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 10 medicine consists in the recognition and differentiation by bacteriological research of those minute organisms which disseminate cholera and fever, tubercle and anthrax. The importance of the infinitely little is incalculable. Poison a well at Mecca with the cholera bacillus, and the holy water which the pilgrims carry off in their bottles will infect a continent, and the rags of the victims of the plague will terrify every seaport in Christendom.

Trained as he has been to notice and appreciate minute detail, Dr. Doyle saw how he could interest his intelligent readers by taking them into his confidence, and showing his mode of working. He created a shrewd, quick-sighted inquisitive man, half doctor, half virtuoso, with plenty of spare time, a retentive memory, and perhaps with the best gift of all—the power of unloading the mind of all the burden of trying to remember unnecessary details. Holmes tells Watson: "A man should keep his little brain-attic stocked with all the furniture that that he is likely to use, as the rest he can put away in the lumber-room of his library, where he can get it if he wants it." But to him the petty results of environment, the sign-manuals of labour, the stains of trade, the incidents of travel, have living interest, as they tend to satisfy an insatiable, almost inhuman, because impersonal curiosity. He puts the man in the position of an amateur, and therefore irresponsible, detective, who is consulted in all sorts of cases, and then he lets us see how he works. He makes him explain to the good Watson the trivial, or apparently trivial, links in his chain of evidence. These are at once so obvious when explained, and so easy, once you know them, that the ingenuous reader at once feels, and says to himself, I also could do this; life is not so dull after all; I will keep my eyes open, and find out things. The gold watch, with its scratched keyhole and pawn-brokers' marks, told such an easy tale about Watson's brother. The dusty old billy-cock hat revealed that its master had taken to drinking some years ago, and had got his hair cut yesterday. The tiny thorn-prick and fearsome footmark of the thing that was neither a child nor a monkey enabled Holmes to identify and capture the Andaman Islander. Yet, after all, you say there is nothing wonderful; we could all do the same.

The experienced physician and the trained surgeon every day, in their examinations of the humblest patient, have to go through a similar process of reasoning, quick or slow according to the personal equations of each, almost automatic in the experienced man, laboured and often erratic in the tyro, yet requiring just the same simple requisites, senses to notice facts, and education and intelligence to apply them. Mere acuteness of the senses is not enough. Your Indian tracker will tell you that the footprint on the leaves was not a redskin's, but a paleface's, because it marked a shoe-print, but it needs an expert in shoe-leather to tell where that shoe was made. A sharp-eyed detective may notice the thumb-mark of a grimy or bloody hand on the velvet or the mirror, but it needs all the