Rocky Brook, age 13, of Visalia, California, for his question:

Why don't the feet of horses freeze in cold weather?

When you go out in freezing weather, your skin and flesh become chilled but your hair is not bothered by the nippy weather and neither are the nails on your fingers and toes. This is because your hair and nails are made from dead, dry cells with no nerves or blood vessels. The hoofs of a horse are made of horny material, somewhat similar to the nails on our fingers and toes. This biological material does not feel the cold because it has no sensitive nerves to register discomfort. When a skilled blacksmith is shoeing a horse, the noble animal does not even feel the nails that go into his hoofs.

Fleshy tissues are moist and hence likely to freeze at the freezing point of water. Hoofs are hard, dry material and less likely to freeze at this temperature. Hence, horses, cattle and other hoofed animals are able to walk on frosty ground without chilling their tootsies.