新GRE写作名人素材库：巴斯德

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　　Chemist and biologist, famous for his germ theory and for the development of vaccines. Born December 27, 1822 in the small town of Dole, the son of a tanner. He studied in the college of Arbois and at Besancon, where he graduated in arts in 1840. As a student preparing for the prestigious Ecole Normale Superieure of Paris, he did not doubt his ability. When he gained admittance by passing fourteenth on the list, he refused entry; taking the examination again, he won third place and accepted. For his doctorate his attention was directed to the then obscure science of crystallography. This was to have a decisive influence on his career.

　　Under special dispensation from the minister of education, Pasteur received a leave of absence from his duties as professor of physics at the lyc of Tournon to pursue research on the optical properties of crystals of the salts of tartrates and paratartrates, which had the capacity to rotate the plane of polarized light. He prepared 19 different salts, examined these under a microscope, and determined that they possessed hemihedral facets. However, the crystal faces were oriented differently; they were left-handed or right-handed, thus having the asymmetrical relationship of mirror images. Furthermore, each geometric crystal variety rotated the light in accordance with its structure, while equal mixtures of the left- and right-handed crystals had no optical activity inasmuch as the physical effects canceled each other. Thus he demonstrated the phenomenon of optical isomers.

　　Pasteur was elated. He repeated his experiment under the exacting eyes of Jacques Biot, the French Academy s authority on polarized light who had brought Eilhardt Mitscherlich s work to Pasteur s attention. The confirmation was complete to the last exacting detail, and Pasteur, then 26, became famous. The French government made him a member of the Legion of Honor, and Britain s Royal Society presented him with the Copley Medal.

　　In 1852 Pasteur accepted the chair of chemistry at the University of Strasbourg. Here he found an opportunity to pursue another dimension of crystallography. It had long been known that molds grew readily in solutions of calcium paratartrate. It occurred to him to inquire whether organisms would show a preference for one isomer or another. He soon discovered that his microorganism could completely remove only one of the crystal forms from the solution, the levorotary, or left-handed, molecule.

　　In 1854, though only 31 years old, Pasteur became professor of chemistry and dean of sciences at the new University of Lille. The course of his activities is displayed in the publications which he gave to the world in the next decades: Studies on Wine , Studies on Vinegar , Studies on the Diseases of Silkworms , and Studies on Beer .

　　Soon after his arrival at Lille, Pasteur was asked to devote some time to the problems of the local industries. A producer of vinegar from beet juice requested Pasteur s help in determining why the product sometimes spoiled. Pasteur collected samples of the fermenting juices and examined them microscopically. He noticed that the juices contained yeast. He also noted that the contaminant, amyl alcohol, was an optically active compound, and hence to Pasteur evidence that it was produced by a living organism .

　　Pasteur was quick to generalize his findings and thus to advance a biological interpretation of the processes of fermentation. In a series of dramatic but exquisitely planned experiments, he demonstrated that physical screening or thermal methods destroyed all microorganisms and that when no contamination by living contagion took place, the processes of fermentation or putrefaction did not take place either. Pasteurization was thus a technique that could not only preserve wine, beer, and milk but could also prevent or drastically reduce infection in the surgeon s operating room. Another by-product of Pasteur s work on fermentation was his elucidation of the fact that certain families of microbes require oxygen whereas others do not. This insight divided the scientific community, and it was only in 1897, two years after his death, that the dispute was resolved.