42 ANATOMY AND PHYSIOLOGY 



terior sacral foramina; seen from the back, the posterior sacral 

 foramina (both are for the passage of nerves). The angle formed 

 by the sacrum and the fifth lumbar vertebra projects sharply 

 forward and is called the promontory. 



Coccyx. The terminal bone of the spinal column, and formed 

 of four very rudimentary vertebrae. The base is joined to the 

 sacrum; the apex is directed downward and forward. 



FIG. 37. SACRUM, ANTERIOR ASPECT. 

 i, i, i, i, Bodies of sacral vertebrae with trans- 

 verse lines of union; 2, 2, 2, 2, anterior sacral foram- 

 ina; 3, base; 4, auricular surface of lateral aspect; 

 5, its inferior portion; 6, articular surface of base; 

 7, notch for formation of last lumbar intervertebral 

 foramen; 8, superior articular process of first sacral 

 vertebra; 9, apex of sacrum; 10, cornu; n, notch 

 for transmission of fifth sacral nerve. (Sappey.) 



FIG. 38. COCCYX, ANTE- 

 RIOR ASPECT. 

 i, Base; 2, 2, cornua; 3, 

 second coccygeal vertebra; 



4, third coccygeal vertebra; 



5, fourth coccygeal vertebra; 



6, fifth coccygeal vertebra. 

 (Sappey.) 



THE ARTICULATIONS OF THE SPINAL COLUMN 



The bodies of the vertebrae are connected by discs of fibro- 

 cartilage which are placed between them. They serve not only 

 to connect the vertebrae but to give flexibility to the column, so 

 that it may bend in any direction, and they also make it elastic. 

 The bodies are further connected by fibrous bands on their anterior 

 and posterior surfaces. (Slightly movable 'or yielding joints.) 



The arches are connected by broad thin ligaments between the 

 laminae, thus completing the spinal or neural canal, which contains 

 the spinal cord. (These ligaments are an exception to the rule, 

 in that they are elastic; they are called the ligamenta flava.) The 

 articular processes are covered with cartilage and enclosed by 

 capsules which are lined with synovial membrane, forming true 

 movable joints. These are gliding joints. (Arthrodia.) 



The only independent movements of the head are provided for 



