Stilbestrol as a factor modifying the toxicity of Ekatin for the Pharaoh quail (Coturnix coturnix Pharaoh). I. Young birds.

1. The noted fall of the erythrocyte count, haemoglobin and haematocrit levels after stilbestrol indicate that this hormone disturbs erythropoiesis, probably by depressing the maturation of erythroid cells in the bone marrow. 2. The reaction of the erythrocyte system of birds intoxicated with Ekatin indicates that this pesticide has a haemolytic influence on the morphotic elements of the blood. 3. Estrogenisation enhances the action of Ekatin on the erythrocyte system by as it seems increasing the susceptibility of the red blood cells to the haemolytic action of this pesticide. 4. The high heterophilic leucocytosis in birds receiving stilbestrol is evidence that this hormone causes by an increased release of corticoids, hyperplasia of the granulopoietic tissue in the bone marrow and depresses the marrow barrier for heterophils. 5. Changes in the leucocyte system of quails intoxicated with Ekatin indicate a stressogenic action of this poison. 6. The reaction of the latter system to Ekatin administered after estrogenisation seems to be an indication that stilbestrol reduces the susceptibility of the quails to the stressogenic action of the pesticide.