of your getting tea when you came out, and she hit it off again. And then she took one chance too many; she assumed that you probably took sugar in your tea, and she was wrong."
"We are taking it for granted that the sugar was prepared," I remarked.
"Yes. Our explanation is entirely hypothetical and may be entirely wrong. But it all hangs together, and if we find any poisonous matter in the sugar, it will be reasonable to assume that we are right. The sugar is the Experimentum Crucis. If you will hand it over to me, we will go up to the laboratory and make a preliminary test or two."
I took the lump of sugar from my pocket and gave it to him, and he carried it to the gas-burner, by the light of which he examined it with a lens.
"I don't see any foreign crystals on the surface," said he; "but we had better make a solution and go to work systematically. If it contains any poison we may assume that it will be some alkaloid, though I will test for arsenic too. But a man of Weiss's type would almost certainly use an alkaloid, on account of its smaller bulk and more ready solubility. You ought not to have carried this loose in your pocket. For legal purposes that would seriously interfere with its value as evidence. Bodies that are suspected of containing poison should be carefully isolated and preserved from contact with anything that might lead to doubt in the analysis. It doesn't matter much to us, as this analysis is only for our own information and we can satisfy ourselves as to the state of your pocket. But bear the rule in mind another time."
