246 ANTERIOR FEMORAL REGION. 



pelvis, with the gemellus superior. By its lower border witn the gemellus 

 inferior. 



The GEMELLUS INFERIOR arises from the posterior point of the tuberosity 

 of the ischium, and is inserted into the lower border of the tendon of thn 

 obturator internus, and into the trochanteric fossa of the femur. 



Relations. By its superficial surface with the gluteus maximus, and 

 ischiatic vessels and nerves. By its deep surface with the external surface 

 of the pelvis, and capsule of the hip joint. By its upper border with the 

 tendon of the obturator internus. By its lower border with the tendon of 

 the obturator externus and quadratus femoris. 



In this region the tendon only of the obturator externus can be seen, 

 situated deeply between the gemellus inferior and the upper border of the 

 quadratus femoris. To expose this muscle fully, it is necessary to dissect 

 it from the anterior part of the thigh, after the removal of the pectineus, 

 adductor longus and adductor brevis muscles. 



The OBTURATOR EXTERNUS muscle (obturare, to stop up) arises from 

 the obturator membrane, and from the surface of bone immediately sur- 

 rounding it anteriorly, viz. from the ramus of the os pubis and ischium : 

 its tendon passes behind the neck of the femur, to be inserted with the 

 external rotator muscles, into th'e trochanteric fossa of .the femur. 



Relations. By its superficial or anterior surface with the tendon of the 

 psoas and iliacus, pectineus, adductor brevis and magnus, the obturator 

 vessels and nerve. By its deep or posterior surface with the obturatoi 

 membrane and the margin of bone which surrounds it, the lower part of 

 the capsule of the hip joint and the quadratus femoris. 



The QUADRATUS FEMORIS (square-shaped) arises from the external bor 

 der of the tuberosity of the ischium, and is inserted into a rough line on 

 the posterior border of the trochanter major, which is thence named linea 

 quadrati. 



Relations. By its posterior surface with the gluteus maximus, and is- 

 chiatic vessels and nerves. By its anterior surface with the tendon of the 

 obturator externus, and trochanter minor, a synovial bursa often separating 

 it from the latter. By its upper border with the gemellus inferior ; and by 

 the lower border w r ith the adductor magnus. 



Actions. The glutei muscles are abductors of the thigh, when they 

 take their fixed point from the pelvis. Taking their fixed point from the 

 thigh, they steady the pelvis on the head of the femur ; this action is pe- 

 culiarly obvious in standing on one leg ; they assist also in carrying the 

 leg forward, in progression. The gluteus minimus being attached to the 

 anterior border of the trochanter major, rotates the limb slightly inwards. 

 The gluteus medius and maximus, from their insertion into the posterior 

 aspect of the bone, rotate the limb outwards ; the latter is, moreover, a 

 tensor of the fascia of the thigh. The other muscles rotate the limb out- 

 wards, everting the knee and foot ; hence they are named external rotators. 



./Interior Femoral Region. 



Tensor vaginae femoris, Vastus internus, 



Sartorius, Vastus externus, 



Rectus, Crureus. 



Dissection. Make an incision along the line of Poupart's ligament, 

 r rom the anterior superior spinous process of the ilium to the spine of the 



