956 DISEASES CAUSED BY FILTRABLE VIRUS 



Much might be written about the various substances that can 

 be applied to the skin and clothing to keep insects away, but none 

 of these means are infallable or sufficiently safe to be relied upon. 

 The best possible method, after all, is the use of shower baths of 

 hot water, the plentiful use of soap, combined with steam disin- 

 festation of the clothing, and clipping of hair and beard, etc. 



Gaseous Disinfectants for Rooms, Clothing, etc. It is an im- 

 portant practical fact that formaldehyd, in spite of its powerful 

 action upon bacteria, is a weak insecticide and cannot be relied upon 

 to kill lice, mosquitoes, or fleas. 



Better than formaldehyd is S0 2 gas used in quantities of two 

 to three pounds of sulphur per 1,000 cubic feet, with the simultaneous 

 evaporation of water. (Clayton apparatus.) 



Hydrocyanic acid gas is also very efficient, but of course ex- 

 tremely poisonous and dangerous unless used in a proper way. 



The most important facts concerning these gases, their generation 

 and application, have been dealt with in a preceding section. 



For the wholesale disinfestation of clothing, fomites, etc., in 

 connection with louse infested populations, clothing, blankets, etc., 

 the experience of the late war has shown that the most practical 

 systems are those depending upon the application of heat. 



Heat may be applied as dry heat or moist heat. 



Our own experience has taught us that the surest and most 

 foolproof method of disinfesting large quantities of material during 

 epidemics is by the use of large autoclave drums placed on trucks 

 such as the Foden-Thresh autoclave lorries, which consist of large 

 autoclaves with steam jackets so arranged that clothing, etc., can 

 be exposed to steam under slight pressure (about five pounds), then 

 the connection between the inner and outer jackets closed and the 

 material dried in the same chamber before removal. The steam is 

 supplied from the motor since such lorries are usually steam driven. 



In the field, dry heat chambers can be constructed consisting of 

 well sealed huts within which small brick furnaces or tin stoves, 

 with stovepipe arrangements surrounding the walls are used for 

 heating purposes. These dry heat disinfestors are not as uniformly 

 practical or foolproof as are the methods in which steam under 

 pressure is applied, but it may be necessary to use them when other 

 means are not available. Detailed descriptions cannot be given here, 

 but a little ingenuity with attention to proper size in relation to 

 heating apparatus, proper distribution of heat with tin pipes, and 



