189I.] NEW-YORK MICROSCOPICAL SOCIETY. 89 



rilizition, resulting in the present method of preserving foods. 

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

 expressed by a line, required years of labor to ascertain, and 

 really follows the improvement in the microscope. In 1837 

 Cagniard-Latour described yeast as a collection of globules which 

 multiplied by budding. In 1838 Turpin described the yeast 

 plant in beer, and named it Torula c.erevisice. 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 gen- 

 eral principles of the germ theory of minute forms of life, in place 

 of the theory of spontaneous generation. The theory so com- 

 pleted, revolutionizing current ideas, met with vigorous opposi- 

 tion, but the microscopical demonstration 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 

 which interests they were undertaken. He saved the French 

 silk industry from threatened destruction by investigating the 

 parasitic diseases of the silkworm, and suggested a remedy. 

 His investigations led to the antiseptic treatment in surgical 

 operations which is now considered indispensable. His extensive 



