MORPHOLOGY AND PHYSIOLOGY OF BACTERIA. II 3 



are said to have been obtained from the soil. When cultivated 

 at a temperature as high as 42° C. the anthrax bacillus becomes 

 incapable of forming spores. Spores themselves do not mul- 

 tiply, nor do they manifest any activity. Spores may be located 

 at the center of the bacillus, or nearly at one end; in the latter 

 case the end of the bacillus is likely to enlarge, making a form 

 having the shape of a drumstick, as takes place with tetanus 

 bacilli (Fig. 44). When a bacillus assumes a spindle shape on 

 account of having the middle part bulged through the formation 

 of a spore it is called a Clostridium. With rare exceptions, a single 

 bacillus contains but one spore. Under favorable conditions 

 the spores germinate, as it is called, and develop to the adult 

 form of the organism. This may be witnessed in hanging-drop 

 preparations. 



Fig. 45. — Bacteria Showing Flagella. 



Motility. — MotiHty is rarely exhibited by micrococci; some 

 bacilli possess it and some do not; while nearly all of the spirilla 

 are motile. The phenomenon is observed in the hanging-drop. 

 The degree of motihty is variable, being sometimes slight and 

 sometimes very active. When seen under a high power the 

 little particles taken from a culture of a motile organism may 

 look Hke a writhing mass of maggots or Kke tadpoles in a pool. 

 The motility is most active in young cultures. The movement 

 results from the vibration of little processes, or flagella (Fig. 45). 

 Of these there may be one or several, placed singly or in 

 groups, at the end, or scattered around the sides. They are 

 extremely difficult to demonstrate except by special staining 

 methods, which, furthermore, are quite uncertain of result. 



