26 ESSENTIALS OF BACTERIOLOGY 



it, or had become infiltrated with detrimental products, the 

 bacterium-cell produced spores, or rather turned itself into a 

 spore to escape annihilation; but we believe now that only 

 when conditions are the most favorable to the well-being of 

 the cell does it produce fruit, just as with every other type of 

 plant or animal life, a certain amount of oxygen and heat 

 being necessary for good spore formation. The question is 

 still unsettled, however. 



Asporogenic Bacteria. Bacteria can be so damaged that 

 they will remain sterile not produce any spores. This con- 

 dition can be temporary only or permanent. 



Arthrosporous. In the other group, called arthrospores, 

 individual members of a colony or aggregation leave the same, 

 and become the originators of new colonies, thus assuming the 

 character of spores. 

 'The micrococci furnish examples of this form. 



Some authorities have denied the existence of the arthro- 

 sporous formation. 



Resistance of Spores. Because of the very tenacious en- 

 velop, the spore is not easily influenced by external measures. 

 It is said to be the most resisting object of the organic world. 



Chemic and physical agents that easily destroy other life 

 have very little effect upon it. 



Many spores require a temperature of 140 C. dry heat for 

 several hours to destroy them. The spores of a variety of 

 potato bacillus (Bacillus mesentericus) can withstand the 

 application of steam at 100 C. for four hours. 



CHAPTER II 



BIOLOGIC AND CHEMIC ACTIVITIES 



Origin of Bacteria. As Pasteur has shown, all bacteria 

 develop from preexisting bacteria or the spores of the same. 

 They cannot arise out of nothing. 



Distribution. The wide and almost universal diffusion 

 of bacteria is due to the minuteness of the cells and the 



