THE LOWER LIMB 445 



The muscular (sural) branches are usually five in number, 

 which are distributed as follows : one to the external head of 

 the gastrocnemius, one to the plantaris (which sometimes comes 

 from the preceding), one to the internal head of the gastroc- 

 nemius, one to the soleus, and one to the popliteus. The nerve to 

 the popliteus descends over the popliteal fascia, lying to the outer 

 side of the popliteal vessels. On arriving at the lower border of 

 the popliteus, it turns round that border and enters the deep surface 

 of the muscle. This ner\-e, besides supplying the popUteus, fmnishes 

 the following branches : articular to the superior tibio-fibular joint ; 

 medullary, which enters the large nutrient or medullary foramen 

 on the back of the tibia ; vascular to the anterior and posterior 

 tibial arteries ; and interosseous. The interosseous branch is a long 

 nerve which descends in the interosseous membrane to terminate in 

 the inferior tibio-fibular joint. 



External Popliteal or Peroneal (Fibular) Nerve. — ^This nerve is 

 the other terminal branch of the great sciatic, and it derives its 

 fibres from the dorsal divisions of the descending branch of the 

 fourth lumbar, the fifth Irnnbar, and the first and second sacral 

 nerves. It commences at the superior angle of the popliteal space, 

 and descends obliquely downwards and outwards as low as the 

 back of the neck of the fibvila, where it passes forwards between 

 the bone and the peroneus longus, to end on the outer side of 

 the fibular neck in its terminal branches. The nerve lies at first 

 close to the inner border of the biceps femoris, and then it rests 

 upon the back of the external head of the gastrocnemius, between 

 which and the biceps tendon it may be regarded as lying. 



Branches. — ^The branches are articular, cutaneous, and terminal. 



The articular branches are three in number, as follows : superior, 

 accompanying the superior external articular artery ; inferior, 

 going with the inferior external articular artery, which it reaches 

 as the vessel is about to pass beneath the biceps tendon ; and 

 recurrent articular, accompanying the anterior tibial recurrent 

 artery. 



The cutaneous branches are two in number, as follows : lateral 

 cutaneous branch, which supplies the integmnent of the outer 

 side of the leg over about its upper two- thirds, as well as the 

 adjacent integument of the sural region ; and ramus communicans 

 fibularis, which passes downwards and inwards over the external 

 head of the gastrocnemius and beneath the deep fascia to the centre 

 of the calf, where it pierces the deep fascia and shortly afterwards 

 joins the ramus communicans tibialis, to form the external or short 

 saphenous nerve. 



The terminal branches are three in number, as follows : recurrent 

 articular, already referred to ; anterior tibial (see p. 509) ; and 

 musculo-cutaneous (see p. 503). 



For the geniculate branch of the obturator nerve, see p. 474. 

 . Popliteal Lymphatic Glands. — These are usually four in niunber, 

 jand lie in close contact with the popliteal artery, one being 



