54 THE CAT. [CHAP. in. 



Adjacent spinous processes are also connected together by mem- 

 branes (Fig. 26, B, i), called interspinous ligaments. Narrow bundles 

 of fibres, forming a sort of cord, pass backwards along the spinous 

 processes. These are the supraspinous ligaments. 



A forward prolongation of these supraspinous ligaments is termed 

 the ligamentiim nuchw, and passes from the cervical neural spines to 

 the skull. 



Adjacent transverse processes are also connected together by 

 fibrous bands termed the inter-transverse ligaments. These are 

 largest in the lumbar region, while they are rudimentary in the 

 vertebra of the neck. 



The mobility of the spinal column is different in different regions, 

 being greatest of course in the tail (save in some breeds), which can 

 be bent freely in any direction owing to the absence of interlocking 

 bony processes, except in the most anterior caudal vertebra. After 

 the sacrum, the mobility is least in the dorsal region, on account of 

 the overlapping of the neural Iamina3. In the cervical region there 

 is much mobility, even apart from the axis and atlas, the motions of 

 which will be treated of separately. Lateral bending and rotation 

 are variously limited by the direction of the articular surfaces of the 

 zygapophyses, which, as has been noted, are different in different 

 regions. 



20. The AXIS and ATLAS articulate together in a manner 

 altogether peculiar. The atlas (with the head to which it is attached) 

 can turn round to a great extent in either direction upon the odon- 

 toid process as on a pivot, being retained in place by ligaments. 

 Synovial membranes are interposed between the articular surfaces of 

 the atlas and axis, which surfaces are kept in apposition by capsular 

 ligaments. 



The odontoid process is kept in place by the transverse ligament 

 of the atlas, which extends across above that process and between 

 the internal margins of the anterior articular surfaces of the atlas. 

 From the midst of this transverse ligament two bundles of fibres 

 are'given off in opposite directions, one bundle passing backwards 

 to the centrum of the axis, the other forwards to the skull, thus 

 giving rise to the figure of a cross. 



A synovial membrane is placed both above and below the odontoid 

 process, corresponding with the two smooth surfaces which have 

 already been noted as existing upon it. 



Three ligaments pass forwards from the odontoid process to the 

 skull, i.e., one from its tip to the margin of the opening of the skull 

 in front, and two others (called alar or check ligaments) from the 

 sides of the summit of the process to the inside of the condyles of 

 the skull. 



These crucial and odontoid ligaments are covered over above and 

 sheltered by another called the occipito-amal ligament, which is 

 placed in the ventral part of the neural canal between them and the 

 most anterior part of the dorsal common ligament. It passes up 

 from the centrum of the axis to the inside of the floor of the skull. 



