THE CW INNOMINATUM 



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to the upper part of the acetabulum, is a roughened surface (sometimes a depres- 

 sion), from which arises the reflected tendon of the Rectus femoris muscle. 



The lower or acetabular part of the external surface enters into the formation 

 of the acetabulum, of which it forms rather less than two-fifths. It is separated 

 from the gluteal portion by a prominent rim, which forms part of the margin 

 of the acetabular cavity. 



TRANSVERSUS PERINEI. 

 ERECTOR PENIS. 



COMPRESSOR URETHRAE./ 



Crus penis. 

 FIG. 168. Right os innominatum. Internal surface. 



The internal surface (Fig. 168) is bounded above by the crest; below it is con- 

 tinuous with the pelvic surface of the os pubis and ischium, a faint line only 

 indicating the place of union; and before and behind it is bounded by the 

 anterior and posterior borders. It presents a large, smooth, concave surface, 

 called the iliac fossa (fossa iliaca), which lodges the Iliacus muscle, and presents 

 at its lower part the orifice of a nutrient canal, and below this a smooth, rounded 

 border, the iliopectinal line (linea arcuata}, which separates the iliac fossa from that 



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