Unnerving and Cocaining.
Chronic lameness is done away with by skilful obliteration of the large nerves which supply the affected parts with sensation. The operation is termed nerving or unnerving in common parlance and, properly, as neurectomy. It consists in cutting down upon the nerve and then removing a portion so that its function is destroyed so far as the portion below the seat of operation is concerned. Unnerving is most often done to hide the lameness caused by navicular disease which is incurable: it may also be practised on account of ringbone, side-bone, founder or other unsoundness of the foot. After unnerving the horse does not evince pain when the parts below the seat of the operation are pinched or pricked. The operation merely does away with pain and lameness. It is in no way a cure.
Cocaine or eucaine solution injected by means of a hypodermic syringe upon the nerves at the points where neurectomy would be performed will temporarily have an effect like that of the operation. Just after the injection a swollen or puffed place may be discovered at the point where the hypodermic needle was inserted, and local soreness may be present after the effects of the drug have subsided.