Then I grew up, and at the age of eighteen or nineteen became possessed of a desire for knowledge, and took to reading and studying literally every minute of the day and a good part of the night. I seldom let myself go to sleep before two o'clock in the morning, and was always up by seven and ready for work again. I did this for ten years or so, until nature brought me to a complete stop. During these ten years I was a regular experiment station in health; that is, I had every kind of common ailment, and had it over and over again, so that I could try all the ways of curing it, or failing to cure it, and keep on trying until I was sure, one way or the other. I came recently upon a wonderful saying by John Burroughs, which will be appreciated by every author. "This writing is an unnatural business. It makes your head hot and your feet cold, and it stops the digesting of your food." This trouble with my digestion began when I was writing my second novel, camping out on a lonely island at the foot of Lake Ontario. I went to see a doctor in a nearby town, and he talked learnedly about dyspepsia. The cause of it, he said, was failure of the stomach to secrete enough pepsin, and the remedy was to take artificial pepsin, obtained from the stomach of a pig. He gave me this pig-pepsin in a bottle of red liquid, and I religiously took some after each meal. It helped for a time; but then I noticed that it helped less and less. I got so that a simple meal of cold meat and boiled potatoes would stay in my stomach for hours, in spite of any amount of the pig-pepsin; I would lie about in misery, because I wanted to work, and my accursed stomach would not let me. All the time, of course, I was using my mind on this problem, groping for causes. I found that the trouble was worse if I worked immediately after eating. I found also that it was worse when I was writing books. When I got sufficiently desperate, I would stop writing books and go off on a hunting trip. I would tramp twenty miles a day over the mountains, looking for deer, and I would come back at night too tired to think, and in a week or two every trace of my trouble would be gone. So my life regimen came to be--first the writing of a book, and then a hunting trip to get over the effects of it. But as time went on, alas, I noticed that the recuperation was more slow and less certain. The working times grew shorter, and the hunting times grew longer, until finally I had got to a point where I couldn't work at all; I would go to pieces in a few days if I tried it. It was apparently the end of my stomach, and the end of my sleeping, and the end of my writing books. My teeth were decaying, not merely outside but inside; I would have abscesses, and most frightful agonies to endure. I would lie awake all night, and it would seem to me that I could feel my body going to pieces--an extremely depressing sensation!