THE SUPERIOR AND INFERIOR GEMELLUS. 589 



The descending set (fig. 199, 2 ) supply the integuments of the upper 

 third of the thigh at the inner and posterior aspects. One of these branches 

 ( 3 ), which is larger than the others, is distributed to the genital organs, 

 and is named inferior pudendal (p. 394) ; as it courses to the perinceum, 

 it turns below the ischial tuberosity, and perforates the fascia lata at the 

 inner part of the thigh to end in the scrotum. 



The great sciatic (fig. 200, 6 ) is the largest nerve in the body. It is 

 the source of all the muscular, aud most of the cutaneous branches dis- 

 tributed to the limb beyond the knee, as well as of the muscularjbranches 

 at the back of the thigh. 



At its origin it appears to be a prolongation of the sacral plexus. It is 

 directed through the buttock to the posterior part of the thigh, and rests 

 on the external rotator muscles below the pyriformis. Commonly it does 

 not supply any branch to the buttock, but it may give origin to one or two 

 filaments to the hip joint. Frequently the nerve is divided into two large 

 trunks at its origin, and one of them pierces the fibres of the pyriformis 

 muscle. 



The pudic nerve (fig. 200, 5 ) winds over the small sacro-sciatic liga- 

 ment by the side of its companion artery, and is distributed with this 

 vessel to the perinaeum and the genital organs (p. 391). No branch is 

 supplied to the buttock. 



Muscular branches of the sacral plexus are furnished to the gluteus 

 maximus, and to the external rotators except the obturator externus. 



Branches of gluteus. One or more branches of the plexus enter the 

 top of the gluteus maximus (fig. 200). 



Two branches of the pyriformis enter the under surface, and are learnt 

 with the sacral plexus in the pelvis. 



The nerve to the obturator internus (fig. 201, 5 ) arises from the upper 

 part of the plexus, and is directed to its muscle through the small sacro- 

 sciatic notch with the pudic nerve : its termination is seen in the dissec- 

 tion of the pelvis. 



The nerve to the superior gemellus (fig. 201, 7 ) is a very small twig, 

 and arises separately from the following : it enters the inner end of the 

 muscle on the superficial surface. 



The nerve to the inferior gemellus and the quadratus (fig. 201, 6 ) is a 

 slender branch, which passes with a companion artery beneath the gemelli 

 and the obturator internus, to end in the two muscles from which it re- 

 ceives its designation. This nerve will be seen more fully in a subse- 

 quent dissection, when articular filaments from it to the hip-joint may be 

 recognized. 



Dissection. To see the remaining small rotator muscles, hook aside the 

 great sciatic nerve, and take away the branches of the sciatic artery if it 

 is necessary. In cleaning these muscles the limb should be rotated in- 

 wards. The gemelli are to be separated from the tendon of the obturator 

 internus. 



The SUPERIOR GEMELLDS (fig. 200, ) is the highest of the two mus- 

 cular slips along the sides of the tendon of the obturator muscle. Inter- 

 nally it is attached to the outer and lower part of the ischial spine, and 

 externally it is inserted with the obturator into the great trochanter. 

 Oftentimes the muscle is absent. 



The INFERIOR GEMELLUS (fig. 200, K ) is larger than its fellow. Its 

 origin is connected with the upper part of the ischial tuberosity, along 

 the lower edge or lip of the hollow for the obturator internus muscle ; 



