Windows may or may not be made to open. Some of them should open, in order that the stable may, upon certain occasions, receive an extraordinary airing. But for constant and necessary ventilation there must be apertures which can never be wholly closed.

Window-shutters, in some situations, are useful for three purposes. By darkening the stable they encourage a fatigued horse to rest through the day; they keep out the flies in the hot days of summer; and in winter they help to keep the stable warm. They may be made of wood, of basket-work, or of matting, according to the purpose for which they are wanted. In some stables the windows are removable, so that in summer they can be taken out and their place filled by a piece of basket-work or framed canvass, which may be wet in hot weather. The stables are thus kept cool; the flies and the heat of the sun are excluded. Some horses are sadly annoyed by flies. They do not enter a dark stable.