234 MUSCLES OF THE LOWER LIMB. 



of which they may be said to form a considerable portion. The muscle 

 consists of nnmerous short fibres extendinoj obliquely between two 

 aponeurotic expansions, which are continued upwards and downwards 

 on the opposite sides of the muscle for three fourths of its length from 

 the superior and inferior tendons. 



JRelafhns. — The inferior tendon of the semimembranosus muscle is separated 

 fi'om the tendon of the inner head of the gastrocnemius by a large bui'sa. The 

 muscle rests on the adductor magnus. 



The hamstiing muscles descend in contact -with one another, being bound dovm 

 by the fascia lata ; but inferiorly they diverge, the biceps passing to the outside, 

 and the semimembranosus and semitendinosus to the inner side of the knee, . 

 forming the superior borders of a diamond-shaped hollow at the back of the knee 

 — the popliteal space. The great sciatic nen^e is concealed by them while they 

 are ui contact, and its principal division, the mternal popliteal, lies in contact 

 with the semimembranosus muscle in the popliteal space, while the smaller or 

 external popliteal division runs along the edge of the biceps muscle. 



]'arirfirs. — The semimembranosus muscle has been found absent ; again it has 

 been found double or it may have its origin for the most part from the gi-eat 

 sciatic ligament. 



Nerves." — The hamstring muscles are all supplied with branches from the great 

 sciatic nerve. 



Actions. — The liam.stving miisclps extend the hip and flex the knee. It is to be 

 observed, however, that in ordinary circumstances these movements take place 

 together, and that therefore it is by the occurrence of simultaneous action of 

 other muscles that it is determined whether flexion of the one or extension of 

 the other will occur-. 



The xhort head of the J/cv^w is the only flexor of the knee which passes over 

 that joint alone. The action of the whole muscle produces external rotation of 

 the leg. 



ANTERIOR MUSCLES OF THE THIGH. 



The iLio-PSOAS muscle, the great flexor of the hip-joint, is divisible 

 into two parts, a broad outer part, the iliacus, and an elongated inner 

 part, the psoas magnus, which are inserted together into the small 

 trochanter. 



The iliacus muscle arises from the iliac fossa of the innominate 

 bono, and from the anterior border of the same, likewise from the base 

 of the sacrum, the ilio-lumbar ligament, and the capsule of the hip- 

 joint. Its fibres converging, as they pass downwards and inwards, are 

 inserted for the most part into the tendon of the psoas muscle ; while 

 some are prolonged to a special triangular impression on the upper part 

 of the femur, in front of and below the small trochanter. 



lichitlona. — Above Poupart's ligament this muscle is covered by the iliac fascia, 

 the external iliac artery, the ilio-inguinal and external cutaneous nerves. Outside 

 the pelvis it lies on the capsule of the hip-jomt ; in front of it lie the anterior 

 crural nerves; at its outer border are the origins of the sartorius and rectus 

 femoris muscles, and at its inner is the psoas. 



Var'ictij. — The chief variety consists in the presence of the iliacus minor or 

 -iUo-capsHlaris. a small detached portion of the iliacus major. It arises from the 

 anterior inferior spine of the ilium, and is inserted into the anterior intertro- 

 chanteric line of the femur. It is closely united to the front of the capsule of 

 the hip- joint. 



The psoas magnns muscle arises by five fleshy slips from the anterior 

 surface and lower margin of the transverse processes of the lumbar 

 vertebras near their bases ; also from the bodies of the last dorsal and 



