24 



like that with liquid media, is the uncertainty of steriliz- 

 ing the nourishing medium; further, the occasional 

 settlement and growth of foreign organisms in the 

 vicinity of those planted. Yet these accidents are in this 

 method, in distinction from others, detected with ease 

 and certainty (Fig. 5). For there is no diffusion through 



Fig. 4. Anthrax bacilli showing spore formation. X 300. 



this solid medium of growing bacteria ; each organism, 

 whether intentionally planted or not, remains in one 

 spot, any admixture must occur by continuity of growth. 

 By this method, then, there is ocular demonstration that 

 the organisms of the successive cultures proceed as con- 

 tinuities of structure from those of the first ; we may see 



