624 A MANUAL OF BACTERIOLOGY 



of the cyclone burner described by Forbush and Fernald 

 has been favourably reported on by Stiles. The apparatus 

 consists of a portable tank, from which paraffin gas oil 

 is driven by a pump through a hose (such as is used for the 

 delivery of oil) to which is attached a pole, consisting of 

 an iron pipe 12 ft. long, which is protected by a covering 

 of wood, and to the end of which is attached a cyclone 

 nozzle. The fine spray from the nozzle is ignited, and the 

 resulting fierce flame passed over the surfaces to be dis- 

 infected. The thorough wetting with water of all such 

 surfaces would practically abolish danger from fire, and 

 by proper adjustment of the power of the flame, and 

 experience on the part of the operator, the method is an 

 efficient one. 



Dry heat may also be used, and forms the basis of some 

 disinfectors (Ransome's), but is not nearly such an efficient 

 means as moist heat. The objections to dry heat are, 

 that to ensure the destruction of bacteria and spores the 

 temperature must be high and the heating prolonged. 

 Koch and Wolfhiigel found that two hours at 150 C. did 

 not always ensure sterilisation, and Gaflky and Loffler 

 state that the spores of some organisms are killed only 

 by exposure to hot air at 140 C. for three hours. Moreover, 

 dry heat has little power of penetration, and it requires 

 many hours for the centre of a mass of bedding, or the 

 like, to attain the temperature requisite for sterilisation, 

 while some articles and fabrics are distinctly injured by 

 the prolonged heating. The highest temperature which 

 can be safely adopted for a dry-heat disinfector is about 

 120 C., and then if large masses have to be treated the 

 heating has to be continued for from eight to ten hours. 

 A rise of 5 C. above this temperature is sufficient to 

 damage many woollen goods, which enhances the objections 

 to a dry-heat disinfector, as it is difficult to keep the 

 temperature of a large chamber constant. 



