892 ULNAR NEURECTOMY. 



forward and to protrude between the lips of the incision in the 

 aponeurosis. When the nerve does not appear, it is usually sufficient 

 slightly to alter the position of the limb. The most serious difficulty 

 to be feared is from injury to the veins in this neighbourhood, and 

 every care must be taken to avoid such a complication. 



Peters, and after him others, showed that division of the median 

 nerve alone may remove lameness resulting from bilateral lesions — 

 that is to say, occupying both sides of one of the lower parts of the 

 leg, or encircling these regions. The results are explained by the 

 preponderating influence of the median nerve in the innervation of 

 structures below the knee, a preponderance due to the fact that at 

 a variable point in the fore-arm the nerve terminates by dividing 

 into two branches, one of which is continued as the internal plantar 

 nerve, while the other joins the ulnar and is continued as the external 

 plantar nerve. 



Cadiot and others have seen horses in which lameness, arising 

 from various chronic affections (strained tendons, splints and ring- 

 bones), has been removed, or certainly diminished, by resection of 

 the median nerve. But cases occur in which section of the median 

 fails to remove lameness caused by lesions on the outer side of the 

 limb, or at times even on the inner. The persistence of pain and 

 lameness in the latter case may sometimes be explained by the 

 existence of recurrent fibres. Under such circumstances, ulnar, 

 or external plantar neurectomy may prove useful. 



Ulnar neurectomy. Throughout the whole extent of the fore- 

 arm the ulnar nerve, accompanied by the ulnar artery and vein, 

 is situate between the oblique and external flexors of the metacarpus, 

 and under the fascia uniting them. By palpation with the finger 

 tips the muscular interspace which indicates the line of incision 

 is readily discovered. 



In performing this operation the horse is cast on the sound side. 

 The affected limb is left in the hobbles, but held extended by means 

 of two strips of webbing, one fixed on the upper portion of the cannon 

 bone being pulled backwards, the other, attached to the coronet, 

 in a forward direction. Two assistants, holding the free ends, keep 

 the parts steady. The operator kneels in front of the upper part 

 of the fore-arm ; the point selected is about four inches above the 

 pisiform bone. The parts having been prepared, he makes at the 

 point just indicated an incision about 1 to lh inches long through 

 the skin, subcutaneous connective tissue, and the fascia which unites 

 the aponeurotic covering of the two muscles. 



With forceps and bistoury the connective tissue surrounding the 



