While clinical and experimental efforts toward achieving effective control of cancer, through improved diagnostic and therapeutic methods, have had a measured amount of success, the condition is not yet conquered as smallpox and typhoid have been controlled.
The far reaching control of the infectious diseases attained during the past seventy-five years depended on the successful identification of the causative microorganisms and on extensive and laborious epidemiologic studies. As long as the specific causative agents responsible for over 99 per cent of human cancer remain unknown, rapid progress cannot be made.
Although many important and, apparently, fundamental differences exist between infectious diseases and cancer, their similarities also are numerous. Observations as to the number and types of extrinsic carcinogenic factors suggest that exogenous and endogenous carcinogens may include agents differing as widely as those concerned with infectious diseases. The recently discovered species specificity of carcinogenic agents is analogous to the species-specific