n breed, has occasioned much of the
disappointment of which breeders have had occasion to complain.

The principle here laid down is one of broad application, and should
never be lost sight of in attempts at improvement by crossing. Another
point worthy special attention is that all crossing, to insure
successful results, should be gentle rather than violent; that is,
never couple animals possessing marked dissimilarity, but endeavor to
remedy faults and to effect improvement by gradual approaches. Harmony
of structure and a proper balancing of desirable characteristics, "an
equilibrium of good qualities," as it has been happily expressed, can
be secured only in this way.

It may not be out of place here to say, that much of the talk about
_blood_ in animals, especially horses, is sheer nonsense. When a
"blood horse" is spoken of, it means, so far as it means any thing,
that his pedigree can be traced to Arabian or Barbary origin, and so
is possessed of the peculiar type of structure and great nervous
energy which usually attaches to "thorough-bred" horses. When a bull,
or cow, or sheep is said to be of "pure blood," it means simply that
the animal is of some distinct variety--that it has been bred from an
ancestry all of which were marked by the same peculiarities and
characteristics.

So long as the term "blood" is used to convey the idea of definite
hereditary qualities it may not be objectionable. We frequently use
expressions which are not strictly accurate, as when we speak of the
sun's rising and setting, and so long as every body knows that we
refer to apparent position and not to any motion of the sun, no false
ideas are conveyed. But to suppose that the hereditary qualities of
an animal attach to the blood more than to any other fluid or to any
of the tissues of the body, or that the blood of a high-bred horse is
essentially different from that of another, is entirely erroneous. The
qualities of an animal depend upon its organization and endowments,
and the blood is only the vehicle by which these are nourished and
sustained;--moreover the blood varies in quality, composition and
amount, according to the food eaten, the air breathed and the exercise
taken. If one horse is better than another it is not because the fluid
in his veins is of superior quality, but rather because his structure
is more perfect mechanically, and because nervous energy is present in
fitting amount and intensity.

For illustration,