The Negro, however, has been tested on an extensive scale.

Curiously enough man's body and his mind appear to differ in their climatic adaptations.

As a matter of fact, an ordinary desert supports a much greater variety of plants than does either a forest or a prairie.

For the source of any characteristic so widespread and uniform as this adaptation to environment we must go back to the very beginning of the human race.

The human organism inherits so delicate an adjustment to climate that, in spite of man's boasted ability to live anywhere, the strain of the frozen North eliminates the more nervous and active types of mind.

A journey of four hundred and thirty miles can be made in any part of the United States, but in Turkey it takes as many days.

The whole history of life is a record of cycles.