DISSECTION OP THE POSTERIOR LIMB. 69 



The Deep Gluteus, or gluteus internus (Plate 16, and Fig. 2), is 

 placed above the hip-joint, in immediate contact with the capsular 

 ligament. It is a comparatively small muscle, with coarse fasciculi 

 having a slightly spiral direction. It arises from the rough lines on 

 the gluteal surface of the shaft of the ilium just above the cotyloid 

 cavity, and from the supracotyloid ridge (superior ischiatic spine). It 

 is inserted to the inner side of the convexity of the great trochanter. 

 Action. — It is an abductor and inward-rotator at the hip-joint. 

 The Obturator Internus and the Pyriformis (Plate 16, and Fig. 2) 

 are two muscles arising within the pelvis, the former taking origin from 

 the bone around the obturator foramen, and the latter from the pelvic 

 surface of the ilium. They have a common tendon, which emerges from 

 the pelvis by the lesser sacro-sciatic opening, where it plays over a 

 smooth portion on the external border of the ischium. The tendon is 

 inserted into the trochanteric fossa. 



Action. — To produce outward rotation at the hip. 

 The Gbjielli. In Plate 16 a bundle of muscular fibres is seen at 

 each edge of the above-mentioned common tendon. If this common 

 tendon be cut where it appears at the lesser sciatic opening, and raised 

 outwards, what previously seemed two distinct muscular bundles will 

 now be seen to be the edges of a single flattened muscle, which arises 

 from the ischium below and at the edges of the smooth surface for the 

 passage of the common tendon, and becomes inserted in common with 

 that tendon. 1 



Action. — The same as the two preceding muscles. 



Directions. — The tensor vaginse femoris and the gluteus internus 

 should now be out away, care being taken not to injure the capsular 

 ligament, on which the latter muscle rests. The rectus femoris, vastus 

 externus, and rectus parvus are then to be dissected. The last- 

 mentioned muscle will be found by dissecting deeply into the upper part 

 of the interstice between the other two muscles, and at the same point 

 the iliaco-femoral artery will be found. 



The Iliaco-Femoral Artery is one of the terminal branches of the 

 internal iliac (Plate 48). It comes out between the iliacus and the 

 shaft of the ilium, and penetrates between the rectus femoris and 

 the vastus externus. 



The Rectus Femoris (Plate 18) arises by two heads — one from each 

 of the depressions on the shaft of the ilium, above and in front of the 

 cotyloid cavity. The central portion of the muscle is thick and fleshy, 

 and rests in a groove formed by the two vasti, with which it is confounded 

 at its lower extremity. It is inserted into the anterior face of the patella. 



1 In man this muscle consists of two separate slips, and from this disposition it is 

 named. I do not hesitate to give it the same designation here, although I have never 

 found it double as it is usually described. 



