The great medical congresses of those brave days were exciting debating societies about microbes, about immunity, and it was in the weeks before a congress (Metchnikoff always went to them) that his laboratory buzzed with an infernal rushing to and fro. “We must hurry,” Metchnikoff exclaimed, “to make all of the experiments necessary to support my arguments!” The crowd of adoring assistants then slept two hours less each night; Metchnikoff rolled up his sleeves, too, and seized a syringe. Young rhinoceros beetles, green frogs, alligators, or weird Mexican axolotls were brought from the animal house by the sweating helpers (sometimes the ponds were dredged for perch and gudgeon). Then the mad philosopher, his eyes alight, his broad face so red that it glowed like some smoldering brush-fire under his beard, his mustaches full of bacilli spattered into it by his excited and poetic gestures--this Metchnikoff, I say, proceeded to inject swarms of microbes into one or another of his uncomplaining, cold-blooded menagerie. “I multiply experiments to support my theory of phagocytes!” he was wont to say. VI It is amazing, when you remember that his brain was always inventing stories about nature, how often these stories turned out to be true when they were put to the test of experiment. A German hunter had claimed: “There is nothing to Metchnikoff’s theory of phagocytes. Everybody knows that you can see microbes inside of phagocytes--they have undoubtedly been gobbled up by the phagocytes. But these wandering cells are not defenders, they are mere scavengers--they will only swallow dead microbes!” The London Congress of 1891 was drawing near; Metchnikoff shouted for some guinea-pigs, vaccinated them with some cholera-like bacilli that his old friend, the unfortunate Gamaléia, had discovered. Then, a week or so later, the big-bearded philosopher shot some of these living, dangerous bacilli into the bellies of vaccinated beasts. Every few minutes, during the next hours, he ran slender glass tubes into their abdomens, sucked out a few drops of the fluid there, and put it before the more or less dirty lens of his microscope, to see whether the phagocytes of the immune beasts were eating up Gamaléia’s bacilli. Presto! These roundish crawling cells were crammed full of the microbes! “Now I shall prove that these microbes inside the phagocytes are still alive!” cried Metchnikoff. He killed the guinea-pig, slashed it open, and sucked into another little glass tube some of the grayish slime of wandering cells which had gathered in the creature’s belly to make meals off the microbes. In a little while--for they are very delicate when you try to keep them alive outside the body--the phagocytes had died, burst open, and the _live_ bacilli they had swallowed galloped out of them! Promptly, when Metchnikoff injected them, these microbes that had been swallowed, murdered guinea-pigs who were not immune.