THE PELVIS. 



179 





the internal surface below the linea ilio-pectinea, the Obturator internus to the 

 internal surface of the posterior superior spine, and the Multifidus spinse ; to the 

 anterior border, the Sartorius and straight tendon of the Rectus. To theischium, 

 thirteen. To the outer surface of the ramus, the Obturator externus and Adductor 

 magnus ; to the internal surface, the Obturator internus and Erector penis. To the 

 spine, the Gemellus superior, Levator ani, and Coccygeus. To the tuberosity, the 

 Biceps, Semitendinosus, Seinimembranosus, Quadratus femoris. Adductor magnus, 

 Gemellus inferior, Transversus perinsei, Erector penis. To the os pubis, sixteen: 

 Obliquus externus, Obliquus internus, Transversalis, Rectus, Pyramidalis, Psoas 

 parvus, Pectineus, Adductor magnus, Adductor longus, Adductor brevis, Gracilis, 

 Obturator externus and internus, Levator ani, Compressor urethrae, and occasion- 

 ally a few fibres of the Accelerator urinae. 



The Pelvis (Figs. 123, 124). 



The Pelvis, so called from its resemblance to a basin (L. pelvis), is stronger 

 and more massively constructed than either the cranial or thoracic cavity ; it is a 

 bony ring, interposed between the lower end of the spine, which it supports, and 

 the lower extremities, upon which it rests. It is composed of four bones : the two 

 ossa innominata, which bound it on either side and in front, and the sacrum and 

 coccyx, which complete it behind. 



The pelvis is divided by an oblique plane passing through the prominence of 

 the sacrum, the linea ilio-pectinea, and the upper margin of the symphysis pubis 

 into the false and true pelvis. 



The false pelvis is the expanded portion of the pelvic cavity which is situated 

 above this plane. It is bounded on each side by the ossa ilii ; in front it is 



FIG. 123. Male pelvis (adult). 



incomplete, presenting a wide interval between the spinous processes of the ilia 

 on either side, which is filled up in the recent state by the parietes of the abdomen ; 

 behind, in the middle line, is a deep notch. This broad, shallow cavity is fitted 

 to support the intestines and to transmit part of their weight to the anterior wall 

 of the abdomen, and is, in fact, really a portion of the abdominal cavity. The 

 term false pelvis is incorrect, and this space ought more properly to be regarded 

 as part of the hypogastric and iliac regions of the abdomen. 



The true pelvis is that part of the pelvic cavity which is situated beneath the 



