22 ESSENTIALS OF BACTERIOLOGY. 



brane begiris to swell, and it now assumes the shape and size 

 of the cell from which it sprang, the capsule having burst, so as 

 to allow the young bacillus to be set free. 



Requisites for Spore Formation, It was formerly thought that 

 when the substratum could no longer maintain it, or had become 

 infiltrated with detrimental products, the bacterium-cell pro- 

 duced spores, or rather turned itself into a spore to escape anni- 

 hilation ; but we know now that only when the 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 cer- 

 tain amount of oxygen and heat being necessary for good spore 

 formation. 



Asporogenic Bacteria. Bacteria can be so damaged that they 

 will remain sterile, not produce any spores. This condition can 

 be temporary only, or permanent. 



Arthrosporous. All the above remarks relate to Endospores, 

 spores that arise within the cells. 



In the other group called Arthrospores, individual members 

 of a colony or aggregation leave the same and become the origi- 

 nators 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 envelope, 

 the spore is not easily influenced by external measures. It is 

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



Chemical 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. 



