1 34 Lectures on Bacteria. [ xii. 



Since this form in its want of virulence, its formation of super- 

 ficial films, and its power of independent movement is more 

 like the hay-bacillus, B. subtilis, than the virulent form, Buch- 

 ner maintained that the virulent B. Anthracis had been entirely 

 changed by cultivation into the harmless B. subtilis, and the 

 matter excited much attention, since there was here apparently 

 an evident case of the conversion of a species held to be distinct 

 into another. But, as was shown on page 34, he has not yet 

 proved his point. Buchner certainly tried the reverse process 

 also, and endeavoured to convert the harmless B. subtilis into 

 the virulent B. Anthracis by cultivating successive generations 

 of it in various solutions containing albumen, which I must not 

 enumerate here. The results obtained were for the most part 

 distinctly negative, and the few which were said to be positive 

 are open to so many objections, that without insisting on strict 

 morphological proof we must consider them as quite uncertain. 

 Here too the morphological proof has been omitted. It is quite 

 possible that the usually harmless B. subtilis may by breeding be 

 endowed with an exceptional virulence ; but its specific character 

 would no more be affected by this, than is that of B. Anthracis 

 by its attenuations, nor would the fact that the latter is the 

 ordinary exciting cause of anthrax be rendered at all doubtful. 



Pasteur and Toussaint, led by experience derived from other 

 sources which will be noticed again presently, have attempted 

 with success to use the attenuated Bacillus of anthrax for pro- 

 tective inoculation against the virulent Bacillus. If an animal is 

 inoculated with the Bacillus attenuated to the degree requisite 

 for it, that is for that species, it either does not sicken or it 

 sickens slightly and recovers from the disease. It resists then 

 infection with less attenuated Bacillus, and at the next inocula- 

 tion it resists the Bacillus which possesses the highest degree of 

 virulence. The certainty of these results, and their special im- 

 portance at the same time in reference to the practical art of 

 the breeder, is differently appreciated in different quarters; 

 Koch especially and his colleagues have brought forward well- 



