DUST AND ITS DANGERS. 93 



by some formed, minute, living thing, either 

 plant or animal. This leads us to the further 

 definite conclusion that whenever one of the 

 contagious or infectious diseases is conveyed 

 from one person to another, this is done by 

 formed material which must pass from one to 

 another, either in the shape of palpable solid 

 matter or by fine floating dust-particles. 



Now, when we interpret this rather long 

 exposition of facts and inferences into every- 

 day experience, we find that it means some- 

 thing like this : When we have in the house 

 a victim of one of the infectious diseases, such 

 as diphtheria or consumption, and want to 

 protect the house-mates against it, both while 

 it is active and after it is over, we no longer 

 grope after some mysterous, intangible thing, 

 before which we must bow down or burn 

 something, as if it were some demon which we 

 would exorcise. We say to ourselves, if we 

 can at once destroy, by boiling it or burning it 

 or soaking it in some suitable disinfectant, all 

 the material which is discharged from the 

 patient's body, he will cease to be a source 

 of contagion the poison cannot spread from 



