24 ANTHROPOLOGY. 



PI. 123, j^o-. 40. A dorsal vertebra from the side: ', body; ", articulating 

 face for the head of a rib ; ', intervertebral notch ; \ oblique process ; 

 ", transverse process ; ', spinous process. 



Fig. 41. A lumbar vertebra from above : ', transverse process ; \ oblique 

 process ; ^, spinous process. Fig. 42. The same from the side : ', inferior 

 oblique process. 



The sacrum {figs. 43, 44) is a broad flattened triangular bone, concave 

 anteriorly, convex posteriorly, inserted like a wedge between the two ossa 

 innominata, and articulating with the lumbar vertebra above, with the 

 coccyx below. In the young skeleton it is clearly seen to consist of five 

 distinct vertebra?, which become fused together or anchylosed with age, 

 always, however, leaving traces of the original separation, especially on the 

 anterior face. In fact, all the elements of true vertebrae are here present, 

 although in no high condition of development. The upper anterior pro- 

 jecting edge of the sacrum is termed the promo7itory, behind which is the 

 triangular aperture of the sacral or spinal canal. On either side of this 

 canal is the oblique or articular process. The inferior extremity of the 

 sacrum, or the ajKx, is dh-ected downwards, sometimes a little forwards ; it 

 presents a small transverse, oval, convex surface, for articulation with the 

 coccyx. The anterior concave surface is marked by four transverse lines 

 {fig. 43 '^), at the extremities of which on each side are four large holes (the 

 anterior sacral). These transmit the anterior sacral nerves, veins, and arte- 

 ries. The posterior surface is roughened by four horizontal eminences in 

 the median line, corresponding with the spinous processes. On each side 

 of this median ridge is a rough groove, in which are four posterior sacral 

 foramina {fig. 44 ■'), which transmit the posterior sacral nerves and some 

 bloodvessels. The inferior extremity of the sacral canal is bounded poste- 

 riorly by a ligament, and laterally by two tubercles, cornua sacralia, which 

 descend to meet similar processes from the coccyx. 



The ossa coccygis or coccyx {pi. 122, fig. 31) correspond to the caudal 

 vertebrse of animals. They consist of three or four, rarely of five pieces, 

 which in the young are divisible into three parts, while in the adult 

 they are united into one or two. Considering the combination into one 

 piece, this in the adult is of triangular shape, serving to prolong ante- 

 riorly the curve of the sacrum {fig. 5 *). The base above is broad, and 

 bounded by two cornua {fig. 31 '), which interlock with those of the 

 sacrum. 



B. Articulations and Ligaments of the Spine. 



Articulation of the head with the spine {articulus capitis). This is a 

 double arthrodia, the condyles of the occipital bone being received into the 

 superior oblique processes of the atlas. The motion is quite limited, and 

 restricted almost entirely to a forward and backward movement of the 

 head. The capsular ligament on each side arises from the circumference of 

 the condyle, and is inserted into the circumference of the glenoid cavity of 

 the atlas. The interior of each capsule is lined by a synovial membrane. 

 Anterior and posterior occipito-atlantal ligaments {pi. 124, fig 4\ fig. 5''") 

 730 



