“A man who, night after night, falls like a lump of lead upon his bed, and ceases to live until the moment when he wakes and rises, will such a man ever dream of making, I do not say great discoveries, but even minute observations upon sleep? He barely knows that he does sleep. A little insomnia is not without its value in making us appreciate sleep, in throwing a ray of light upon that darkness. A memory without fault is not a very powerful incentive to studying the phenomena of memory.”