Muscles are in a most intimate and peculiar sense the organs of the will.

Every theory of love, from Plato down, teaches that each individual loves in the other sex what he lacks in himself.

The years from about eight to twelve constitute a unique period of human life.

Abundance and vigor of automatic movements are desirable, and even a considerable degree of restlessness is a good sign in young children.

Being an only child is a disease in itself.

Adolescence as the time when an individual 'recapitulates' the savage stage of the race's past.