218 INTRODUCTION TO BOTANY 



for them were attacked by these preventable diseases, the 

 matter would not be so serious, for in that case disease and 

 the resulting deaths would tend to eliminate those who do not 

 act upon the knowledge of sanitation which we now possess ; 

 but many innocent people suffer because others do not take 

 proper precautions against the spread of diseases over which 

 they might have control. As one means of protecting the 

 public many states have laws preventing the use of public 

 drinking cups. Attempts are made to have school children 

 drink from running water, so as to make sure that all con- 

 taminated water flows away. We need many more regulations 

 of the same kind in order to guarantee a reasonable security 

 against the needless spread of disease. 



PROBLEMS 



1. How can you show that the process of decay is of advantage to 

 living things ? Would decay take place without the action of dependent 

 organisms ? 



2. What are the relative advantages and disadvantages of prevent- 

 ing the decay of food by refrigeration and by the use of chemicals? 

 Why are chemicals sometimes used where other means of preservation 

 might be adopted ? 



3. What are the surest methods of preventing the spread of bacterial 

 diseases of plants, such as pear blight and the black rot of cabbage ? 



4. Would the fight against typhoid fever be won more quickly by 

 destroying all flies that carry typhoid or by destroying all infecting 

 material from persons who have typhoid? 



5. In your school and community what are the chief needs for a 

 better understanding of the nature of bacterial diseases? 



6. What are your local regulations in regard to quarantining persons 

 ill with infectious diseases ? in regard to preventing the introduction of 

 diseased fruit trees ? of diseased animals ? 



7. What bulletins has your state agricultural experiment station or 

 your state board of health published dealing with the relation of bac- 

 teria to human disease, diseases of farm animals, dairying, household 

 industries, or agriculture? 



