16 APPLIED BACTERIOLOGY FOR NURSES 



plying, arrange themselves in groups of two each, and 

 these are termed diplococci, while still others arrange 

 themselves in groups of fours, and these are termed 

 tetrads. In medical bacteriology besides bacilli and 

 spirilla, the streptococci, staphylococci, and diplococci 

 play an important role. 



In a preceding paragraph it was stated that bacteria 

 multiplied when placed in proper surroundings. On 

 the other hand, there is considerable variation in the 



Fig. 3. Bacillus tetani, showing spores. Pure culture on agar. 

 Fuchsin stain (Kolle and Wassermann). 



behavior of different species of bacteria when placed in 

 unfavorable surroundings. Many quickly perish; others 

 live for some time, and then gradually die off. Still 

 others undergo a peculiar transformation into a highly 

 resistant form known as spores. A spore is a round or 

 oval body, usually highly refractive, and possessing a 

 high degree of resistance against various destructive 

 agents. Spores, as such, do not multiply, and may, 

 therefore, be compared to seeds. A bacterium produces 



