irection, then stops and flows in the opposite direction;
just as through a rudely-organized society, the distribution of
merchandize is slowly carried on by great fairs, occurring in different
localities, to and from which the currents periodically set. Only
animals of tolerably complete organizations, like advanced communities,
are permeated by constant currents that are definitely directed. In
living bodies, the local and variable currents disappear when there grow
up great centres of circulation, generating more powerful currents by a
rhythm which ends in a quick, regular pulsation. And when in social
bodies there arise great centres of commercial activity, producing and
exchanging large quantities of commodities, the rapid and continuous
streams drawn in and emitted by these centres subdue all minor and local
circulations: the slow rhythm of fairs merges into the faster one of
weekly markets, and in the chief centres of distribution, weekly markets
merge into daily markets; while in place of the languid transfer from
place to place, taking place at first weekly, then twice or thrice a
week, we by-and-by get daily transfer, and finally transfer many times a
day--the original sluggish, irregular rhythm, becomes a rapid, equable
pulse. Mark, too, that in both cases the increased activity, like the
greater perfection of structure, is much less conspicuous at the
periphery of the vascular system. On main lines of railway, we have,
perhaps, a score trains in each direction daily, going at from thirty to
fifty miles an hour; as, through the great arteries, the blood moves
rapidly in successive gushes. Along high roads, there go vehicles
conveying men and commodities with much less, though still considerable,
speed, and with a much less decided rhythm; as, in the smaller arteries,
the speed of the blood is greatly diminished and the pulse less
conspicuous. In parish-roads, narrower, less complete, and more
tortuous, the rate of movement is further decreased and the rhythm
scarcely traceable; as in the ultimate arteries. In those still more
imperfect by-roads which lead from these parish-roads to scattered
farmhouses and cottages, the motion is yet slower and very irregular;
just as we find it in the capillaries. While along the field-roads,
which, in their unformed, unfenced state, are typical of _lacunae_, the
movement is the slowest, the most irregular, and the most infrequent; as
it is, not only in the primitive _lacunae_