12 BACTERIOLOGY FOR NURSES 



are taking place. The spore-stage is considered a 

 resting state in which the organisms are able to 

 resist harmful influences to a much greater degree 

 than when in the vegetative state. As soon as fav- 



FIG. 3. Showing spore-formation. 



orable conditions of moisture, temperature, and 

 food return, the spores develop again into the same 

 kind of cells from which they originated. 



Spore-formation is not common, occurring most 

 frequently in bacilli, less so in spirilla, and rarely 

 in micrococci; however, it is supposed that spore- 

 formation may take place in species growing under 

 natural conditions, but which are impossible to 

 cultivate under artificial surroundings. 



The vitality of the spore may remain dormant 

 for months or years, perhaps indefinitely, a fact 

 which is of peculiar significance in the consideration 

 of certain infectious diseases^ 



Masses of Cells or Colonies. By implanting 

 upon suitable medium one or more cells of a species 

 of bacteria, and subjecting the culture to favorable 

 conditions of moisture and temperature for a few 



