The question then is, whether this excellence of Horses is in the blood or the mechanism; whoever is for blood, let him take two brothers of any sort or kind, and breed one up in plenty, the other upon a barren heath; I fancy he will find, that a different mechanism of the body will be acquired to the two brothers by the difference of their living, and that the blood of him brought up on the barren heath, will not be able to contend with the mechanism of the other, brought up in a land of plenty. Now if this difference of shape will make a difference in the performance of the animal, it will be just the same thing in its consequences, whether this imperfection of shape be produced by scarcity of foot, or entailed by the laws of nature; if so, does it signify whether the colt be got by Turk, Barb, or what kind of blood his dam be of? or where shall we find one certain proof of the efficacy of blood in any Horse produced in any age or any country, independent of the laws of mechanics. If it should be urged, that these foreign Horses get better colts than their descendants, that therefore the blood of foreign ones is best, I answer, no; for that according to the number of foreign Stallions we have had in this kingdom, there have been more reputed and really bad than good ones, which would not happen in the case of Horses, who come from the same country, and are of the same extraction, if this goodness was in the blood only. But the true reason why foreign Horses get better colts than their descendants, if they do get better, is that (mechanism alike) their descendants from which we breed, are generally such Horses as have been thoroughly tried, consequently much strained, and gone through strong labour and fatigue; whereas the foreign Horse has perhaps seldom or never known what labour was; for we find the Turk a sober grave person, always riding a foot pace, except on emergencies, and the Arab preferring his Mare to his Horse for use and service. As a proof of this truth, let us take two sister hound bitches, and ward them both with the same dog; let us suppose one bitch to have run in the pack, and the other by some accident not to have worked at all, it will be found that the offspring of her who has never worked, will be much superior to the offspring of her who has run in the pack.