THE SPINAL COLUMN 



43 



by the arrangement of the atlas and axis. The cup-like articular 

 processes of the atlas receive the condyles of the occipital bone to 

 allow the nodding motion of the head. The occipital bone is held 

 to the atlas by ligaments, arid rotation of the atlas around the tooth 

 of the axis turns the head also, from side to side. 



The ligamentum nuchae is a name given to a thick elastic band 

 (not a true ligament) which stretches from 

 the occipital protuberance to the seventh 

 spinous process. It helps to sustain the 

 weight of the head while bending forward, 

 and is particularly well developed in the 

 larger grazing animals. 



From the seventh cervical down to the sacrum 

 a supraspinous ligament is stretched, attached to all 

 the spinous processes. 



The movements of the spinal column are 

 flexion, extension, lateral flexion, and rota- 

 tion. Motion is freest in the cervical re- 

 gion, and most restricted in the dorsal. . 



Clinical note. The limited motion be- 

 tween neighboring bones becomes a wide 

 range in the column as a whole and may 

 be increased by frequent and judicious ex- 

 ercises. 



THE SPINE AND THE SPINAL 

 CURVES 



The length of the spine is about 27 inches. 

 The solid portion is a flexible and elastic 

 column which bears the weight of the head 

 and its delicate organs without giving them 

 the full force of the jar caused by walking, 

 running, etc. The flexibility of the column 

 allows the whole body to move with freedom and grace, while the 

 strength of the spine makes it suitable for the attachment of the 

 extremities. The arches, connected by their ligaments, enclose 

 the spinal or neural canal, which extends through the sacrum to 



FIG. 39. SPINE 

 AND SPINAL CURVES. 

 (Sappey.) 



