Experience proves that the health of stabled horses, other conditions being equal, varies according to the purity of the air in the building, which, under ordinary circumstances in cold and moderate climates, varies inversely as the difference between the temperature of the air of the stable and that of the air outside; for this difference will be chiefly due to the heat given off by decomposing urine and dung, and by noxious exhalations from the lungs and skin of the animals. Besides, the warmer the stable, especially when the floor is kept in a wet condition, the damper and consequently the more unhealthy will be its atmosphere. Heat directly promotes the contamination of the air of a stable, by encouraging the volatilisation of ammonia and ammonium carbonate. Damp and heat combined, exert a very favourable influence on the cultivation of disease germs. In hot damp stables, contagious pleuro-pneumonia is often a resident; the microbes of influenza and other diseases find a favourable breeding ground; and ophthalmia, with the frequent result of cataract, is common, from the constant irritation to the eyes caused by the presence of ammonia in the air. Veterinary surgeons have often observed that during outbreaks of influenza (pink-eye), the disease is rarer and less severe in stables which have waterproof floors, than in those the flooring of which soaks up moisture, and then, under the influence of heat, continues to distribute it in the form of vapour throughout the building. Also, the substitution of waterproof floors for absorbent floors has frequently proved to be a valuable safeguard against disease in the stables. "Formerly in the French army the mortality among the horses was enormous. Rossignol states that previous to 1836 the mortality of the French cavalry horses varied from 180 to 197 per 1,000 per annum. The enlargement of the stables and the increased allowance of air has reduced the loss in the present day to 24.2 per 1,000. In the English cavalry and in English racing stables the same facts are well known. The annual mortality of cavalry horses, which was formerly great, is now (1895) reduced to 23.7 per 1,000" (Notter and Firth).

Experience also teaches us that if horses are protected from draughts and damp, liberally fed, comfortably bedded down, and clothed according to their requirements, they will thrive even if the temperature of the stable is as cold as that of a Siberian winter. We should bear in mind that the effect of heat is to lessen the number of respirations; that is to say, it diminishes the action of the lungs. In the influence of residence in high altitudes on cases of phthisis (pulmonary consumption), we have a good instance of the beneficial effect, on the lungs, of a climate which acts as a stimulant to them.

The least objectionable form of artificially warming the inhabitants of a dwelling, is by radiated heat, which, as we have seen, has the property of heating the object upon which it falls, without raising the temperature of the medium through which it passes. Consequently, in a room with an open grate and a brightly burning fire, we may keep warm, even when the air inside the room remains cold. With a system of heating by conduction - as for instance by hot-water pipes or hot air - the persons or animals inside the room become warmed solely by contact with the heated air, which, as we have seen, has a depressing effect on the lungs. The application to stable management of radiated heat acting directly on horses, is of course out of the question in ordinary circumstances.

I have had many opportunities in Russia of comparing the relative healthiness, during very cold weather, of hot stables and of those kept at a natural temperature. In large towns in Russia, the practice throughout the winter is to have stables at a temperature of from 500 to 65° F., the difference between the temperature inside and outside being not unfrequently over 8o° F. Consequently, influenza, inflammation of the eyes, and diseases of the organs of breathing, especially roaring among big horses, are common in these abodes. In the Russian cavalry remount depots (cadres), an entirely different course is pursued; for the stables at these places are immensely roomy, very lofty, and are ventilated so freely and kept so clean, that even in the early mornings before the horses are taken out, the air inside is free from any suspicion of "closeness." It is instructive to note that the horses kept in them, maintain their health during the extremely cold winter, in the same excellent manner as they do in summer. Some years ago a change was made in the stables of the cadres at Liski on the Don, to the old plan of closing more or less perfectly all inlets and outlets of air; but it was followed by such a marked increase of cases of illness among the horses, that the new system of free ventilation was again put into force and with the happiest results.

In our own cases, we find the advantage, even in winter, of having the air we breathe more or less at the same temperature as that in the open. Even at night, we are far less apt to catch cold, if we make a practice of always keeping one or more of our bedroom windows open, than if we have them all closed; supposing of course that we have plenty of warm bed clothes. The success of the open air treatment of consumption is a proof of the good sanitary influence of free ventilation. The argument is all the stronger when applied to horses than to us; because they, contrary to the custom observed by human beings, spend a considerable portion of at least the early part of their life in field or paddock without clothing. In the attempt to keep our stables cool, we must not lose sight of the fact that in our climate, a cold draught of air on a stabled horse is very likely to give him a chill, which, as we have seen, is a frequent cause of equine illness. Every experienced horseman knows that draughty stables in England are unhealthy stables.

The great cause of the popularity of hot stables among grooms, is the fact that horses kept in them have a glossier coat while in the stable, than animals which are housed in better ventilated abodes. The difference is all the other way, when the horses are brought into the cold air outside.