What do microbes 
live on? 
22 WORLD OF INVISIBLE LIFE 
ing more microbes by splitting themselves, un¬ 
der certain conditions can reproduce by the for¬ 
mation of eggs, called spores. Such an egg, or 
spore, is able to withstand much harder condi¬ 
tions than an ordinary microbe can; it will 
sometimes remain alive, though inactive, for 
years, even without food or moisture. So when 
one of the microbes which has this spore-form¬ 
ing ability finds itself in a dry place or in one 
without food, instead of dividing, it forms a 
spore, which continues to live where the mi¬ 
crobe itself could not. Then, when conditions 
are more favorable, the spore becomes a living 
microbe. 
Almost all microbes live on other plants and 
animals. Some are able to obtain the food with 
which to keep themselves alive from dead plant 
or animal matter, while others feed only on 
living bodies of plants and animals and quite 
naturally are injurious to the life of the indi¬ 
vidual upon which they feed. In mankind they 
produce?almost all the diseases from which we 
suffer, for most disease-germs are of this class. 
