This section is from the book "Hints To Purchasers Of Horses", by Charles Knight. Also available from Amazon: Hints to Purchasers of Horses.
Here be it observed, a horse in all his paces should go clear, and not cut, or touch one leg with the other. He cannot go too near if he does not go to cut. Those horses go to cut their fore-legs, that hook in their heels; when low actioned, and in their slow paces, they hit their ancles; and when high goers, and moving fast they hit their knees; sometimes they hit midways, on the splent bone, between knee and ancle. Nothing is more objectionable than such interfering action; the wound it inflicts creates always of necessity inflammation and filling of the leg; and it frequently occasions a horse to fall very suddenly. The act of cutting with the hind legs, though not of such consequence as with the fore, makes the joints large, and weakens them by the repeated sore it occasions. Cutting behind results either from the hocks being open and wide apart, in which case the toe comes in contact with the ancle; or from the hocks being in clined too much inward, in this case the end of the heel does the mischief. There are very few horses that do not hit their hind-legs some time or other; particularly when young, and weak, and often when weary with long and great exertion. But observe, those that cut from natural causes, either behind or before, never receive any permanent benefit from an alteration in shoeing; which method of remedy unavoidably curtails the natural size, and alters the natural shape of the foot, and not only does not obviate the imperfection, but, if persisted in, occasions lameness in addition. I should strongly recommend that a horse, who goes to cut his legs, be rejected.
Those horses that dish the foot outwards, never cut their fore-legs; and though some judges do not consider such method of going to be perfect action, it is by no means objectionable. Where coach-horses and others worked upon the stones, from the state of the pavement, necessarily slip and slide about and are unable to deliver their feet with any degree of certainty, dishing the foot outwards quite precludes the possibility of hitting, notwithstanding the difficulty they experience in obtaining foot-hold.
It is also particularly desirable that a horse in all his paces be a quick stepper, and that he go very lightly with his fore-legs, but hit the ground hard with his hind-legs; or to use a horse-dealer's phrase, he should trot over a street paved with eggs without breaking one with his fore-legs, but bore holes with his hind.
Horses with quick light action, seldom wear their legs out, if they are not used when too young, which ruins all horses; and the reason of their lasting is, that they do not hammer the ground, and shake themselves all to pieces, which heavy slow movers do, but going free of all concussion, they do their work without detriment to themselves, and with pleasure to their riders.
But action is in a great degree referable to the position and make of the shoulders; and having already mentioned what their shape ought to be, I shall now give the reason why it depends so much upon their form and situation. In the first place, when the shoulders are low and upright, the weight the animal carries is directly upon his fore-legs; it is not then to be wondered at, that he experiences difficulty in using them lightly; and as, instead of being from him, they stand quite under him, he has equal difficulty in putting them forward. He is therefore evidently more liable to stumble; and when he does trip, the load he carries being almost more forward than his fore-legs, prevents him recovering himself, and down he comes. When the shoulders are themselves loaded at top, as well as upright, there is a double imperfection; for then there is a natural weight, as well as the weight artificial; and when they are loaded at the points, they occasion great heaviness of action, and if the animal is a high goer, he hits the ground so much the more forcibly; the objection to which has been already stated. Horses with bad shoulders may go well for a short time; but after six or seven miles' journey they begin to make mistakes, and as their shape is not calculated for movement, so their action cannot continue.
Though the fore-legs, from their very situation, always bear the greatest portion of weight, yet, when the shoulders lie back, more of the weight is communicated to the spine; and being thus removed from the fore-legs, they have less impediment to motion, and their position being then forward, is naturally more favourable to the office they have to perform.
Good action may be considered equivalent to strength. This is confirmed by the fact of many horses with great substance, when bad goers, failing in their joints; while slighter horses with good action are seldom found to give way, even carrying the same weight. Of this I have seen very many instances; which circumstance alone shews how necessary it is that a horse be a good goer.
 
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