Surfactant prevents this collapse by reducing the surface tension of the fluids that line the lungs and helping to equalize the pressures between large and small air spaces. Surface tension is a measure of the attraction molecules of a fluid have for each other.
Buffalo Bill Cody, who later became famous for his Wild West Show, was a rider for the Pony Express and wrote of his experiences. We join Bill's story as he is hired - at the age of 15 - to ride a section of the trail that lies in modern-day Wyoming:
Russell, Majors, and Waddell organized and put together the Pony Express in two months in the winter of 1860. The undertaking assembled 120 riders, 184 stations, 400 horses, and several hundred personnel during January and February 1861.