_In the case of Lameness Persisting after the healing of all appreciable lesions_, then neurectomy is followed by good results. The animal, apparently recovered, is for a long time useless. Lameness persists for several months, as if the nail had at the moment of its penetration caused lesions, which doubtless it sometimes does, similar to those of navicular disease. Examination of the foot in this case reveals no lesion, and the pain has evidently a deep origin. The lameness caused by it is subject to variation. Frequently it becomes lessened during rest, and increased by hard work, while sometimes it is very much more pronounced at starting than after exercise. It is here that neurectomy is called for. The operation does nothing to impede the work of healing going on, and allows free movement of the foot and pastern to take place. At the same time suffering and emaciation cease, and the animal is rendered workable.[A] [Footnote A: _Veterinary Record_, vol. ii., p. 371.] C. CORONITIS (SIMPLE). TREAD, OVERREACH, ETC. 1. _Acute_. _Definition_.--Under the heading of simple coronitis in its acute form we intend to describe those inflammatory conditions of the skin and underlying structures of the coronet occurring without specific cause. Specific coronitis will be found described in Chapter IX. _Causes_.--This condition is almost invariably set up by an injury--either a bruise or an actual wound--to the coronet. By far the most common among such injuries are those inflicted by the animal himself by means of the shoes. That known as 'tread' is caused by the shoe on the opposite foot, and may happen in a variety of ways. More often than not it is met with in the feet of heavy draught animals, and is there caused by the calkin, either when being violently backed or suddenly turned round. It may also occur in horses with itchy legs, as a result of the animal rubbing the leg with the shoe of the opposite limb. The irritation in this case is nearly always due to parasitic infection (_Symbiotes equi_), and becomes sometimes so unbearable as to render the animal unmindful of the injury he may be inflicting so long as he experiences the relief obtained by the rubbing. Self-inflicted tread is also sometimes met with when horses are worked abreast at plough. The animal in the furrow, with one foot sometimes in and sometimes out of the hollow, is caused to make a false step, and so brings the injury about. Animals worked in pairs are further liable to receive a tread from the foot of their companion. This is commonly seen in heavy animals at agricultural labour in fields, where the walking is uneven, and abrupt turning constant. It is not uncommon either in animals at work in vans in town, and is occasionally met with in the feet of carriage-horses.