1. Evans' blue and suspended charcoal inoculated into the amniotic sac of 11- and 13-day-old embryos rapidly appears in the gastro-intestinal tract. None is detected in the respiratory tract.

  2. Suspended radioactive chromic phosphate inoculated into the amniotic sac of 10- to 13-day-old embryos also rapidly appears in the gastro-intestinal tract, but in 13-day-old embryos a small amount reaches the lungs.

  3. Soluble P32 in the form of Na2HPO4 introduced into the amniotic sac becomes dispersed in the allantoic fluid, the blood, and the body of the embryo. After 72 hours little, if any, remains in the amniotic fluid.

  4. When soluble P32 is inoculated into the allantoic sac of 10- to 13-day-old embryos, it tends to remain in this position. Relatively small amounts appear in the blood and the body of the embryo and none or only a trace is found in the amniotic fluid.

  5. Soluble P32 inoculated into the yolk sac soon appears in the blood and the body of the embryo and to a lesser degree in the allantoic fluid. None is found in the amniotic fluid.

  6. Soluble P32 injected intravenously is found in highest concentration in the blood and in the body of the embryo, but a considerable amount enters the allantoic fluid. None or only a trace appears in the amniotic fluid.

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