The Lower Extremity and Pelvis 



121 



PELVIS. 



Notice first of all the position of the pelvis : it is placed so that the cavity it 

 encloses opens forwards as well as upwards, and the ilio-pectineal lines on the innomi- 

 nate bones are directed obliquely downwards and forwards. This, combined with the 



crest". 



Anf-sup.jp. 



auricular surface 

 Qartiiulaf) 



Hio-pecKneal line 



falrijorm line 



FIG. 98. Right innominate bone from the inner side. 



direction of the sacrum, produces the position of the whole pelvis that is often described 

 as " oblique." 



The cavity is divided into two parts by an oblique plane that corresponds with the 

 level of the ilio-pectineal lines. These lines, with the promontory of the sacrum 

 behind and the upper part of the pubes in front, constitute what is termed the brim 

 of the pelvis, and the cavity below the level of the brim is that of the true pelvis, while 

 the expanded and open portion above the brim forms the abdominal or false pelvis : 

 it is really a part of the true abdominal cavity. 



The passage through the level of the brim into the true pelvis is called the inlet 

 or upper aperture of that cavity, and the lower opening is termed the outlet or lower 



