THE LOWER LIMB 



473 



The adductor muscles come into action.in riding upon horseback, enabling 

 the rider to grasp the saddle with his thighs, and they are hence called ' the 

 rider's muscles.' In this act the adductor longus is specially subjected to 

 strain, and its narrow round tendon of origin is occasionally ruptured. At 

 the seat of rupture ossification sometimes takes place, thus giving rise to the 

 so-caUed ' rider's bone.' 



Obturator Externus — Origin. — (i) The external surface of the 

 obturator membrane over its inner half ; (2) the adjacent portion of 



Obturator Externus 

 Quadntus Femoris 



Adductor Brevis 



k 



_ Adductor Magnus 



Toidon of Adductor Magnus 



Fig. 232. — The Right Internal Femoral Muscles (.\nterior View). 

 I, 2, 3, 4, Openings for the Perforating Arteries. 



the anterior or femoral surface of the body of the os pubis ; and 

 !3) the front of the ischio-pubic ramus close to the obturator fora- 

 men. 



Insertion. — The digital or trochanteric fossa of the femur. 



Xerve-supply. — ^The deep or posterior division of the obturator 

 nerve as it passes through the upper part of the muscle. 

 : Action. — The muscle is an external rotator and adductor of the 



fhigh. 



