The Soil as a Source of Microorganisms Antagonistic to Disease-Producing Bacteria.

Bacteria pathogenic for man and animals find their way to the soil, either in the excreta of the hosts or in their remains. If one considers the period for which animals and plants have existed on this planet and the great numbers of disease-producing microbes that must have thus gained entrance into the soil, one can only wonder that the soil harbors so few bacteria capable of causing infectious diseases in man and in animals. One hardly thinks of the soil as a source of epidemics. What has become of all the bacteria causing typhoid, dysentery, cholera, diphtheria, pneumonia, bubonic plague, tuberculosis, leprosy, and numerous others? This question was first raised by medical bacteriologists in the eighties of the last century. The soil was searched for bacterial agents of infectious diseases, until the conclusion was reached that these do not survive long in the soil. It was suggested that the cause of the disappearance of these diseaseproducing organisms in the soil is to be looked for among the soil-inhabiting microbes, antagonistic to the pathogens and bringing about their rapid destruction in the soil. Pasteur (Pasteur and Joubert, 1877) deserves the credit for having first shown, in 1877, that the production of anthrax in susceptible animals can be repressed by the presence of other microorganisms (". . . on peut introduire A profusion dans un animal la bactdridie charbonneuse sans que celui-ci contract le