condition remains almost unaltered, and with it many mental
characteristics: their love of display and of bright colors, their
fondness for tune and the power of music to move them, their weird and
fantastic belief in ghosts and spirits, in signs, omens and charms, and
many other traits, still bear witness to their savage origin. But even
these are fading away, and these men are slowly but not the less surely
becoming civilized and _white_.

The point of departure for every structural change in a living organism
lies in the apparatus by which nutrition is maintained; and this in the
higher classes is the blood. Most complex and wonderful of fluids, it
contains in unexplained and inscrutable combination salts of iron, lime,
soda and potassa, with water, oil, albumen, paraglobulin and fibrinogen,
which united form fibrine--in fact, at times, some part of everything we
eat and all that goes to form our bodies, which it everywhere permeates,
vitalizes and sustains. Borne in countless numbers in its ever-ebbing
and returning streams are little disks, flattened, bi-concave, not
larger in man than one-three-thousandth of an inch in diameter, called
red corpuscles, whose part it is to carry from the lungs to the tissues
pure oxygen, without which the fire called life cannot be sustained, and
back from the tissues to the lungs carbonic acid, one of the products of
that fire; and larger, yet marvelously small, bodies called leucocytes
or white corpuscles, whose precise origin and use to this day, in spite
of all the labor that has been spent upon their study, remain unknown.
But that which makes the blood wonderful above all other fluids is its
vitality. Our common expression, "life's blood," is no idle phrase. The
blood is indeed the very throne of life. If its springs are pure and
bountiful, if its currents flow strong and free, muscle, bone and brain
grow in symmetry and power, and there is cunning to devise and the
strong right arm to execute. But if it be thin and poor, and its
circulation feeble and uncertain, the will flags, the mind is weak and
vacillating, the muscles grow puny, and the man becomes an unresisting
prey to disease and circumstance. If it escape through a wound, strength
ebbs with it, until at length life itself flows out with the unchecked
crimson stream. Thus, then, by acting upon the blood, climate has
wrought and is working such changes upon man. But why are
constantly-acting causes so slow in producing