4io ABDOMEN 



brim. The margin of this plane is the linea terminalis which 

 is separable into sacral, iliac, and pubic portions. The sacral 

 part of the linea terminalis is formed by the upper border 

 of the anterior surface of the first sacral vertebra and the 

 anterior margins of the ulae of the sacrum. The ilio-pectineal 

 lines of the iliac and pubic bones and the crest of the pubic 

 bones constitute the iliac and pubic portions. The part 

 above the plane is the pelvis major (O.T. false pelvis), which 

 has already been studied as part of the abdomen. The part 

 below the plane is the pelvis minor (O.T. true pelvis). The 

 inner aspect of the wall of the pelvis minor is partially 

 covered by the following muscles. Posteriorly, on the front 

 of the sacrum, are the two piriformes muscles. Laterally, 

 on the inner surface of each hip bone, is the obturator internus 

 muscle. Anteriorly is the urq-genital diaphragm, formed by the 

 deep transverse perineal muscles and the sphincter urethra, 

 membranacetz. The inner surfaces of the muscles mentioned 

 and the intervening skeletal structures are covered by a con- 

 tinuous layer of fascia, the parietal pelvic fascia. The wall 

 of the pelvis minor may, therefore, be regarded as consisting 

 of three strata, viz. i. A bony stratum. 2. A muscular 

 stratum. 3. A membranous stratum. 



The pelvis minor is separated into an upper part and a 

 lower part by the pelvic diaphragm and the fascia covering 

 it. The pelvic diaphragm is formed by the two levatores ani 

 and the two coccygei muscles. In the following account the 

 upper part will be spoken of as the pelvis minor. The lower 

 part has already been called the perineum. 



The pelvis minor, as thus defined, is the smaller, basin- 

 shaped, lower part of the abdominal cavity above the pelvic 

 diaphragm. It communicates with the upper portion through 

 a somewhat constricted aperture, the superior aperture of the 

 pelvis minor. 



The contents of the pelvic cavity differ in the two sexes \ 

 in both, however, the bladder occupies the anterior part of the 

 space, and the rectum and pelvic colon the posterior part. 

 The difference is to be found in the generative organs and 

 their blood-vessels. It is necessary, therefore, to describe 

 the male and the female pelvis minor separately. 



