For years after Murchison announced, in 1858, that typhoid fever was produced by emanations from decaying organic material, sewer-gas was held responsible for many infectious diseases. The cause of the large mortality from "zymotic" disease in cities by many was traced largely to sewer-gas poison. While other causes were not wholly excluded, to bad plumbing was attributed the principal part in causing "pythogenic" pneumonia, peritonitis, inflammatory rheumatism, typhoid and malarial fevers, croup, diphtheria and many kindred diseases.
According to the germ theory of disease, sewer-air can cause infectious diseases directly only by the conveyance of germs, and the question whether it actually does convey germs has received much attention. Bacteriologic examinations of the air in sewers showed it to contain only a small number of bacteria, and these were common to street air rather than to sewage. These results, coupled with the absence of any reliable indications from the study