OSTEOLOGY OF BIMANA. 



577 



plane with that of the cotylo-sacral tract of the ilium. In this 

 section, « «' is the line oi fulcrum falling in the transverse vertical 

 plane of the trunk ; c c' is the line of iveiglit passing through the 

 centre of the sacro-iliac joint ; b b' is the line of power, or pubic 

 projection, giving attachment to the extensor muscles of the thio-h ; 

 d d' is the line of sacral projection ; e f gives the ' cotylo-sacral 



400 401 



Section through cotylo-sacral arch : Human 

 pelvis, cv. 



Angles of inclination and axes : Female pelvis, cv, 



curve; ' a' Z*' is the pubic arm of the lever; a' c^ is the cotylo- 

 sacral arm ; a' d' gives the length of the gluteal arm ; c' d' that 

 of the posterior spinal arm. In the diagram, fig. 401, the lines 

 a e, e c, mark the angle of inclination of the pelvis, or the ' pelvi- 

 vertebral angle ; ' f g d gives the inferior angle of inclination of 

 the pelvis, which is about 10° with the horizon, y d. The two 

 lines of the superior and inferior planes, when prolonged ante- 

 riorly, cut each other at c, and include an angle of about 50°, 

 e cf. The ' sacro-vertebral angle ' is shown at « <? i, which is 

 about 117° in the male and 130° in the female. The angle abk, 

 VOL. rr. r r 



