play a part in the blood-clotting mechanism, but are still understood. TIonizing radiations to the entire body produce & other effects a reduction in the number of blood platelets f some instances, actual total cessation of platelets. In thif con- The platelets can now be typed and grouped, much as red cells are before normal blood transfusions. There is no corte however, between the platelet groups discovered and the famiBi groups of red blood cells. Continued efforts may prove of signifi-~ a blood disease in which bleeding occurs under the skin and In adults suffering from this type of hemorrhagic disease, failure of repeated platelet transfusions may be due to inco of the donor's platelets with those of the patient. A simil Rh incompatability. Effects of Prenatal X-irradiation on Mice. changes at specific radiation susceptible times. irradiated at stages of development corresponding to ages of 1-1/2 days, 2-1/2 days, and so on to 13-1/2 days after concerpi At birth the skeleton of each embryo was studied in detail. found that each skeletal abnormality was, in general, induced ation during only a short period of prenatal development and has obtained with high incidence when radiation was applied in thht period. The “critical periods" for the characteristics studied fell between 6-1/2 and 13-1/2 days after conception, during which time irrpdiation produces very little mortality. The abnormalities produced by irradiation resemble, but do not exactly coincide to, some of the ab ormalities produced by previously identified mitant genes in the mogse. Civil Defense Dissemination of Weapons Test Information. A recent meeting Was held with members of AEC, the DepartMent of Defende, and the Federal Civil Defense Administration. The discussions covered the transmission to FCDA of classified weapons effects information cerfves from mn ited : é 4 i ° -f ait > OURO EE eS i * c ane