"A popular but inexcusable error," said the doctor. "It is the tarry
by-products of tobacco which cause that stain. Nicotine itself, of
course, is a volatile alkaloid base of which there is only the merest
trace in tobacco. It is one of the deadliest of nerve poisons and is
quite colourless. There is enough of that stain upon your fingers--if it
were nicotine--to kill a dozen men."

"The hell you say!"

"Nevertheless, it is an indubitable fact. A lump of nicotine the size of
the head of a pin placed on the tongue of a horse will kill the beast
instantly."

The cowpuncher pushed back his hat and scratched his head.

"This is worth knowin'," he said, "but I'm some glad that Mame ain't
heard it."

"Concerning the Cumberlands," said the doctor, "I--"

"Concerning the Cumberlands," repeated the cattleman, "it's best to
leave 'em to their own concerns." And he started to turn away, but the
thirst for knowledge was dry in the throat of the doctor.

"Do I understand," he insisted, "that there is some mystery connected
with them?"

"From me," replied the other, "you understand nothin'." And he lumbered
down the steps and away.