54 INFECTION AND IMMUNITY 



Experiments made during the past twenty years 

 have shown that fumigation by burning sulphur is not 

 by any means so reliable a method of disinfection as 

 was formerly supposed. It has very little value un- 

 less the articles to be disinfected are in a moist con- 

 dition. This may be effected by introducing steam 

 into the room together with the sulphur fumes. There 

 is a class of diseases, however, in which sulphur fumi- 

 gation is a most valuable method of disinfection : I 

 refer to yellow fever and the malarial fevers, in which 

 diseases the infectious agent is transmitted by mos- 

 quitoes. Such mosquitoes, after filling themselves 

 with blood from the sick person, hang about the room, 

 attached to the ceiling, to window-curtains, etc., for 

 the purpose of digesting their meal and supplying 

 themselves with another when occasion offers. The 

 room is infected because of the presence of these 

 infected mosquitoes, which with the blood of the 

 patient have taken in the disease germs present in 

 such blood. Disinfection in such a case consists in 

 the destruction of the infected mosquitoes, and this is 

 very readily accomplished by means of sulphur fumi- 

 gation. Owing to the superior germicidal power of 

 formaldehyd and its non-toxic properties, this gas has 

 to a considerable extent taken the place of sulphur 

 fumigation for disinfecting purposes. 



Formaldehyd is generated either by the application 



