ADDUCTOR MAGNUS 361 



3. ADDUCTOR MAGNUS 



The adductor magnus — named from its aetion and its great size — is a thick 

 fan-sliaj)ed sheet, forming a riglit-angled triangle, the right angle of which is 

 contained l^etween the side corresponding to the insertion of the muscle at the back 

 of the fenuu- and the side formed by tiie free upper border of the muscle. 



Origin. — (1) The lower part of the outer border of the tuber ischii; (2) the 

 outer surface of the ascending ramus of the ischium near its inner border; (3) the 

 front of the outer surface of the descending ramus of the pul)es. 



Insertion. — (1) The back of the femur, in a line beginning at the lower 

 extremity of the linea quadrati, and extending along the inner ])order of the gluteal 

 ridge and the middle of the linea aspera down to its l)ifurcation; (2) the adductor 

 tubercle on the upper and jjosterior part of the internal condyle; (3) the loAver part 

 of the internal intermuscular septum. 



Structure. — Its origin and insertion are by short tendinous fibres, with the 

 exception of the insertion of the bundle of til^res which passes from the tuber ischii 

 to the adductor tubercle. These arise by a long tendon above, and again become 

 tendinous three or four inches (7 to 10 cm. ) above the knee-joint, so as to form a 

 long and conspicuous tendon on the lower part of the inner border of the muscle. 

 Between this part of the insertion of the muscle and the linea aspera, the fibres are 

 attached to the back of the internal intermuscular septum and to a tendinous arch 

 which allows of the passage of the superficial femoral artery and vein from Hunter's 

 canal into the upper part of the popliteal space. Between the origin and insertion 

 the fibres diverge; the anterior fibres of origin passing horizontally outwards to their 

 insertion into the upper part of the back of the femur, Avhile the fibres which arise 

 behind pass vertically downwards from the tuber ischii to the internal condyle. 

 Moreover, the muscle is twisted upon itself so that the surface which above looks 

 inwards and rather Ijackwards is directed forwards below. A deep longitudinal 

 groove is thus formed upon tlie upper part of the back of the muscle, in which lie 

 the hamstring muscles and the great sciatic nerve. The ujjper part of the muscle, 

 which arises in front, and is inserted into the inner border of the gluteal ridge, 

 forms a triangular sheet, usually separate from the rest, and sometimes descriljed 

 as a distinct muscle, the adductor minimus. 



In addition to the opening for the superficial femoral vessels, the muscle is 

 pierced close to the bone by the perforating arteries and the terminal branch of the 

 profunda femoris. Upon its anterior surface it receives a membranous expansion 

 from the vastus internus, which passes inwards beneath the sartorius to the adductor 

 longus and magnus, forming the anterior wall of a sort of tunnel Avhich contains 

 the superficial femoral vessels in the middle third of the thigh, and is called 

 Hunter's canal. 



Nerve-supply. — Chiefly from the third and fourth nerves of tiie lumbar plexus 

 by the deep division of the ol:»turator nerve Avhich supplies the nuiscle upon the 

 outer part of its anterior surface. The lower fil>res of the muscle, however, are 

 supi)lied upon their posterior surface by the great sciatic nerve, a branch of the 

 sacral ])lexus. 



Action. — This muscle is the most powerful of the adductors. The upper three 

 fourths of its fibres Avill also rotate outwards the femur, while that part of the 

 nniscle which arises from the tuber ischii and is inserted into the inner condyle 

 will tend slightly to rotate the thigh inwards, and will at the same time extend as 

 well as adduct the thigh. 



Duchenne suggests that this is the part (A the muscle which e(|Ucstnans should 

 especially develop. Otherwise the adduction of the thighs in gripping the saddle 

 is apt to throw out the toes, which is ungainly, and, if the rider have spurs on, 

 may lead to unpleasant consequences. 



Relations. — In front lie the adductor brcA'is and longus, and lower down the 

 vastus internus. Behind are the hamstring muscles, the gluteus maximus, and the 

 great sciatic nerve. At its ujiper Itorder are the quadratus femoris and obturator 

 externus. Along its inner border lie the gracilis and ]inrt of the sartorius. It is also 

 in relation with the superficial and deep femoral vessels, and the obturator nerve. 



