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Human neurons are so small that they require a microscope in order to be seen. However, some neurons can be up to 3 feet long, such as those that extend from the spinal cord to the toes.
More than 50% of American adults have oral herpes, which is commonly known as "cold sores" or "fever blisters." The herpes virus can be active on the skin surface without showing any signs or causing any symptoms.
About 60% of newborn infants in the United States are jaundiced; that is, they look yellow. Kernicterus is a form of brain damage caused by excessive jaundice. When babies begin to be affected by excessive jaundice and begin to have brain damage, they become excessively lethargic.
Adult head lice are gray, about ? inch long, and often have a tiny dot on their backs. A female can lay between 50 and 150 eggs within the several weeks that she is alive. They feed on human blood.
More than 34,000 trademarked medication names and more than 10,000 generic medication names are in use in the United States.
![California sea lions are common prey for mammal-eating killer whales on the west coast of North Amer](https://biology-forums.com/gallery/47/medium_27599_22_04_12_6_56_25.jpeg)
![Gallbladder with gallstones. Note the stones in the hepatic duct, gallbladder, and common bile duct.](https://biology-forums.com/gallery/47/medium_14755_30_09_12_4_40_41_91531880.jpeg)