58 PRACTICAL BACTERIOLOGY. 



are to be seen. The colonies which develop in the 

 body of the gelatine mtiy present appearances quite 

 different from these surface ones, even if they belong 

 to the same species. This variation in form is due 

 either to the favourable or unfavourable influence 

 exerted by the air, or to the effect produced by the 

 surrounding gelatine, which prevents the colony from 

 spreading itself out as much us it otherwise would. 

 Particularly interesting and important disclosures are 

 revealed to us, if we examine the colonies with a low 

 power ( X 40 — 80) of the miscroscope. For instance, 

 in a young anthrax colony various' peculiar wavy 

 scattered masses may be observed, which might be 

 mistaken for a bundle of curly hair ; this is not seen in 

 any other colonies. If a somewhat higher power is 

 used, these wavy bundles are shown to consist of 

 bacterium threads, which are lying one above the 

 other in a mass. The edge of such a colony is gen- 

 erally seen with the miscroscope to have quite a 

 characteristic appearance ; it is true that sometimes it 

 still looks sharp and clear, but generally the border, 

 which with the naked eye or magnifying glass appeared 

 quite sharp, now shows a notched, indented, or in- 

 distinct edge. 



Such striking peculiarities are, of course, sufficient 

 to distinguish the anthrax bacillus from all others, 

 but most bacteria have less remarkable developments 

 in the gelatine, and hence quite different methods 



