Full of confidence Koch went to Professor Rudolph Virchow, by far the most eminent German researcher in disease, an incredible savant, who knew more than there was to be known about a greater number of subjects than any sixteen scientists together could possibly know. Virchow was, in brief, the ultimate Pooh-Bah of German medical science. He had spoken the very last word on clots in blood vessels and had invented the impressive words, _heteropopia_, _agenesia_, and _ochronosis_, and many others that I have been trying for years to understand the meaning of. He had--with tremendous mistakenness--maintained that consumption and scrofula were two different diseases; but with his microscope he had made genuinely good, even superb descriptions of the way sick tissues look and he had turned his lens into every noisome nook and cranny of twenty-six thousand dead bodies. Virchow had printed--I do not exaggerate--thousands of scientific papers, on every subject imaginable, from the shapes of little German schoolboys’ heads and noses to the remarkably small size of the blood vessels in the bodies of sickly green-faced girls. Properly awed--as any one would be--Koch tiptoed respectfully into this Presence. “I have discovered a way to grow microbes pure, unmixed with other germs, Herr Professor,” the bashful Koch told Virchow, with deference. “And how, I beg you tell me, can you do that? It looks to me to be impossible.” “By growing them on solid food--I can get beautiful isolated colonies of one kind of microbe on the surface of a boiled potato.... And now I have invented a better way than that ... I mix gelatin with beef broth ... and the gelatin sets and makes a solid surface, and----” But Virchow was not impressed. He made a sardonic remark that it was so hard to keep different races of germs from getting mixed up that Koch would have to have a separate laboratory for each species of microbe.... In short, Virchow was very sniffish and cold to Koch, for he had come to that time of life when ageing men believe that everything is known and there is nothing more to be found out. Koch went away a bit depressed, but not one jot was he discouraged. Instead of arguing and writing papers and making speeches against Virchow he launched himself into the most exciting and superb of all his microbe huntings--he set out to spy upon and discover the most vicious of microbes, that mysterious marauder which each year killed one man, woman, and child out of every seven that died, in Europe, in America. Koch rolled up his sleeves and wiped his gold-rimmed glasses and set out to hunt down the microbe of tuberculosis. VI