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Dear Jane:
Brace yourself. Your fingernails and toenails are made of the same stuff that makes up your hair!
Its called keratin and its also the main ingredient in steer's horns, a cat or dog's claws, and
even a bird's feathers. Who knew that you and that robin hunting (dare I say it?) for that worm had
so much in common?
This substance called keratin is like some kind of miracle plastic. It's strong, tough, and
flexible enough to bend more often than it breaks!
Your nail grows from an area hidden under the skin at the base of your nails. While most of it
isn't alive itself, your nail rests on a bed of living tissue, filled with blood vessels. Hence the
natural pink color of your nail. Near the base of the nail, you may notice a white half-moon shape.
Called the lunula, it's thought that it's different color may be because there are active nail
cells growing is this area.
So why do mammals like you have nails, anyway? Different animals have different kinds of nails
for different functions. For active hunters, like lions and tigers, nails are claws that snag prey
and then rip and tear them apart. For horses, their "nails," or hooves, help them to hold onto
stony ground and gallop quickly. For others, like monkeys, claws help dig and climb.
For you humans, nails are obviously something to paint all sorts of colors! But your nails on
top, your soft skin on the bottom, and the combination of muscles, joints and bones inside your
hand make it very easy for you to grab and manipulate things in the complex way that you humans do!
While nails grow on average about a millimeter a day, it is thought that fingernails grow four
times faster than toenails, and that the nail on your middle finger grows the fastest of all! But
why don't you do your own research to find out if this is true. Make a small mark on several
different finger and toe nails and then measure the growth, a day, a week or even a month later and
see what you find out!
Signed,
Wendell
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