Frozen grapes are delicious served with chocolate truffles and cream.  If you let them warm up a bit, you can bite through them and feel the cold juice squirt around your mouth.  But Roz found this difficult.   

‘I can’t eat these. I have sensitive teeth.’

‘Well just try swallowing them and feel the cold go all the way down,’ I suggested. ‘Look it’s easy.’  And with that I popped one into my mouth, let it roll down back into my pharanx and swallowed, then waited for the wave to slide it down.   

The grape was as hard as a marble and cold as a lump of ice.  It got so far and stopped just behind the sternal notch, generating a dull ache that spread like a band around my chest.   I swallowed again. It still wouldn’t budge.  In fact I could feel it coming back up again and the pain intensified.  I swallowed a third time.  Nothing.  I could feel my face turning red and a wave of nausea rising up from my stomach. 

I stood there, my neck sunk into my chest, eyes bulging, not sure what to do. Simon was laughing, tears rolling down his face. ‘You’re such a  daft bugger!’

At that I started laughing too and then stopped.  There was a real risk of asphyxiation and while it might be a good way to go, I wasn’t ready for that yet. I needed to stay calm. I breathed gently in and out and when I felt in control, swallowed some water and felt the grape move painfully down.   

I turned to Judy, who was a scientist.  ‘Why don’t you write this up as an experiment  – the induction of reverse peristalsis by an ice cold bolus?  But first we need to test its reproducibility.’  Emboldened by experience,  I took another grape and swallowed.  The  obstruction behind my breastbone was exquisitely painful this time and it was so hard not to laugh when others were swaying about with general mirth.  But another glass of water did the trick.  Eureka! 

‘Now, Judy, we need to try this on somebody else. What about Roz?  And we need a genetic control.  Simon would do. And then you must do a series.  You could put a capillary tube down and measure pressures or you could fill the grape with contrast medium before freezing and then X-ray your volunteers.  Reverse oesophageal peristalsis is controversial in humans, but this could be the proof.  You could be famous, Judy.  It could be known as the Donnelly Provocation Test.  You could patent it.’ 

Ah well,  you can lead a scientist to water, but ………  Judy was not impressed.  Another opportunity missed! 

All of this reminded me of a demonstration forty five years ago in Cambridge. Dr Giles Brindley, then a young lecturer in physiology, stood on his head on the class bench and swallowed water through a rubber tube from a large Winchester bottle, just to prove that swallowing does not occur by gravity but by persistalsis.  The next issue of the Med. Soc. magazine demonstrated the trick.  Beneath the bench was the laboratory assistant who was opening a stop cock to drain the bottle. 

Who said science wasn’t theatre?

A Health and Safety Warning.  These experiments are risky. Please don’t be tempted to try them at home.

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