496 SURGICAL APPLIED ANATOMY [Chap. xxm. 



portions of the skin supplied by cutaneous branches 

 of the nerve. 



Paralysis of the internal popliteal nerve. 



In this condition there is inability to extend the 

 ankle and to flex the toes (flexor longus digitorura, 

 flexor proprius pollicis, tibialis posticus, gastrocnemius, 

 arid soleus). The patient is unable to stand upon the 

 toes owing to loss of function in the two last-named 

 muscles. The power of adducting the foot and of 

 raising its inner border is impaired (tibialis posticus), 

 and lateral movements in the various toes are lost 

 owing to the paralysis of all the small muscles of the 

 sole. Sensation is impaired over the plantar aspect 

 of the toes, the sole of the foot, and in part of the 

 lower half of the back of the leg. 



In paralysis of the external popliteal nerve 

 the action of the muscles on the front of the leg is 

 lost. The foot hangs down and the toes catch the 

 ground in walking. The foot can be neither flexed 

 nor abducted (extensor communis digitorum, extensor 

 propius pollicis, peroneal muscles). Adduction is im- 

 perfectly performed, owing to paralysis of the tibialis 

 anticus. Extension of the toes is only possible to the 

 slight extent effected by the interossei muscles. The 

 arch of the foot becomes flattened owing to loss of 

 the support furnished by the peroneus longus. Sen- 

 sation is impaired over the front and outer side of 

 the leg and on the dorsum of the foot, and also over 

 some part of the back of the leg, owing to paralysis of 

 the communicans peroriei. 



When the great sciatic nerve is paralysed 

 there will be, in addition to the effects produced by 

 loss of function in the two preceding nerves, an in- 

 ability to flex the knee, owing to paralysis of the 

 hamstrings, while rotation of the limb may be 

 impaired by loss of power in the quadratus femoris 

 and obturator internus muscles. 



