THE BACTERIA 215 



the direct light of the sun has a destructive effect upon them, 

 and that fresh air is likely to contain fewer tubercle bacilli 

 than the close air of rooms in which many people have been. 

 Plenty of fresh air, sunshine, and wholesome food are most 

 important factors in preventing attacks of tuberculosis, and 

 these, together with good general vitality of the body, are the 

 best guaranty against this disease. On the other hand, poor 

 food, bad air, dark rooms, and low vitality render the body a 

 favorable growing place for these germs, when once they are 

 introduced. These predisposing factors are of tremendous im- 

 portance in relation to tuberculosis. The nature of the occu- 

 pations and habits of men have much to do with predisposing 

 and exposing them to this disease. In 1898 an Englishman 

 named Newsholme showed by records that for each 100 agri- 

 culturists who died from tuberculosis and other respiratory 

 diseases there were 453 potters and earthenware workers, 407 

 cutters, 373 plumbers, and 335 glassmakers who died from 

 these same diseases. 



201. Prevention of disease. Bacteria are distributed into 

 almost every nook and corner of the earth in soil, air, 

 water, and dust, and upon and within the bodies of plants 

 and animals. Disease-producing bacteria are common, though 

 far less abundantly distributed than forms which do not cause 

 disease. It must be kept clearly in mind that if all disease- 

 producing bacteria from patients who have disease were 

 immediately killed, there would soon be no danger of distri- 

 bution of disease by any of the ordinary agencies. A good 

 deal is known about the methods of distribution and infec- 

 tion of the most dangerous disease-producing forms, though 

 our knowledge is by no means complete. Polluted water and 

 milk have often been the means of wholesale distribution of 

 typhoid germs (fig. 171). There are numerous records of cases 

 in which the typhoid pollution of rivers has been directly fol- 

 lowed by outbreaks of typhoid in cities that get their water 

 from these rivers. There are also instances where typhoid- 

 polluted milk has left a trail of typhoid wherever it was used. 



