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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.
The modern decimal position system was the invention of the Hindus (around 800 AD), involving the placing of numerals to indicate their value (units, tens, hundreds, and so on).
Ether was used widely for surgeries but became less popular because of its flammability and its tendency to cause vomiting. In England, it was quickly replaced by chloroform, but this agent caused many deaths and lost popularity.
It is widely believed that giving a daily oral dose of aspirin to heart attack patients improves their chances of survival because the aspirin blocks the formation of new blood clots.
The first monoclonal antibodies were made exclusively from mouse cells. Some are now fully human, which means they are likely to be safer and may be more effective than older monoclonal antibodies.