Pasteur had glimpses of another world beyond the phenomena of fermentation--the world of virus ferments. Two centuries earlier, an English physicist, Robert Boyle, had said that he who could probe to the bottom the nature of ferments and fermentation would probably be more capable than any one of explaining certain morbid phenomena. These words often recurred to the mind of Pasteur, who had, concerning the problem of contagious diseases, those sudden flashes of light wherein genius is revealed. But, ever insisting on experimental proofs, he constrained his exalted imagination so as to follow calmly and patiently the road of experimental method. He could not bear the slightest error, or even hasty interpretation, in the praises addressed to him. One day, during the period of the most ardent polemics, in the midst of the struggle on spontaneous generation, a medical man named Déclat, who declared that Pasteur’s experiments were “the glory of our century and the salvation of future generations,” gave a lecture on “The Infinitesimally Small and their Rôle in the World.” “After the lecture,” relates Dr. Déclat himself, “M. Pasteur, whom I only knew by name, came to me, and, after the usual compliments, condemned the inductions I had drawn from his experiments. ‘The arguments,’ he said, ‘by which you support my theories, are most ingenious, but not founded on demonstrated facts; analogy is no proof.’” Pasteur used to speak very modestly of his work. He said, in a speech to some Arbois students, that it was “through assiduous work, with no special gift but that of perseverance joined to an attraction towards all that is great and good,” that he had met with success in his researches. He did not add that an ardent kindness of heart was ever urging him forward. After the services rendered within the last ten years to vinegar makers, silkworm cultivators, vine growers, and brewers, he now wished to tackle what he had had in his mind since 1861--the study of contagious diseases. Thus, with the consistent logic of his mind, showing him as it did the possibility of realizing in the future Robert Boyle’s prophecy, he associated the secret power of his feelings; not to give those feelings their share would be to leave one side of his nature entirely in the shade. He had himself revealed this great factor in his character when he had said, “It would indeed be a grand thing to give the heart its share in the progress of science.” He was ever giving it a greater share in his work.