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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.
After a vasectomy, it takes about 12 ejaculations to clear out sperm that were already beyond the blocked area.
Blood is approximately twice as thick as water because of the cells and other components found in it.
Prostaglandins were first isolated from human semen in Sweden in the 1930s. They were so named because the researcher thought that they came from the prostate gland. In fact, prostaglandins exist and are synthesized in almost every cell of the body.
The first documented use of surgical anesthesia in the United States was in Connecticut in 1844.