Vertebral Column 45 



terminate, which runs to the back of the bone from the lower sacral opening, and the 

 coccygeal nerve, which turns out behind the first segment. The " ano-coccygeal 

 ligament " and external sphincter are attached to the end of the bone. 



Thus the coccyx could be described as embedded in fibrous tissue and affected by 

 the contractions of the muscular pelvic floor and the Gluteus maximus : the fibrous 

 tissue on its dorsum contains filaments of the posterior primary divisions of the 

 coccygeal and last sacral nerves. 



The rudiments of at least six coccygeal vertebrae are to be found in embryonic life. 

 The distal ones fuse, and there are usually four at birth, still cartilaginous. Ossification 

 begins usually in the first year in the first segment, but this is very variable in indi- 

 viduals. The ossification of the succeeding segments goes on with wide limits until 

 puberty, or even after this. Centres are also described for the cornua and for epiphysial 

 plates in each segment : also a fifth segmental ossification has been described, fusing 

 later with the fourth. Possibly some, at any rate, of these ran be looked on as 

 individual variations 



Ossification appears to be later in women than in men. 



