ABSTRACT
To know the circumstances in which a given infectious disease prevails excessively is most helpful in its prevention. Hence, the great value of studies of disease in relation to inimical industrial and social circumstances, and of its more general epidemiology. Louis Pasteur's earlier investigations on crystallography were followed in 1856 by a study of the problems of fermentation. Pasteur intermitted his studies of alcoholic fermentation in order to ascertain whether yeast was or was not concerned in lactic fermentation. It was in this investigation that he first employed the process of "sowing" and repeatedly sowing a minute trace of the veil of yeast of this fermenting liquid into a new solution and thus setting up fresh fermentation, which made subsequent progress in bacteriology possible. The great step forward made by him was enunciated in the words: "fermentation is thus shown to be correlated to the life and formation of the globules, and not to their death or putrefaction".
