Petsafe ppa00-11323 Manual De Instrucciones página 10

PET DOORS OF THE PAST
Did you know that pet doors are not a twentieth century invention?
Admittedly, the pet doors of our forefathers were not the sophisticated
draught and rain-proof devices that provide today, but even in the Middle
Ages, pet owners realised that their animals needed both indoor comfort
and outdoor freedom.
One amusing story concerns the English scientist Isaac Newton. He was
a great cat lover and in order that his cat could sleep in the warmth of his
barn, he cut a small opening in the door, so that she could come and go
freely. Soon the cat had kittens and Newton cut a smaller hole in the barn
door for the kittens to use. It is possible that Newton may have been
conducting an experiment on cat behavior, but it is more likely that he
simply had not realised that the kittens could have easily used their
mother's "pet door".
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