41 



branch appears to go to the biceps femoris but in reality it passes through 

 the muscle and is distributed subcutaneously to the external face of the 

 tibial region. The large N. peronaeus communis is given off from the 

 N. ischiadicus at the level of the gemelli muscle; it lies at the side of the 

 N. tibialis until it reaches the M. gastrocnemius where it diverges from the 

 N. tibiahs and passes between the external head of this muscle and the 

 biceps femoris (PI. IV, 29). Beginning at the posterior border of the biceps 

 femoris slit the tibial aponeurosis lengthwise the tibia and turn aside the 

 aponeurosis and the distal end of the biceps femoris (PL IV, 10', 11'). 

 Now trace the N. peronaeus communis to the place where, between the 

 M. peroneus (or lateral digital extensor) and the extensor pedis, it dips into 

 the anterior tibial group of muscles. Shortly before the nerve enters these 

 muscles it divides into two terminal branches — ^the N. peronaeus super- 

 ficialis and the N. peronaeus profimdus (PL IV, 32, 33). The N. peronaeus 

 superficialis is much the smaller of the two and is for the most part sub- 

 aponeurotic. Near its origin it gives off a muscular branch to the M. 

 peroneus or lateral digital extensor (PL IV, 32'). Trace the superficial or 

 subaponeurotic portion of the nerve (PL IV, 32") to its place of distribu- 

 tion near the middle of the metatarsus. Note the relation of the nerve to 

 the extensor pedis, peronaeus and to the tibial aponeurosis. 



N. peronaeus profundus (PL IV; 33). Just as this nerve passes between 

 the extensor pedis and peroneus it divides into several branches of which 

 all but one are distributed to the extensor pedis and the tibialis anterior 

 (PL VI, 34). Cut the extensor pedis below the middle of the tibia and draw 

 it aside. The remaining branch of the peronaeus profundus lies deeply 

 between the extensor pedis and the tibialis anterior (PL VI, 34^). In 

 tracing this branch to its termination in the digital region the tendons of 

 the extensor pedis and peroneus may be cut near the middle of the metatar- 

 sus and drawn aside. As the nerve crosses the tarsus it gives off several 

 small branches to this region and to the M. extensor digitalis brevis. At 

 the tarsus the nerve divides into two main portions of which one accompanies 

 the A. metatarsea dorsalis (lateralis) to the region of the fetlock (PL VI, 

 35) ; the other portion of the nerve extends obliquely across the anterior 

 face of the large metatarsal bone and may be traced as far as the fetlock 

 and often even beyond that joint. 



N. saphenus externus arises from the N. tibialis at the level of the third 

 trochanter (PL IV, 35; PL VI, 36). It extends along the postero-extemal 

 part of the gastrocnemius, accompanied by a vein, to near the beginning 

 of the tendo Achillis. At this point it occasionally receives a small 



