It seemed to occur to him instantly, however, that he was committing an inhospitable breach, for he produced his Durham and brown papers with a start and extended them towards the doctor.
"Smoke ?" he asked.
"I use tobacco in no form," said the doctor.
The cowboy stared with such fixity that the match burned down to his fingertips and singed them before he had lighted his cigarette.
"'S that a fact ?" he queried when his astonishment found utterance.
"What d'you do to kill time?
Well, I been thinking about knocking off the stuff for a while.

Mame gets sore at me for having my fingers all stained up with nicotine like this." He extended his hand, the first and second fingers of which were painted a bright yellow.
"Soap won't take it off," he remarked.
"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.