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Direct measurements of membrane fluidity by fluorescence anisotropy of protoplasts fromKloeckera apiculata andSaccharomyces cerevisiae, a low and a high ethanol tolerant strain respectively, are presented. The comparison of the behaviour of the two strains grown with or without ethanol enabled us to demonstrate the existing relationship between ethanol tolerance and membrane fluidity.

1. Intravenous injections of India ink into guinea pigs caused a decided drop in the complement titer which set in as early as 15 minutes after the injection, but did not reach its maximum for 3 hours. This drop was followed by a return to normal within the first 24 hours following the injection. 2. India ink mixed in vitro with guinea pig serum adsorbs the complement almost immediately to its full extent. 3. By means of reduction tests (methylene blue and nitroanthraquinone) it was shown that the respiration of the cells of the liver and spleen of guinea pigs was markedly impaired for the first 8 hours, following an intravenous injection of ink. Evidences of a return to normal functional vitality, however, became apparent by the end of the 1st day after the injection.

1. Guinea pigs injected intravenously with massive doses of India ink before active sensitization exhibited occasionally a more or less marked, decreased sensitiveness to the reinjection of the antigen. 2. The serum of rabbits which had received massive doses of India ink before the sensitizing injections, showed approximately the same titer of anaphylactic antibodies as that of sensitized normal control animals, as demonstrated by the degree of passive sensitization induced in guinea pigs. 3. The precipitin titer of sensitized rabbits blocked with massive doses of India ink was somewhat lower than that of sensitized normal controls. In one instance, the intravenous injection of smaller doses of India ink was followed by a higher precipitin titer. No uniform relation was found between the height of the precipitin titer and the anaphylactic power of the antiserums. 4. One blocking injection of India ink given to guinea pigs before passive sensitization did not interfere with the occurrence of anaphylactic shock nor alter its nature.