Insensitivity of Paramecium to Cyanide

Some recent work, no tab ly tha t of Dixon and Elliott , 1 has indicated tha t not all cells and tissues are complete ly cyanide-sensit ive in the sense tha t they reduce their ra te of respiration in the presence of cyanides. Alien ~ has pointed out tha t not all the resp i ra tory exchange in Planaria m a y be inhibited b y cyanides. This has indicated tha t there m a y be other oxidation sys tems in the cells besides those affected by cyanides. Lund ~ found some years ago tha t K C N had litt le or no effect on oxygen consumption b y Paramecium. We proposed to reinvest igate this question and to determine if iron is present in the p ro top lasm of Paramecium, acting as the respirat ion ca ta lys t according to the theory of Warburg , and to note if addit ion of iron would cause an increase in the ra te of respiration in the Paramecium.