300 THE INFERIOR EXTREMITY 



divided and the peculiarities of its deep surface have been 

 examined (see p. 293). 



M. Quadratus Femoris. The quadratus femoris lies 

 between the gemellus inferior and the adductor magnus. It 

 arises from the lateral border of the ischial tuberosity, and 

 proceeds horizontally to gain insertion into the quadrate 

 tubercle, and into a line which extends distally from it, on 

 the back of the femur, for about two inches (Figs. 121, 122). 



Dissection. The nerve to the quadratus femoris should now 

 be traced to its termination. It lies deep to the two gemelli, 

 the obturator internus, and the quadratus femoris. The obtu- 

 rator internus has already been divided. Now divide the two 

 gemelli muscles, lateral to the nerve. Raise the medial parts 

 and follow the nerve behind them. As the inferior gemellus 

 is approached secure the twig which the nerve supplies to it. 

 Lastly, divide the flat quadratus femoris, midway between the 

 tuberosity of the ischium and the femur and throw the two parts 

 aside. When the dissection is completed not only is the whole 

 length of the nerve to the quadratus femoris exposed, but also a 

 considerable portion of the posterior aspect of the capsule of the 

 hip joint is laid bare ; further, part of the obturator externus 

 muscle, the termination of the medial circumflex artery, and 

 the insertion of the ilio-psoas are brought into view. The 

 exposed posterior part of the capsule of the hip joint consists 

 largely of circularly arranged fibres. 



Nerve to the Quadratus Femoris. The small nerve to 

 the quadratus femoris runs distally on the hip bone and 

 passes successively anterior to the following structures : the 

 sciatic nerve, the gemellus superior, the tendon of the obturator 

 internus, the gemellus inferior. It gives the nerve of supply 

 to the gemellus inferior and a twig to the hip joint, and ends 

 by sinking into the deep surface of the quadratus femoris. 



M. Obturator Externus. The terminal part of the obturator 

 externus muscle can now be seen winding round the neck of 

 the femur. It ends in a rounded tendon which is implanted 

 into the fossa trochanterica of the femur (Fig. 122, p. 271). 

 Its origin has already been examined (p. 277). 



Arteria Circumflexa Femoris Medialis. The medial cir- 

 cumflex artery comes to an end at the proximal border of 

 the adductor magnus by dividing into its ascending and trans- 

 verse terminal branches. The ascending branch runs obliquely 

 upwards and laterally, anterior to the quadratus femoris 

 and upon the posterior surface of the obturator externus. 

 Its terminal twigs ramify in the neighbourhood of the 

 trochanteric fossa, where they anastomose with twigs from 



