30 



THE FUNDAMENTAL PRINCIPLES. 



III. The Spirillum. 



The spirilla or curved or spiral bacteria develop either 

 singly or in pairs or in long twisted or corkscrew filaments. 



The Variations in Development of Each Species. 

 Though under varied conditions of growth the form of 

 any one species may vary considerably, yet these three main 

 divisions under similar conditions are permanent that is, 

 micrococci always develop into micrococci, bacilli into bacilli, 

 and spirilla into spirilla. 



FIG. 2. 



00 o <*> , 

 * d 



e a e 



a. Staphylococci b. Streptococci, c. Diplococci. d. Tetrads, e. Sarcinse. (Abbott.) 



FIG. 3. 



Diplococcus of pneumonia, with surrounding capsule. (Park.) 



