THE GREAT SCIATIC NERVE 165 



front of the great sciatic nerve, from which it is detached usually as 

 the latter crosses the gemelli muscles. It takes a course which is down- 

 wards and forwards, and passes between the outer head of the gastroc- 

 nemius and the biceps femoris muscle, and thus appears on the outer 

 aspect of the limb near the stifle joint, behind the external lateral ligament 

 of which it will be found. Here the external popliteal nerve terminates 

 by dividing into the musculo-cutaneous and anterior tibial nerves. 

 These nerves will be dealt with later. 



During its course the external popliteal gives off a branch which 

 passes downwards and slightly backwards over the outer aspect of the 

 gastrocnemius muscle to communicate with the external saphena 

 nerve in the manner described below. 



About two inches below the point at which the above branch is 

 detached the peroneal-cutaneous branch is given off from the external 

 popliteal nerve. It leaves the parent nerve just above the gastrocnemius 

 muscle, and, passing across the inferior extremity of the biceps femoris, it 

 becomes superficial and splits up into a large number of slender filaments, 

 which ramify on the outer aspect of the stifle joint and the upper portion 

 of the leg. 



Occasionally the above nerve of communication with the external 

 saphena nerve is given off as a collateral branch of the peroneal 

 cutaneous nerve. 



3. A short and thick branch is given off at the curve formed by the 

 parent nerve before it descends the thigh and as it crosses the gemelli 

 muscles. It splits up almost immediately into a number of branches, 

 which are distributed to the semimembranosus, the lower two-thirds 

 of the semitendinosus, and the inferior portion of the biceps femoris. 

 Some filaments also run between the semimembranosus and the adductor 

 magnus, and terminate in the latter muscle. 



4. The 'External Saphena Nerve. — This branch is given off" by the great 

 sciatic nerve about four to six inches above the point where the latter 

 disappears between the two heads of the gastrocnemius muscle. The 



