If any man who doubts this excellence to be in the blood, should ask how it came to pass that we often see two full brothers, one of which is a good racer, the other indifferent, or perhaps bad, I know of but two answers that can be given; we must either allow this excellence of the blood to be partial, or else we must say, that by putting together a Horse and a Mare, different in their shapes, a foetus may be produced of a happy form at one time, and at another the foetus partaking more or less of the shape of either, may not be so happily formed.  Which shall we do? shall we impute this difference of goodness in the two brothers, to the difference of their mechanism? or shall we say this perfection of the blood is partial?  If the latter, then we must own that blood is not to be relied on, but that the system of it, and whatever is built on that foundation, is precarious and uncertain, and therefore falls to the ground of its own accord.  Whilst this continues to be the rule of breeding, I mean of putting male and female together, with no consideration but that of blood and a proper cross, it is no wonder so few good racers are produced, no wonder mankind are disappointed in their pleasures and expectations; for this prejudice does not only extend to blood, but even to the very names of the breeders, and the country where the Horses are bred, though it is beyond all doubt, that the North claims the preference of all other places in this kingdom; but that preference is allowed only from the multiplicity of Mares and Stallions in those parts, and from the number of racers there bred.

I would not be thought in this to prefer my own opinion of shape and make to the known goodness of any Stallion, but would prefer the latter before the opinion of all mankind.  What then?  It is not every Horse that has been a good racer will get good colts; some have suffered too much in their constitution by hard and continual labour, whilst others have some natural infirmity that may probably be entailed on their generation.

But the most material thing in breeding all animals, and to which we pay the least regard, either in the race of men or Horses, is the choice of the female, who not only joins in the production of the foetus, but in the formation of it also.  And that the female has even the greatest share in the production of the foetus, will be proved by this instance:  if you take a dunghill cock and put to a game hen, and also put a brother of that game hen to a sister of the dunghill cock, those chickens bred from the game hen will be found much superior to those chickens bred from the dunghill hen.

And here I beg leave to be allowed (without the imputation of pedantry) one quotation from Virgil, who is supposed to have well understood the laws of nature.  In his description of the choice of animals for procreation, in the third chapter of his Georgic’s, and the 49th verse, you will find it thus written: 

“Seu quis Olympiacea mieratus praemia palme,
“Pascit Equos, feu quis fortes ad aratra Juvencos,
“Corpora praecipue matrum legat.”