DISINFESTATION 49 



tion is carried out in a steamer or an oven, as 

 far as the lice alone are concerned. When it is 

 necessary to guard also against the infectivity of 

 their excreta, which always cling to the fibres 

 of infested garments, a steaming heat must be 

 used. The infecting power of the excreta of lice 

 infected with trench fever is not destroyed by 

 the dry heat to which garments are usually 

 exposed. A garment which has been worn by a 

 lousy person who has trench fever, if freed from 

 lice by dry heat as ordinarily used, is liable 

 to cause an attack of the disease in a healthy 

 man who wears it, as the still virulent excreta 

 may enter small scratches (see Chapter XI.). 

 Exposure to wet or dry heat at a temperature of 

 130 F. (55 C.) for twenty minutes or 140 F. 

 (60 C.) for fifteen minutes will kill all lice and 

 nits, provided that the time is calculated from the 

 moment when penetration of the garment con- 

 taining them has been completed by the heat. 

 It should not be calculated from the moment at 

 which the garments are put into the chambers. 

 So far as our knowledge at present goes, to destroy 

 the trench fever virus of the excreta and render 

 them harmless a steaming atmosphere of a 

 temperature of 60 C. for twenty minutes is 

 necessary, and this should be the minimum used. 

 Knowledge of the time necessary for the thorough 

 penetration of the garments being treated can 

 only be gained by experiment with the type of 

 hot chamber used. 



E 



