Abstract
1. The results of previous workers on the action of plasmoquine on avian malaria, Plasmodium relictum (Grassi and Feletti, 1891), have been confirmed and extended. Sterilisation was obtained in a large proportion of birds (16 out of 33) treated during the normal incubation period.2. Thirteen new synthetic quinoline compounds were found to have antimalarial action.3. Two of these compounds, R 25 = 8-γ-aminopropylamino-6-ethoxy-quinoline and R 36 = 8-γ-anunopropylamino-6-methoxyquinoline, have therapeutic indices of 1: 16, are nearly equal to plasmoquine in potency and resemble it in action.4. A third compound, R 44 = 8-γ-aminopropylamino-6-n-butoxyquino-line, has a therapeutic index of only 1 : 8, but its sterilising action is equal to or greater than plasmoquine, R 25 and R 36.5. The remaining compounds have therapeutic indices of 1 : 8 or 1 : 4 and vary in their sterilising action.6. Experiments are described which show the formation of methaemo-globin in vitro through the action of plasmoquine, R 25 and R 36. In this respect the order of activity of the compounds is R 36, R 25, plasmoquine.