1. In young persons, that is, adults, or those of a middle age; as from the flexibility of their vessels, the strength of their muscles, and the abundance of their vital spirits, they can more easily sustain the loss thence occasioned. 2. In robust persons, who lose no more than is speedily replaced. 3. In sprightly individuals, and such as are particularly addicted to pleasure; for the stronger the natural and legal desire, the less hurtful is its gratification. 4. In married persons who are accustomed to it; for nature pursues a different path, according as she is habituated to the reabsorption or the evacuation of this fluid. 5. With a beloved object; as the power animating the nerves and muscular fibres is in proportion to the pleasure received. 6. After a sound sleep, because then the body is more energetic; it is provided with a new stock of vital spirit, and the fluids are duly prepared;--hence the early morning appears to be designed by nature for the exercise of this function; as the body is then most vigorous, and being unemployed in any other pursuit, its natural propensity to this is the greater; besides, at this time a few hours sleep will, in a considerable degree restore the expended powers. 7. With an empty stomach; for the office of digestion, so material to the attainment of bodily vigour, is then uninterrupted. Lastly. 8. In the vernal months; as nature at this season in particular, incites all the lower animals to sexual intercourse, as we are then most energetic and sprightly; and as the spring is not only the safest, but likewise the most proper time with respect to the consequences resulting from that intercourse. It is well ascertained by experience that children begotten in spring are of more solid fibres, and consequently more vigorous and robust, than those generated in the heat of summer or cold of winter. It may be collected from the following circumstances, whether or not the gratification of the sexual intercourse has been conducive to the well-being of the body; namely, if it be not succeeded by a peculiar lassitude; if the body do not feel heavy, and the mind averse to reflection, these are favourable symptoms, indicating that the various powers have sustained no essential loss, and that superfluous matter only has been evacuated. Farther, the healthy appearance of the urine in this case, as well as cheerfulness and vivacity of mind, also prove a proper action of the fluids, and sufficiently evince an unimpaired state of the animal functions, a due perspiration, and a free circulation of the blood. There are times, however, in which the gratification is the more pernicious to health, when it has been immoderate, and without the impulse of nature, but particularly in the following situations.