Koch sent him on a tube that swarmed with wee virulent comma microbes. And so Pettenkofer--to the great alarm of all good microbe hunters--swallowed the entire contents of the tube. There were enough billions of wiggling comma germs in this tube to infect a regiment. Then he growled his scorn through his magnificent beard, and said: “Now let us see if I get cholera!” Mysteriously, nothing happened, and the failure of the mad Pettenkofer to come down with cholera remains to this day an enigma, without even the beginning of an explanation. Pettenkofer, who was foolhardy enough to try such a possibly suicidal experiment, was also sufficiently cocksure to believe that his drinking of the cholera soup had settled the question in his favor. “Germs are of no account in cholera!” shouted the old doctor. “The important thing is the _disposition_ (whatever that means) of the individual!” “There can be no cholera without the comma bacillus!” said Koch in reply. “But I have just swallowed millions of your alleged fatal bacilli, and have not even had a cramp in my stomach!” came back Pettenkofer in rebuttal. As it is so often the case, alas, in violent scientific controversies, both sides were partly right and partly wrong. Every event of the past forty years has shown that Koch was right when he said that people can never have cholera without swallowing his comma bacillus. And the years that have gone by have revealed that Pettenkofer’s experiment pointed out a mystery behind the curtains of the unknown, and these obscuring draperies have not now even begun to be lifted by modern microbe hunters. Murderous germs are everywhere, sneaking into all of us, yet they are able to assassinate only some of us, and that question of the strange resistance of the rest of us is still just as much an unsolved puzzle as it was in those days of the roaring eighteen-eighties when men were ready to risk dying to prove that they were right. For, make no mistake, Pettenkofer walked within an inch of death; other microbe hunters have since then swallowed cultures of virulent cholera microbes by accident--and died horribly. But we come to the end of the great days of Robert Koch, and the exploits of Louis Pasteur begin once more to push Koch and all other microbe hunters into the background of the world’s attention. Let us leave Koch while his ambitious but well-meaning countrymen prepare, without knowing it, a disaster for him, a tragedy that, alas, has partly tarnished the splendor of his trapping of the microbes that murder animals and men with anthrax and cholera and tuberculosis. But before you read the perfect and brilliant _finale_ of the gorgeous career of Pasteur, I beg leave to remove my hat and make bows of respect to Koch--the man who really _proved_ that microbes are our most deadly enemies, who brought microbe hunting near to being a science, the man who is now the partly forgotten captain of an obscure heroic age.