36 



Indiviiliially susceptibility to impure air difi'ers widely. AVhen impure 

 air is badly borne and bodily functioning is not carried on normally, we 

 speak of ill-health and disease. Disease may result from the use of bad 

 air, and in a general way, bad air means air contaminated l)y dust, as 

 already mentioned. 



Ailments and diseases have a cause, just lilce all other phenomena in 

 this world. Some diseases are due to parasites, the preying of one form 

 of life upon another. Some forms of life flourish only at the expense of 

 human beings and are constantly transferred from one person to another. 

 Some diseases and their causes are always among us. such as consump- 

 tion and malaria; others come and go, as cholera and yellow fever. Some 

 diseases are transferred mainly through the drinking water, as typhoid 

 fever and cholera; other diseases are propagated by the bite of the mos- 

 quito, as j-ellow fever and malaria. Some diseases are transmitted 

 through the agency of dust, and hence vr( speak of air-borne diseases. 

 like tuberculosis, pneumonia, bronchitis and the like. 



Some diseases are well defined and can be readily diagnosed, such 

 as those just mentioned; others are obscure and their causes ill-detiiUHl. 

 In a general way it may be said that the names of diseases and ailments 

 in common use are names of ill-defined application, that is. there is 

 nothing definite about them, and they are not used in the best medical 

 literatiu-e of today. The words "cold," "biliousness," "catarrh," "rheu- 

 matism," and the like, do not express anything definite. 



Air-borne diseases like tuberculosis and pneumonia are known as 

 specific diseases due to a definite cause; if the cause is absent then the 

 effect, the disease, will also be absent. Ailments are minor affections 

 and are not always due to some one definite cause: headache or a pain 

 in the arm are ailments and may arise from a variety of causes. 



It is scarcely necessary to make any specific reference to the science 

 of bacteriology— which concerns itself with what are popularly known as 

 "germs," or to the number of established facts which it eml)races. Any- 

 one arguing in opposition to bacteria as a cause of diseases will not even 

 get a respectful hearing from a qualified bacteriologist— it seems to him a 

 waste of time. A man might as well deny the theory of univers;ii gi'avita- 

 tion as to deny the germ theory of disease. 



Ailments Due to Infected Dust: Inhaling city dust may liring on a 

 variety of ailments, as well as definite diseases. City residents may com- 

 plain of various pains and aches during or after the prevalence of a dust 



