On the presence of erythropoietins in the plasma from sheep foetuses during the latter half of gestation.

Summary. In order to demonstrate the presence of erythropoietins in foetal plasma, the following experiments were performed. 1  Controls. Plasma from pregnant ewes and adult, non-pregnant sheep was injected intraperitoneally into 6 rabbits, immunized against sheep plasma. The adult plasma caused a slight eythro-cytosis and reticulocytosis on the 1st day after injection, which was on the 2nd day replaced by erythropenia, with a normal percentage of reticulocytes. 2  Plasma from 5 sheep foetuses aged from 71 to 121 days was injected into 8 immunized rabbits. An erythrocytosis was observed on the 2 first days after injection, and a remarkable increase in the percentage of reticulocytes took place. The red cell values were decreased below the initial level on the 4th and 5th day, though never as low as in the control group on corresponding days. The reticulocytosis lasted for 4 days. The increase in the red cells and reticulocytes compared to that in the control group was found statistically significant. It is concluded, that the fontal plasma near term is more active in promoting erythrocytosis than adult plasma. The active substance contained in the plasnia probably has a role in stimulating the foetuses' bone marrow.