Anything that has a tendency to undermine the health, repeated sufficiently often, will ultimately cause a complete breakdown. How often do we see the strength and beauty of early manhood blighted and turned to premature old age and death as a consequence of disregarding the warnings that have just been given! How frequently do we observe young men rejoicing in the emancipation from home and school and spurred on by the fatal delusion that while others might suffer they will not, becoming in the end the victim of that arch enemy of early manhood, consumption! Every practicing doctor has seen this, not once, but hundreds of times, and in the vast majority of instances he can say with truth that the frightful result is a consequence of overwork--too often associated with nocturnal dissipation. The man who works during the day, and devotes his nights to alcohol and gay company when he should be sleeping, will assuredly, sooner or later--and usually sooner--suffer the inevitable consequences. To those who live sedentary lives, active out-door exercise is very essential, but inasmuch as this little volume is being written for those who live a saner and more healthful existence, it is not deemed necessary to discuss here this phase of the subject. _Value of Sleep._--Closely connected with the subject just discussed is sleep. Here also we have no rules, or laws, from which we can clearly determine the amount required in individual cases. Overwise philosophers have asserted that seven hours for a man, eight hours for a woman, and nine hours for a fool, was the allotted time for sleep. As a matter of fact, the necessity for repose varies greatly in different individuals, some of them requiring less while others demand more. It is a safe rule to follow that every man should sleep as long as he naturally desires, for nature is a much better mentor than any man could be--however learned. The majority of men require at least eight hours of sleep for the day and night, and this should be secured if possible at such a time as will permit it to be undisturbed; hence it is that man usually prefers to sleep at night, and, all things considered, it is probably the time best suited for his repose. We read many marvelous stories of certain great men who required little or no sleep. Within recent years the press has frequently contained articles recounting the extraordinary fact that a certain prominent inventor of this country lived daily on a mere spoonful or so of food, and only slept a few hours now and then when there was nothing else particularly to do. Such stories should be accepted only on absolute proof, as, irrespective of their utter improbability, one may observe that they are generally insisted upon in and out of season with a pertinacity that would indicate that they were conceived and are scattered abroad with the sole idea of impressing the general public with what a marvelous and unusual person the individual in question is.