When your friend orders his whiskey, start off as follows:
Tell him you take it for granted that he knows all about the mucous membrane. He will say that he does—for it is our American mania to want to appear wise.
Casually state that of course he knows the covering of his eyeball is identical in all important respects—especially as regards sensitiveness—with the lining of his stomach; in fact, of his whole interior from his mouth down.
He will assent and gravely pour out his poison.
Then say to him:
"Just dip the tip of your finger in that whiskey and put the finger to your eye-ball."
If he does so he will feel the eye smart. The eyeball will become inflamed, and sight for a moment will be difficult.
Then let him dilute the whiskey with water—four or five parts water to one of whiskey. That dilution, rubbed into the other eye, instead of irritating it, will act as a gentle stimulant. It will produce an agreeable effect.
When your friend has experimented with the whiskey "straight" and diluted, deliver to him this little lecture:
"One drop of pure whiskey on your eyeball makes it hard to use the eye. That glass of whiskey that you are now pouring into yourself would blind you absolutely, at least for a time. If straight whiskey has such an effect on the covering of the eyeball, must not its effect be equally injurious to the covering of the stomach and intestines, which is the same as that of the eye?