474 THE MUSCULATURE 



Nerve-supply. — A branch from the anterior division of the main obturator trunk gives off 

 several twigs which enter the middle third of the deep surface of the muscle. Occasionally a 

 small branch from the femoral (anterior crural) nerve enters the muscle. This is probably- 

 sensory in nature. 



Action. — To adduct and flex the thigh, and rotate it medialward. 



Relations. — The sartorius, the vastus mediahs, and the femoral vessels lie antero-lateral 

 to it. Behind it lie the adductor brevis and adductor magnus muscles. Between these and 

 the longus run the profunda vessels. Its lateral border touches the pectineus above, but is 

 separated from it toward the insertion. 



Variations. — It may be fused with the other adductors, including the pectineus. It may 

 be doubled. The femoral insertion may extend to the medial epicondyle. 



The adductor brevis (fig. 412). — Origin. — From the medial part of the outer surface of the 

 inferior ramus of the pubis directly, and by means of short tendinous processes or a short flat 

 tendon. 



Structure and insertion. — From their origin the fibre-bundles diverge into a sheet which is 

 inserted by short tendinous bands into the distal two-thirds of the pectineal line and the upper 

 third of the linea aspera. The muscle is more or less completely divided into two fasciculi near 

 its insertion. The place of division is near where the intertrochanteric Une curves away from 

 the linea aspera. 



Nerve-supply. — Usually from the anterior but also sometimes from the posterior branch 

 of the main obturator trunk. The rami enter the middle third of the muscle near the proximal 

 border. 



Action. — It is chiefly an adductor and to a less extent a flexor and a lateral rotator of the 

 thigh. 



Relations. — In front lie the pectineus and adductor longus; behind, the obturator externus 

 quadratus femoris and adductor magnus. It is crossed by the profunda artery. The first 

 perforating artery passes usually between the two fasciculi of the insertion. 



Variations. — It may be fused with other members of the group. It may be divided com- 

 pletely into two fasciculi, rarely into three. 



The adductor magnus (figs. 409, 412). — The origin of this muscle begins on the inferior 

 ramus of the pubis posterior to the origins of the adductor brevis and gracilis muscles. From 

 here it extends backward along the inferior margin of the ventro-lateral surface of the ischium 

 to the tuberosity. The muscle in passing from this curved origin to its extensive femoral in- 

 sertion presents posteriorly a longitudinal groove in which rest the hamstring muscles. The 

 adductor magnus is composed of three superimposed fasciculi, of which the first is frequently 

 fairly distinct and is called the adductor minimus, while the other two are normally fused, but 

 are occasionally distinct. 



The superior fasciculus (adductor minimus) arises directly from the inferior rami of the 

 pubis and ischium. From here the fibres diverge to form a thin sheet inserted by tendinous 

 bands to the medial side of the gluteal ridge and the superior part of the linea aspera. The 

 middle fasciculus arises directly from the inferior margin of the ventro-lateral surface of the 

 inferior ramus and the tuber of the ischium, and from a tendon which descends along the dorso- 

 medial margin of the muscle from the tuber ischii. The fibre-bundles diverge to be inserted 

 between the lamellse of a narrow flat tendon attached to the distal three-fourths of the linea 

 aspera. This tendon is pierced by the perforating vessels. The inferior fasciculus arises 

 dorsal to and in common with the middle fasciculus. The fibre-bundles converge toward a 

 strong tendon which begins in the distal third of the thigh and is inserted into a tubercle at the 

 distal end of the medial supracondylar ridge. 



Nerve-supply. — The chief nerve-supply is from the posterior ramus of the obturator. 

 This enters by one or more branches the proximal portion of the ventral surface of the muscle 

 about midway between its pubic and femoral attachments. It also receives a branch from 

 the sciatic which enters the dorsal surface of the muscle in the middle third of the thigh. To 

 the adductor minimus a branch may be sent from the nerve to the quadratus femoris. 



Action. — It is the strongest of the adductors. The superior and middle fasciculi rotate 

 the thigh medialward and flex it; the inferior rotate it lateralward when the thigh is extended, 

 but medialward when the thigh is flexed. The latter also extend the thigh. 



Relations. — In front are the pectineus, the short and long adductor and the vastus medialis 

 muscles, and the profunda artery. Behind lie the hamstring muscles and the gluteus maximus. 

 Medially lies the gracilis muscle. The femoral and perforating arteries pass through its attach- 

 ment to the shaft of the femur. 



Variations. — The divisions of the muscle may be more or less distinct. It may be ]:)artly 

 fused or exchange fasciculi with neighbouring muscles — the semimembranosus, quadratus 

 femoris, adductor brevis, and adductor longus. 



BuRSiE 



B. m. pectinei. — A small bursa frequently present between this muscle and the ilio-psoas 

 and small trochanter. B. anserina. — A fairly large bursa which lies between the tendons of 

 the sartorius, gracilis, and scmitendinosus muscles and the tibial collateral ligament of the knee- 

 joint, (See also B. M. Sautorii Propria, p, 471.) 



3. The Posterior (Hamstring) Group 



(Figs. 408, 413) 



The mu.scles of this p;roup are the scmitendinosus, semimembranosus, and 

 biceps. 'J'hey flex tlu; log and extend and adduct the thigh. The scmitendinosus 



