148 THE AMERICAN MONTHLY. [July, 



How early minute forms of life were suspected of causing bodily 

 ailments or decomposition in fluids is uncertain. The Egyptians 3,500 

 years ago knew how to practically prevent decomposition in bodies 

 and wooden utensils, so that they have been preserved to the present 

 time. More recently, Robert Boyle, 200 years ago, expressed the opin- 

 ion that ferments had something to do with fevers. Leuwenhoek, 1633 

 to 1723, made small lenses, and described the ferment of yeast as ovoid 

 or spherical bodies, and discovered bacteria in the mouth and in fluids 

 undergoing decomposition. The power and use of the early simple 

 microscopes were too limited to definitely establish the functions of the 

 minute forms or their relations to the higher orders. The belief, how- 

 ever, was becoming more and more general that the minute forms had 

 something to do with bodily ailments and fermentations, but without 

 microscopical aid it could not be clearly demonstrated. As must be 

 expected, some extravagant views were adopted, while others were 

 close approximations to the truth. Boerhaave, in 1693, distinguished 

 three kinds of fermentations, viz., alcoholic, acetous, and putrefactive. 

 Linnaius stated that a certain number of diseases resulted from ani- 

 mated invisible particles dispersed through the air. Spallazani, in 

 1769, started his series of experiments upon spontaneous generation 

 and sterilization, resulting in the present method of preserving foods. 

 Opinions were very conflicting, and the truth which may now be ex- 

 pressed in a line required years of labor to ascertain, and really follows 

 the improvement in the mici'oscope. In 1837 Cagniard-Latour de- 

 scribed yeast as a collection of globules which multiplied by budding. 

 In 1838 Turpin described the yeast plant in beer and named it Toriila 

 cerevisicc. Many chemists were unwilling to admit the important 

 part played by yeast in fermentations, and ascribed it to " catalysis," 

 or action by presence. In 1843 the celebrated French chemist, Dumas, 

 from microscopical and chemical examinations, clearly explained the 

 physiological function of the living ferment yeast. The truth was now 

 proven, but it made little progress until Louis Pasteur, some ten years 

 later, took up the work of studying under the microscope the ferments 

 of yeast, vinegar, and wine, demonstrating conclusively that a germ 

 must be present to start fermentation or decomposition in fluids, that 

 the definite knowledge he learned of the functions of the minute forms 

 of life attracted attention. 



Pasteur, by his systematic work with his microscope, tracing the life- 

 history of many ferments from the spore, ascertained the laws of growth, 

 so he could induce fermentation or check it as desired. The ability to 

 keep liquids for years when freed from germs, which under ordinary 

 circumstances would ferment or decompose in a few hours, enabled 

 Pasteur to confirm and clearly set forth the general principles of the 

 germ theory of minute forms of life in place of the theory of spontane- 

 ous generation. The theory so completed, revolutionizing current 

 ideas, met with vigorous opposition, but the microscopical demonstra- 

 tion was so complete it has proven invulnerable, and upon it has been 

 formed the important branch of science, bacteriology. We are too near 

 to estimate the value of the demonstration. It will require time to show 

 its full value, for its application is but really commenced. 



Pasteur's work has been pre-eminently practical, and the results of 

 his investigations at once applied to the French industries, in whic!i 



