1 . - Per Cent of Blast Cells and Labeled Cells in Cultures of Human Fetal Circulating and Thymic Lymphocytes Stimulated

A study was made of PHA-stimulated formation is age-related. Until the 18th thymic lymphocyte transformation in 10 week of gestation, the per cent of transhuman fetuses ranging from 12 to 22 formed thymic lymphocytes is comparaweeks of gestation. The results were ble to that of blood lymphocytes. After compared with those obtained using cirthe 18th week of gestation, the per cent culating blood lymphocytes of the corof transformed thymic lymphocytes diresponding fetuses in seven cases. The minishes to the level of adult thymic degree of transformation of blood lymlymphocytes. The significance of these phocytes is independent of fetal age. On findings is discussed. the other hand, thymic lymphocyte trans-