1899] MICROSCOPICAL JOURNAL 363 



In order to decide these points and to complete the 

 work begun two years ago, those experiments were un- 

 dertaken. It was deemed advisable, first, to determine 

 accurately the effect of dry heat alone upon the organ- 

 isms selected, which was in reality a question of penetra- 

 tion, because the lowest temperature in any series, 80° 

 C, would kill diphtheria and typhoid in less than one hour; 

 second, to ascertain the germicidal effect of formaldehyd 

 in large quantity at ordinary temperature, 25°-30° C; 

 and third, to decide upon the most efficient combination 

 of heat and formaldehyd. All experiments were carefully 

 controlled by 1 to 3 tubes for each germ. 



In 26 experiments of cultures buried in hair pillows, or 

 in feather pillows, inside lightly rolled blankets, in cot- 

 ton mattresses, between mattresses or free in a chamber, 

 with temperature of chamber at 80° C ; time, one hour ; 

 and vacuum, none, or 15 inches; there were both moist 

 and dried cultures. As was to be expected, typhoid and 

 diphtheria were killed under most conditions, but the de- 

 gree of heat was not sufficient to destroy the more resist- 

 ant anthrax spores. The feather pillow, the tightly roll- 

 ed blanket, and the cotton mattress were not always 

 penetrated. In the third series, the killing of the an- 

 thrax in several instances can only be accounted for on 

 the theory that formaldehyd reached it from some source. 



The effect of formaldehyd in considerable quantity at 

 room temperature, about 30° C. was not to penetrate the 

 ten thicknesses of cheese cloth, the only protection around 

 the cultures free in the chamber, in sufficient quantity to 

 kill anthrax, and it also failed to reach the typhoid and 

 diphtheria, save under the first condition. Repetition of 

 this set of experiments with identical results prove that 

 when the exposure is limited to one hour, formaldehyd, 

 even in large percentage, at room temperature is practi- 

 cally inert as a disinfectant. The disinfection of bulky 

 articles, such as mattresses and pillows, could not be ac- 



