Why Must the Scots Always Have Hallucinations

Tune: Noel Coward's "Why Do the Wrong People Travel?"

Why must the Scots always have hallucinations
At the sight of a drop of blood?
At the first hint of plasma,
A gory phantasma
Besets my dreams and robs my rest;
By 2:00 a.m., I'm bucking for a Rorschach test.

The Birnam Wood
Has politely stood
Where it stood from time immemorial,
So I can't think why
Every passer-by
Should be suddenly looking so arboreal.

Lord knows, we Scots aren't like superstitious Haitians—
We've a far higher class of mud;
So why, oh why all these weird visitations

At the sight of a drop of blood?
Is this a dagger—
Or a drop of the royal blood?
—I see before me?
I suspect that it's only blood.
I'm merely asking:
What's the deal with the Scots and blood?