702 DISTRIBUTION AND HABITAT OF THE BACTERIA. 



On the other 

 hand spores 

 once formed 

 are well 

 preserved. 



Preservation 

 of non-spore- 

 bearing 

 bacteria. 



spores in the case of anthrax bacilli ; on the contrary, the 

 bacilli form spores in the superficial and somewhat dry 

 layers of the soil in the same manner perhaps here and 

 there somewhat quicker, but certainly not to any marked 

 degree -as in portions of the bodies of animals which 

 have died of anthrax and which are lying on the surface, 

 in the dejecta of anthracic animals, on nutrient vegetable 

 materials, in marshy flats, &c. 



It is conceivable that in the case of some other patho- 

 genic bacilli, which are less disposed to the formation of 

 spores than the anthrax bacilli, spore formation may 

 occur in a more exclusive manner and much more 

 favourably under the conditions peculiar to the soil ; as 

 yet, however, we have no evidence in favour of such a 

 view. 



On the other hand, pre-existing spores, or those formed 

 in the soil, are perhaps better preserved there than in 

 any other superficial substrata. In the latter, as the 

 result of rains, or of currents of water and air, which 

 may bring new nutrient materials, may again moisten 

 the dried masses, or may carry the spores to other 

 parts rich in nutriment, the spores may very readily 

 sprout and form bacilli, which then succumb to the 

 saprophytes present. In the soil, on the other hand, 

 the unfavourable nutrient conditions, and the unfavour- 

 able conditions of temperature, can almost always pre- 

 vent the sprouting of the spores, and thus we have an 

 explanation of the fact that existing spores can remain 

 there for a long time, and that we so often find in the 

 soil large numbers of resisting spores. 



But even without previous spore formation the soil 

 may possibly preserve various kinds of bacteria, including 

 pathogenic ones. We saw previously that the chief reason 

 why non-spore-bearing bacteria so readily died under 

 natural conditions, was either because they were present 

 in fluid media, and were then exposed to the danger of 

 being overgrown by other bacteria, or because the loss of 

 water and the drying of the nutrient substratum led to 

 their death. 



We can readily conceive that such complete drying of 



