OSTEOLOGY. 47 



articulatory surfaces than the anterior, but not the smallest 

 in the neck. They come into contact with the anterior 

 oblique processes of the first dorsal vertebra. This ver- 

 tebra, at the supero-posterior and lateral parts of the body, 

 has a concave synovial facet on each side for the head of 

 the first ribs. The first and second cervical vertebrae 

 require more detailed description. 



ATLAS is the first cervical vertebra, and in it we see a 

 manifestation of analogy with the cephalic vertebrae in the 

 expansion of its parts. Its ring is very large, ovoid from 

 side to side anteriorly, circular posteriorly. It accommo- 

 dates the commencement portion of the spinal cord with 

 its membranes, the commencement portion of the basilar 

 and of some meningeal arteries, the spinal accessory nerve, 

 some venous sinuses and fat. Also posteriorly the odontoid 

 process of the dentata, with its ligaments. The body is very 

 small, flattened from above downwards. Its superior sur- 

 face anteriorly has a roughened groove, extending on either 

 side outwards and backwards for attachment of the odon- 

 toid ligaments. Posteriorly it presents an articulatory 

 surface concave from side to side, surrounded by a ridge, 

 continuous with the articulatory surface upon the posterior 

 part of the bone. The inferior surface is convex. Anteriorly 

 it has the lower part of the articulatory surfaces for the 

 condyles of the occiput, converging inferiorly, where they 

 are separated by a groove to which their synovial mem- 

 branes are attached, and which is continuous with a small 

 triangular space on the antero -inferior part, which is occu- 

 pied by a ligament. At the postero-inferior part of the 

 body is a prominence looking backwards, tubercle or in- 

 ferior spinous process, to which longus colli (and the 

 inferior vertebral ligament) is attached. On either side of 

 this the bone is rough for attachment of obliquus capitis 

 anticus. Opposite the articulatory surfaces it is convex 

 and bulging, between these somewhat concave and smooth. 

 The pedicles run obliquely upwards and outwards from the 

 lateral parts of the body of the bone, being concave and 

 rough internally, convex externally, and expanded at either 

 extremity, forming those portions of this vertebra which 

 correspond to oblique processes of others. Anteriorly the 

 expanded part presents an articulatory facet for union with 

 a condyle of the occiput. It superiorly looks downwards 

 and slightly forwards, running outwards. It then becomes 



