39 



medius and one to the posterior edge of the gluteus superficiaUs. The 

 second posterior gluteal nerve, posterior ventral gluteal, originates from the 

 I St and 2d sacral nerves but to a very slight extent however, from the ist 

 sacral. This nerve also passes posteriorly between the sacro-sciatic liga- 

 ment and the M. gluteus medius. Eight or ten centimeters from its origin 

 it divides into two branches of which one enters the semitendinosus im- 

 mediately dorsal to the ischial tuberosity as already demonstrated (PI. IV, 

 25). This branch of the posterior gluteal nerve gives off a filament that 

 imites with the N. pudendus as already demonstrated. The other branch 

 of the posterior ventral gluteal nerve emerges near the middle of the outer 

 surface of the ischial tuberosity and may be seen between the biceps femoris 

 and the semitendinosus, upon turning aside the latter muscle (PI. IV, 25') ; 

 it is distributed subcutaneously to the region just below the ischial tubero- 

 sity. In addition to the gluteal nerves already mentioned there is given 

 off from the N. ischiadicus another small nerve which extends nearly par- 

 allel to the N. ischiadicus and is distributed to the M. gluteus profundus. 

 Sometimes this small nerve originates from the gluteal nerve that supplies 

 the tensor fasciae latae and the gluteus superficialis. 



A. profunda femoris (continued). 



Draw out the middle one of the three portions into which the biceps 

 femoris has been cut and note the large A. profunda femoris (and veins) 

 that enters the muscle a .little above the level of the external small tro- 

 chanter (PL IV). Cut the vessels, turn back this portion of the muscle as 

 far as possible and trace the artery to its distribution in the biceps femoris 

 principally; small twigs are supplied to the gluteus medius, the quadratus 

 femoris and the adductor magnus. 



A. obturatoria (continued). 



Remove piecemeal a portion of the semimembranosus and trace the 

 artery to this muscle; one or more branches go to the semitendinosus and 

 one to the biceps femoris. 



Nerves to the Mm. gemelli, obturator internus and quadratus femoris. 



Place the specimen with the gluteal region uppermost, clean up the 

 N. ischiadicus (PI. IV, 26) and identify the following muscles — the gemelli, 

 the tendon of the obturator internus and the quadratus femoris. The 

 one or two small nerves that supply these muscles originate from the deep 

 or internal face of the N. ischiadicus at nearly the same level as the posterior 

 ventral gluteal nerve and lie between the N. ischiadicus and the sacro- 

 sciatic ligament so that in order to see them the N. ischiadicus must be 



