MUSCLES OF THE OS FEMORIS. 377 



a little above which, the femoral artery takes a spiral turn 

 towards the ham, passing between this muscle and the bone. 



Use of these three muscles, or triceps. To bring the thigh 

 inwards and upwards, according to the different directions of 

 their fibres ; and, in some degree, to roll the thigh outwards. 



5. Obturator Externus, 



Arises, fleshy, from the lower part of the os pubis, and fore- 

 part of the inner crus of the ischium ; surrounds the foramen 

 thyroideum ; a number of its fibres, arising from the membrane 

 which fills up that foramen, are collected like rays towards a 

 centre, and pass outwards around the root of the back part of 

 the cervix of the os femoris. 



Inserted, by a strong tendon, into the cavity at the inner and 

 back part of the root of the trochanter major, adhering in its 

 course to the capsular ligament of the thigh bone. 



Use. To roll the thigh bone obliquely outwards, and to pre- 

 vent the capsular ligament from being pinched. 



Behind are, 



First layer, 



Gluteus Maximus, 



Arises, fleshy, from the posterior part of the spine of the os 

 ilium, a little higher up than the joining of the ilium with the 

 OS sacrum, from the whole external side of the os sacrum, be- 

 low the posterior spinous process of the os ilium ; from the 

 posterior sacro-ischiatic ligament, over which part of the in- 

 ferior edge of this muscle hangs in a folded manner, and from 

 the OS coccygis. All the fleshy fibres run obliquely forwards, 

 and a little downwards, to form a thick broad muscle, which is 

 divided into a number of strong fasciculi. The upper part of 

 it covers almost the whole of the trochanter major, between 

 which and the tendon of this muscle there is a large bursa mu- . 

 cosa, and where it is inseparably joined to the broad tendon of 

 the tensor vagina femoris. 



Inserted, by a strong, thick, and broad tendon, into the upper 

 and outer part of the linea aspera, which is continued from the 

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