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, 873 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. 
