278 MUSCLES OF THE LOWER LIMB. 



external to the lower part of the origin of the adductor brevis, from the 

 rainl of the pubes and ischium, and from the tuberosity of the ischiura near 

 the pubic arch. The muscular fibres diverge from their origin, somewhat 

 like the ribs of a fan from their central pivot ; those from the pubes, shorter 

 than the resb, pass transversely outwards, and are inserted below the linea 

 quadrati into the line prolonged from the linea aspera to the great trochanter ; 

 others pass with increasing degrees of obliquity downwards and outwards, to 

 be inserted into the whole length of the linea aspera, and into a part of 

 its internal bifurcation below ; finally, some of the fibres descend almost 

 vertically, forming the inner border of the muscle, and terminate in a 

 narrow tendon, which ia inserted into the tuberosity of the inner condyle of 

 the femur. 



Below the level of the inferior bifurcation of the linea aspera, between 

 the tendinous and fleshy portions of the insertion of the muscle, an interval 

 is left for the transmission of the femoral vessels backwards into the popliteal 

 space, and along the femoral attachment the insertion is interrupted by three 

 or more tendinous arches through which pass the perforating arteries. 



This muscle is in contact with the long and short adductors and the vastus internus 

 in front, with the hamstring muscles and gluteus maxiinus behind, with the gracilis 

 muscle internally, and with the obturator externus and quadratus femoris muscles 

 superiorly. 



ACTIONS OP THE MUSCLES OF THE HIP AND THIGH. 



The gluteus maximus muscle is the chief extensor of the hip-joint. By means of it 

 the bent thigh is brought into aline with the body; but its most important action, and 

 that in connection with which it is so largely developed in the human subject, is to 

 extend the trunk upon the thigh when supported on the ground by the limbs, and in 

 so doing the muscles of both sides act in combination. The upper part of the muscle 

 has an abducting, and the lower part an adducting power upon the limb. Although 

 the full contraction of the glutei maximi is required to bring the body into the erect 

 posture, it is not necessary for its maintenance, that being effected chiefly by the ten- 

 sion of certain ligaments and fasciae passing over the joints, and the body in that pos- 

 ture being so poised that the centre of gravity of the trunk is placed slightly behind 

 the vertical plane passing through the middle of the hip-joints. The gluteus medius 

 and minimus are powerful abductors of the thigh, and along with the tensor vaginae 

 femoris, come principally into action in supporting the body on one limb, which is 

 done to a certain extent in each step in walking. Their anterior fibres draw forwards 

 the great trochanter, and rotate the limb inwards, and the more the thigh is flexed 

 the greater the number of fibres which will exercise this action. 



The tensor vagince femoris is generally held to assist the action of the other muscles 

 by making tense the fascia lata. It likewise aids the preceding muscles in rotating 

 the limb inwards : its action in this respect is exactly opposed by the upper fibres of 

 the gluteus maximus, which fibres, together with the tensor vaginae femoris, being con- 

 tinued into a band of the fascia lata descending to the outer tuberosity of the tibia, 

 must act as supporters of the thigh at the knee-joint, and are considered by Meyer 

 (op. cit. p. 222) to act as extensors of the knee. 



The pyriformis, obturator internus, and gemelli muscles support the hip-joint poste- 

 riorly, and rotate the limb outwards. Their greatest contraction is admitted when 

 the thigh is extended and the toes are directed outwards ; they may be supposed there- 

 fore to give stability to the erect posture. 



The quadratus femoris is partly an adductor and partly a rotator outwards. This 

 muscle, as well as the pyriformis, obturator internus and gemelli, and obturator 

 externus, come to be extensors when the thigh is strongly flexed. 



The obturator externus has its origin and insertion most approximated when the 

 thigh is flexed, adducted, and rotated outwards, as is the case in the uppermost of the 

 two limbs when we cross the knees in sitting. It supports the hip-joint posteriorly 

 and inferiorly, and is a rotator outwards. 



