Bacteria and the aetiology of cancer of the large bowel.

Cancer of the large bowel shows marked variations in geographical distribution (Doll, 1967; Doll, Payne, and Waterhouse, 1966; Davis, Knowelden, and Wilson, 1965) and, with the exception of Japan, the disease is more prevalent in developed than in underdeveloped countries.The reason for this variation is not known but epidemiological evidence suggests that environmental factors may be involved.It is claimed that immigrants from areas with a low incidence of cancer of the large bowel tend to show the same high incidence of this cancer as the local population (Haenszel and Dawson, 1965; Buell and Dunn, 1965).Changes in dietary habit may be especially important (Wynder and Shigematsu, 1967;