What does 
temperature 
do to them? 
24 WORLD OF INVISIBLE LIFE 
of microbes, however, that can live on both liv¬ 
ing tissues and dead matter. They can produce 
diseases when they live in the human body. 
They can also live on the bodies of dead animals 
and plants. 
In addition, there are certain kinds of soil 
microbes that can exist without depending on 
any other plant or animal material, alive or 
dead. They have the ability to make their food 
from substances in the soil and air, just as plants 
do. So they need have nothing to do with 
other animals or plants. 
Every microbe has a temperature at which 
it lives best, and each has a low point below 
which it is too cold for its life to continue, as 
well as a high point above which it is too hot 
for it to live. These points differ greatly for 
every type, and the low point for one kind of 
microbe may be higher than the high point 
for another. One kind of soil microbe can not 
grow, under certain conditions, below 116 de¬ 
grees of heat, while the microbe of tuberculosis 
cannot live for any length of time above the 
