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I received a few versions of this, one from the very perspicacious Dragnet,
who lives a bit southwest...

A Worried Wife

Concerned about her husband’s temper, Sadie Bloom seeks advice from
Dr. Schmidt.

Dr. Schmidt asks: "What's the problem?"

Mrs. Bloom says: "Dr. Schmidt, I don't know what to do. Every day my
Edwin seems to lose his temper for no reason. It scares me."

Dr. Schmidt replies: "I have a cure for that. When it seems that your
husband is getting angry, just take a glass of water and start swishing it
in your mouth. Just swish and swish but don't swallow it until he either
leaves the room or calms down."

Two weeks later Mrs. Bloom comes back to visit Dr. Schmidt, looking fresh
and reborn.

Mrs. Bloom says: "Dr. Schmidt, I want to tell you that was a brilliant idea!
Every time my Edwin started losing it, I swished with water. I swished and
swished, and he calmed right down! How does a glass of water do that?"

Dr. Schmidt tells her: "The water itself does nothing. It's keeping your
mouth shut that does the trick."
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