A Study in Scarlet

*He seized me by the coat-sleeve in his eagerness, and drew me over to the table at which he had been working. *Let us have some fresh blood,* he said, digging a long bodkin into his finger, and drawing off the resulting drop of blood in a chemical pipette. *Now, I add this small quantity of blood to a litre of water. You perceive that the resulting mixture has the appearance of pure water. The proportion of blood cannot be more than one in a million.

I have no doubt, however, that we shall be able to obtain the characteristic reaction.* As he spoke, he threw into the vessel a few white crystals, and then added some drops of a transparent fluid. In an instant the contents assumed a dull mahogany colour, and a brownish dust was precipitated to the bottom of the glass jar.*