pirit of FRATERNITY.

THE AUTHOR.

PREFACE TO SIXTH EDITION.

The cordial reception given to this little book by the medical
profession, by educators, and especially by the young men of the
country, have by their demands for the book necessitated the
appearance of new editions in such rapid succession that no
far-reaching changes in the text have been possible even if they had
been needed. Happily, no extensive changes have been required.

In the second edition several corrections, typographical and verbal,
were made and additions made to the appendix. To the third edition the
chapter on Development was added. The fourth and fifth editions
received verbal changes here and added paragraphs there.

The sixth edition differs from the fifth in the addition of the
author's portrait as a frontispiece, the addition of an answered
question to the appendix and the listing of certain lecture topics,
with press notices and letters.

The book seems to be meeting a demand for accurate information briefly
and clearly stated.

THE AUTHOR.

Chicago, November 1, 1908.

FOREWORD.

Several years ago the author was asked by his students to present to
them some of the facts of Sexual Physiology and Hygiene. The plea of
"not a specialist in that line" was not accepted; so after a few weeks
devoted to a careful study of the literature the subject was
presented. It seemed to be acceptable, and other invitations followed
in successive years not only from the author's own institution but
from many others.

In the last few years the subject has been presented at all of the
leading institutions of learning in the middle west--at some of them
several times and always to large audiences.

In response to repeated requests for "a book" the author has finally
prepared this brief volume in which he has endeavored to present a
difficult subject in the true university spirit, frankly calling
things by their right names, always keeping in close accord with the
latest researches.

It is hoped that the chapter on Hygiene will in itself be a
justification for the book.

WINFIELD S. HALL,
December, 1906. Chicago.

CONTENTS.

Chapter I.

REPRODUCTION FROM THE STANDPOINT OF BIOLOGY.

1. General Activities of Living Organisms 11
A. The Egoistic