OF THE SPINE WITH THE CRANIUM. 



193 



below, to the upper edge of the laminae of the axis. This ligament supplies the 

 place of the ligamenta subflava, and is in relation, behind, with the Inferior oblique 

 muscles. 



The Transverse Ligament (figs. 119 and 120) is a thick and strong ligamentous 

 band, which arches across the ring of the atlas, and serves to retain the odontoid 

 process in firm connection with its anterior arch. This ligament is flattened from 

 before backwards, broader and thicker in the middle than at either extremity, and 

 firmly attached on each side of the atlas to a small tubercle on the inner surface of 

 each of its lateral masses. As it crosses the odontoid process, a small fasciculus 

 is derived from its upper and lower borders ; the former passing upwards, to be 

 inserted into the basilar process of the occipital bone ; the latter downwards, to 



Fig. 119. Articulation between Odontoid Process and Atlas. 



be attached to the root of the odontoid process : hence, this ligament has received 

 the name of cruciform. The transverse ligament divides the ring of the atlas into 

 two unequal parts : of these, the posterior and larger serves for the transmission 

 of the coed and its membranes ; the anterior and smaller serving to retain the 

 odontoid process in its position. The lower border of the space between the atlas 

 and transverse ligament being smaller than the upper, on account of the transverse 

 ligament embracing firmly the narrow neck of the odontoid process, this process 

 is retained in firm connection with the atlas when all the other ligaments have 

 been divided. 



The Capsular Ligaments are two thin and loose capsules, connecting the articu- 

 lar surfaces of the atlas and axis, the fibres being strongest on the anterior and 

 external part of the articulation. 



There are four Synovial Membranes in this articulation. One lining the inner 

 surface of each of the capsular ligaments ; one between the anterior surface of the 

 odontoid process and anterior arch of the atlas ; and one between the posterior 

 surface of the odontoid process and the transverse ligament. The latter often 

 communicates with those between the condyles of the occipital bone and the 

 articular surfaces of the atlas. 



Actions. This joint is capable of great mobility, and allows the rotation of the 

 atlas, and, with it, of the cranium upon the axis, the extent of rotation being 

 limited by the odontoid ligaments. 



III. ARTICULATION OF THE SPINE WITH THE CRANIUM. 



The ligaments connecting the spine with the cranium may be divided into two 

 sets : 1. Those connecting the occipital bone with the atlas ; 2. Those connecting 

 the occipital bone with the axis. 

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