GENERAL CHARACTERS OF BACTERIA 23 
putrefy. Those organisms which feed upon lifeless bodies include 
the vast majority of bacteria. There are, however, other species 
that are capable of living upon the bodies of animals and plants 
while these are still alive. Inasmuch as they can feed upon living 
organisms they are liable to produce disease and constitute in 
general the disease bacteria. Bacteria feeding upon living 
animals and plants are called parasites. Bacteria feeding upon 
dead animals and plants are called saprophytes. Both sapro- 
phytes and parasites are of great importance. 
