The rationale of practice must be based on the avoidance of adverse effects on the host attributable either directly or indirectly to polypoid lesions. The known adverse effects are summarized. The gross, morphological. and dynamic taxonomies of polypoid lesions are grouped to assist in predicting adverse effects known to occur within the human life span. Based on data from the vital statistics, autopsy studies, and clinical management reviews, a rationale of practice has been developed that is intended to keep adverse effects of polypoid lesions to a minimum with the avoidance of unnecessary cost, nonbeneficial clinical effort, and morbidity. The greatest potential lies in avoidance of polypoid lesions altogether. Consequently, etiology is also discussed in the search for knowledge that can be exploited to avoid the development of polypoid lesions.
RATIONALE IS "AN EXPLANATION OF CON-
A trolling principles of opinion, belief, practice or phenomenon."s6 T h e controlling opinion or belief is that medical knowledge anti technology should be used in a systematic wav that will minimize the morbidity and mortality attributable either directly or indirectly to polypoid lesions of the colon at a cost in time and money tolerable to the individual patient and the public. By definition, polypoid lesion is any "projecting mass of swollen and hypertrophied or tumorous mem-Iirane."
Knowledge of etiology is also discussed in search for information that could be used to avoid polypoid lesions. I n the absence of a well-tested technique for prevention, a control system must be designed. Knowledge of the natural history of polypoid lesions can be used to plan a systematic use of the available technology to alter the natural history to a less adverse pattern without substituting morbidity f'rorn the technology itself. T h e resulting system of therapeutics becomes the rationale of Prrsented at the National Conference on Cancer of the Colon and Rcctum,