OSTEOLOGY. 49 



is also situated in tlie concavity of tlie under surface of the 

 wing. 



The DENTATA OR AXIS is tlie largest and tlie longest 

 of the true vertebrae, and has the largest superior spinous 

 process ; it is the second cervical vertebra. Its body is 

 very long, but superiorly presents the usual arrangement 

 for venous sinuses and the attachment of the superior 

 vertebral ligament. Anteriorly it presents a synovial sur- 

 face for union with atlas, and centrally the odontoid 

 process : superiorly this process is separated from the rest 

 of the upper surface of the body by a rough line from 

 which another runs forward to the anterior margin. The 

 space on either side between the ridges is concave ; to the- 

 transverse ridge is attached the broad, to the concavities 

 the short odontoid ligaments. The anterior margin is 

 convex, the lateral margins sharp and elevated. Theinfero- 

 lateral surface of the process is convex and articulatory,. 

 coming into connection with the postero-superior part o£ 

 the body of the atlas. It is most prominent at the centre 

 of the posterior part, forming a small tubercle. It is con- 

 tinued on either side on to the antero-extornal part of the 

 body as a rounded synovial surface, looking obliquely 

 upwards and outwards. The under surface of the body 

 centrally presents a prominent ridge, sharp posteriorlyy 

 roughened anteriorly. It affords attachment to longus colli 

 and to the inferior vertebral ligament. Anteriorly it does 

 not extend as far as the odontoid process, from which it is 

 separated by a groove, which extends completely round the 

 anterior part, affording attachment to the capsular' liga- 

 ment of the atlo-axoid articulation, separating the inferior 

 spinous ridge from the outer circumferent margin of the 

 anterior articulatory' surfaces, which here cause expansion 

 of the bone. Posteriorly the body laterally presents tv/o sur- 

 faces, converging towards the inferior ridge roughened for 

 attachment of longus colli. From the supero-lateral part, 

 of the body the transverse processes run obliquely upwards 

 outwards, and backwards ; they have two roots, a broad 

 concave one, inferiorly separated by the vertebral foramen 

 from a smaller one superiorly situated. This process is 

 undivided at its free extremity. The pedicles are long and 

 high, thus rendering the foramen magnum longest verti- 

 cally ; their inner surface is rough and concave, their outer 

 roiicjli and straight. The posterior margin is concave, assist- 



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