See note 81, below.

31 S. C. Roberts, in Dr. Watson, wonders whether Stamford’s strange look and hesitation meant that he foresaw his impending destiny as “one of the great liaison-officers of literary history”—comparable, in Roberts’s view, to Tom Davies, who introduced Boswell to Dr. Samuel Johnson. The analogy is apt in light of Holmes’s own characterisation of Watson as “my Boswell” (“A Scandal in Bohemia”).

32 Watson comes to develop a slightly more sceptical view of Holmes’s faculties, as in listing Holmes’s “limits” he will soon deem Holmes’s knowledge of anatomy “[a]ccurate, but unsystematic.”

33 Alkaloids, which occur naturally in plants, are known for their powerful physiological effects on humans and animals. (Morphine, strychnine, quinine, nicotine, cocaine, and curare are but a few examples.) The first alkaloid to be isolated and crystallized was morphine, extracted from the poppy plant in 1805–1806. By 1878, Holmes may have been able to experiment with various isolated alkaloids, which tend to be odourless and bitter in taste; but at the same time, not much was yet known definitively about their properties.

Alkaloids appear throughout the Canon: morphine in “The Man with the Twisted Lip,” cocaine in “A Scandal in Bohemia,” and quinine in The Sign of Four; the alkaloid tubocurarine, a muscle relaxant, is the active ingredient in curare, the South American poison that plays a significant role in both The Sign of Four and “The Sussex Vampire.” Of course, nicotine, which originates in the tobacco plant, is ubiquitous in the smoke-filled rooms of Baker Street and elsewhere. Stamford’s shrewd observation here remarkably foreshadows Holmes’s experimentation on Watson and himself in “The Devil’s Foot,” although whether Radix pedis diaboli is an alkaloid is unsettled.

34 Holmes’s fondness for experimentation on corpses was not limited to human cadavers; in “Black Peter,” Watson records that Holmes tested the sticking-power of harpoons on the carcasses of pigs at the shop of Allardyce the butcher.

35 Named after Robert Wilhelm Bunsen, the German chemist who introduced (but did not invent) it in 1855, the Bunsen burner combines a hollow metal tube with a valve at the base that allows for regulation of the supply of air. Flammable gas and air together are forced upward through the tube and then lit to produce a hot flame. The principles behind the Bunsen burner paved the way for the invention of the gas-stove burner and the gas furnace.

36 In “Some Observations on Sherlock Holmes and Dr. Watson at Bart’s,” Adrian Griffith notes that in the memoirs of Sir Norman Moore, Moore recounts that he and an unnamed other student were private students of Augustus Matthiessen, who lectured in chemistry at Bart’s from 1870 onward. In 1869, Matthiessen, an employee of Friedrich Bayer & Co.—then a manufacturer of textile dyes—removed two atoms of hydrogen and one of oxygen from morphine to derive the subsidiary alkaloid apomorphine. Its primary function was to induce vomiting, and Bayer marketed it as a purgative similar to castor oil. It was later touted as a treatment for Parkinson’s disease and a “cure” for homosexuality, and today it is sold as a sexual-enhancement drug for both men and women. Griffith suggests that Holmes was the unnamed student of Matthiessen. Considering Matthiessen’s work on alkaloids, Holmes’s interest in the subject may well have started at Bart’s, and Moore’s recollections of Matthiessen’s career suggest to Griffith that Holmes and Matthiessen may have even collaborated on the occasional project.

37 An instrument for piercing holes.

38 If Holmes’s discovery were valid, argues Remsen Ten Eyck Schenck, in “Baker Street Fables,” it would be universally used today. The fact that it is not leads Schenck to label “unfounded” the notion that only hæmoglobin caused the agent to react. “Presumably,” Schenck continues, “[Holmes] discovered on further study that a similar result was obtained with other common substances, or else that it was not due to hæmoglobin at all, but rather to some other ingredient present in the blood, but not peculiar to it.” Holmes was even wrong about the concentration of his blood solution: Schenck estimates that the ratio of a “drop” of blood to a litre of water would have actually been about one part blood to 30,000 parts water, rather than the “one in a million” proportion Holmes cites shortly (although a “drop” is an imprecise unit, the smallest unit used in medicine is a “minim,” .06 of a millilitre, which would produce a ratio of 1 to 60,000). The detective “no doubt soon bitterly regretted that he had even mentioned his test, even to Watson,” Schenck concludes, “and this could well explain why it was never again referred to.”

But Leon S. Holstein, in “7. Knowledge of Chemistry—Profound” disagrees, suggesting that the test was an early version of the present-day hæmochromogen test, which is used to identify bloodstains. When blood is present, hæmochromogen crystals turn pinkish, which is perhaps, as Holstein surmises, a shade not that far removed from the “dull mahogany colour” that Holmes observes.

Christine L. Huber, in “The Sherlock Holmes Blood Test: The Solution to a Century-Old Mystery,” identifies the test as one “rediscovered” in the 1930s, when it was “discovered” that hæmoglobin A is denatured by sodium hydroxide (“white crystals”) and then precipitated with saturated ammonium sulfate (a “transparent fluid”). “[T]he Holmes Test … has been in almost daily use in hospitals and research laboratories, as a part of the electrophoretic process, since its rediscovery,” she claims. “How it was lost in the first place and why Holmes never received acknowledgment for it remains a mystery.”

39 In another test for hæmoglobin (and consequently for the presence of blood), the greenish-brown resin of the guaiacum tree, or lignum vitae, was mixed with alcohol; this substance was added to the liquid being tested and then shaken with a few drops of hydrogen peroxide in ether. The presence of hæmoglobin would turn the mixture bright blue. The test was first reported in 1861 in a modified form by J. Van Deen.

R. Austin Freeman describes this test in The Shadow of the Wolf (1925), an account of the great medico-legal detective Dr.