42 



accessory branch from the N. peronaeus communis (PL VI, 31). The N. 

 saphenus externus then gains the interval between the tendo AchilUs 

 and the M. perforans and extends the length of this space, immediately 

 beneath the tibial aponeurosis, accompanied by the V. saphena externa. 

 Trace the nerve to its subcutaneous distribution at the outer face of the 

 tarsal and phalangeal regions (PI. VI, 36). 



Demonstrate the popliteal lymph gland, 6 cm. long by 2 cm. wide, in 

 the space between the biceps femoris and semitendinosus immediately 

 posterior to the gastrocnemius. 



N. tibialis is the larger of the two terminal branches of the N. ischiadicus 

 (PI. IV, 34; PI. VI, 29). It lies beneath the biceps femoris until it reaches 

 the gastrocnemius. Just as it passes between the two heads of the gastroc- 

 nemius it gives off, anteriorily, a large fasciculus to the muscles on the 

 posterior side of the tibia (PI. VI). To demonstrate the branches of this 

 fasciculus careftilly dissect up the external head of the gastrocnemius and 

 transect it a little below the middle of its fleshy portion taking care not to 

 cut the flexor perforatus which is partially embedded in the gastrocnemius 

 (PL VI, II, II', 12). The Nn. saphenus externus and peronaeus communis 

 should also be left intact. The several branches of the fasciculus just 

 mentioned should now be traced to their respective muscles, viz., one branch 

 to the external head and one to the internal head of the gastrocnemius; 

 a somewhat smaller branch to the flexor perforatus. Transect the perfora- 

 tus a little below the nerve supplied to it and draw aside the proximal part 

 of the muscle. Trace the remaining branches of the fasciculus to the 

 popliteus and flexor perforans (PL VI). The N. tibialis passes between the 

 two heads of the gastrocnemius and for a short distance runs along the 

 posterior surface of the flexor perforatus; it then gradually crosses the 

 inner face of this muscle and accompanied by a small artery, descends to 

 the tarsus in the space at the inner side of the leg, between the tendo Achillis 

 and the flexor perforans. Place the leg with its inner or medial surface 

 uppermost and expose the N. tibialis in this part of its course taking care 

 not to injure the one or more small arteries that accompany the nerve. 

 At the tarsus the N. tibialis divides into two terminal branches — the N. 

 plantaris medialis and the N. plantaris lateralis. Note very carefully the 

 relation of the N. tibialis to the internal saphena vein and artery and to the 

 tibial aponeurosis. 



Nn. plantaris medialis and lateralis. These two nerves are the terminal 

 branches of the N. tibialis. They follow the tendon of the flexor perforans 

 through the tarsal sheath and, diverging somewhat from each other, descend 



