either because the types of cells affected are long-living and may not reproduce themselves for a long period, or because shorter-lived cells keep reproducing their aberrant or unusual forms. Man normally has aberrant cells in his blood, which may have reached him through the genetic material given to him by his parents, or through the exposure to certain nonradioactive chemicals, or from other sources. Radiation has been found to cause aberrant forms since people irradiated have more aberrations than nonexposed. The effect or influence of these unusual cells has been and is being thoroughly studied, although just exactly what relation they may have to the development of cancer, including leukemia, has not been definitely proven. The UN report of 1964 stated that: "4, The mechanisms of carcinogenesis in general are not well understood. However, the evidence is that the neoplastic change occurs at the cellular level and is frequently associated with observable modifications in cell structure (particularly chro- mosomal constitution) and function.” (95, p. 181) Simply put, this means that how cancer develops (mechanisms) is not clear. Evidence shows that neoplastic change (the formation of new cells -- | in this case referring to those of cancer) begins at the cell as a result of changes produced in the cell, especially in the arrangements of chromosomes. In short, the scientists, like detectives, have a lot of "circun- stantial evidence" that radiation causes cancer. causes aberrations. They have found that it They have found that persons irradiated develop more cancer than those not irradiated. They do not know exactly how this happens. They can only strongly suspect that the "accused" radiation is really the "guilty party." WM soiorgy °