12 



BACTERIA 



Division may occur in one, two, or three directions, or planes. 



By cell division bacteria multiply by geometrical progression. 

 One cell at the end of an hour becomes two, and at the end of a 

 second hour these two become four; at the end of another hour these 

 four become eight; after twenty-four hours they may number many 

 millions. 



It is well that the food supply soon gives out and that the products 

 of bacterial metabolism, such as acids and ferments, inhibit their 

 growth. By this rapid bacterial multiplication, carcasses of animals 

 are disintegrated and the higher nitrogenous compounds are re- 

 duced to simple gases that are quickly dissipated in the air. 



SPORULATION. Sporulation is of two kinds: the first and 

 most important for hygiene is that into which some pathogenic 

 bacteria go when they meet unfavorable conditions and it affords 



FIG. 10. The formation of 

 spores. (After Fischer from 

 Frost and McCampbell.) 



FIG. n. Spores and their location in bacterial 

 cells. (After Frost and McCampbell.) 



protection against all but the most vigorous disinfection; the second 

 kind is a specialized function of the higher bacteria and moulds by 

 which reproduction occurs. In the latter case it is not impossible 

 that some sexual specialization occurs. The first mentioned 

 are called Endospores. 



Vegetative sporulation corresponds to the flowering of the higher 

 plants, and is observed under the most favorable vital conditions. 



