GROWTH OF BACTERIA 125 



spores are capable of subsequently germinating into 

 new individuals like those that produced them and thus 

 continuing the race (Fig. 53, b). 



Not all bacteria produce spores, and the question 

 whether any species of bacteria forms spores is a matter 

 of most extreme significance in connection with its func« 

 tions ; for these spores are covered 

 by a little shell which is hard 

 and tough and capable of resisting ^^-^ ^--_ _^r\ 

 various adverse conditions. Spore- 

 bearing bacteria may be dried with- 

 out injury, for their spores protect 

 them from destruction. They may 

 be heated to a high temperature, 

 even to boiling, without being killed. 

 Thus the presence of spores will 

 make a great difference in the j.,^^^ showing bacteria 

 ease with which any material can with spores. At « are free 

 be sterilized by heat. Bacteria not spores, and at b germi- 

 capable of producing spores are "^ '"^ spores, 

 very easily killed by heat, while the spore-bearing forms 

 are destroyed with much greater difficulty. 



Growth of Bacteria 



Rapidity of Growth. The most striking fact in regard 

 to bacteria is their wonderful rapidity of multiplication ; 

 for upon this are dependent their extraordinary powers. 

 Bacteria growth and multiplication mean the same thing, 

 and the rapidity with which they can multiply is almost 

 inconceivable. Certain kinds of common bacteria can 



