This may be due to exhaustion after severe exertion, to a weak or diseased condition of the heart, or as the result of a debilitating disease. There are usually no premonitory signs, the horse falling, and lying perfectly still and unconscious, the breathing being perhaps slower than natural, and the pulse weak and small. An indication that the animal is unconscious is in the tongue not being retracted when it is drawn out of the mouth.

To promote recovery, sponge out the mouth with cold water, and allow the animal to swallow some, if he can. If possible, place the head down hill, or on a lower level than the body. Hand-rub the legs and ears well, after removing the bridle and slackening the girths. When the horse can swallow, give a stimulant, which may be one or two wine-glassfuls of spirit in a quart of water, or a quart of old ale warmed, with some powdered ginger added. When the horse gets up the surface of the body should be well rubbed, wisped, and dried.