His attentive penetration of things in themselves, coupled with a creative imagination, was the force which enabled him to open out new prospects and new paths.
On looking back upon his own life, he used to say that the period spent at the Pasteur Institute had been the happiest, the most favourable to his scientific work; he therefore remained deeply attached to it until the end of his life.
Opposition to the phagocyte theory--Scientific controversies --Experiments in support of the phagocyte theory--Behring and antitoxins--The London Congress--Inflammation.
As long as Metchnikoff was but a zoologist, the scientific atmosphere around him remained calm and serene. But everything changed suddenly when he entered the domain of pathology with his theory of phagocytes and phagocytosis.
Here was the realm of secular traditions, deeply rooted, and of theories generally admitted but resting on no biological basis. Attacks and objections against his theories came following upon each other with a rush, only to be compared with the racing clouds of a stormy sky or the hurrying waves of a tempestuous sea. An epic struggle began for Metchnikoff which was to last for twenty-five years, until the moment when the phagocyte theory, his child now grown up, emerged victoriously. To each attack, to each objection, he answered by fresh experiments, fresh observations annihilating objections; his theory was assuming a wider and wider scope, becoming more solid, more convincing.... But only his intimates knew how much the struggle cost him in vital force, what sleepless nights, due to continuous cerebral tension and to the effort to conceive some new and irrefragable experiment, what alternations of hope and depression.... In an ardent, stormy life such as this, each year counted for many.
As soon as he arrived at the Pasteur Institute he undertook active researches with the object of developing and defending the phagocyte theory.
By experiments on the _rouget_ of pigs he refuted the objections of Emmerich, who affirmed that, in that disease, the destruction of the microbes was not due to phagocytes. By experiments on the anthrax of pigeons he answered the attacks of Baumgarten and his pupils. To Behring, who affirmed that immunity was due to the bactericidal power of the serum, he replied by a series of experiments on the anthrax of rats.