28. What amounts to unsoundness.

If at the time of sale a horse has any disease or defect which actually diminishes, or in its ordinary progress will diminish, its natural usefulness, it is not sound1. A congenital defect, such as convexity of the cornea of the eye, which causes short-sightedness and induces the habit of shying, is unsoundness2. The slightness of the disease, or the ease with which it is cured, may affect the amount of damages, but does not affect the principle, unless it is of so trifling a character as not to amount to unsoundness at all