This section is from the "Impaired Health: Its Cause And Cure" (Volume 1) book, by John H. Tilden. Also available from Amazon: Impaired health its cause and cure: A repudiation of the conventional treatment of disease
The only two men who persistently practiced sterilizing their food and drink lived semi-invalid lives, and died at that time in life when mind should be at the acme of value. I have reference to Professors Pasteur and Metchnikoff. There may have been others--perhaps Koch--but I do not now recall them. These two men were the fathers of bacteriology.
We :have seen that digestive secretions--enzymes--unorganized ferments--are necessary to dissolve food and prepare it for absorption, and that bacteria--organized ferments--are necessary to dissolve food and prepare it for expulsion from the body. Bacteria are necessary to dissolve food taken in excess of what can be liquefied and utilized by enzymic digestion. Organized ferments--germs--belong to the health department of our bodies; they keep the sewers, gutters, and alleys clean. If they ever become a menace, it is when they become too officious and try to dictate, as the health departments of our cities sometimes do. Their failure, however, is often due to an oversupply of work.
The bacteria cause acetic and alcoholic fermentation of the carbohydrate (starchy) foods; and the same bacteria cause a putrefactive decay in the nitrogenous or proteid (animal) foods, with the development of toxin and the giving-off of offensive gases which are toxic.