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."

"How about the Senora?" I put in.

"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.

I slept late, but Kennedy was about early at the laboratory, verifying
his experiments and checking over his results, carefully endeavoring to
isolate any other of the closely related mydriatic alkaloids that might
be contained in the noxious fumes of the poisoned tobacco. Though he was
already convinced of what was going on, I knew that he considered it a
matter of considerable medico-legal importance to be exact, for if the
affair ever came to the stage of securing an indictment, the charge
could be sustained only by specific proof.

Early in the forenoon Kennedy left me alone in the laboratory and made a
trip downtown, where he visited a South American tobacco dealer and
placed a rush order for a couple of hundred cigarettes, duplicating in
shape and quality those which Senor Mendoza doza preferred, except,
however, the deadly drug which was in those he was smoking.

I had some writing to do and was busily engaged at my typewriter when I
suddenly became con