The ventilation of the stable is of supreme importance, as probably one-half of the diseases from which horses suffer may be traced directly or indirectly to defective ventilation. The method found most satisfactory is by the introduction of a small glazed ventilator (fig. 578) in the stable-wall, as high above the horse's head as possible. The fresh air, being thrown upward towards the ceiling, carries the air as heated and contaminated by the horse's breath towards the back of the stable. From this one or more shafts should be provided, according to the size of the stable, but at least one to every three or four horses, up through the loft, and discharging (if possible) at the ridge through a suitable ventilating-cowl. The whole system of ventilation is shown in fig. 574. Wherever practicable, windows ought to be provided in the front and back walls of a stable, and if another window can be placed in the gable ending, extending upwards to the ceiling, it will be a great improvement. These windows not only admit light, but, if made to open, can be adjusted to serve both as inlets and outlets for air.

Combined Window and Air inlet.

Fig. 578. - Combined Window and Air-inlet.

In ventilation, as in everything else about a stable, simplicity is of the first importance. Beware of elaborate contrivances that look pretty upon paper, but require constant attention to ensure their proper working. An automatic system, depending solely upon the flow of the atmospheric currents, and the poise and the counterpoise always going on between the inner and outer temperature, and consequent weight of the air, may fail during some rare calm, or on an exceptionally hot day; but, on the other hand, it is independent of the stableman, who probably understands but little of the theory of ventilation, and is liable to be careless or indifferent even when he does.

Another method of ventilation, first suggested by Mr. Alfred Water-house, E.A., is a modification of that generally known as "Tobin's". The end of the stall-division nearest the horse's head is cast hollow, in the form of an oblong tube, at the lower end of which the air is introduced by a grating in the outside wall, and, passing up the hollow with an impetus towards the ceiling, spreads out all round without draught.

As before stated, the heated air from the stable should not be allowed to escape into the hay-loft, either through traps in the ceiling or through other openings; a special air-shaft should be provided, and the hay brought down through a shoot if possible in an outside passage, or in the fodder-room. The loft stairs also should not rise directly from the stable. To render the stable ceiling completely air-tight may not be easy, for plaster is not desirable under a hay-loft, and boarding, even when grooved and tongued, is apt to shrink and become far from impervious. Felt, or at least brown paper, laid under the floor-boarding, or over the ceiling-boarding, answers the purpose well, however, and is not expensive. The hay-lofts should, of course, be well ventilated by louvred windows, arranged to allow a full current of air through every part of the loft.