Throughout the Sherlock Holmes stories by Sir Arthur Conan Doyle, characters regularly consult Dr. Watson for his medical advice. In the second Holmes novel, "The Sign of Four," we learn this is a horrible idea.
Here, Watson has just discovered that some other characters stand to inherit an extravagant treasure:
Sherlock Holmes took his bottle from the corner of the mantel- piece, and his hypodermic syringe from its neat morocco case. With his long, white, nervous fingers he adjusted the delicate needle and rolled back his left shirtcuff. For some little time his eyes rested thoughtfully upon the sinewy forearm and wrist, all dotted and scarred with innumerable puncture-marks. Finally, he thrust the sharp point home, pressed down the tiny piston, and sank back into the velvet-lined armchair with a long sigh of satisfaction.
Three times a day for many months I had witnessed this performance, but custom had not reconciled my mind to it. On the contrary, from day to day I had become more irritable at the sight, and my conscience swelled nightly within me at the thought that I had lacked the courage to protest. Again and again I had registered a vow that I should deliver my soul upon the subject; but there was that in the cool, nonchalant air of my companion which made him the last man with whom one would care to take anything approaching to a liberty. His great powers, his masterly manner, and the experience which I had had of his many extraordinary qualities, all made me diffident and backward in crossing him.
Yet upon that afternoon, whether it was the Beaune which I had taken with my lunch or the additional exasperation produced by the extreme deliberation of his manner, I suddenly felt that I could hold out no longer.
"Which is it today," I asked, "morphine or cocaine?"
He raised his eyes languidly from the old black-letter volume which he had opened.
"It is cocaine," he said, "a seven-per-cent solution. Would you care to try it?"
"No, indeed," I answered brusquely. "My constitution has not got over the Afghan campaign yet. I cannot afford to throw any extra strain upon it."
He smiled at my vehemence. "Perhaps you are right, Watson," he said. "I suppose that its influence is physically a bad one. I find it, however, so transcendently stimulating and clarifying to the mind that its secondary action is a matter of small moment."
"Are you holding?"