Open it up and it's like the Tardis, defying the space-time continuum, much bigger on the inside. Like a part of me, I can find what I want without looking, just by rummaging around, blithely ignoring the risk of being stabbed by an errant scalpel.
Stethoscope, sphyg, ophthalmoscope (for theatrical purposes), thermometer, torch, prescription pad, these are but the bare bones; my bag is multipurpose.
If you get hungry while warding off the forces of darkness, you can have a snack; there's always a half-eaten sandwich somewhere in the depths, or a few ancient toffees stuck to the lining. And an ersatz tracheostomy kit - an old ball-point pen, in case someone needs an emergency tracheostomy, after which Meg Ryan will sleep with me in gratitude (I've seen this on film, so it must be true).
The fancy climate-controlled aluminium gigs are not for me. I prefer vintage, a visible manifestation of our ancient profession's authority. And vintage is heavier, which can come in handy.
'Don't mind the dog,' is one of the those Phrases That GPs Do Not Like To Hear (along with 'He's pulling at his ears,' and 'It all began when I was child ...'). The guard dog, apparently half-sheepdog and half-hyena, was in a frenzy, leaping up and snapping at the car door, spattering the window with drool, such was his excitement at the prospect of tasting family doctor flesh.
I'm a lover, not a fighter, but there was a patient waiting with an 'awful' sore throat and my vocation - to cure sometimes, comfort always, be sarcastic whenever possible - would not be denied.
Cometh the hour, cometh the doc; if you can't stand the heat, get out of general practice.
'Say hello to my little friend,' I snarled in my best Al Pacino accent, swinging my trusty black bag like the sword of retribution and bludgeoning the surprised dog into a corner of the barnyard.
'Now the beast cannot harm you,' I declaimed to the world.
I don't know about the patient, but after that visit, I know that I certainly felt much better.
- Dr Farrell is a GP from County Armagh.
- Follow him on Twitter @drlfarrell.