“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 instant the contents assumed a dull mahogany colour, and a brownish dust was precipitated to the bottom of the glass jar.

“Ha! ha!” he cried, clapping his hands, and looking as delighted as a child with a new toy. “What do you think of that?”

“It seems to be a very delicate test,” I remarked.

“Beautiful! beautiful! The old Guiacum test was very clumsy and uncertain. So is the microscopic examination for blood corpuscles. The latter is valueless if the stains are a few hours old. Now, this appears to act as well whether the blood is old or new. Had this test been invented, there are hundreds of men now walking the earth who would long ago have paid the penalty of their crimes.”

“Indeed!” I murmured.

“Criminal cases are continually hinging upon that one point. A man is suspected of a crime months perhaps after it has been committed. His linen or clothes are examined, and brownish stains discovered upon them. Are they blood stains, or mud stains, or rust stains, or fruit stains, or what are they? That is a question which has puzzled many an expert, and why? Because there was no reliable test. Now we have the Sherlock Holmes’ test, and there will no longer be any difficulty.”

His eyes fairly glittered as he spoke, and he put his hand over his heart and bowed as if to some applauding crowd conjured up by his imagination.

“You are to be congratulated,” I remarked, considerably surprised at his enthusiasm.

“There was the case of Von Bischoff at Frankfort last year. He would certainly have been hung had this test been in existence. Then there was Mason of Bradford, and the notorious Muller, and Lefevre of Montpellier, and Samson of New Orleans. I could name a score of cases in which it would have been decisive.”

“You seem to be a walking calendar of crime,” said Stamford with a laugh. “You might start a paper on those lines. Call it the ‘Police News of the Past.’”