I70 THE SURGICAL ANATOMY OF THE HORSE 



THE INTERNAL POPLITEAL NERVE 



As already stated, this nerve is the direct continuation of the great 

 sciatic. It is a short nerve, beginning where the great sciatic passes 

 between the two heads of the gastrocnemius muscle, and being directly 

 continued under the name of the posterior tibial nerve when it arrives at 

 the inferior border of the popliteus muscle. The nerve thus passes in 

 an almost vertical manner over the back of the stifle joint, its position at 

 the back of the joint being indicated in Plate VII, It follows for a short 

 distance the posterior border of the flexor perforatus muscle, and for the 

 remainder of its course it lies on the popliteus. It is a nerve of con- 

 siderable thickness, and distributes filaments to both heads of the gastroc- 

 nemius muscle, the flexor perforatus, the soleus, the popliteus, the flexor 

 accessorius, and the flexor perforans. It thus supplies all the muscles 

 behind the tibia. 



PARALYSIS OF THE INTERNAL POPLITEAL NERVE 



The position of this nerve affords it such a considerable degree of 

 protection against external injury that cases in which it is paralysed are 

 extremely rare. A reference to Plate VII. will reveal its adequate protec- 

 tion by the gastrocnemius muscle, &c., against injury from without. 

 Beneath the nerve again we have soft structures of considerable thickness, 

 which include the popliteus muscle, so that there is little risk of the 

 nerve being injured from a blow received externally over the area 

 through which the nerve passes, during the movements of the joint, or 

 from fracture of the neighbouring bones, except in cases of fractured 

 femur when the fracture occurs immediately above the condyles and the 

 healing is accompanied by the formation of an enormous amount of 

 callus. 



