The influence of _light_, which has no effect upon venom preserved in a dry state, is, on the contrary, very marked upon venom in solution. Solutions of venom that are destined for physiological experiments should therefore not be employed without controls, if they be several days old. Apart from the fact that, if care be not taken to render them aseptic, they very soon become contaminated with the germs of all kinds of microbes, it is found that they gradually lose a large part of their activity, especially when they remain in contact with the air. By filtering them through a Chamberland candle and keeping them in the dark, in a refrigerator, in perfectly closed phials, they may be kept unimpaired for several months. The addition of _glycerine_ in equal parts to a concentrated solution of venom is also an excellent means of preservation. * * * * * Phisalix has shown that the emanations from _radium_ attenuate and then destroy the virulence of Cobra- and also of Viper-venom. “Dry Viper-venom, dissolved in _aqua chloroformi_ in the proportion of 1 in 1,000, is put up in four tubes, three of which are irradiated, the first for six hours, the second for twenty hours, and the third for thirty-six hours. Three guinea-pigs, of equal weight, are inoculated with equal quantities of the irradiated venom; a control receives the non-irradiated venom. The latter dies in ten hours; the animal inoculated from the first tube dies in twelve hours; the one inoculated from the second tube in twenty hours, and the third proves resistant without any symptom of poisoning. A second inoculation produces a transitory lowering of the animal’s temperature by half a degree. At the end of four days it dies after inoculation with a lethal dose.” The nature of the solvent exerts a great influence upon the action of the emanations from radium: if the same experiment be performed with venom dissolved in a 50 per cent. mixture of glycerine and water, the attenuation is merely relative after six hours. * * * * * Auguste Lumière and Joseph Nicolas, of Lyons, conceived the idea of studying the effect upon venom of the prolonged action of the intense _cold_ produced by the evaporation of liquid air.[13] The Cobra-venom employed by these investigators was in solution at a strength of 1 in 1,000. It was submitted to the action of liquid air, partly for twenty-four hours and partly for nine days at -191° C. Its toxicity was in no way diminished. * * * * *