The first cardinal principle of horse breeding was formulated in England a century and a half ago in the expression: “Like begets like.” This rule has been followed in the creation and maintenance of all the great horse types in the civilized world, and singularly enough all of them, both great and small in size, have descended from Arab and Barb stock. This concise rule of breeding, “Like begets like,” has been misunderstood by some who did not take a sufficiently comprehensive view of it. This likeness does not refer merely to one thing; not to blood alone, nor to conformation, nor to performance; but to blood and to conformation and performance, but most of all to blood. Where blood lines, as to likeness, are disregarded, and conformation and performance are alone considered, the result is sure to be a lot of mongrels, some of them, it is true, of most surpassing excellence, but as a general thing, quite incapable of reproducing themselves with any reasonable certainty. The great danger always in breeding horses and other domestic animals with the idea of improving a type or a family, is that mongrels may be produced. A mongrel is an animal that results from the union of dissimilar and heterogeneous blood. An improved and established reproducing type has hitherto been, and probably always will be, the result of the mingling of similar and homogeneous blood, crossed and recrossed until the similar becomes consanguineous. The Arab and Barb, I have said, are the foundation in blood of all the great types from the Percheron to the Thoroughbred. To be sure, other and dissimilar blood was used in the beginning of the making of all the types, but there was such crossing and recrossing, such grading up by a selection of mates, that the blood became similar, and the rule: “Like begets like,” being constantly followed a type becomes established.