Hi Bill,
I also found out that the tube worked both ways and considered it a party trick to clinch my abbs and watch it come back into the surenge. My wife made me laugh one day when I was "feeding" myself and that is how I found out.
The other nasty part about the tubes is the cap wears out after a while. One night I woke up in a pile of stomach contents that came out of the uncapped tube. Not pleasant.
Jim