334 MUSCLES AND FASCIA. 



an angular interval is left, tendinous in front, fleshy behind, for the passage of 

 the femoral vessels into the popliteal space. The external portion of the muscle 

 is pierced by four apertures ; the three superior, for the three superior perforating 

 arteries, the fourth for the passage of the profunda. This muscle gives off an 

 aponeurosis, which passes in front of the femoral vessels, and joins with the Vastus 

 internus. 



Relations. By its anterior surface, with the Pectineus, Adductor brevis, Adduc- 

 tor longus and the femoral vessels. By its posterior surface, with the great 

 sciatic nerve, the Gluteus maximus, Biceps, Semi-teudinosus, and Semi-membra- 

 nosus. By its superior or shortest border, it lies parallel with the Quadratus 

 femoris. By its internal or longest border, with the Gracilis, Sartorius, and fascia 

 lata. By its external or attached border, it is inserted into the femur behind the 

 Adductor brevis and Adductor longus, which separate it, in front, from the Yastus 

 internus, and in front of the Gluteus maximus and short head of the Biceps, which 

 separate it from the Yastus externus. 



Nerves. All the muscles of this group are supplied by the obturator nerve. 

 The Pectineus receives additional branches from the accessory obturator and ante- 

 rior crural ; and the Adductor magnus an additional branch from the great sciatic. 



Actions. The Pectineus and three Adductors adduct the thigh powerfully ; they 

 are especially used in horse-exercise, the flanks of the horse being firmly grasped 

 between the knees by the action of these muscles. From their oblique insertion 

 into the linea aspera, they rotate the thigh outwards, assisting the external Eotators, 

 and when the limb has been abducted, they draw it inwards, carrying the thigh 

 across that of the opposite side. The Pectineus and Adductor brevis and Adduc- 

 tor longus assist the Psoas and Iliacus in flexing the thigh upon the pelvis. In 

 progression, also, all these muscles assist in drawing forwards the hinder limb. 

 The Gracilis assists the Sartorius in flexing the leg and drawing it inwards ; it is 

 also an Adductor of the thigh. If the lower extremities are fixed, these muscles 

 may take their fixed point from below and act upon the pelvis, serving to maintain 

 the body in the erect posture ; or, if their action is continued, to flex the pelvis 

 forwards upon the femur. 



GLUTEAL EEGION. 



Gluteus Maximus. . Gemellus Superior. 



Gluteus Medius. . Obturator Internus. 



Gluteus Minimus. Gemellus Inferior. 



Pyriformis. Obturator Externus. 



Quadratus Femoris. 



Dissection (fig. 189). The subject should be turned on its face, a block placed beneath the 

 pelvis to make the buttocks tense, and the limbs allowed to hang over the end of the table, the 

 foot inverted, and the limb abducted. An incision should be made through the integument along 

 the back part of the crest of the ilium and margin of the sacrum to the tip of the coccyx, from 

 which point a second incision should be carried obliquely downwards and outwards to the outer 

 side of the thigh, four inches below the great trochanter. The portion of integument included 

 between these incisions, together with the superficial fascia, should be removed in the direction 

 shown in the figure, when the Gluteus maximus and the dense fascia covering the Gluteus medius 

 will be exposed. 



The Gluteus Maximus, the most superficial muscle in the gluteal region, is a 

 very broad and thick fleshy mass, of a quadrilateral shape, which forms the pro- 

 minence of the nates. Its large size is one of the most characteristic points in 

 the muscular system in man, connected as it is with the power he has of main- 

 taining the trunk in the erect posture. In structure it is remarkably coarse, being 

 made up of muscular fasciculi lying parallel with one another, and collected 

 together into large bundles, separated by deep cellular intervals. It arises from 

 the superior curved line of the ilium, and the portion of bone, including the crest, 



