CHAPTER VI 



TESTS OF DISINFECTION 



\ \ 7 HAT means have we of proving that the infect- 

 ing power of infectious material has been de- 

 stroyed ? 



Evidence of disinfection may be obtained : (a) from 

 the practical experiments experience of those en- 

 gaged in sanitary work ; (f) by inoculation experi- 

 ments upon susceptible animals ; (c) by experiments 

 made directly upon known disease germs. 



(a) It is a matter of common experience that, when 

 a room has been occupied by a patient with an infec- 

 tious disease, such as smallpox, scarlet fever, or 

 diphtheria, susceptible persons are liable to contract 

 the disease weeks or even months after the patient 

 has been removed from it, unless in the meantime it 

 has been disinfected. If a second case does occur 

 from exposure in such a room, it is evident that it has 

 not been disinfected. But the non-occurrence of sub- 

 sequent cases cannot always be taken as evidence 



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