NERVES 173 



External cutaneous : winds round ghueus maximus, supplies 

 the integument over lower part of buttock. 



Terminal: to integument of thigh, popliteal region, and 

 calf of leg. 



GREAT SCIATIC : the largest nerve in the body, and is the 

 main continuation of the sacral plexus, lies in pelvis on pyri- 

 formis ; it is derived from the lumbo-sacral cord, the ist, 2nd, 

 and 3rd sacral nerves. It passes out of pelvis below the 

 pyrifoimis, and between the tuber ischii and great trochanter. 

 resting upon the gemelli, obturator internus, quadratus 

 femoris, and adductor magnus. It is at first external to the 

 biceps, then between its two heads of origin, finally between 

 it and semi-membranosus, and is accompanied by the sciatic 

 artery, which supplies a branch to its substance (comes nervi 

 ischiadici). At a variable distance between the sacral plexus 

 and lower part of the thigh, but generally about the middle 

 of the thigh, the nerve bifurcates into external and internal 

 popliteal. 



Branches of the Trunk : 



Muscular : given off under biceps to semi-membranosus, 

 semi-tendinosus, both heads of biceps, and to the inner part 

 of adductor magnus. 



INTERNAL POPLITEAL: larger terminal branch, passes along 

 middle of popliteal space to lower border of popliteus, where 

 it gets the name of posterior tibial; it is at first superficial to 

 and outside the artery, but at the lower end of the space, 

 under the gastrocnemius, crosses to the inner side. 



Branches : 



Articular (3) : one accompanies each of the upper and 

 lower internal articular arteries, the third the azygos. 



Muscular : to the gastrocnemius, one for each head, the outer 

 one supplying also the plantaris. To the soleus and to the 

 Popliteus ; the nerve to the latter turns round lower border of 

 muscle and enters it upon its anterior surface. 



Tibial communicating : passes down leg superficially between 

 two heads of the gastrocnemius, pierces the deep fascia about 

 middle of leg, there joining the peroneal communicating from the 

 external popliteal, and is now known as the external or short 

 saphenous nerve ; it then follows the course of the external 

 saphenous vein round outer malleolus, and supplies integu- 

 ment of outejr side of foot and little toe, communicating with 

 the musculo-cutaneous on the dorsum. 



POSTERIOR TIBIAL (continuation of internal popliteal): 

 begins at the lower border of the popliteus, and runs with 



