My grandmother, who always kept a weight on her lavatory seat because a rat once came out of her privy and bit the family maid on the bottom, would have been utterly unfazed at rats in the attic, but friends and colleagues go pale with horror at the tale.

It's as though rats call on some atavistic racial memory, of plagues and Marburg virus and long ago episodes of Dr Who. True, it wasn't nice hearing them in the attic at night, plotting, and it took the electrician two days and 40 cups of tea to find all the cabling they had gnawed, but I've never been a 'screaming at rats' person.

The last time I screamed at anything that was not on Britain's Got Talent was when the cat regurgitated three live helminths of monstrous proportions, at which I shrieked like a Victorian heroine and fled the kitchen.

Even I was surprised, though, when I lay back happily in the bath and what appeared to be a giant rat came swimming towards me through the rose-scented froth. My initial thought was that this was quite interesting, purely from an animal behaviour point of view... until closer inspection revealed it to be my daughter's hair extensions, which had been draped over the taps to dry. As soon as I realised its true nature I flung it from the water with a shriek.

Abandoned bits of people are kind of nasty when they invade our personal space - yet when you reflect on the numbers of abandoned bits of people that pass across our professional desks you would think I'd be a bit more stoical.

Nail clippings, urine, stools, pots of phlegm, unmentionable stuff on swabs... all the unwanted detritus of the human body sits in pots on my desk all day, and while I would not share my bath with any of them I don't go running from the room.

Perhaps doctors simply are not wired like other people, says my daughter, retrieving the hair from the bathroom floor and stroking it lovingly. I think she might be right - but which of us is normal?

• Catch up with Mary's Road to Revalidation blog here