John Evelyn Thorndyke—whose cases, like those of Holmes, were written up in several other books, from The Red Thumb Mark (1907) to The Jacob Street Mystery (1942). After pouring some tincture of guaiacum on a questionable stain, Thorndyke watches as the liquid spreads outward, then adds the ether and allows the two liquids to mix. “Gradually the ether spread towards the stain,” Freeman writes, “and, first at one point and then at another, approached and finally crossed the wavy grey line; and at each point the same change occurred: first the faint grey line turned into a strong blue line, and then the colour extended to the enclosed space until the entire area of the stain stood out in a conspicuous blue patch. ‘You understand the meaning of this,’ said Thorndyke. ‘This is a bloodstain.’ ”

P. M. Stone asserts, in “The Other Friendship: A Speculation,” that Holmes and Thorndyke actually met and exchanged views at some point. “[I]t is not unlikely,” comments Edgar Smith in his introduction to the essay, “that Sherlock Holmes … was inclined to seek variety—and shall we say relief?—in intellectual converse on the higher plane with someone whose capacities and inclinations were just a little closer to his own.”

There were in fact eleven original tests for haemoglobin developed between 1800 and 1881, and numerous variations were proposed. The tests, several of which remain in modern use, are summarised in Raymond J. McGowan’s “Sherlock Holmes and Forensic Chemistry.”

40 Michael Harrison surmises that Holmes offered his test to the British police, who snubbed him. It is no wonder, then, Harrison suggests, that Holmes, “nursing an unconquerable prejudice against the British police system, preferred to go his own highly individual way.”

41 D. Martin Dakin notes that “Muller” cannot have been “the Franz Müller who was the first railway murderer (1864) since he was convicted and that not by bloodstains, but by his absentmindedly going off with his victim’s hat!”

42 Owen Dudley Edwards observes, “Holmes is evidently shooting off these names at great speed with the obsessiveness of a devotee determined to bombard his audience with proofs of their own ignorance in a field he intends to evangelize.”

43 The provenance of the “Baker” in “Baker Street” is somewhat unclear. According to Hector Bolitho and Derek Peel’s Without the City Wall: An Adventure in London Street-names North of the River, most of the streets in the western part of the Marylebone district were named after members of the family of William Henry Portman (of Orchard Portman in Somerset), who inherited the land in the mid-1700s. Baker Street was, for some reason, an exception to this rule. Some scholars believe that the street was named after Sir Edward Baker, a neighbour and friend of Mr. Portman’s in Dorset. Bolitho and Peel, however, claim that a William Baker leased a number of acres near Portman Square from Mr. Portman for the purposes of development, and that it was after this Baker that the street was named.

44 Ian McQueen remarks, “The pair must rank as two of the most famous smokers of their time. [This] exchange of details about their smoking habits forms the very first swapped confidence between them …”

45 Was Watson referring to ship’s tobacco, or did he favor some particular brand? Sherry Keen, in “Ship’s or ‘ship’s?’: That is the Question,” notes that both A Dictionary of Slang and Unconventional English, by Eric Partridge, and Soldier and Sailor, Words and Phrases, by Fraser and Gibbons, refer to “ship’s” as a “naval cocoa tobacco.” Yet Jack Tracy’s Encyclopedia Sherlockiana unhesitatingly identifies “Ship’s” as “Schippers Tabak Special, a strong tobacco blend manufactured in the Netherlands and much favoured by sailors.” William Baring-Gould suggests that Watson took up “Ship’s” on board the Orontes. But remember that Watson, in returning to England, was in a much weakened state, nearly an invalid; and on that basis, W. E. Edwards surmises that he learned the habit on his voyage to India. In any event, concludes Baring-Gould, the tobacco was a “passing fancy,” for in “The Crooked Man,” Watson has returned to smoking “the Arcadia mixture of [his] bachelor days.”

46 The bull pup is never again mentioned in the Canon, and a variety of explanations have been offered for its mysterious disappearance. Robert S. Morgan, in “The Puzzle of the Bull Pup,” suggests that the dog met with a fatal accident shortly after Watson’s move, resulting in a shock to Watson’s nervous system and a permanent injury to his memory. Thomas Tully’s theory, in “Bull Pup,” is that Watson was only keeping the dog temporarily. More ingeniously, Carol P. Woods, in “A Curtailed Report on a Dogged Investigation,” speculates that Watson misidentified his pet as a dog when it was, in fact, a ferret. After Holmes called him on this error, an embarrassed Watson never mentioned the animal again. But Watson’s new roommate might have been responsible for getting rid of the animal.