DISSECTING MANUAL. 



oval body of the fifth sacral vertebra. The sacral canal is tri- 

 angular above but flattened below, where it is deficient pos- 

 teriorly. [86] 



Coccyx. This consists of four (sometimes five, or three) 

 rudimentary vertebrae, more or less fused. The first piece, the 

 largest, has superiorly an oval facet, for the sacrum, and pos- 

 teriorly two processes (cornua coccygea) which project up- 

 ward to join the sacral cornua. A rudimentary transverse 

 process projects on each side and may join the sacral inferior 

 angle. The second vertebra has only rudimentary transverse 

 processes and pedicles. The lower segments are mere nodules 

 of bone. [86] 



Os Innominatum. Each consists of three, originally sepa- 

 rate, parts (ilium, ischium, and pubis) which have fused in and 

 around the acetabulum. It belongs properly to the lower ex- 

 tremity. [214] 



Ilium. This, the upper part, is a quadrilateral plate. The 

 superior border (crest) curves with a double bend; externally 

 it is convex in front and concave behind. It is thick and pre- 

 sents an outer lip, an inner lip, and an intermediate space; it 

 ends in a pointed process (anterior superior spine) in front, and 

 another (posterior superior spine) behind. The anterior bor- 

 der, descending from the spine to the margin of the acetabulum, 

 is thin above but forms a thick process (anterior inferior spine) 

 below. The posterior border, descending from the spine, is 

 sharp and ends below in a prominent angle (posterior inferior 

 spine) ; in front of this the edge of the bone becomes rounded 

 and curves forward and downward to the acetabulum, forming 

 a wide notch (ilio-sciatic, or great sciatic notch) . [214] 



The external surface is divided into upper (gluteal) and 

 lower (acetabular) parts, the latter forming nearly two-fifths 

 of the acetabulum. The gluteal portion is concavo-convex 

 antero-posteriorly and traversed by three curved ridges (curved 

 lines). The inferior curved line begins just above the ante- 

 rior inferior spine and runs toward the great sciatic notch. 



[184]' 



