THE NERVES. 419 



major, close upon the rotator muscles, covered by glutceus maxi- 

 mus, directly to the posterior surface of the thigh. It here lies 

 enveloped in fat, and accompanied by no [large] vessel, before the 

 long head of m. biceps and before m. semitendinosus, then in the 

 fossa between the two; behind m. adductor magnus. [Above 

 gemellus sup. it gives off a branch which, passing behind the two 

 gemelli and obturator intern. , is lost in quadratusfemoris.'] 



Distribution. At the breadth of three to four fingers above the 

 knee-joint (the commencement of the popliteal space) ; even beforeor 

 after its exit from the pelvis it divides into two principal branches. 

 Branches / superior : to mm. biceps, semitendinosus, -membra- 

 nosus, adductor magnus ; inferior : to caput breve bicipitis, to the 

 fat of the knee-joint, to the outer side of the patella. 



a. N. peroneus s. fibularis s. poplitceus externus, the smaller 

 external branch, descends on the external side of biceps, obliquely 

 outwards through the popliteal region, then behind condylus extern, 

 femoris and tibice, between the tendons of the biceps and the outer 

 head of gastrocnemius ; outwards and rather forwards, behind the 

 superior attachment of m. solceus to the capitulumfibuke, where 

 it divides into one of two superficial and deep branches. Branches : 

 to biceps and knee-joint (see n. ischiadic.) ; farther : 



a. Posterior cutaneous branches, rr. cutanei cruris peroncei 

 posteriores. 



1. N. cutan. medius internus, descends under the fascia in the 

 middle of the posterior surface of the calf as far as the inferior 

 extremity of the leg. 



2. N. cutan. medius externus s. communicans fibularis passes 

 along the outer half of the calf and the tendo Achillis, then 

 under the external malleolus to the back of the foot, supplies 

 the skin on its outer half, the dorsal surface of the outer side 

 of the fifth, and the collateral surfaces of the fourth and fifth 

 toes ; and unites with n. communicans tibialis (which see). 



3. N. cutaneus externus, supplies the skin of the outer border 

 from the superior to the inferior extremity of the leg. 



j3. The superficial terminal branches of n. peronceus. 



4. Ramus super jicialis externus s. N. cutaneus dorsipedis me- 

 dius, passes on the outer side of the fibula, gives branches to 

 gastrocnemius extern., peronceus tertius, extensor hattucis 

 longus ; betakes itself to the middle of the anterior surface 

 of the leg, perforates the fascia, supplies the skin of this part 

 and about the external malleolus ; divides dichotomously on 



