SAPROPHYTES AND PARASITES 123 



bacteria far outnumber the disease germs. We should 

 not therefore be frightened when we learn that bacteria 

 are all around us, in the food we eat, the water we drink, 

 and the air we breathe. Most of them are harmless or 

 beneficial, and need cause us no uneasiness. 



It should also be noted, finally, that some bacteria can 

 live both upon living tissues, like parasites, and upon 

 dead material, like saprophytes. Such microorganisms 

 are partly parasitic and hence are capable of producing 

 disease. They are also capable of living outside the body 

 in various localities in nature. They may be of serious 

 importance to the health of man, inasmuch as they are 

 capable of living a parasitic life if they can get into the 

 living body ; but are also able to live an independent life 

 in nature. All disease bacteria either belong to this class 

 or are strict parasites, while the harmless bacteria belong 

 to the class of saprophytes. 



