THE SKELETON 



41 



As already stated, the presence of a free rib in connection 

 with the last cervical vertebra (Fig. 27, A) is somewhat rare in 



Fio. 25. DIAGRAM OF A TRANSVERSE SECTION OF THE HIP GIRDLE AND SACRUM : A., OF 

 A SALAMANDER ; B., OF MAN (young stage in which the separate parts of the sacral 

 vertebrae are still distinct). 



b.v., body of sacral vertebrae ; a.n., arch of same ; r.s., sacral rib ; il., ilium ; 

 p., pubis ; c.h., coelom ; ac. , acetabulum. 



adults, but the vestige of such a rib, and even of a second (some- 

 what less attached) near the sixth cervical vertebra, is almost always 



Fia. 26. A, FIRST THORACIC SKELETAL SEGMENT FOR COMPARISON WITH B, FIFTH 

 CERVICAL VERTEBRA (MAN). 



c., first sternal rib ; c', cervical (rib which has become united with the transverse process 

 (tr.)) the two enclosing the costo-transverse foramen (f.c.t.) ; zy., articular process 

 of the arch (zygapophysis) ; b.v., body of vertebra ; st., sternum. 



found in the embryo. The five anterior cervical vertebrae show 

 no such distinct vestiges, although their former presence is clearly 



