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" Smell is certainly an intensely personal experience. “I think the single most extraordinary aspect of olfaction is that we all smell the world differently,” Beauchamp says. “Although we all have 350 to 400 types of odor receptor, only about half of them are common to all people. That means that we don’t smell the same things.” He reached into his desk and pulled out a vial, which he uncapped and passed to me to sniff. I could smell nothing at all. “It’s a hormone called androsterone,” Beauchamp explained. “About a third of people, like you, can’t smell it. One-third smell something like urine, and one-third smell sandalwood.” His smile broadened. “If you have three people who cannot even agree on whether something is pleasant, revolting, or simply odorless, you begin to see how complicated the science of smell is. "
― Bill Bryson , The Body: A Guide for Occupants
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" For the longest time, the crucial importance to health of just moving around was hardly appreciated. But in the late 1940s a doctor at Britain’s Medical Research Council, Jeremy Morris, became convinced that the increasing occurrence of heart attacks and coronary disease was related to levels of activity, and not just to age or chronic stress, as was almost universally thought at the time. Because Britain was still recovering from the war, research funding was tight, so Morris had to think of a low-cost way to conduct an effective large-scale study. While traveling to work one day, it occurred to him that every double-decker bus in London was a perfect laboratory for his purposes because each had a driver who spent his entire working life sitting and a conductor who was on his feet constantly. In addition to moving about laterally, conductors climbed an average of six hundred steps per shift. Morris could hardly have invented two more ideal groups to compare. He followed thirty-five thousand drivers and conductors for two years and found that after he adjusted for all other variables, the drivers—no matter how healthy—were twice as likely to have a heart attack as the conductors. It was the first time that anyone had demonstrated a direct and measurable link between exercise and health. "
― Bill Bryson , The Body: A Guide for Occupants