In regard to the aetiology of infectious diseases we must abandon the notions conceived in time of Koch, Ehrlich and Pasteur on the 'pathogenic' nature of the microorganisms of external and internal media. In the full sense of the word it is not the bacteria themselves that are pathogenic, but those physiological correlations which exist in the given organism at a particular moment and which are organically connected with the disturbances in its regulative systems and nervous mechanisms. There are no special 'pathogenic' microbes in nature; there are, however, no end of factors that promote susceptibility in a normally resistant subject, and vice versa.
