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Pope Sylvester II tried to introduce Arabic numbers into Europe between the years 999 and 1003, but their use did not catch on for a few more centuries, and Roman numerals continued to be the primary number system.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.
The first documented use of surgical anesthesia in the United States was in Connecticut in 1844.
The term bacteria was devised in the 19th century by German biologist Ferdinand Cohn. He based it on the Greek word "bakterion" meaning a small rod or staff. Cohn is considered to be the father of modern bacteriology.
The heart is located in the center of the chest, with part of it tipped slightly so that it taps against the left side of the chest.