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Vaccines prevent between 2.5 and 4 million deaths every year.
When blood is deoxygenated and flowing back to the heart through the veins, it is dark reddish-blue in color. Blood in the arteries that is oxygenated and flowing out to the body is bright red. Whereas arterial blood comes out in spurts, venous blood flows.
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.
Women are two-thirds more likely than men to develop irritable bowel syndrome. This may be attributable to hormonal changes related to their menstrual cycles.
In ancient Rome, many of the richer people in the population had lead-induced gout. The reason for this is unclear. Lead poisoning has also been linked to madness.