232 ANATOMY OF THE LOWER EXTREMITY. 



descends between the trochanter and tnberosity of the 

 ischium, and will be further seen in the dissection of the 

 posterior region of the thigh. It supplies the heads of the 

 posterior muscles of the thigh, and gives off some small 

 branches which ramify on the capsule of the hip-joint. 

 Not unfrequently it is split into two trunks, one of which 

 passes through the pyrifbrmifi ; sometimes the whole nerve 

 perforates that muscle. 



The internal pudic artery emerges below the pyriformis 

 muscle, in front of the ischiatic artery, at the great sacro- 

 ischiatic foramen, passes under the greater sacro-ischiatic 

 ligament, and ascends along the ramus of the ischium ; it 

 is accompanied by the internal pudic nerve ; its branches 

 and distribution have already been described (p. 205). 



In dissecting these arteries, the following muscles will 

 have been exposed. 



The GLUTEUS MINIMUS MUSCLE arises, fan-shaped, from 

 the surface of the ilium, between the acetabulum and the 

 middle curved line of that bone, and is inserted into the 

 summit and inside of the great trochanter; anteriorly this 

 muscle is blended with the glutens medius. 



The PYRIFORMIS MUSCLE, arising from the sacrum, has 

 already been described as seen within the pelvis (p. 212) ; 

 the part external to the pelvis will now be found narrowing 

 to its inseftion and separated from the gluteus minimus by 

 the gluteal artery. It arises from the concave surface of 

 the sacrum, between the first and fourth anterior sacral 

 foramina, from the greater sacro-ischiatic ligament, and 

 from a portion of the ilium ; forming a thick, flattened 

 belly, it passes out at the great sacro-ischiatic notch, tapers 

 to a rounded tendon, blending with that of the gluteus 

 minimus, and is inserted into the digital fossa of the great 

 trochanter. 



Some little difficulty is often experienced by the student in deter- 

 mining the three next muscles. A bundle of muscular fibres presents 

 itself just below the pyriformis, and crossed by the great sciatic nerve ; 

 it is composed of the tendon of the internal obturator muscle sur- 

 rounded by its two dependent muscles, the gemelli ; if this bundle 

 of fibres be carefully separated longitudinally, the glistening tendon 

 of the obturator will be exposed, and the two gemelli may be distinctly 

 defined, on one side and the other, though they cannot be isolated 

 from the obturator tendon. 



The OBTURATOR INTERNUS MUSCLE has been partly seen 

 in another dissection (p. 212) ; it arises within the pelvis 



