Professor Dewees, of Philadelphia, enjoins that, for the enjoyment of marriage and the production of children, matrimony should not be engaged in, until the body is healthily and completely developed; until then the most scrupulous continency should be preserved. From the 23d to the 25th year is the suggested period for the male; from the 19th to the 21st, the female. These observations apply to Europeans chiefly; for in India, women become mothers at ten, owing to their early development. Precocious marriages bring premature decay on the father and mother, and entail on their offspring, diminutive stature, debility of body, and imbecility of mind, thus generating consumption, scrofula, insanity, &c. Well-regulated marriages contribute to social and lasting happiness, and the prosperity of the nation at large; but ill-assorted ones, those where the peace of either is infringed by opposing tempers, or by the after-discovery of hitherto concealed physical incapacities, present a scene of wretchedness and disappointment to which death itself were preferable. These remarks might be considerably amplified; but enough has been said, to induce those who approach to manhood, to be provident of that which, once lost, is, under all circumstances, difficult to regain; and those on the eve of embarking in the most binding and solemn obligation of all human contracts, marriage, to ponder well, ere they compromise the happiness of others as well as themselves, by engaging in a compact, they may know themselves incapable of fulfilling or of efficiently performing; one from which they can not with honor retreat, and one that, once sealed, demands a rigid compliance with its recognised duties. The gist of the present article may then thus be summed up: That self-indulgence and excessive sexual cohabitation are hurtful in the highest degree; that they induce early impuissance, and bring down a load of menial and corporeal ailments. That premature marriages are destructive to health and long life, and that weak and sickly children are the general result where impregnation of the female follows. That entire continence was never ordained, and is alike productive of disease. That moderate copulation propagates the human kind, preserves health, and promotes longevity, and the sexual capability is thereby retained to the latest verge of senility. That it is unnatural and unjust for impuissant persons to intermarry with those having healthy expectations, and the power of enjoyment; and that it behooves all who have a doubt as to their own capacity, to have that doubt removed; but, if rendered evident, to abstain from shipwrecking their own happiness, or from occasioning disappointment to others. THE HEREDITARY TRANSMISSION OF DISEASE.