ino 



SPORE-FOKMING BACTERIA ^"^ 



first eight tests are excluded it is only 5,300, an almost negUgible 



"^Tmight be concluded from these data that some vegetative 

 forms do exist in normal soil and for this reaon a higher count 

 was obtained eighteen times from the -"Seated mtusion; wh^e 

 in the other eight cases a higher count was "btmned from the 

 heated infusion because clumps were broken up by the heat. 

 ItTs improbable, however, that these two factors sl-^W orf " 

 narily so nearly neutraUze each other; nor is it possible, if tins 

 explanation is used, to account for the greater average difference 

 rthrfirst eight tests than in those in which lower tempera^^ 

 were used. It seems more reasonable to explam most of the 

 Ifferences in either direction as lying withm the experiment^ 

 erroi^a perfectly plausible assumption m view of the high 

 dilutions used— or if this is not enough to explam all the cases 

 fn wMchX Ugher count was obtained from the unheated in- 

 fusfon to assume that an occasional less resistant spore wa^ 

 S'by the temperatures employed. The evidence all seems 

 to ndicate that the three organisms investigated do not occu 

 in soil under normal conditions as active vegetative forms but 

 a" spores It is true that there are other spore-forn^ng bacter a 

 fn Toil besides these three types, in regard to which definite 

 data could not be obtained because their eol-- "^f ^-^f 

 teristic enough to be recognized with certainty, but none ot 

 them ar as constantly present as the three types studied, and 

 what evidence is at hand suggests that the same facts are true 

 to regard to them as in regard to B. mycotdes, B. cereus and 



^■rsTandft: reason, however, that these bacteria, so univer 

 sallv present in soil, must grow and multiply under some natural 

 Tonditions It is known that they ordinarily thnve m «ie pre. 

 ence of organic matter; so it seemed not improbabeha^thy 

 would multiply if manure were added to soil. A single experi 

 menthrbeen undertaken to test out this point, but with negative 

 Results In a pot of soil, mixed with a heavy application of 

 rel horse manure, kept under observation for two months, 

 hi was at first a' very great increase in the number of non- 



