FERMENTS, FERMENTATIONS, AND LIFE. Peni, 
condition of mankind. We may now regard it as firmly 
established; but let us not forget that its establishment 
has cost two centuries of investigations and labors. Leeu- 
wenhoek, in the middle of the seventeeth century, was the 
first to reveal the microscopic world of the air, and to con- 
jecture its momentous functions. What severe toil, what 
struggles and tedious trials, since the observations of the 
Dutch micrographer to the time of the experimental 
studies of our contemporary and compatriot, Pasteur! 
