s about him." As he spoke, we
turned down a narrow lane and passed through a small side-door, which
opened into a wing of the great hospital. It was familiar ground to me,
and I needed no guiding as we ascended the bleak stone staircase and
made our way down the long corridor with its vista of whitewashed
wall and dun-coloured doors. Near the further end a low arched passage
branched away from it and led to the chemical laboratory.

This was a lofty chamber, lined and littered with countless bottles.
Broad, low tables were scattered about, which bristled with retorts,
test-tubes, and little Bunsen lamps, with their blue flickering flames.
There was only one student in the room, who was bending over a distant
table absorbed in his work. At the sound of our steps he glanced round
and sprang to his feet with a cry of pleasure. "I've found it! I've
found it," he shouted to my companion, running towards us with a
test-tube in his hand. "I have found a re-agent which is precipitated
by hoemoglobin, [4] and by nothing else." Had he discovered a gold mine,
greater delight could not have shone upon his features.

"Dr. Watson, Mr. Sherlock Holmes," said Stamford, introducing us.

"How are you?" he said cordially, gripping my hand with a strength
for which I should hardly have given him credit. "You have been in
Afghanistan, I perceive."

"How on earth did you know that?" I asked in astonishment.

"Never mind," said he, chuckling to himself. "The question now is about
hoemoglobin. No doubt you see the significance of this discovery of
mine?"

"It is interesting, chemically, no doubt," I answered, "but
practically----"

"Why, man, it is the most practical medico-legal discovery for years.
Don't you see that it gives us an infallible test for blood stains. Come
over here now!" 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 i