considering the substantial depletion of the amounts of both sivler grains and radioactivity after the relatively short time of 5 hrs , we conclude that the greater portion of the thiamine passes quickly across the placenta to the fetus , where it is used in the metabolism of the fetal organs , and that only a small part of the thiamine is retained in the placenta for its own metabolism .
C0032043
placenta
C0242669
retained