An argument for a mathematics program that is more compatible with the nature of the learner is therefore an argument for a greater degree of involvement with manipulative materials and exploitation of appropriate mathematical applications.
The Germ theory of disease, developed in the 1860s and 1870s by Louis Pasteur, states that tiny living beings are the cause of infectious diseases. The theory was developed to explain puerperal fever, or Child bed fever.
Another significant discovery facilitated by the germ theory was the nature of contagious diseases. Pasteur's intuited that if germs were the cause of fermentation, they could just as well be the cause of contagious diseases. This proved to be true for many diseases such as potato blight, silkworm diseases, and anthrax.