1 66 THE SURGICAL ANATOMY OF THE HORSE 



external saphena nerve then takes a downward course over the external 

 aspect of the outer head of the gastrocnemius. At a point which 

 is in line with the position where the anterior tibial nerve disappears 

 between the peroneus and extensor pedis muscles it receives a branch of 

 communication from the external popliteal nerve. It then takes its course 

 down the limb in front of the tendo-Achilles, and immediately beneath 

 the fibrous aponeurosis of the leg. It is in close relationship to the 

 external saphena vein. Crossing the postero-external aspect of the hock, 

 its terminal ramifications are distributed superficially in the metatarsal 

 region. 



PARALYSIS OF THE GREAT SCIATIC NERVE 



Paralysis of this large nerve has not infrequently occurred. As would 

 naturally be gathered from the number of muscles supplied by the nerve 

 and its continuations, there is loss of power in almost the whole limb, 

 particularly in those parts controlled by the hamstring muscles and the 

 muscles in front of and at the back of the tibia. Flexion of all the 

 joints from the hip downwards is interfered with, and the animal is 

 capable of extending only the hip and stifle. Sensation is also lost in 

 the skin, which, it will be remembered, derives its supply from the large 

 number of cutaneous filaments which this nerve and its branches and 

 continuations give off. 



Since the extensors of the stifle are not affected, the animal can fix 

 this joint, and in consequence weight can be placed on the limb. 



Moller recorded a case which at first he thought was one of paralysis 

 of the external popliteal nerve only, but afterwards discovered that the 

 whole sciatic nerve was affected. The subject was an eight-year-old 

 Belgian gelding, which was found to be lame in the stall without any 

 apparent cause. Next day he appeared to show symptoms of partial 

 paralysis, but the symptoms gradually became more definite, and it was 

 seen that the right leg only was affected. " Whilst the left hind limb 



