Anti-chorioallantoic membrane (CAM) serum was made fetal-specific by absorbing it in a mixture of egg white, fresh yolk and chicken serum, plus liver, lung, heart and spleen from a laying hen. 2. By immunoelectrophoresis, the CAM extract shows three soluble transitory proteins, an oncofetal protein (alpha-fetoprotein) and a soluble organ permanent protein from some of the organs used in the absorption. 3. By assaying crossed heterologous systems, alpha fetoprotein was found in the allantoic, amniotic and yolk fluids after 14 days of incubation; all three proteins were found in amniotic, but neither in allantoic nor in yolk fluid.
