DISTRIBUTION AND HABITAT OF THE BACTERIA. 701 



influence of the soil, and of the impurities of the soil, 

 but on the contrary rather an unfavourable action. 



If, however, we ask whether the soil favours the pre- 2. Are patho- 

 servationof pathogenic bacteria, our answer must perhaps preserved in 1 * 

 be somewhat different. This might occur if circum- the soil ? 

 stances were present which favoured spore formation 

 or long preservation of preformed spores, or of those 

 formed in the soil, or retention of vitality by non-spore- 

 bearing bacteria. Soyka* has recently observed, in a 

 series of experiments with anthrax bacilli, that spores ' 

 are formed more quickly when the fluid containing them 

 is mixed with soil than when they are kept in the 

 original fluid under conditions otherwise similar (at the 

 same temperature, &c.). Now spore formation in the No important 

 case of anthrax bacilli occurs chiefly at the surface of the spore Ce 

 fluids, and hence spores are the more numerous, and formation, 

 the earlier formed in a fluid the thinner the layer in 

 which it is spread out. In soil which is not saturated 

 with moisture, any fluids poured on it are quickly dis- 

 tributed in very thin layers, and thus offer the best 

 conditions for spore formation. But these conditions 

 are also furnished on any substratum when the fluids 

 are spread out in thin layers on the surface. 



According to Soyka, acceleration of the spore forma- 

 tion is most marked when the soil contains such an 

 amount of moisture that from 25 to 75 per cent, of the 

 pores are filled with fluid. This gives a very large 

 margin, which besides was never sharply defined in his 

 series of experiments, for numerous spores w r ere found, 

 and the delay in their formation was only trivial when a 

 hundred per cent, of the pores were filled, while where 

 the proportion was under 25 per cent, the spores were 

 so widely distributed that comparison was impossible. 



Soyka was unable to observe spore formation in the 

 anthrax bacilli when the temperature of the soil was 

 below 18 C., or under conditions which would hinder 

 spore formation in fluids. 



From these results it is evident that the soil exercises 

 no marked or specific influence on the formation of 



* Fortschrilte d. med., 1886, Nr. 9. 



