[LM_NET] elementary book identification

[Clara Bolton <clbolto@KCKPS.ORG>]

Can anyone help me identify this book for a good friend? She remembers
reading it in the 50s, so late 40s to 50s publication date. A little boy
shrinks and shrinks, he becomes so small that his father makes him a
tiny saddle and he rides a sea gull. She thinks the gull's name was Gus.
The little boy trains an army of mice and teaches them to march in rows.
At the end of the book, the father comes up with some kind of antidote,
and the boy returns to normal size.

She loved this book and I would really like to help her identify it.

TIA,

Claire Bolton
Arrowhead MS
Kansas City  KS

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