THE GLUTEAL REGION. 517 



angle over the inner surface of the tuberosity of the ischium, which is grooved for 

 their reception : the groove is covered with cartilage and lined with a synovial 

 bursa. The muscle leaves the pelvis by the lesser sacro-sciatic notch, and the 

 tendinous bands unite into a single flattened tendon, which passes horizontally 

 outward, and, after receiving the attachment of the Gemelli, is inserted into the 

 inner surface of the great trochanter in front of the Obturator externus. A 

 synovial bursa. narrow and elongated in form, is usually found between the tendon 

 of this muscle and the capsular ligament of the hip : it occasionally communicates 

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

 forming a single sac. 



In order to display the peculiar appearances presented by the tendon of this muscle, it must 

 be divided near its insertion and reflected outward. 



Relations. Within the pelvis this muscle is in relation, by its anterior surface, 

 with the obturator membrane and inner surface of the anterior wall of the pelvis; 

 by its posterior surface* with the pelvic and obturator fasciae, which separate it from 

 the Levator ani ; and it is crossed by the internal pudic vessels and nerve. This 

 surface forms the outer boundary of the ischio-rectal fossa. External to the pelvis 

 it is covered by the great sciatic nerve and Gluteus maximus, and rests on the back 

 part of the hip-joint. 



The Gemelli are two small muscular fasciculi, accessories to the tendon of the 

 Obturator internus, which is received into a groove between them. They are called 

 superior and inferior. 



The Gemellus superior, the smaller of the two, arises from the outer surface 

 of the spine of the ischium, and. passing horizontally outward, becomes blended 

 with the upper part of the tendon of the Obturator internus, and is inserted with 

 it into the inner surface of the great trochanter. This muscle is sometimes 

 wanting. 



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

 sciatic vessels and nerves ; by its deep surface, with the capsule of the hip-joint ; 

 by its )ipp> r }'r<l>:r. with the lower margin of the Pyriformis ; by its lower border, 

 with the tendon of the Obturator internus. 



The Gemellus inferior arises from the upper part of the tuberosity of the 

 ischium. where it forms the lower edge of the groove for the Obturator internus 

 tendon, and, passing horizontally outward, is blended with the lower part of the 

 tendon of the Obturator internus, and is inserted with it into the inner surface of 

 the great trochanter. 



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

 sciatic vessels and nerves ; by its deep surface, with the capsular ligament 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. 



The Quadratus femoris is a short, flat muscle, quadrilateral in shape (hence 

 its name), situated between the Gemellus inferior and the upper margin of the 

 Adductor magnus. It arises from the external lip of the tuberosity of the ischium, 

 and. proceeding horizontally outward, is inserted into the upper part of the linea 

 quadrati : that is. the line which crosses the posterior intertrochanteric line. A 

 synovial bursa is often found between the under surface of this muscle and the 

 lesser trochanter. to which it extends. 



Relations. By its posterior surface, with the Gluteus maximus and the sciatic 

 vessels and nerves ; by its anterior surface, with the tendon of the Obturator 

 externus and trochanter minor and with the capsule of the hip-joint ; by its 

 upper border, with the Gemellus inferior. Its lower border is separated from the 

 Adductor magnus by the terminal branches of the internal circumflex vessels. 



Dissection. In order to expose the next muscle (the Obturator externus), it is necessary 

 to remove the Psoas. Iliacus, Pectineus, and Adductor brevis and longus muscles from the front 

 and inner side of the thigh, and the Gluteus maximus and Quadratus femoris from the back 

 part. Its dissection should, consequently, be postponed until the muscles of the anterior and 

 internal femoral regions have been explained. 



