54 DR. E. KLEIN. 



and so on, for then we could no doubt get millions of genera- 

 tions in the very first cultivation that we established with the 

 bacillus taken from the blood. But even if in a cultivation 

 spores are formed this cultivation need not represent one gene- 

 ration only, because the spores first formed may, and as a rule 

 do, germinate into new bacilli ; these or their offsprings again 

 form spores, then germinate into bacilli, and so on within the 

 same cultivation as long as nourishment is present. But in 

 Buchner's case there must have been cultivations in which 

 spores were never formed. In whatever way we look at it we 

 cannot fix the meaning of the term " generation," and therefore 

 we cannot speak of a cultivation as a *' generation." 



At the commencement of my experiments I used white mice 

 for testing the activity of fluids and cultivations containing 

 Bacillus anthracis, since, as is well known from Koch and 

 others, these animals are very susceptible to anthrax. Inocu- 

 lation with a given cultivation of blood bacillus in neutral pork 

 broth kills mice, guinea-pigs, and rabbits, when used during 

 the first few days of incubation ; but soon a difference sets in, 

 for after the first few days inoculation of mice with the same 

 cultivation proved fatal only in a certain percentage of cases, 

 and after several days more a good many mice remained per- 

 fectly unaffected by the cultivation. My cultivations were 

 typical and perfectly pure, as I ascertained by microscopic ex- 

 amination and further experiments ; there were the typical con- 

 voluted cable-like bundles of the threads ; on staining they were 

 beautifully " cellular" in structure ; inoculations of new cul- 

 tivations which I made came up very finely ; and inoculations 

 with infinitesimal doses in guinea-pigs and rabbits produced 

 typical anthrax. The above mice were inoculated, some by 

 Pravaz syringe, others by deep incision, and placing into this a 

 drop of the cultivation. The inoculation was repeated in some 

 instances, but without effect ; the mice remained perfectly free 

 of illness. This result was obtained with the cultivation, in 

 some cases within a week, in others after a longer period. 

 How could this be explained ? Were all these mice refractory to 

 anthrax. Were they refractory only to the artificially-cultivated 



