GLUTEUS MINIMUS AND PYRIFORMIS. 587 



head of the rectus femoris muscle. The anterior border lies by the side of 

 the other gluteus; and the posterior is covered by the pyriformis muscle. 

 A bursa is placed between the tendon and the bone. 



Action. It acts as an abductor and rotator out of the femur when this 

 bone is hanging; and in walking, it and the medius will be employed in 

 bringing forwards the limb. 



Both legs being fixed, the muscles are used in balancing the pelvis. In 

 standing on one leg the gluteus pitches the pelvis over the supporting 

 limb with the preceding muscle. 



Dissection. Cut through the smallest gluteus muscle near the innomi- 

 nate bone, and define the tendinous part of the rectus femoris underneath 

 it, close above the hip joint. Whilst detaching the gluteus from the parts 

 underneath, the student cannot fail to notice the connection between its 

 tendon and the capsule of the joint. 



The deep vessels to the articulation may be observed and followed as 

 the muscle is removed. 



The outer head of the rectus femoris is a tendon as wide as the little 

 finger, and about two inches long, which is fixed into the groove above 

 the margin of the acetabulum. In front it joins the other tendinous piece 

 of the rectus, which is attached to the anterior inferior iliac spine; and 

 balow, it is connected with the capsule of the hip joint. 



The PYRIFORMIS (fig. 200, B ) arises in the pelvis from the front of the 

 sacrum (p. 542), and leaves that cavity through the great sacro-sciatic 

 notch. Outside the pelvis it ends in a rounded tendon, which is inserted 

 into the upper edge of the great trochanter, between the two smaller 

 glutei. 



As the muscle passes through the sacro-sciatic notch it divides that 

 space into two parts the upper giving passage to the gluteal vessels and 

 nerve, and the lower transmitting the sciatic and pudic vessels and the 

 sacral plexus. Its upper border is contiguous to the gluteus medius, and 

 its lower, to the gemellus superior. Like the other rotator muscles in this 

 situation, it is covered by the gluteus maximus, and by the gluteus medius 

 at the insertion ; it rests on the gluteus minimus, which separates it from 

 the hip joint. Its tendon is united by fibrous tissue to that of the obturator 

 and gemelli. 



Action. The use of this and the other external rotators is altered by 

 the position of the femur. If that bone hangs the pyriformis rotates it 

 out ; but if the hip joint is bent the muscle abducts the limb from its 

 fellow. 



Both limbs being fixed the muscles balance the pelvis, and help to make 

 the trunk erect after stooping to the ground. In standing on one leg, 

 besides assisting to support the trunk, the pyriformis turns the face to the 

 opposite side. 



Dissection (fig. 201). The pyriformis may be cut across and raised 

 towards the sacrum, to allow the dissector to follow upwards the sciatic 

 and pudic vessels, and to trace the accompanying nerves to their origin in 

 the lower part of the sacral plexus. 



Some small nerves to the obturator iriternus ( 5 ), the gemellus superior 

 ( 7 ), and the hip joint, are to be sought in the fat at the lower part of the 

 plexus. A branch to the inferior gemellus and the quadratus ( 6 ) will be 

 found by raising the trunk of the great sciatic nerve ; but it will be fol- 

 lowed to its termination after the muscles it supplies have been seen. 



