DUST AND ITS DANGERS. 55 



bacterial disease by means of dust is of such 

 extreme importance that we must be very cer- 

 tain that we are dealing with facts and not with 

 conjectures, when we consider the relationship 

 one to the other. Let us then get the facts 

 together first. 



There is a large number of diseases which 

 physicians call infectious ; these all have cer- 

 tain ways of manifesting themselves, certain 

 family traits which would justify this grouping 

 of them together even without a knowledge of 

 the particular agent which causes them. The 

 more important of these infectious diseases 

 are : consumption or tuberculosis, diphtheria, 

 small-pox, yellow-fever, Asiatic cholera, ty- 

 phoid-fever, scarlatina, measles, pneumonia, 

 erysipelas, and blood-poisoning. There are 

 others of less frequent occurrence in this re- 

 gion, which we need not mention here. 



Now within the past few years we have found 

 out positively and without question that the 

 particular and exclusive agent which causes 

 some of these diseases is one or other form of 

 bacteria. Each disease has its special form of 

 bacteria, without which it can by no possibility 



