SOME important results have recently been obained by Heider, who has been experimenting with disinfectants at higher temperatures and testing the effect produced upon their bactericidal properties. The author's first contributions in this direction were published in 1891. In Heider's original communication, “Ueber die Wirksamkeit von Desinfektionsmitteln bei höherer Temperatur” (Central-blatt für Backteriologie, vol. ix. 1891, p. 221), temperatures of 55° and 75° C. were employed, and the spores of anthrax were selected for investigation. Although these spores, it was ascertained, survived an immersion during 36 days in a 5 per cent, solution of carbolic acid kept at the ordinary temperature of the room, they were destroyed in from one to two hours in a similar solution at 55°C. Weaker solutions of this acid (1 percent, and 3 per cent.), even when maintained at the higher temperature for seven and eight hours, produced no effect upon the anthrax spores. On the temperature being raised to 75° C, however, (three minutes' exposure to a 5 per cent, solution of carbolic acid, fifteen minutes to a 3 per cent, solution, from two to two and a half hours to a 1 per cent, solution sufficed to annihilate these spores. Other materials were also investigated at these high temperatures, and equally satisfactory results obtained. Heider has brought together all his researches on this interesting subject in an elaborate memoir, “Ueber die Wirksamkeit der Desinfectionsmittel bei erhöhter Temperatur,“ which has been published in the Archiv. für Hygiene, vol. xv. p. 341. It is pointed out how great an effect upon the powers of resistance possessed by micro organisms may be exercised by the nature of their surroundings, and that it may be taken that they are, as a rule, more refractory in their normal environment than when purposely introduced into various materials. This has been shown by Yersin, in respect to the tubercle bacillus, which succumbs more readily to certain temperatures when exposed in artificial cultures than in sputum. Heider also found that particular culture media had a remarkable effect in this respect upon bacteria, that, for example, those grown in sugar broth (3 per cent, cane sugar) proved far more capable of resisting exposure to a high temperature than those introduced into ordinary broth. In conclusion, it having been distinctly proved that the bactericidal action of the majority of disinfecting materials is markedly increased when they are employed at a higher temperature, the author recommends that in all those cases where the destruction of spores is required, instead of applying these materials in cold solutions, they should be employed hot, or even boiling. The advantages derived by so doing are not alone the greater security obtained and saving of time, but economy in the cost of material, inasmuch as effectual sterilisation may be accomplished by the use of less concentrated solutions.