THE PELVIS. 103 



sides, by the bodies of the ischia and a small part of the ilia ; 

 and, in front, only by the length of the bodies of the pubes. 



The upper orifice of the lesser pelvis is called its superior 

 strait: it is somewhat oval, and looks obliquely forwards and 

 upwards. Its axis may be indicated by a line drawn from the 

 extremity of the coccyx to a point an inch, or thereabouts, be- 

 low the umbilicus. The inferior orifice of the lesser pelvis is 

 called the inferior strait. Its margins in the naked skeleton are 

 very unequal, for it presents three very deep notches, two late- 

 rally, and one in front. The first are formed by the external 

 margins of the sacrum and coccyx, contributing to deepen the 

 sciatic notch, which already is formed in each os innominatum- 

 The third one is formed by the convergence of the rami of 

 the pubes and ischia of the opposite sides, and constitutes the 

 arch of the pelvis of authors, sometimes called the arch of the 

 pubes. The axis of the lower strait, it is clear, must have 

 a very different direction from the axis of the superior, and 

 is indicated by a line drawn from the lower part of the first 

 bone of the sacrum, through the centre of this opening. The 

 cavity of the lesser pelvis is increased considerably behind, by 

 the curvature of the sacrum; this, however, is not uniform, as 

 the sacrum is much more curved, as well as longer in some indi- 

 viduals than in others. The planes of the ischia are not paral- 

 lel with one another, but converge slightly from above, in con- 

 sequence of which the transverse diameter of the lower strait is 

 rather smaller than the transverse diameter of the superior strait. 



Difference of the Pelvis in the Male and Female. 



There are several well marked peculiarities in the fully de- 

 veloped pelvis of either sex. 



The ossa ilia are larger, less concave, and more horizontal in 

 the female. The superior strait is also larger, and more round: 

 its transverse diameter always exceeds the antero-posterior; 

 whereas, the latter, in the male, frequently is found the longest. 

 The lesser pelvis is also more capacious in women. The crura 

 of the pubes and ischia, are not so long as in men; but they di- 

 verge more, and join at the under part of the symphysis pubis 

 by a large, regularly rounded arch; whereas, in men, the arch 

 as it is called, is merely an acute angle. 



