THE PELVIS 



239 



the parietes of the abdomen; behind is a deep notch on either side between the ilium 

 and the base of the sacrum.' It supports the intestines, and transmits part of their 

 weight to the anterior wall of the abdomen. 



The Lesser or True Pelvis (pelvis minor). The lesser pelvis is that part of the 

 pelvic cavity which is situated below and behind the pelvic brim. Its bony walls 

 are more complete than those of the greater pelvis. For convenience of descrip- 

 tion, it is divided into an inlet bounded by the superior circumference, and outlet 

 bounded by the inferior circumference, and a cavity. 



The Superior Circumference. The superior circumference forms the brim of the 

 pelvis, the included space being called the superior aperture or inlet (apertura pelvis 

 [minoris] superior) (Fig. 238). It is formed laterally by the pectineal and arcuate 

 lines, in front by the crests of the pubes, and behind by the anterior margin of the 

 base of the sacrum and sacrovertebral angle. The superior aperture is somewhat 

 heart-shaped, obtusely pointed in front, diverging on either side, and encroached 

 upon behind by the projection forward of the promontory of the sacrum. It has 

 three principal diameters: antero-posterior, transverse, and oblique. The antero- 

 posterior or conjugate diameter extends from the sacrovertebral angle to the sym- 





Fro. 238. Diameters of superior aperture of lesser pelvis (female). 



[hysis pubis; its average measurement is about 110 mm. in the female. The 

 transverse diameter extends across the greatest width of the superior aperture, 

 from the middle of the brim on one side to the same point on the opposite; its aver- 

 age measurement is about 135 mm. in the female. The oblique diameter extends 

 from the iliopectineal eminence of one side to the sacroiliac articulation of the 

 opposite side; its average measurement is about 125 mm. in the female. 



The cavity of the lesser pelvis is bounded in front and below by the pubic sym- 

 physis and the superior rami of the pubes; above and behind, by the pelvic surfaces 

 of the sacrum and coccyx, which, curving forward above and below, contract 

 the superior and inferior apertures of the cavity; laterally, by a broad, smooth, 

 quadrangular area of bone, corresponding to the inner surfaces of the body and 

 superior ramus of the ischium and that part of the ilium which is below the arcuate 

 l ; ne. From this description it will be seen that the cavity of the lesser pelvis 

 is a short, curved canal, considerably deeper on its posterior than on its anterior 

 vrall. It contains, in the fresh subject, the pelvic colon, rectum, bladder, and some 

 of the organs of generation. The rectum is placed at the back of the pelvis, in 

 the curve of the sacrum and coccyx; the bladder is in front, behind the pubic sym- 

 physis. In the female the uterus and vagina occupy the interval between these viscera. 



