472 THE MUSCULATURE 



inserted behind the short and long adductors into the whole length of the linea 

 aspera, and by a special tendon into the adductor tubercle of the femur. The 

 deepest muscle of the group, the obturator externus, which arises from the outer 

 surface of the bones bouncling the ventral two-thirds of the obturator foramen, 

 and is inserted by a tendon into the trochanteric (digital) fossa, has been described 

 in connection with the ischio-pubo-femoral muscles of the hip. 



All the muscles of this group adduct the thigh. The gracilis, obturator ex- 

 ternus, adductor brevis and the lower part of the adductor magnus (when the 

 thigh is extended) rotate it lateralward. The pectineus, adductor longus, and 

 the adductor magnus rotate it medialward. Those attached to the pubis flex 

 the thigh. The gracilis flexes the leg and rotates it medialward. The inferior 

 part of the adductor magnus extends the thigh. 



The muscles of this group are supplied by the obturator nerve, except the 

 pectineus, which usually gets its whole supply from the femoral (anterior crural) 

 nerve, and the adductor magnus, which gets a part of its supply from the sciatic 

 nerve. 



In embryonic development the pectineus arises in close conjunction with the obturator 

 group, and in the adult it may get the whole or a part of its nerve-supply from the obturator 

 nerve or from the accessory obturator nerve. In the lower mammals the nerve-supply may 

 come from the femoral (anterior crural) or the obturator nerve or from both. It is not certain 

 whether the innervation from the femoral nerve indicates that the muscle belongs phylo- 

 genetically, if not ontogenetically, with the primitive dorsal musculature of the limb. By 

 some it is considered to be derived in part from the primitive dorsal, in part from the primitive 

 ventral, musculature. The adductor magnus arises in the embryo as two distinct portions, one 

 connected with the flexor group of muscles, the other with the adductor group. These two 

 portions later become fused. Primitively the sciatic portion of the adductor magnus and the 

 semimembranosus constitute a single medial flexor muscle. 



The gracilis (figs. 408, 411). — Origin. — By a flat tendon from the medial margin of the 

 inferior ramus of the pubis and the pubic extremity of the inferior ramus of the ischium. 



Structure and insertion. — The nearly parallel fibre-bundles which arise between two lamina? 

 of the tendon form a thin band of muscle which is narrower and thicker distally than proximally. 

 They are inserted on a tendon which begins as an aponeurosis on the posterior border and medial 

 surface of the muscle in the distal third of the thigh, becomes free as a rounded cord a little 

 proximal to the medial condyle of the femur, runs behind the condyle, and then turns forward 

 to be inserted by an expanded process into the tibia below the medial condyle. 



Nerve-supply.- — The nerve enters the deep surface of the muscle near the junction of the 

 superior and middle thirds. 



Action. — ^To adduct, flex and (slightly) rotate the thigh lateralward, and flex the leg. 

 With the knee flexed, it acts as a medial rotator of the leg. 



Relations. — It occupies a position beneath the fascia lata and superficial to the adductor 

 brevis, longus, and magnus muscles. Distally the sartorius lies in front, the semimembranosus 

 behind. Its tendon crosses the tibial collateral ligament of the knee-joint and the tendons 

 of the semitendinosus and the semimembranosus, and is overlapped by that of the sartorius. 



Variations. — The pubic origin of the muscle may be much reduced or may be double. 

 Its tendon of insertion may give rise to an accessory fasciculus which extends distally in the 

 leg. In some of the apes the tendon descends normally much farther down the leg than in man. 



The pectineus (fig. 411.) — Origin. — (1) From the pecten (crest) of the os pubis, the bone 

 in front of this, and the pectineal fascia near this origin; and (2) from the anterior margin of 

 the obturator sulcus and from the pubo-capsular ligament. Laterally the two areas of origin 

 are usually separated by most of the superior surface of the body of the pubis. Medially _they 

 come together. 



Structure and insertion. — From each area of origin a separate lamina arises. The fibre- 

 bundles of each layer take a nearly parallel course antl terminate between two tendinous lamella; 

 which fu.se to lie inserted into the upper half of the pectineal line behind the small trochanter. 

 The fibre-bundles of the superficial layer cross those of the deep slightly obliquely. The muscle 

 faces ventrally at its origin, laterally at its insertion. 



Nerve-supplij. — From a branch of the femoral (anterior crural) nerve, which passes behind 

 the femoral artery and vein and through the; pectineal fascia to enter the ventral surface of the 

 muscle. It may also l)e supijlied by the accessory obturator nerve, when present, or by a branch 

 from the obturator. When both the femoral (anterior crural) and obturator nerves supply this 

 muscle, the femoral supplies tlic superficial, the obturator, the deep lamina (Paterson). 



Action. — To Hex and adduct the thigh (as in crossing the legs). 



Relations. — It is covered by the pectineal fascia, lies between the ilio-psoas and the adductor 

 longus muscles, and crosses the obturator externus and adductor brevis muscles. The medial 

 circumflex artery runs between it and the ilio-psoas, the deep femoral artei'y between it and the 

 adductor longus. 



Variations. — The extent of the division of the pectineus into superficial and deep portions 

 varies considerably. It may also l)e divided into a lateral and a medial division. Often the 

 pectineus is fused with the adducttor longus. It may receive an accessory fasciculus from the 

 capsule of the hip-joint, the iliacus muscle, the obturator externus, or the adductor brevis 

 muscles, or the small tro(;hanter. It may send a fas('iculus to the sartorius. 



The adductor longus (fig. 411). — Origin. — From the medial corner of the superior ramus 



