periodically as its mode of progress.

The natural effect of slavery has been a selection of two sorts of
individuals along the lines of the survival of the adapted. It has
tended to perpetuate in the breed the qualities of the strong which
would make them stronger, and certain qualities in the weak which
would increase their weakness. For parasitism and likewise slavery
infallibly entail the degradation of certain structures and an
overgrowth of others by the law of use and disuse. The type of organ
which would function normally, were not its possessor parasitic in
that function, invariably degenerates or disappears. Parasitic insects
lose their wings. An entire anatomical system may even be lost. So the
tapeworm, which feeds upon the digested food present in the intestines
of its host, has no alimentary canal of its own because it needs none.
On the other hand, the organs of attack and combat grow by a constant
use into the most remarkable of efficient weapons.

In human society the process continues. Out of the tapeworm nature,
the tiger nature, the wolf nature, the simian nature, human nature
evolves. Repeated episodes of subjugation and suppression mixed with
countless incidents of predaceous cupidity and rapacity have made
Man what he is today. Indeed, by a sort of instinct, society has
constructed its institutions upon empirical observations and
assumptions agreeing with this principle. The deductions concerning
human nature and human traits that an interplanetary visitor would
draw from a study of our common law would be at least slightly
humiliating to our incorrigible pride. Law courts, codes of civil
contract and criminal procedure, the systems of subordination in
armies and navies, castes and classes, men and women, employers and
employees, teachers and pupils, parents and children, are based upon