4 io THE INFERIOR EXTREMITY 



stomosis (p. 418) ; and (c) a descending branch, which joins 

 the anastomosis round the knee-joint. 



2. The Medial Circumflex, which frequently arises from 

 the femoral, takes origin opposite the lateral circumflex, and 

 runs backwards between the pectineus and the psoas major. 

 It passes below the neck of the femur and ends in the crucial 

 anastomosis (p. 418). 



3. The four perforating arteries arise from the profunda 

 more distally. They wind round the back of the femur, giving 

 off branches to the adductors, and gain the back of the thigh. 

 There they form a series of anastomotic arches with one another. 

 In addition, the first perforating joins the crucial anastomosis 

 (p. 418), and the fourth, which is the terminal branch of the 

 profunda, anastomoses freely with branches from the popliteal 



(P- 445)- 



The Pectineus arises from the superior ramus of the pubis, and passes 

 laterally and distally to be inserted into the posterior aspect of the proximal 

 part of the shaft of the femur. It is supplied by the femoral nerve (L. 2 and 

 3), and acts as an adductor and flexor of the thigh. 



The Adductor group consists of four muscles, and they are all supplied 

 by the obturator nerve (L. 2, 3, 4). 



1. The Gracilis is a thin, flattened muscle which extends from the margin 

 of the pubic arch along the medial side of the thigh. As it is inserted into 

 the proximal part of the tibia near the semitendinosus (p. 441), it acts more 

 powerfully as a flexor of the knee than as an adductor of the hip. In paralysis 

 of the ham-strings, flexion of the knee-joint is carried out satisfactorily 

 by the gracilis, assisted by the sartorius. 



2. The Adductor Longus (p. 398) helps to form the floor of the femoral 

 trigone and the posterior wall of the adductor canal, and consequently 

 supports the femoral artery in a considerable part of its course. It is the 

 most anterior of the three principal adductors, and is inserted into the linea 

 aspera. 



3. The Adductor Brevis lies behind the upper part of the adductor 

 longus. It extends from the front of the pubis to the back of the femur. 

 Its upper border is in contact with the outer surface of the obturator externus. 



4. The Adductor Magnus is the largest and most posterior of the three 

 principal adductors. It arises from the margin of the pubic arch and from 

 the lower part of the ischial tuberosity. The upper fibres are horizontal 

 and reach the femur just distal to the quadrate tubercle ; the lower fibres 

 are almost vertical, and are inserted into the adductor tubercle (p. 443) ; 

 the other fibres extend obliquely to the linea aspera and the medial supra- 

 condylar ridge. By reason of its vertical fibres, the muscle possesses a 

 secondary action as an extensor of the hip-joint. In its upper part the an- 

 terior surface of the magnus is covered by the brevis, but below the lower 

 border of that muscle it is in contact with the longus, and, below the longus, 

 the magnus forms the posterior wall of the adductor canal. In the latter 

 part of its extent it possesses a large gap, the hiatus tendineus, which trans- 

 mits the femoral vessels to the popliteal fossa. 



The adductor magnus receives an additional nerve-supply from the sciatic 

 (L. 4, 5, and S. i). 



The Obturator Externus arises from the outer surface of the obturator 



