650 ABDOMEN 



The pelvic portions of the sympathetic cords are 

 described on p. 609. 



The position and constitution of the coccygeal body 

 are given on p. 609. 



THE PELVIC DIAPHRAGM. 



This is described on pp. 556, 604. The dissector should 

 note that the levator ani muscle passes downwards and back- 

 wards and that it gives support to the lateral border of the 

 vagina ; he should note also that the anterior borders of 

 the two levatores ani muscles embrace the lower part of the 

 vagina very closely, and exert a sphincter action upon it. 



Dissection. After he has studied the pelvic diaphragm the dissector 

 should remove the levator ani to display the obturator interims, and 

 examine the attachment and arrangement of that muscle (see p. 612). He 

 should then study the piriformis (see p. 612), and should complete his 

 dissection of the pelvis by an examination of the pelvic articulations. 



The Pelvic Articulations. These are described at p. 612. 

 In the later months of pregnancy the ligamentous structures 

 of the various pelvic joints become softened and thickened 

 by the infiltration of fluid. The pelvic bones are thus 

 separated from each other to some extent, and the calibre 

 of the pelvic canal is increased in preparation for the passage 

 of the child. 



