Translated from the French by Mrs. R.L. Devonshire, here we have the fascinating biography of Louis Pasteur 1822-1895, French microbiologist, chemist, and founder of modern microbiology. We learn of his investigation into the ways of excluding the airborne microorganisms which were responsible for fermentation in milk, beer, and other liquids using heat, today known as pasteurisation, and of his development of vaccines for anthrax, rabies, and chicken cholera.