抄録
Chicks were given 0, 3, 9, and 27 ppm of pyrimethamine contained in a diet for12 consecutive weeks and examined both clinically and histopathologically. The healingprocess of the pyrimethamine-induced Iesion was also observed.l. Clinically, chicks exhibited remarkable hyperchromic anemia and retardedgrowth after 27 ppm administration. They showed slight anemia after 9 ppm adminis-tration, but scarcely any after 3 ppm.2. Pathologically, cl?icks showed remarkable reduction in ertyhropoiesis in bonemarrow, lymphocytic decrease in all the lymphatic tissues and swelling of reticulum cellsafter 27 ppm administration. They showed medium reduction in erythropoiesis after9 ppm, and only slight damage after 3 ppm.3. Peripheral red blood cell count and hemoglobin value were lowered after Tweeks administration of 27 ppm, but were restored approximately to the initial level inl week. Histologically, however, erythropoiesis in the bone marrow and the Iesion oflymphatic tissues were not sufficiently cured within this period of time.4. It has become clear from these results that pyrimethamine, which is usuallyemployed for the prevention of Leucocytozoon caulleryi infection in chickens, willscarcely produce any damage on chicks in a dose of 3 ppm or below, even if it is admin-istered continually over a long period.
