The Effects of Roentgen Radiation on the Thymonu- cleic Acid Content of Transplantable Mammary Carcinomas*

Roentgen radiation has the ability to produce histologic changes in tissues and the death of cells. Many kinds of tumor cells are more sensitive to its lethal effects than the corresponding normal cell types from which they arise, but the intracellular mechanism by which the rays cause the death of normal and neoplastic cells is not definitely known. It has been suggested by Henshaw (9) that they alter the molecular structure of vital nuclear material, perhaps of the proteins of the chromosomes, in a manner that is incompatible with the further life of the cell. Because of the importance of nucleoproteins in the vital function of normal and neoplastic cells it is desirable to understand how they are altered by roentgen energy. To determine the effects of roentgen rays on the thymonucleic acid content of transplantable mammary carcinomas in rats and in mice, two series of experiments were undertaken.