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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).
Many medications that are used to treat infertility are injected subcutaneously. This is easy to do using the anterior abdomen as the site of injection but avoiding the area directly around the belly button.
Bisphosphonates were first developed in the nineteenth century. They were first investigated for use in disorders of bone metabolism in the 1960s. They are now used clinically for the treatment of osteoporosis, Paget's disease, bone metastasis, multiple myeloma, and other conditions that feature bone fragility.
Giardia is one of the most common intestinal parasites worldwide, and infects up to 20% of the world population, mostly in poorer countries with inadequate sanitation. Infections are most common in children, though chronic Giardia is more common in adults.
Cancer has been around as long as humankind, but only in the second half of the twentieth century did the number of cancer cases explode.