In the higher forms of animal life, each animal has its offspring as well as itself to maintain.

In a state of nature, that is in a state unaffected by man's rational interference, defective offspring and weaker brethren were the victims of the inexorable law of natural selection.

When Christ gave _his_ reply to the question, "Am I my brother's keeper ?" the defective and the weakling became the special care of their stronger brother.

They constituted thenceforth The Fit Man's Burden.

The work a man has to do during life, in order to support himself, is the unit of measurement of the burden he has to bear.