QUADRATUS AND OBTURATOR EXTERNUS. 



591 



ratus (in this position of the body) to the pit of the trochanter, where it 

 anastomoses with the gluteal and sciatic arteries, and supplies the bone. 

 The other (A) passes between the quadratus and adductor magnus to 

 the hamstring muscles, and communicates with a branch of the profunda 

 artery. 



The OBTURATOR EXTERNUS (fig. 201, L ) has been dissected at its origin 

 in the front of the thigh (p. 580). The part of the muscle now laid bare, 

 winds below the hip-joint, and ascends to be inserted into the pit at the 

 root of the great trochanter. 



Fig. 201. 



Muscles. 



A. Gluteus maximus, cut. 



B. Tensor fasciae latse. 



c. Gluteus minimus. 



D. Gluteus medius, cut. 



F. Pyiiformis. 



G. Gemellus superior 



H. Obturator intei nus, cut. 

 I. Gemellus inferior. 

 K. Quadratus femoris, cut. 

 L. Obturator exteruus. 

 N. Adductor magnus. 



0. Hamstrings. 



p. Great sacro-sciatic lig-a- 



ment. 

 Arteries. 

 a. Gluteal. 



6. Its upper and, and c, its 

 lower piece. 



d. Sciatic. 



e. Pudic. 



/. Iiiternal circumflex ; g, 

 its ascending, and /i, its 

 transverse offset. 



t'. First perforating. 



Jr. External circumflex. 

 Nerves. 



1. Superior gluteal. 



2. Sacral. 



3. Small sciatic, cut. 



4. Pudic. 



5. Nerve to obturator inter- 



ims. 



6. Nerve to quadratus and 



inferior gemellus. 



7. Nerve to upper gemellus. 



8. Large sciatic nerve. 



THIRD VIEW OF THE DISSECTION OF THE BUTTOCK (Illustrations of Dissections). 



On the back of the pelvis the obturator externus is covered by the quad- 

 ratus, except near the femur where the upper border is in contact with 

 the inferior gemellus. As it turns back to its insertion it supports the 

 hip-joint. 



Action. Like the other muscles of the same group it rotates out the 

 hanging limb ; but it differs from them in having the same action even 

 when the hip-joint is bent. 



With the limb fixed, Theile supposes it to help in bending the hip-joint 



