THE OS INNOMINATUM. 



173 



it terminates, it becomes less marked, and is often altogether lost. Behind this 

 line is a narrow semilunar surface, the upper part of which is rough and affords 

 attachment to part of the Gluteus maximus ; the lower part is smooth and has no 

 muscular fibres attached to it. The middle curved line, the longest of the three, 

 commences at the crest, about an inch behind its anterior extremity, and, taking a 

 curved direction downward and backward, terminates at the upper part of the great 

 sacro-sciatic notch. The space between the superior and middle curved lines and 



COMPRESSOR URETHR/C. / 



X TRANSVERSUS PERINEI. 

 ERECTOR PENIS. 



Cms penis. 

 FIG. 121. Right os innominatum. Internal surface. 



the crest is concave, and affords attachment to the Gluteus medius muscle. Near 

 the central part of this line may often be observed the orifice of a nutrient foramen. 

 The inferior curved line, the least distinct of the three, commences in front at the 

 notch on the anterior border, and, taking a curved direction backward and down- 

 ward, terminates at the middle of the great sacro-sciatic notch. The surface of 

 bone included between the middle and inferior curved lines is concave from above 

 downward, convex from before backward, and affords attachment to the Gluteus 

 minimus muscle. Beneath the inferior curved line, and corresponding to the upper 



