CHAPTER V 



BACTERIA IN DISEASE 



ATTENTION has already been called to the role played 

 by saprophytic bacteria in ridding the world of the dead 

 bodies of plants and animals. Mention may also be 

 made of the use made of bacteria in the industries, as 

 the bacillus whose growth in cream imparts the agree- 

 able flavor to butter and cheese, the bacteria used in 

 the manufacture of vinegar; even in tilling the soil ad- 

 vantage is now taken of the property of nitrifying 

 bacteria to extract nitrogen from the atmosphere to 

 enrich the soil and take the place of chemical fertilizers. 



But to the nurse the most important thing in connec- 

 tion with the whole subject of bacteriology is the part 

 played by bacteria in the production of disease. By far 

 the greater number of diseases to which the animal world 

 is heir are due to bacteria, and even the vegetable is not 

 exempt, and has its germ diseases. 



Koch's Rules. Koch laid down certain rules which 

 he held must be complied with to prove that any bac- 

 terium was the cause of any particular disease: 



First: It must be found in the tissues or secretions of 

 the animal having the disease. 



