“He is the Napoleon of crime, Watson. He is the organizer of half that is evil and nearly all that is undetected in this great city. He is a genius, a philosopher, an abstract thinker. He has a brain of the first order.”

“Come, Watson, come!" he cried. The game is afoot.”

“Very sorry to knock you up, Watson,' said he [Holmes], 'but it is a common lot this morning. Mrs Hudson has been knocked up, she retorted upon me, and I on you.”

“A man should keep his little brain attic stocked with all the furniture that he is likely to use, and the rest he can put away in the lumber room of his library, where he can get it if he wants it.”

“I consider that a man's brain originally is like a little empty attic, and you have to stock it with such furniture as you choose. A fool takes in all the lumber of every sort that he comes across, so that the knowledge which might be useful to him gets crowded out, or at best is jumbled up with a lot of other things, so that he has a difficulty in laying his hands upon it. Now the skillful workman is very careful indeed as to what he takes into his brain-attic. He will have nothing but the tools which may help him in doing his work, but of these he has a large assortment, and all in the most perfect order. It is a mistake to think that that little room has elastic walls and can distend to any extent. Depend upon it there comes a time when for every addition of knowledge you forget something that you knew before. It is of the highest importance, therefore, not to have useless facts elbowing out the useful ones.”

“Well," he said, "I say, now, as I said then, that a man should keep his little brain-attic stocked with all the furniture that he is likely to use, and the rest he can put away in the lumber-room of this library, where he can get it if he wants it.”

“I say, Watson,’ he whispered, ‘would you be afraid to sleep in the same room as a lunatic, a man with softening of the brain, an idiot whose mind has lost its grip?’‘Not in the least,’ I answered in astonishment.‘Ah, that’s lucky,’ he said, and not another word would he utter that night.”