Every boy――every person――should sleep alone. Think of what I have said about the skin and its emanations. You do not want to be under the sheets with another boy who is throwing off from his skin poisons; breathing some of them, letting others be absorbed by your own pores. Try to get two dogs to sleep under the same blanket――respectable dogs, such as you or I would own. In about two minutes each will get from under cover with distended nostrils and deep breathing. They’ll sleep together without covering; but never under it. Sleep alone under as light coverings as possible for comfort. This will aid you in getting big and strong. Don’t forget this advice. CHAPTER III HOW ALL LIFE COMMENCES We have seen that the human body after it gets started is quite as much a physical apparatus as a chemical laboratory, and the harmonious working of all its parts is to a considerable extent a matter of mechanics. You will find that this is true for every disease or disturbance of the body. For instance; nervousness or headache from eyestrain. This strain may come through insufficient light or light wrongly entering the pupil of the eye. The nervousness may come because there is too much effort to adjust the lenses of the eyes by a constant pull on the tiny muscles. Even that peculiar nervousness that many unwise men and women are suffering from which makes them take ruinous drugs, is due to a chemical disturbance of the nerve cells. All the drugs in the world will not help them――it only increases the chemical disturbance. These sufferers need the poison out of their system; not more put in. And so it goes on throughout the whole system; some of the physical or chemical elements are unevenly balanced or worn out for the time. In diseases due to a particular germ――like diphtheria or pneumonia――it is the disturbance of the chemical elements in the body which brings about the disease. But we have finished with the chemistry and machinery of the body and now enter upon the wonderful and interesting part of life which deals with reproduction――the continuance of species. Every living thing――flowers, fishes, animals, man――is reproduced by laws all having the same principles. The underlying facts in all these different forms of life are the same. There is absolutely no exception to the law of reproduction. Every living thing is the result of the mating of the male element with that of the female. We shall not have much to say about botany or zoology, you can read all about these sciences in your books. What I shall tell you in the rest of our chats are things which you do not get from your books or teachers.