Latent period in the induction of reticuloendothelial blockade

Double intravenous injections of colloidal carbon in the mouse, with variation of the time between doses and with blood disappearance curves taken after the second dose, revealed a delay of over 3 hours in onset of reticuloendothelial blockade due to the first carbon dose. This was so despite the virtual disappearance of the latter from the blood within two hours. The degree, duration and approximate time of onset of blockade did not change when the blocking dose was varied twofold. Carbon phagocytic rates returned to normal between 3 and 6 days after the first dose, without indicating any secondary period of phagocytic stimulation. Evidence is presented that carbon phagocytosis in the mouse is a complicated reaction sequence whose over-all rate is neither independent of particle concentration nor directly proportional to it.