Let us next inquire what information we can gather from the science of Anatomy, concerning the laws of motion:  it teaches us, that the force and power of a muscle consists in the number of fibres of which it is composed; and that the velocity and motion of a muscle consists in the length and extent of its fibres.  Let us compare this doctrine with the language of the jockey:  he tells us, if a Horse has not length, he will be slow; and if made to slender, he will not be able to bring his weight through.  Does not the observation of the jockey exactly correspond with this doctrine?  If we now inquire into the motion of Horses, we shall find the bones are the levers of the body, and the tendons and muscles (which are one and the same thing) are the powers of acting applied to these levers.  Now when we consider a half-bred Horse running one mile or more, with the same velocity as a Horse of foreign extraction, we do not impute that equality of velocity to any innate quality in the half-bred Horse, because we can account for it by external causes:  that is by an equality of the length, and extent of his levers and tendons.  And when we consider a half-bred Horse running one mile, or more, with the same velocity as the other, and then giving it up, what shall we do? shall we say the foreigner beats him by his blood, or by the force and power of his tendons? or can we, without reproaching our own reason and understanding, impute that to be the effect of occult and hidden causes in the one of these instances and not in the other? both of which are demonstrated with certainty, and reduced to facts by the knowledge of anatomy and the principles of mechanics.

How many instances have we of different Horses beating each other alternately over different sorts of ground! how often do we see short, close, compact Horses beating others of a more lengthened shape, over high and hilly coursed, as well as deep and slippery ground; in the latter of which, the blood is esteemed much better, and whose performances in general are much better!

And how comes it to pass that Horses of a more lengthened shape, have a superiority over Horses of a shorter make, upon level and flat courses?  Is this effected by the difference of their mechanical powers, or is it affected by the blood? if, by the latter, then this blood is not general, but partial only, which no reasoning man will be absurd enough to allow.  But I much fear our distinctions of good and bad blood are determined with much partiality; for every jockey has his particular favourite blood, of which he judges from events, success, or prejudice:  else, how comes it to pass, that we see the different opinions and fashions of blood varying daily! nay, we see the very same blood undergoing the very same fate; this year rejected, the next in the highest esteem; or this year in high repute, the next held at nothing.  How many changes has the blood of Childers undergone! once the best, then the worst, now good again!