THE INTERNAL FEMORAL OR ADDUCTOR MUSCLES, 255 



be the muscle principally concerned in producing the posture assumed by the tailor in sitting-, 

 and hence its name. 



The quadriceps extensor cruris extends the knee-joint ; but its action is not requisite for 

 the maintenance of the erect attitude (see p. 189), the knee-joint remaining- in complete 

 extension without muscular aid while the foot is firmly planted on the ground. This may be 

 tested by the fact that the patella of a person standing 1 with the knee extended will be found 

 to lie quite loosely, but will become at once fixed when an attempt is made to lift the foot. 

 The rectus femoris, besides extending the knee, also flexes the hip : it acts mainly from its 

 anterior head of origin when the thigh is fully extended, and the posterior head alone is tense 

 when the thigh is bent. The lower fibres of the vastus interims draw the patella inwards 

 during extension of the knee. 



THE INTERNAL FEMORAL OR ADDUCTOR MUSCLES. 



The gracilis or adductor gracilis muscle, long and slender, arises by an aponeu- 

 rotic tendon from the inner margin of the pubic bone, along the lower half of the 

 symphysis and the whole length of the inferior ramus. Thin and flat at first, the 

 muscle becomes narrower and thicker as it descends ; and in the lower third of the 

 thigh it ends in a rounded tendon which curves forwards below the knee, and, becom- 

 ing flattened and expanded, is inserted into the inner side of the tibia, on the same 

 plane with but higher than the semitendinosus, and under cover of the tendon of the 

 sartorius. 



Relations. This muscle is covered by the fascia lata, except where its tendon is over- 

 lapped by the sartorius ; the deep surface rests against the adductor brevis and adductor 

 magnus, and the tendon crosses the internal lateral ligament of the knee-joint. A bursa 

 separates it from that ligament. 



The pectinens muscle (fig. 252, 8 ; 253, 6), flat and oblong, arises from theilio- 

 pectineal line, and slightly from the surface of bone in front of it, between the ilio- 

 pectineal eminence and the pubic spine ; a few superficial fibres spring also from the 

 upper part of the fascia covering the muscle. Inclining outwards and backwards as 

 it descends, it is inserted by a flat tendon into the femur behind the small trochanter, 

 and into the upper part of the line which connects the linea aspera with that pro- 

 minence. 



Relations. The pectineus is in relation, by its anterior surface, with the pubic portion of 

 the fascia lata and the femoral vessels ; by the posterior surface, with the obturator nerve,, 

 the external obturator and adductor brevis muscles, and the capsular ligament of the hip-joint. 

 Its outer border is in contact with the psoas magnus, and the internal circumflex vessels pass- 

 between the two ; its inner border touches the adductor longus. 



The adductor longus (fig. 252, 9), a flat triangular muscle, internal to the pec- 

 tineus and lying in the same plane, arises by a short tendon from the body of the 

 pubis below the crest and near the angle, and is inserted into the inner margin of the 

 linea aspera, by an aponeurotic tendon which is closely united to the vastus internus- 

 in front and the adductor magnus behind. 



Relations. This muscle is covered by the fascia lata, the sartorius, and the femoral 

 vessels ; the posterior surface rests on the adductor brevis and adductor magnus, the deep 

 femoral artery and the superficial portion of the obturator nerve. The outer border touches 

 the pectineus above, but is separated from it by a small interval below ; the inner border is in 

 apposition with the gracilis and forms the inner boundary of Scarpa's triangle. 



The adductor brevis (fig. 253, 7), thick above and broad below, has a fleshy 

 and tendinous origin, from the femoral surface of the body and inferior ramus of 

 the pubis, below the adductor longus and between the gracilis and obturator externus ; 

 directed obliquely backwards and outwards, it is inserted by a flat tendon into the 

 whole of the line leading from the small trochanter of the femur to the linea aspera, 

 immediately behind the insertion of the pectineus. 



