[Frank Muir]
The term 'tooth-comb' actually originates from agricultural folk-law. Farmers who bred chickens for egg production were well aware that very occasionally a chick would be born with a small deformity in its beak. As it grew older, this would cause it's upper beak to misalign with its lower and as a consequence it would not be able to peck in the ground for grain and insects. The only way it could gather enough nutrition would be to feed off the eggs of the other hens. Its beak deformity or "hens tooth" actually made it easier for the hen to break the egg shells before eating the contents.
Clearly this was not in the farmer's interest to have an egg consuming hen in its flock, so he would try to identify these very rare toothed hens. Because the deformity did not develop until the hen was much older, it was said that a skilled farmer could spot a potential problem hen because before its tooth was fully developed, its comb tended to be very slightly narrower than that of a normal healthy hen.
With modern industrial scale farming, it is sadly no longer necessary to be able to identify a fine tooth-comb, although organic free-range farmers still claim to be able to spot them.
[/Frank Muir]
