A child's body has 60,000 miles of blood vessels -- Bacteria outnumber human cells in the body -- Humans glow like fireflies -- Short-term memory lasts 30 seconds -- Stomach acid can destroy metal -- The body contains billions of miles of dna -- The body makes four pints of saliva a day -- The body sheds a lot of skin each year -- The human heart pumps 2,000 gallons a day -- The nose knows 1 trillion smells -- Tongues are like tentacles and trunks -- Yawning cools the brain.