When Pasteur was an infant of two years his parents removed to the town of Arbois, and here he spent his youth and received his early education. After a period of indifference to study, during which he employed his time chiefly in fishing and sketching, he settled down to work, and, thereafter, showed boundless energy and enthusiasm. Pasteur, whom we are to consider as a biologist, won his first scientific recognition at the age of twenty-five, in chemistry and molecular physics. He showed that crystals of certain tartrates, identical in chemical composition, acted differently upon polarized light transmitted through them. He concluded that the differences in optical properties depended upon a different arrangement of the molecules; and these studies opened the fascinating field of molecular physics and physical chemistry. Pasteur might have remained in this field of investigation, but his destiny was different. As Tyndall remarked, "In the investigation of microscopic organisms--the 'infinitely little,' as Pasteur loved to call them--and their doings in this, our world, Pasteur found his true vocation. In this broad field it has been his good fortune to alight upon a crowd of connected problems of the highest public and scientific interest, ripe for solution, and requiring for their successful treatment the precise culture and capacities which he has brought to bear upon them." In 1857 Pasteur went to Paris as director of scientific studies in the École Normale, having previously been a professor in Strasburg and in Lille. From this time on his energies became more and more absorbed in problems of a biological nature. It was a momentous year (1857) in the annals of bacteriology when Pasteur brought convincing proof that fermentation (then considered chemical in its nature) was due to the growth of organic life. Again in 1860 he demonstrated that both lactic (the souring of milk) and alcoholic fermentation are due to the growth of microscopic organisms, and by these researches he developed the province of biology that has expanded into the science of bacteriology.