DEVELOPMENT AND COMPOSITION OP BACTERIA 11 



but, as is the case with all organisms, mathematical 

 increase never continues without check or hindrance. 



In the case of bacteria the check arises largely from 

 the products of the bacteria themselves; the organ- 

 isms in their activity upon food substances produce 

 acids and other injurious materials which check 

 further multiphcation. Lack of proper food, or 

 moisture, or favorable temperature, and conflict 

 with other species of organisms, are also checks 

 upon growth and multiplication. 



Spore-formation. — Following a period favorable 

 to reproduction, pertain bacteria (notably bacilli') 

 entec in to a stage kn ow n as spore-form atioiL; this 

 usually occurs when food nears ex haus tion, ^ r 

 injuri ous substances have be en formed, o r unf ayor- 



a.hlp tprppprafiirfi mnditinnp! a.risR, and is character- 

 ized by the develo_p ment of round or oval glisten- 

 ing bodies (spores) within the cell which_ are_iiL 

 dense compact struct ure and posses s^ an extrao.i = 



dinary resi stanc e_JoJieat_(70^:400^_C^ or 158°- 

 212° F.), chemicals, and oth er_Jnj arious subj - 

 s tances. 



A single cell produces but one spore, as a rule, 

 although there are said to be rare exceptions. 



Spore-forming bacteria are said to be in the 

 veg etative stage while growth and ^ reproduction 



