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When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
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.
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.
Malaria mortality rates are falling. Increased malaria prevention and control measures have greatly improved these rates. Since 2000, malaria mortality rates have fallen globally by 60% among all age groups, and by 65% among children under age 5.
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.