-~ 15 the cell is affected is lacking but it is known that the primary site of the biological effects of radiation is in the cell. The irradiation of single cells has resulted in a large variety of effects and has led to two concepts about the basic mechanism of radiation damage; one, that radia- tion strikinga sensitive area of the cell has produced ionpairs which react with neighboring molecules to form new substances that disturb the normal function of the cell; the other, that the ionizing event occurred in the water of the cell and produced highly oxidizing radicals and molecules, which in turn disturb the biochemistry of the cell. The Report of the United Nations Committee on the Effects of Atomic Radiation (1958) also points out the lack of knowledge about the mechanism of radiation damage in the following statement. The effects of ionizing radiations on living matter are extremely complicated, are still largely unknown. and their exact mechanisms The initial disturbance is associated with ionization (and excitation) of molecules which lead to alterations in their properties. Many functions of the cell are thus affected