514 



NEUROLOGY. 



two important branches, the external popliteal and external 

 saphenic nerves. 



The EXTERNAL POPLITEAL NERVE leaves the great sciatic 

 about the level of the gemelli muscles. It passes between the ad- 

 ductor magnus muscle and the gastrocnemius, and arrives at the 

 superior extremity of the leg, behind the lateral ligament of the 

 femoro-tibial articulation, when it terminates in two branches ; 

 one, the anterior tibial nerve, is short, and enters the muscles 

 attached to the superior extremity of the anterior face of the 

 tibia, in which it ramifies ; the other, the musculo- cutaneous 

 nerve, turns downwards by the outer side of 

 the anterior surface of the leg, and, passing 

 the hock, metatarsal bone, and fetlock, 

 terminates at the pastern. It gives off 

 numerous muscular and cutaneous filaments. 

 The EXTERNAL SAPHENIC NERVE is given 

 off shortly before the great sciatic enters the 

 gastrocnemius muscle, descending under the 

 fascia which covers the latter, and accom- 

 panying the external saphenic vein. It passes 

 the tarsal joint, and ramifies on the external 

 aspect of the metatarsus, some of its filaments 

 reaching the digital region. 



In addition to the above, a small nerve 

 is given off from the great sciatic to supply 

 the ischio-femoralis, gemelli, and obturator 

 interims ; also a large branch, the posterior 

 crural, arises as the sciatic nerve bends 

 downwards over the femur, and supplies the 

 muscles of the lateral and posterior femoral 

 regions. A fasciculus of nerves, given off as 

 the sciatic enters the gastrocnemius, assists in 

 supplying th e posterior tibial grou p of muscles. 

 The EXTERNAL and INTERNAL METATARSAL NERVES, formed 

 by the bifurcation of the great sciatic, pass down the side of the 

 flexor tendons, and terminate as the digital nerves. Towards the 

 superior extremity of the cannon bone, the external metatarsal 

 nerve is carried outwards between the splint bone and the tendon, 

 while the internal one is placed on the inner side of the tendon, 

 and follows the posterior border of the inner splint. The digital 

 nerves are distributed in a similar manner to those of the fore foot. 



FIG. 193. 



Tarsal aud metatarsal nerves 

 internal aspect, a, Iiitemal 

 cutaneous branch ; b, External 

 metatarsal ; c, Internal meta- 

 tarsal ; d, Their connecting 

 branch ; e, Internal digital. 



