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start that parade or to run it—it just happened, said the new philosophers with an air of science.

But Pasteur answered: "My philosophy is of the heart and not of the mind, and I give myself up, for instance, to those feelings about eternity that come naturally at the bedside of a cherished child drawing its last breath. At those supreme moments there is something in the depths of our souls which tells us that the world may be more than a mere combination of events due to a machine-like equilibrium brought out of the chaos of the elements simply through the gradual action of the forces of matter." He was always a good Catholic.

Then Pasteur dropped philosophy and set to work. He believed that his yeasts and rods and little animals came from the air—he imagined an air full of these invisible things. Other microbe hunters had shown there were germs in the air, but Pasteur made elaborate machines to prove it all over again. He poked gun cotton into little glass tubes, put a suction pump on one end of them and stuck the other end out of the window, sucked half the air of the garden through the cotton—and then gravely tried to count the number of living beings in this cotton. He invented clumsy machines for getting these microbe-loaded bits of cotton into yeast soup, to see whether the microbes would grow. He did the good old experiment of Spallanzani over; he got himself a round bottle and put some yeast soup in it, and sealed off the neck of the bottle in the stuttering blast lamp flame, then boiled the soup for a few minutes—and no microbes grew in this bottle.

"But you have heated the air in your flask when you boiled the yeast soup—what yeast soup needs to generate little animals is natural air—you can't put yeast soup together with natural unheated air without its giving rise to yeasts or molds or torulas or vibrions or animalcules!" cried the believers in spontaneous generation, the evolutionists, the doubting botanists, cried all Godless men from their libraries and their armchairs. They shouted, but made no experiments.

Pasteur, in a muddle, tried to invent ways of getting un-