"I think those cigarettes have been doped," he went on positively. "It isn't toloache that was used. I think it must be some particularly virulent variety of the jimson weed. Perhaps it is in the preparation of the thing. The seeds of the stramonium, which is the same thing, contain a higher percentage of poison than the leaves and flowers. Perhaps they were used. I can't say."
He took a drop of the liquid he had isolated and added a drop of nitric acid. Then he evaporated it by gentle heat and it left a residue which was slightly yellow.
Next he took from the shelf over his table a bottle marked alcoholic solution, potassium hydrate, and let a drop fall on it. Instantly the residue became a beautiful purple, turning rapidly to violet, then to dark red and finally disappeared.
"Stramonium all right," he nodded with satisfaction. "That was known as Vitali's test. Yes, there was stramonium in those cigarettes--datura stramonium--perhaps a trace of hyocyamino. They are all, like atropine, mydriatic alkaloids, so-called from the effect on the eye. One one-hundred-thousandth of a grain will affect the cat's eye. You saw how it acted. It is more active than even atropine. Better yet, you remember how Don Luis's eyes looked."
"Oh," he answered quickly, "her pupils were normal enough. Didn't you notice that? This concentrated poison which has been used in Mendoza's cigarettes does not kill, at least not outright. It is worse. Slowly it accumulates in the system. It acts on the brain. Of all the dangers to be met with in superstitious countries, these mydriatic alkaloids are among the worst. They offer a chance for crimes of the most fiendish nature--worse than the gun or the stiletto, and with little fear of detection. It is the production of insanity!"
Horrible though the idea was I could not doubt it in the face of Craig's investigations and what I had already seen. In fact, it was necessary for me only to recall the peculiar sensations I myself had experienced after smoking merely a few puffs of one of Mendoza's cigarettes in order to be convinced of the possible effect of the insidious poison contained in the many that he smoked.
It was almost dawn before Craig and I left the laboratory after his discovery of the manner of the stramonium poisoning. I was thoroughly tired, though not so much so that my dreams were not haunted by a succession of baleful eyes peering at me from the darkness.