THE PELVIS AS A WHOLE. 



341 



border become raised from the rest and are inserted into the inner border of the 

 ramus of the ischium, from which they rise in a fold, the falciform ligament, within 

 the pelvis, continuous with the obturator fascia. The ligament at its insertion into 

 the tuberosity is continuous with the fibres of origin of the biceps. 



The lesser or anterior sacro-sciatic ligament ' (Fig. 363), much the smaller, 

 is situated internally to the great, springing from the edge of the sacrum below 

 the junction with the ilium and from the side of the upper part of the coccyx, being 

 more or less continuous with the interior surface of the great. It narrows to its 

 insertion into the spine of the ischium. 



The great sacro-sciatic foramen^ (fig- 362) is bounded above by the ilium, 

 in front by the ilium and the ischium, behind by the great ligament, and below by 

 the lesser. It transmits the pyriformis muscle, the gluteal, sciatic, and internal pudic 

 vessels and nerves, and the nerves to the obturator internus and quadratus femoris. 



The lesser sacro-sciatic foramen^ (Fig- 362) is bounded in front by the 

 body of the ischium, above by the lesser ligament, and below and behind by the 

 oblique border of the great. Through it pass the obturator internus muscle, the 

 internal pudic vessels and nerve, and the nerve to the obturator internus. 



The obturator membrane* (Fig. 363) is attached to the margin of the fora- 

 men of that name, which it completely closes, except for a small space at the top of 

 the groove under the ramus of the pubis. Sometimes there are perforations. The 

 attachment at the inner side is directly to the sharp edge of the rami of the pubis 

 and ischium. At the outer border it passes into the periosteum lining the peh'is. 



THE PELVIS AS A WHOLE. 



The promontory of the sacrum and the ilio-pectineal line separate the true pelvis" 

 below from X\\<i false^ above'. Xhe latter is bounded by the lower lumbar vertebrae 



Fig. 364. 



The pelvis from behind. 



and by the flaring ilia. The true pelvis is bounded by the sacrum and coccyx behind, 

 by the bodies and symphysis of the pubis in front, and by the sacro-sciatic ligaments, 



' Lig. sacrospinosum. - Foram. ischiadicum majus. ^ Foram. isch. minus. * Membraoa obturatoria. ^ Pelvis minor. 

 * Pelvis major. 



