What is an obstinate and often incurable disease of a horse's foot, characterized by separation of the horny portion and the development of fungoid growths; -- usually resulting from neglected thrush called?

canker — (Far.) An obstinate and often incurable disease of a horse's foot, characterized by separation of the horny portion and the development of fungoid growths; -- usually resulting from neglected thrush. (Webster's 1913.)

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