COCCYGEAL VERTEBRA 



49 



Consolidation begins soon after puberty by fusion of the costal processes, and this is followed 

 by ossification from below upward in the intervertebral discs, resulting in the union of the 

 adjacent bodies and the epiphysial plates, the ossific union of the first and second being com- 

 pleted by the twenty-fifth year or a little later. The marginal epiphyses are also united to the 



Fig. 62. — The Sacrum at Four Years of Age (B). The Figure at the Top (A) Shows 

 THE Base Drawn from Above. (Three-fourths natural size.) 



Pedicle and transverse process 



Cartilage 

 Costal process 

 Cartilage 



( 



Cartilage covering lateral mass 



Cartilaginous disc 



Ossification in first piece of coccyx 



sacrum by the twenty-fifth year. Even in advanced life intervertebral discs persist in the 

 more central parts of the bone and can be well seen in sections. 



Coccygeal vertebrae. — The coccygeal vertebrae are cartilaginous at birth and each is usually 

 ossified from a single centre, though there may be two for the first piece. Ossification be- 

 gins soon after birth in the first segment, and in the second from the fifth to the tenth year. 



Fig. 63. — Sacrum at about Twenty-two Years. (Three-fifths natural size.) 



Epiphysial plate on the upper surface of body of first sacral vertebra 



Lateral epiphyses appear at eighteea 

 years and join at twenty-five 



The centres for the third and fourth segments appear just before, and after, puberty respec- 

 tively. As age advances the various pieces become united with each other, the three lower 

 uniting before middle life and the upper somewhat later. In advanced life the coccyx may jom 

 with the sacrum, the union occurring earUer and more frequently in the male than in the female. 



4 



