These studies have been published in various journals at different times.

They are reprinted together because there is some demand for them, and they are not easily accessible. In preparing them for publication in the present form, some of them have been expanded and all of them have been revised.

While each study is complete in itself, the general thesis running through all of them is the same, that the differences in bodily habit between men and women, particularly the greater strength, restlessness, and motor aptitude of man, and the more stationary condition of woman, have had an important influence on social forms and activities, and on the character and mind of the two sexes.