play a part in the blood-clotting mechaisn, but are still not woll understood. fonising radiations to the antire body produce son; other affects a reduction in tho number cf blood platelets cron, in Soma instances, actual total cescation of olatelots. In this con nection, it is interestin: that animals have been nretacted cron lothal effecto through trancfusion of platelets from tho blecu, Zhe olateiots can new bo typed and jreupsed, much as rad bloo.l eolls are before normal bloc. transfusions. There is no corrolation, however, botueon the platelot sroups Jiscoverad and tho faniiiar groupe of red blico: cells. Contimed offorts may prove of simift- cant value in combattine such saladies ao thrombocytopenic unvpura, a blood disanse in vhiich bleccding cceurs undor the clcin ani internally. in adults osufforing frum Nits type of honmorrhacic disease, the cradual failure of repeated platalet transfusions aay be .me to incomatibility of the Jonor'n plataicts with these of the patfemt. i similar coniition alse oceure in newborn Lables and this may be due to nlatelet incompatibility betaween acther and newborn chilc, in a way oainilar to wh incocpatability. uffects of Prenatal i~irradiation on ice. In studios of rociat n of maxmis ana other organisms, it is necessary to observe changes induced in one or more variable organs or organ oystems. In research in progress at Jak Hidse National Jaboratory, the vertebral column and thorax have been used as indicators of radiation damage to the developing mouse. The particular question being investigated is whother radiations cause general damare te the anbryo at amy exposure time or whether radiations cause specific chances st specific radiation susceptible times. Mice embryos were irradiated at stages of development corresponding to ages of 1/2 Jay, 1-1/2 days, 21/2 days, and so on to 13-1/2 days after conception, At birth the skeleton of each anbryo was studied in detail. It was Zound that cach skeletal abnormality was, in general, induced by radiation coring only a short period of prenatal Jevelopmant and was obtainod with high incidence when radiation was applied in that portod. The "eritical pericde” for the characteriotics studied fell between Gel/2 and 13<1/2 Jaye after conception, during which tine irradiation produces very little mortality. The abnommalities produced by irradiation resemble, but Jo not exactly coincida to, some of the ebnormalities preduced by previcusly identified mitant. genes in the mouse. Civil Defense on \ recent of Defense, and the Federal chvil Sefonse Administration, The discussions covered the transmission to PCLA of classified weapons affects information derived fron DO ARCHIVES