II. APLASIA OF MARROW AND FATAL INTOXICATION IN DOGS PRODUCED BY ROENTGEN RADIATION OF ALL BONES

Constant findings were obtained in the acute reaction to the specified amount of heavily filtered radiation over the bony skeleton. 1. There develops without warning a short and fatal intoxication on the 8th or 9th day after the exposure to the radiation. 2. A profound leucopenia appears after 5 to 6 days and is maintained in the peripheral blood (200 white blood cells or less per c. mm.) for the 2 to 3 days before death. 3. The platelets suddenly disappear from the blood smears the day before death. This has some bearing on the life cycle of the platelet. 4. All of the organs and body structures present extensive and generalized capillary hemorrhage of recent origin. 5. The substance of the spleen and lymph nodes is greatly reduced and the germinal centers are visible only as remnants. 6. The red cell hematocrit reading drops from about 50 per cent or normal to approximately 40 per cent. 7. The bone marrow is depleted of all its cells except the connective tissue and fat cells, blood vessel endothelium, phagocytes filled with brown granules, and occasional normoblasts.