'sses from 

 the basilar process of the occiput to the anterior tubercle of 

 the atlas. The deep part is broad, and attached above to the 

 anterioredge of the foramen magnum, and below to the upper 

 margin of anterior arch of atlas. 



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