THIGH AND LEG. 315 



two lateral slips are inserted into the base of the third phalanx. Also notice 

 the relation of the tendons of this muscle to those of the extensor brevis digi- 

 torum. Origin, outer tuberosity of the tibia and anterior surface of fibula. 



The Peroneus Tertius. Find the insertion of this muscle in the base of the 

 fifth metatarsal. (Fig. 215.) Trace it to the anterior surface of the fibula, and notice 

 that it blends with the preceding muscle, a part of which it really is. (Fig. 207.) 



THIGH, ANTERIOR AND INTERNAL REGIONS. 



Remove the deep fascia and expose the vessels, nerves, and muscles. (Figs. 

 218, 219, and 220.) 



First locate the sartorius. (Fig. 218.) Begin at the anterior superior iliac spine 

 (Fig. 226) and expose the muscle to its insertion (Fig. 207) into the tibia, by gently 

 removing all deep fascia. Now lift up the muscle from its bed, taking care not to 

 damage the vessels and nerves that enter it. Notice that this muscle is crossed by 

 one and pierced by another branch of the middle cutaneous nerve. (Fig. 211.) 



Locate the gracilis next, on the inner surface of the thigh. (Figs. 218 and 

 219.) Trace it from the descending ramus of the pubes (Fig. 226) to its inser- 

 tion into the inner surface of the tibia (Fig. 207), taking care not to damage 

 the nerve branches of the obturator that enter it. This dissecting, by which 

 this muscle is separated from its fellow-muscles, must be done with the forceps. 



Locate the adductor longus. (Fig. 218.) Trace it from the anterior surface 

 of the pubes to its insertion into the middle of the middle lip of the linea aspera. 

 (Fig. 227.) Divide the connective tissue between this muscle and the pectineus. 

 (Fig. 218.) Now cut the adductor longus, at its origin, and turn the same 

 aside. (Fig. 219.) Also cut the pectineus and turn it aside. (Fig. 218.) 



Obturator Nerve, Anterior Division (Fig. 219). This you will see lying on 

 the adductor brevis. (Fig. 219.) Take this nerve up gently, and follow out its 

 branches to : (i) The gracilis ; (2) the adductor longus ; (3) the adductor brevis ; (4) 

 the sartorius ; (5) a branch to the hip-joint ; (6) a branch to the femoral artery ; (7) 

 an occasional branch to the pectineus muscle ; (8) a cutaneous branch to assist the 

 long saphenous and internal cutaneous in forming the subsartorial plexus. 



Obturator Nerve, Posterior Division. This lies on the adductor magnus. 

 The adductor brevis muscle then separates the anterior from the posterior divi- 

 sion of the nerve. This division supplies : (i) The obturator externus ; (2) the 

 adductor magnus; (3) an articular branch to the hip-joint; (4) an articular 

 branch to the knee. 



Why does the obturator nerve send a branch to the knee ? 



Because this nerve supplies the sartorius muscle, a muscle that moves the 

 knee-joint. (Fig. 219.) 



Hoiv does the articular branch from the obturator nerve enter the hip-joint / 



It passes through the cotyloid notch. 



When the accessory obturator nerve is present, wliere may it be found / 



To the inner side of the psoas magnus muscle. 



What is the function of the subsartorial plexus? 



To supply the skin over the adductor muscles, and to exercise a sensory 

 balance of power between the obturator and anterior crural nerves. 



The Anterior Crural Nerve (Fig. 219). You will find the main trunk of this 

 nerve deeply buried in a space between the iliacus and psoas magnus. (Fig. 197.) 

 Take this nerve up on your finger and gently follow out its muscular branches to 

 all the muscles on the front of the thigh : (i) Sartorius ; (2) rectus femoris ; (3) 



