186 



THE SKELETON. 



OBTURATOR EXTERNUS. 



Fn;. 127. Right femur. Posterior surface. 



middle of the posterior intertro- 

 chanteric line, and passes vertically 

 downward for about two inches 

 along the back part of the shaft : 

 it is called the linea quadrati, and 

 gives attachment to the Quadra tus 

 femoris and a few fibres of the Ad- 

 ductor magnus muscles. 1 



The Shaft, almost cylindrical in 

 form, is a little broader above than 

 in the centre, and somewhat flat- 

 tened below, from before backward. 

 It is slightly arched, so as to be 

 convex in front and concave be- 

 hind, where it is strengthened by 

 a prominent longitudinal ridge, the 

 linea aspera. It presents for ex- 

 amination three borders, separating 

 three surfaces. Of the three bor- 

 ders, one, the linea aspera, is pos- 

 terior ; the other two are placed 

 laterally. 



The linea aspera (Fig. 127) is 

 a prominent longitudinal ridge or 

 crest, on the middle third of the 

 bone, presenting an external lip, 

 an internal lip, and a rough inter- 

 mediate space. Above, this crest 

 is prolonged by three ridges. The 

 most external one is very rough, 

 and is continued almost vertically 

 upward to the base of the great 

 trochanter. It is sometimes termed 

 the c/luteal ridge, and gives attach- 

 ment to part of the Gluteus maxi- 

 mus muscle ; its upper part is often 

 elongated into a roughened crest, 

 on which is a more or less well- 

 marked, rounded tubercle, a rudi- 

 mental third trochanter. The mid- 

 dle ridge, the least distinct, is 

 continued to the base of the tro- 

 chanter minor, and the internal 

 one is lost above in the spiral line 

 of the femur. Below, the linea 

 aspera is prolonged by two ridges, 

 which enclose between them a tri- 

 angular space, the popliteal surface, 

 upon which rests the popliteal ar- 

 tery. Of these two ridges, the outer 

 yr tendon of one j s the more prominent, and de- 



1 Generally there is merely a slight 

 thickening about the centre of the inter- 

 trochanteric line, marking the point of 

 attachment of the Qnadratus femoris. This 

 is termed by some anatomists the tubercle 

 of the Quiiclratuf. 



