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Though the United States has largely rejected the metric system, it is used for currency, as in 100 pennies = 1 dollar. Previously, the British currency system was used, with measurements such as 12 pence to the shilling, and 20 shillings to the pound.
When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
The first-known contraceptive was crocodile dung, used in Egypt in 2000 BC. Condoms were also reportedly used, made of animal bladders or intestines.
The toxic levels for lithium carbonate are close to the therapeutic levels. Signs of toxicity include fine hand tremor, polyuria, mild thirst, nausea, general discomfort, diarrhea, vomiting, drowsiness, muscular weakness, lack of coordination, ataxia, giddiness, tinnitus, and blurred vision.
Blood is approximately twice as thick as water because of the cells and other components found in it.