380 The Sacral Plexus 



Its course may be chalked by a line which connects the middle of 

 the hollow between the tuberosity and the trochanter with the top of 

 the popliteal space. It is crossed obliquely by the long head of the 

 biceps. The nerve supplies the biceps, semi-tendinosus, and semi- 

 membranosus. Its companion artery, the comes nervi ischiatici, is a 

 branch of the sciatic artery. 



Sciatica is a painful condition of the large nerve, and may be due 

 to spinal disease, to intra- or extra-pelvic pressure, or to a chronic 

 inflammatory condition of the connective tissue in and around the 

 nerve-trunk. In due course it may cause wasting of the muscles and 

 stiffening of the joints. The neuralgia may sometimes be relieved by 

 massage along the back of the thigh, or by acupuncture. 



Bloodless stretching of the nerve may be accomplished by flexing 

 the foot to a right angle, extending the leg on the thigh, and then 

 forcibly flexing the thigh upon the abdomen. A more efficient way of 

 stretching the nerve is through an incision of five or six inches down 

 the back of the thigh, extending downwards from the gluteal fold at a 

 point midway between the tuberosity and the great trochanter. The 

 incision passes through the superficial fascia (fat) and the fascia lata, 

 down to the upper part of the hamstring muscles. These muscles 

 are then drawn inwards, and the nerve is isolated from its bed of fat 

 and connective tissue and steadily hauled upon for some minutes, first 

 downwards, then upwards. 



The internal popliteal nerve is much larger than the outer 

 division of the great sciatic, and it continues the original cdurse of the 

 great nerve. In the upper part of the ham it lies superficial and ex- 

 ternal to the popliteal vessels ; in the inter-condylar notch it is placed 

 directly over them, and at the lower border of the popliteus it is to 

 their inner side. Thence it is continued on as the posterior tibial. 



The internal popliteal nerve gives off three branches to the knee- 

 ioint which accompany the superior and inferior internal articular, and 

 the azygos articular arteries. Muscular branches supply the gastro-cne- 

 mius, soleus, plantaris, and popliteus. The external saphcnous branch 

 descends between the bellies of the gastrocnemius, and, piercing the 

 deep fascia below the calf, is joined by a branch of the external popli- 

 teal. It passes below the outer malleolus with the short saphenous 

 vein, and ends on the dorsal aspect of the outer side of the foot and of 

 the little toe. 



The posterior tibial continues the internal popliteal nerve from 

 the lower border of the popliteus to the inner ankle, where it divides 

 into the two plantars. For the first inch it is placed to the inner side 

 of the posterior tibial artery ; it then passes over the artery and lies 

 for the rest of its extent to the outer side. It is covered by the gastro- 

 cnemius and soleus, and by a second layer of the deep fascia, which 

 separates it from the soleus. It rests upon the tibialis posticus, the 

 flexor longus digitorum, the tibia and the ankle-joint. Behind the 



