This section is from the book "The Stable Book: Being A Treatise On The Management Of Horses", by John Stewart. Also available from Amazon: The Stable Book.
The natural powers of the horse, contrasted with those he acquires, are feeble beyond what a stranger can conceive. Some people are prone to talk nonsense about nature. They would have horses placed as nearly as possible in a wild state, or a state of nature, which, I suppose, means the same thing. In the open fields the horse, it is said, has pure air, a wholesome diet, and exercise good for the limbs and the constitution. God never intended so noble an animal to suffer confinement in a dark and narrow dungeon, nor to eat the artificial food provided by man. Much more is said; but it is not worth repeating. The truth is, setting argument aside, we must have service, even at the hazard of producing diseases that never occur in a state of nature. Before the horse can do all, or half of all that he is capable of doing, he must be completely domesticated. In the artificial management to which he is subjected there are many errors; but instead of condemning the system by wholesale, it were wiser to rectify what is wrong.
A horse, kept in a state of nature, would not last half a day in the hunting-field; and at stage-coaching two or three days would kill him.
Conditioning, Training, and Seasoning, as words, have nearly the same meaning. The first is used most in reference to hunters, but occasionally to all kinds of horses; the second is confined almost entirely to racers: and the third to horses employed in public conveyances, mails, stage-coaches, and so forth. They relate solely to the processes and agents by which strength, speed, and endurance, are conferred. The terms have little or nothing to do with the precautionary measures considered in the first section of this chapter; they are limited to the means by which the horse is inured to severe exertion. As I proceed I use the words synonymously, and employ preparation, or preparing for work, with the same meaning.
The Objects of Training, whether for the turf, the road, or the field, are the same. They vary in degree only, not in kind. For either of these purposes the horse must have speed, strength, and endurance. This last word is not quite so expressive as I wish. It is intended to signify lasting speed; it relates to the distance; speed is in relation to time strength, to the weight carried or drawn. In stables, the words length and stoutness are used for endurance. These three properties are common to all horses, but they exist in various degrees of combination. The age, breed, formation, and condition, exercise great influence upon them.* Young horses generally have more speed than stoutness : at, and after maturity, stoutness is in greater perfection than speed. What are termed thorough-bred horses have speed, strength, and endurance, more of each in combination than any other breed. It would require a long chapter to consider all that might be said in connexion with formation; I pass it over only observing that large, long-striding horses generally have more speed, but less endurance, than lower compact horses. The formation has a great deal to do with strength, and therefore this property is less under the influence of training than the others are.
Training does not enable the horse to carry or draw much more than he can naturally, when in good health and spirits; but it enables him to carry a given weight farther and faster. The condition of the horse is the last circumstance I mention, as influencing his working properties. This is a matter of great importance. A horse, say a racehorse, may be of the right age, his pedigree may have no stain, and his formation no fault; he may be in perfect health, sound in wind and limb, but notwithstanding all this, the horse may be in a very bad condition; that is, for running a race. He may have too much carcass, he may have too much flesh about him, he may be short-winded, and his muscles may be unfit for protracted exertion. To put these into that state which experience has proved the best for a particular kind of work, forms the business of training, conditioning, seasoning. Before considering all the agents and processes employed by the trainer, I would make a few remarks upon the size of the belly, the state of the muscles, the state of the breathing, and the quantity of flesh.
 
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