THE BONES OF THE LOWER LIMB 23 1 



upper border of the symphysis pubis. The brim is therefore directed 

 upwards and forwards. An idea of this obliquity may be obtained 

 by placing a pelvis against a wall in such a way that the anterior 

 superior iliac spines and the upper border of the symphysis pubis 

 will touch the wall so as to lie in the same vertical plane. A line 

 connecting the tip of the cocc5rx with the lower border of the 

 symphysis pubis forms with the horizontal an angle of about 11 

 degrees, and the tip of the coccyx is about f inch above the sub- 

 pubic angle. The direction of the outlet is downwards and back- 

 wards, principally downwards when the coccyx is extended. The 

 plane of the symphysis pubis forms with the horizontal an angle 

 of from 35 to 40 degrees. It is worthy of note that the sacro- 

 vertebral angle is estimated at 117 degrees in the male, and as 

 much as 130 in the female. 



The Axes of the Pelvis. — ^The axes represent imaginary lines 

 intersecting the planes of the brim, ca\aty, and outlet at right angles 

 through their central points. The axis of the brim corresponds 

 with a line drawn from the umbihcus to the sacro-coccygeal articu- 

 lation, and its direction is downwards and distinctly backwards. 

 The axis of the outlet represents a line drawn from the sacral 

 promontory through the centre of the outlet, and its direction is 

 downwards and very slightly backwards. The axis of the cavity 

 intersects planes having different inclinations, and is necessarily 

 cvu^ved, the concavity being directed forwards. It is described as 

 ' the perpendicular of a line drawn from the middle of the symphysis 

 pubis to the centre of the sacro-coccygeal curve.' The average 

 measurements of the axes of the female pelvis are as follows : 



Conjugate. Transverse. ObUqnei 



Brim 4i 5i 5 



Cavity 5 5 5 J 



Outlet 5 4I 4I 



Sexual Differences. — ^The differences in the two sexes are as 

 follows : 



Female. Male. 



Bones smoother and more slender. Bones rougher and more massive 



Acetabula wide apart. Acetabiila not so wide apart. 



True pelvis wider and shallower. True pelvis narrower and deeper. 



Obturator foramen triangular. Obturator foramen oval. 



Ischial tuberosities ^^^der apart and Ischial tuberosities not so wide apart 



everted. and inverted. 



Span of subpubic arch wide. " Span of subpubic arch narrow. 



Inner border of ischio-pubic ramus Inner border of ischio-pubic ramus 



comparatively smooth. strongly marked and everted. 



Brim transversely ovzd. Brim cordate. 



Ilia more vertical. Ilia less verticaL 



False pelvis narrower. False pelvis wider. 



Sacral promontory less projecting. Sacral promontory more projecting. 



Sacrum broader, shorter, and Sacrum narrower, longer, and more 



straighten curved. 



Coccyx more movably articulated Coccyx less movably articulated 



with sacrum. with sacrum. 



Symphysis pubis shallower. - Symphysis pubis deeper. 



