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Academy of the hard job that awaited him; he explained to them why he must not shrink from it, by making a graceful quotation from the great Lavoisier: "Public usefulness and the interests of humanity ennoble the most disgusting work and only allow enlightened men to see the zeal which is needed to overcome obstacles."

So he prepared the stage for his dangerous experiments—years before he entered on them. He prepared a public stage-setting. His proposed heroism thrilled the calm men of science that were his audience. As they returned home through the gray streets of the ancient Latin Quarter they could imagine Pasteur bidding them a farewell full of emotion, they could see him marching with set lips—wanting to hold his nose but bravely not doing it—into the midst of stinking pestilences where perilous microbes lay in wait for him. . . . It is so that Pasteur proved himself much more useful than Leeuwenhoek or Spallanzani—he did excellent experiments, and then had a knack of presenting them in a way to heat up the world about them. Grave men of science grew excited. Simple people saw clear visions of the yeasts that made the wine that was their staff of life and they were troubled at nights by thoughts of hovering invisible putrid microbes in the air. . . .

He did curious tests that waited three years to be completed. He took flasks and filled them part way full with milk or urine. He doused them in boiling water and sealed their slender necks shut in a blast flame—then for years he guarded them. At last he opened them, to show that the urine and the milk were perfectly preserved, that the air above the fluid in the bottles still had almost all of its oxygen; no microbes, no destruction of the milk! He allowed germs to grow their silent swarms in other flasks of urine and milk that he had left unboiled, and when he tested these for oxygen he found that the oxygen had been completely used up—the microbes had used it to burn up,