The coat of the horse being composed of a material (hair) which is a bad conductor of heat, and being capable of holding between the hairs a large amount of air, which is a still worse conductor of heat, it affords an admirable protection to the body against external cold, when it is sufficiently long and thick, and when it is dry. As the presence of dandruff aids in this form of protection, and as grooming tends to remove dandruff and loose hairs from the coat; the less a horse is groomed, the better will he stand cold. When the coat becomes soaked with water, its conductivity is increased, probably, at least twenty times, as we may infer from a comparison between the conducting powers of water, wool, and air. Horses which have long coats, and which remain in the open during cold weather, suffer very little from lying out on dry snow; for the coat is such a bad conductor that it allows the heat of the body to melt only a small amount of the snow with which the coat is in contact, and consequently the portion of the coat that is next the skin remains dry. The skin of the horse, like other kinds of leather, conducts heat far better than hair.

Besides protecting the body from cold by being a bad conductor of heat, the coat guards it from chill, by reason of its great capacity for absorbing and retaining moisture. Therefore, when a horse with a long coat perspires freely after exercise, the sweat, by the action of the heat of the body, quickly leaves the surface of the skin and accumulates near the ends of the hairs, from whence it evaporates slowly, and consequently the animal does not run much risk of getting chilled. With a short coated or clipped horse in similar circumstances, the sweat would be more or less in contact with the skin, which would cool much more rapidly, on account of the sweat (practically water) being a far better conductor of heat than either hair or the air that is imprisoned between the fibres of a long coat. If, however, we placed a rug over the animal, the sweat would become speedily transferred to the woollen material, which, like the outer portion of the hair of a long coated horse, would help to prevent chill by giving off the moisture slowly. In our own cases, a flannel shirt acts in a similar manner.

The efficiency of the unclipped coat as a protection against cold is well shown by the immunity from chill displayed by cab horses in Russia during winter. These animals, which are not clipped, are driven fairly fast in their work, and often, when reeking with sweat, are pulled up and kept standing in the street for a considerable time. In such cases, the perspiration becomes quickly frozen on the outside of the coat into particles which are kept well away from the skin by the hairs being long, and consequently the formation of this icy layer produces little or no bad effect on the horse's health. If these animals were exposed in an unclipped condition to such a trial, they would rarely escape a cough or a cold, if not more serious disease; unless they were covered over with warm clothing the moment their work was stopped, which is a precaution I have never seen taken in that country, except with match trotters. Its neglect does not appear to be accompanied by any bad result; for the coats being left long, the horses keep in health. According to the present regulations in St. Petersburg, when the temperature of the air goes down to - 10° R. (9.50 F.), each cab driver is obliged to provide his horse with a warm loin-cloth, which is not removed during work. The question of the influence of a long coat on work, will be discussed under the heading of "Clipping" (p. 350).