ANATOMY IN A NUTSHELL. 143 



Gluteus minimus. — Description. — (Plate LXV.) — This muscle is situated 

 immediately beneath the Gluteus medius. It is the smallest of the three Gluteal 

 muscles. There is a synovial bursa between its tendon and the great trochanter. 



Origin. — (Plates XLI1I-XLV.) — Outer surface of ilium, between the middle 

 and inferior curved lines, and from the margin of the sacro-sciatic notch. 



Insertion. — (Plate XLVIII.) — Into an impression on anterior border of 

 great trochanter. 



Action. — Adducts the extended thigh, rotates same and supports body 

 on limb. 



Nerve Supply. — Superior gluteal. 



Blood Supply. — Superior gluteal and external circumflex. 



Pyriformis. — Description. — (Plate LXV.) — This muscle is a flat pyra- 

 midal one situated partly within the pelvis at its posterior part and partly at 

 the back of the hip-joint. It lies parallel with the posterior borderof the Glu- 

 teus medius. It passes out of the pelvis through the great sacro-sciatic foramen, 

 thus dividing it into two compartments. The superior gluteal nerve and the 

 gluteal vessels leave the pelvis above this muscle. Below this muscle the in- 

 ferior gluteal nerve, the sciatic vessels and nerves, internal pudic vessels and 

 nerve, and nerves to the Obturator internus and the Quadratus femoris leave 

 the pelvis. 



Origin. — (Plate XLVI.) — Front of sacrum by three fleshy digitations at- 

 tached to the portions of the bone between the first, second, third and fourth 

 anterior sacral foramina, and also from the groove leading from the foramina; 

 also from the margin of the great sacro-sciatic foramen, and from the anterior 

 surface of the great sacro-sciatic ligament. 



Insertion. — (Plate XLIX.) — Upper border of great trochanter behind, 

 and partly blended with, the tendon of the Obturator interims and (iemelli 

 muscles. 



Action. — Draws pelvis forward when inclined backward and assists in 

 steadying it upon the head of the femur." 



Nerve Supply. — First and second sacral nerves. 



Blood Supply. — Sciatic. 



Obturator internus. — Description. — (Plate LXV.) — This muscle, like the 

 Pyriformis, is situated partly within the pelvis and partly at the hack of the hip- 

 joint. The inner surface of the tuberosity of the ischium is grooved for the re- 

 ception of the four or five tendinous bands which are on the deep surface of the 

 muscle. These grooves are covered with cartilage and lined by a synovia] bursa. 

 These tendinous bands unite into a flattened tendon which passes horizontally 

 outward to its insertion. Between the capsular ligament of the hip and the 

 tendon of this muscle is a bursa, which generally communicates with the bursa 

 between the tendon and the tuberosity of the ischium, the two bursa making 

 one sac. It leaves the | dvis through the lesser sacro-sciatic foramen. 



Origin. — (PL- e XLIY.) — From the inner surface of anterior and external 

 wall of pelvis. it surrounds the greater part of the obturator foramen being 



attached to the 'i scending ramus of the os pubis and ramus of ischium, and at 

 theside to the inner surface of the innominate bone below andbehind thepelvic 



