Who are boys?--What are boys for?--Boys the hope of the world--Man the masterpiece--How a noble character is ruined--The marvelous human machine--The two objects of human existence--The nutritive apparatus-- The moving apparatus--The thinking and feeling apparatus--The purifying apparatus--The reproductive apparatus--How a noble character and a sound body must be formed--The downhill road--Self-abuse--A dreadful sin-- Self-murderers--What makes boys dwarfs--Scrawny and hollow-eyed boys-- Old boys--What makes idiots--Young dyspeptics--The race ruined by boys-- Cases illustrating the effects of self-abuse--Two young wrecks--A prodigal youth--Barely escaped--A lost soul--The results of one transgression--A hospital case--An old offender--The sad end of a young victim--From bad to worse--An indignant father--Disgusted with life--Bad company--Bad language--Bad books--Vile pictures--Evil thoughts-- Influence of other bad habits--Closing advice to boys and young men. 419 _A CHAPTER FOR GIRLS_. Girlhood--How to develop beauty and loveliness--The human form divine--A wonderful process--Human buds--How beauty is marred--A beauty-destroying vice--Terrible effects of secret vice--Remote effects--Causes which lead girls astray--Vicious companions--Whom to avoid--Sentimental books-- Various causes--Modesty woman's safeguard--A few sad cases--A pitiful case--A mind dethroned--A penitent victim--A ruined girl--The danger of boarding-schools--A desperate case--A last word--A few words to boys and girls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 470 INTRODUCTION.