The idea that sleep is the result of poisons in the system takes us into the pathological theory of sleep, which regards it as a sort of disease like epilepsy or auto-intoxication. We produce by our own activities the poisons which cause insensibility until the system cleanses itself. Professor Leo Errera of Brussels says that “work in the organism is closely bound up with a chemical breaking down.” Among the products of this breakdown are “leucomaines,” the scientific name for poisons formed in living tissue, and just the opposite to “ptomaines,” which, however, are also virulent poisons. Professor Errera tells us that, during our waking hours, we produce more leucomaines than the oxygen we absorb can destroy. This excess is carried along by the blood and held by the brain centers, and in time produces sleep, just as any poisonous anæsthetic, such as morphine, would produce sleep. While we are sleeping we absorb much oxygen and we recover from the effects of our self-intoxication. Errera maintains that work, fatigue, sleep, and repair are not merely successive events, but phenomena chained together in a regular and necessary cycle. He explains sleeplessness due to overfatigue on the theory that small doses of poisons induce sleep and large doses induce excitement and even convulsions. Manacéïne points out that this theory is good from a purely physical standpoint, but does not explain our power to postpone sleep or the faculty of waking at a fixed hour. We can do both, and any adequate theory of sleep must explain why we can control the tendency to sleep, but cannot control the symptoms of ordinary poisoning. CHAPTER XXVII EARLY THEORIES OF SLEEP Balm that tames all anguish. WORDSWORTH. Mr. Edward Binns of London, as early as 1842, published a book called “The Anatomy of Sleep”—with the subtitle, “The Art of Procuring Sound and Refreshing Slumber at Will.” The subtitle makes one think of the three-volume novels of that time, but the book is fairly concise and worth careful review. Moreover, it is in advance of many works on sleep both before and after. (For ancient surmises see Appendix C.) One of the favorite medical theories of sleep is that it is caused by fatigue, and is, therefore, purely passive in its nature. Binns did not accept this theory. He said, “Sleep is an active and positive faculty, not a negative and passive result of fatigue or weariness.” Some of the more modern writers, notably Manacéïne, agree with Dr. Binns that sleep is not the result of physical fatigue or weariness. Dr. Binns thinks that one proof that fatigue can in no sense be said to be the cause of sleep is that, if we prolong “the state of wakefulness after the usual period of retiring to rest, it is more difficult to induce sleep than if we went at the usual hour.” This is especially true of children, yet the patient may be much more fatigued at the later hour than at the usual bedtime.