PLATE XXX. 



THE DEEP PARTS OF THE BACK OF THE THIGH, 

 ADDUCTOR MAGNUS, GREAT SCIATIC, &c. 



In this dissection the hamstring muscles have been cut away from their origin 

 from the tuber ischii and removed to show the adductor magnus, great sciatic nerve, 

 and the deep portion of the popliteal space. 



The adductor magnus may usually be divided into two parts : 



1. A posterior portion which arises from the tuber ischii and a little of the ramus 



of the ischium and passes to be inserted into nearly the whole length of the 

 linea aspera, the more posterior portion of its origin from the tuber running 

 directly down to be inserted into the adductor tubercle of the femur. 



2. An anterior portion, which is somewhat triangular in shape, arising from the 



rami of the ischium and pubes and passing out to be inserted into the upper 

 half of the linea aspera. It is the upper part of this portion which brings the 

 edge of the adductor magnus up to that of the quadratus femoris, and continues 

 the insertion of the adductor magnus up to the linea quadrati. It is some- 

 tunes called the adductor quartus or minimus. 



The nerve supply to the adductor magnus is from the sciatic, which 

 chiefly supplies the posterior portion, and the deep branch of the obturator, which 

 supplies the whole of the anterior and also sends branches into the posterior. 

 Prof. Wilson has noticed on the other hand a tendency for the sciatic nerve 

 filaments to usurp a portion of the muscle usually supplied by the obturator. 



In the chimpanzee the ischial portion (1) is quite separate from the rest, and is 

 inserted into the adductor tubercle, supplied by a branch of the sciatic nerve, and is 

 altogether more like an additional hamstring than an adductor. The deep or anterior 

 portion (2) had its lower fibres spread out over and inserted into the greater part of the 

 popliteal surface of the femur, extending as low down as the posterior ligament of the 

 knee-joint ; this portion was innervated by the obturator nerve ; and there is thus 

 no difficulty in understanding the channel through which the nerve reaches the posterior 

 aspect of the knee-joint, and when the muscle retires the nerve still persists. Of this 

 fact there are other examples. In the iguana the muscle is supplied from the sacral 

 plexus only. 1 



The adductor magnus is pierced by five arteries, which come through from the 

 front, viz. three perforating arteries from the profunda femoris, as well as its terminal 

 branch, and the femoral artery. 



1 Dr. Hepburn, Journal Anal, and Phyi. vol. xxvi. p. 833. 



