Kennedy paused, making use of the silence for emphasis. “You have all read of the wealth that Cortez found in Mexico. Where are the gold and silver of the conquistadores? Gone to the melting pot, centuries ago. But is there none left? The Indians believe so. There are persons who would stop at nothing—even at murder of American professors, murder of their own comrades, to get at the secret.”
He laid his hand almost lovingly on his powerful little microscope as he resumed on another line of evidence.
“And while we are on the subject of murders, two very similar deaths have occurred,” he went on. “It is of no use to try to gloss them over. Frankly, I suspected that they might have been caused by aconite poisoning. But, in the case of such poisoning, not only is the lethal dose very small but our chemical methods of detection are nil. The dose of the active principle, aconitin nitrate, is about one six-hundredth of a grain. There are no color tests, no reactions, as in the case of the other organic poisons.”
I wondered what he was driving at. Was there, indeed, no test? Had the murderer used the safest of poisons—one that left no clue? I looked covertly at Sato’s face. It was impassive. Doctor Bernardo was visibly uneasy as Kennedy proceeded. Cool enough up to the time of the mention of the treasure, I fancied, now, that he was growing more and more nervous.
Craig laid down on the table the reed stick with the little darkened cylinder on the end.
“That,” he said, “is a little article which I picked up beneath Northrop’s window yesterday. It is a piece of anno-noki, or bushi.” I fancied I saw just a glint of satisfaction in Otaka’s eyes.
“Like many barbarians,” continued Craig, “the Ainus from time immemorial have prepared virulent poisons with which they charged their weapons of the chase and warfare. The formulas for the preparations, as in the case of other arrow poisons of other tribes, are known only to certain members, and the secret is passed down from generation to generation as an heirloom, as it were. But in this case it is no longer a secret. It has now been proved that the active principle of this poison is aconite.”
“If that is the case,” broke in Doctor Leslie, “it is hopeless to connect anyone directly in that way with these murders. There is no test for aconitin.”
I thought Sato’s face was more composed and impassive than ever. Doctor Bernardo, however, was plainly excited.
“What—no test—none?” asked Kennedy, leaning forward eagerly. Then, as if he could restrain the answer to his own question no longer, he shot out: “How about the new starch test just discovered by Professor Reichert, of the University of Pennsylvania? Doubtless you never dreamed that starch may be a means of detecting the nature of a poison in obscure cases in criminology, especially in cases where the quantity of poison necessary to cause death is so minute that no trace of it can be found in the blood.