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Vaccines prevent between 2.5 and 4 million deaths every year.
The liver is the only organ that has the ability to regenerate itself after certain types of damage. As much as 25% of the liver can be removed, and it will still regenerate back to its original shape and size. However, the liver cannot regenerate after severe damage caused by alcohol.
Amoebae are the simplest type of protozoans, and are characterized by a feeding and dividing trophozoite stage that moves by temporary extensions called pseudopodia or false feet.
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.
Side effects from substance abuse include nausea, dehydration, reduced productivitiy, and dependence. Though these effects usually worsen over time, the constant need for the substance often overcomes rational thinking.