Page:Microbe Hunters.djvu/101

"Yes," answered Pasteur, "but———"

"Wait a minute!" interrupted Balard. "Why don't you just try the trick of putting some yeast soup in a bottle, boiling it, then fixing the opening so the dust can't fall in. At the same time the air can get in all it wants to."

"But how?" asked Pasteur.

"Easy," replied the now forgotten Balard. "Take one of your round flasks, put the yeast soup into it, then soften the glass of the flask neck in your blast lamp—and draw the neck out and downward into a thin little tube—turn this little tube down the way a swan bends his neck when he's picking something out of the water. Then just leave the end of the tube open. It’s like this———" and Balard sketched a diagram:

Pasteur looked, then suddenly saw the magnificent ingeniousness of this little experiment. "Why, then microbes can't fall into the flask, because the dust they stick to can't very well fall upward—marvelous! I see it now!"

"Exactly," smiled Balard. "Try it and find out if it works—see you later," and he left to continue his genial round of the laboratories.

Pasteur had bottle washers and assistants now, and he ordered them to hurry and prepare the flasks. In a moment the laboratory was buzzing with the stuttering ear-shattering b-r-r-r-r-r of the enameler's lamps; he fell to work savagely. He took flasks and put yeast soup into them and then melted their necks and drew them out and curved them downward—into swan's necks and pigtails and Chinaman's cues and a half-dozen fantastic shapes. Next he boiled the soup in them—that drove out all the air—but as the flasks cooled down new air came in—unheated air, perfectly clean air.