Days and weeks passed and eight victims of the mad wolf died in the choking throat-parched agonies of hydrophobia. Their screams rang in the ears of this timid--some called him stupid--boy; and the iron that had seared the farmer’s wound burned a deep scar in his memory. “What makes a wolf or a dog mad, father--why do people die when mad dogs bite them?” asked Louis. His father the tanner was an old sergeant of the armies of Napoleon. He had seen ten thousand men die from bullets, but he had no notion of why people die from disease. “Perhaps a devil got into the wolf, and if God wills you are to die, you will die, there is no help for it,” you can hear the pious tanner answer. That answer was as good as any answer from the wisest scientist or the most expensive doctor in the world. In 1831 no one knew what caused people to die from mad dog bites--the cause of all disease was completely unknown and mysterious. I am not going to try to make believe that this terrible event made the nine-year-old Louis Pasteur determine to find out the cause and cure of hydrophobia some day--that would be very romantic--but it wouldn’t be true. It is true though that he was more scared by it, haunted by it for a longer time, brooded over it more, that he smelled the burned flesh and heard the screams a hundred times more vividly than an ordinary boy would--in short, he was of the stuff of which artists are made; and it was this stuff in him, as much as his science, that helped him to drag microbes out of that obscurity into which they had passed once more, after the gorgeous Spallanzani died. Indeed, for the first twenty years of his life he showed no signs at all of becoming a great searcher. This Louis Pasteur was only a plodding, careful boy whom nobody noticed particularly. He spent his playtime painting pictures of the river that ran by the tannery, and his sisters posed for him until their necks grew stiff and their backs ached grievously; he painted curiously harsh unflattering pictures of his mother--they didn’t make her look pretty, but they looked like his mother.... Meanwhile it seemed perfectly certain that the little animals were going to be put permanently on the shelf along with the dodo and other forgotten beasts. The Swede Linnæus, most enthusiastic pigeonholer, who toiled at putting all living things in a neat vast card catalogue, threw up his hands at the very idea of studying the wee beasts. “They are too small, too confused, no one will ever know anything exact about them, we will simply put them in the class of Chaos!” said Linnæus. They were only defended by the famous round-faced German Ehrenberg who had immense quarrels--in moments when he wasn’t crossing oceans or receiving medals--futile quarrels about whether the little animals had stomachs, strange arguments about whether they were really complete little animals or only parts of larger animals; or whether perchance they might be little vegetables instead of little animals.