Hello, my name is Dr. Kara and I have over 20 years of experience as a veterinarian.
I understand that you are curious about the origin of the Fox Terrier breed.
It is not true that they are the result of a female dog bred with a male fox.
True, pure bred Fox Terriers are the result of breeding a registered male Fox Terrier with a registered female Fox Terrier. The origins of the breed aren't completely known but it is speculated that they resulted from a mix of terriers, Beagles and Fox Hounds to get the dog we know today. The breed as we know it was established by the beginning of the 19th century and has been pure since then.
If a female dog of any breed were bred with a fox the resulting litter could not be registered as purebreds.
Please let me know if you have any further questions.