A presentation of Pasteur which is briefly biographical and a placement of the man in his century, and which is extensively a study of his scientific works through a long lifetime of experimentation. As such, it predicates a scientific interest and background beyond the general reader, and a heavy prose destroys the often dramatic incidents of a crusading career. Here is Pasteur, both academician and alchemist, as many years of practical laboratory experimentation were sustained by a visionary dream; the working methods, and the tireless intensity with which he worked. Du Bos, a microbiologist and Rockefeller Foundation scientist of considerable standing, is well qualified to present the evolution of Pasteur's investigations, the shifting point of view from the physicochemical to the biological. The ten years in the field of crystallography; the study of fermentation reactions and processes; the controversial problem of spontaneous generation; the concept of the biochemical unity of life; and lastly the pathogenesis of disease, its contagion and immunology, and the revolutionary germ theory- these are analyzed here intensively. A serious rather than popular contribution.