INTRODUCTION THE name of one of your illustrious countrymen, Louis Pasteur, will for ever be remembered as the founder of the science of bacteriology. It was he who first isolated & identified a specific germ and related it to a definite clinical entity (disease). Following upon his discoveries, medical science concentrated on the laboratory technique for the isolation and identification of a specific germ for each known disease, and (he Koch postulates were accepted as the standard for declaring any germ capable of pathogenesis – of having power to cause disease. The motto of the medical profession is still Tolle Causam, find the cause, and to-day there are many who consider that germs are the only cause •of disease and are working to discover the specific germ of virus for well known clinical entities. It must now be accepted as scientific fact that specific germs, in many cases of disease, can be isolated and identified, but is it a true conclusion that the specific germ is always the cause of the disease ? The subjects is too great to be dealt with in all its aspects in this short session, but a little time must be given to considering the general question, namely the role of the Bacterium in Nature because one’s opinion on this must determine the value one places on the use of bacterial products” vaccine or nosodes in the treatment of disease. As the subject of this paper deals with the intestinal flora, I propose to limit my remarks to consideration of the role played by the B. Coli and coliform organisms found in the intestinal tract. The role of the intestinal bacteria. B.Coli can be isolated from the intestine of all warm blooded animals and have been found on grasses outside the body, where there seemed to be no possibility of faecal contamination Most workers consider the B. Coli to be a harmless saprophyte and to be non-pathogenic in the healthy bowel. Its function is to break up into the more simple substances the complex molecules of the organic combinations which form the bodies of plants and animals, or of the complex substances which result from the digestive processes in the intestinal canal and are excreted. It is important to note this function in the further study of the intestinal flora and its relationship to disease. In nature, where there is balance, there is no dis-ease and the germ, in this case the B. Co!! in the intestinal tract, perform a useful function. Where the intestinal mucosa is healthy the B Coif is non-pathogenic. Any change in the host which affects the intestinal mucosa will upset the balance and will be followed by a change in the habit and the bio-chemistry of the B. Coli, which may then be said to become pathogenic, but it should be noted that the primary change, the J/j-ease originated in the host, which compelled the bacilus to modify its habit in order to survive. I would ask you to keep this sequence of events in mind as a great deal of what I have to say about the intestinal nosodes is based upon this conception which I have confirmed by clinical and laboratory observations over the last twenty years.