THE MUSCLES. 173 



348. 11. Obturator externus. 



Pos. : behind the last muscle and pectinseus, adductor brevis, 

 psoas and iliacus; be fore, fo ram. obturator, and collum femoris ; 

 meets above and externally, gemellus infer. Or. : foram. obtu- 

 rator (anterior circumference). Ins.: fossa of trochant. major 

 (the lowest part). Use : rotates the thigh outwards ; assists in 

 flexing the trunk. 



Nerves: obturator. 



349. Fascia iliaca, s. lumbo-iliaca, 



envelopes mm. psoas and iliacus, arises from the lumbar portion 

 of the diaphragm above, from the bodies of the lumbar vertebra 

 internally, from labium intern, of ilium and the linea arcuata of 

 the pelvic cavity outwards as far as crista pubis. a. The ex- 

 ternal portion divides between spina ilei ant. superior, and the 

 outer angle of the femoral ring into an anterior and posterior layer 

 (between which the Vasa circumflexa ilei pass). 1. The ante- 

 rior layer turns upon the posterior surface of the abdominal 

 muscles, and above passes into the/asc. transv. 2. The posterior 

 layer unites with the outer portion of lig. Poupartii (that is,fasc. 

 ilio-pubicd]. b. The internal portion descends over the m. psoas- 

 iliacus upon the thigh, and unites externally with fasc. femoris. 



B. Muscles of the Thigh. 

 a. On the posterior surface. 



350. 1. Biceps femoris s. flexor fbularis. 



Pos.: on the outer part of the thigh; its longhead covered 

 above by Glutxus max. and skin ; lies upon the short head, ad- 

 ductor magnus, and behind semi-tendinosus ; the short head on 

 vastus externus, in the lower half of the thigh, then behind the 

 popliteal vessels. Forms the outer border of the popliteal space. 

 Or. : 1 . Caput long, from tuber. Ischii. 2. Caput breve from linea 

 aspera oss. femor. Ins. : Capitulum fibulse (and condylus ex- 

 ternus tibisK]. Use: flexes the leg, and accordingly by means of 

 the long head it extends the thigh. The short head rotates the 

 leg outwards. 



351. 2. Semitendinosus. 



Pos. : covers the following muscle between it and cap. long, 

 bicip.; its long tendon is, at the commencement, behind, then 

 between the following muscle and gastrocnem. internus. The 

 tendon commences four or five finger breadths above the knee- 

 joint, winds around the condyl. intern, tibise forwards, behind the 

 tendo sartor., on the inferior border of tendo gracilis ("pes anse- 



