60 DR. E. KLEIN. 



page I have pointed out that already while active growth is 

 going on in the cultivation, some threads undergo degenera- 

 tion, and when the pabulum in the cultivation is exhausted, 

 this degeneration gradually extends over the whole growth. 

 As a rule, as pointed out before, if during active growth the 

 bacillus mass has been kept at the bottom of the fluid, no 

 spores are formed, and therefore degeneration after the exhaus- 

 tion of the pabulum gradually destroys every active particle of 

 the growth. Thus it happens that the cultivation, taken as a 

 whole, gradually loses its virulence, inasmuch as with the pro- 

 gress of the degeneration extending over greater numbers of 

 bacilli, larger doses must be injected into guinea-pigs and 

 rabbits to produce fatal result. But (his must not be taken as 

 identical in meaning with what Buchner calls a diminution in 

 virulence of a cultivation. According to Buchner larger quan- 

 tities have to be used of a later generation (cseteris paribus) 

 to produce the same result as with a former generation, 

 because, he tells us, the Bacillus anthracis is gradually 

 changing its nature, becoming gradually converted into an 

 innocuous hay bacillus. 



In our case the diminution in virulence of a cultivation is 

 entirely due to a diminution in the number of active bacilli, 

 and not to any progressive weakening of the potency of each 

 several bacillus. Wherefore the greater the number of bacilli 

 destroyed, the fewer un destroyed or active bacilli will be found 

 in a given quantity, or what comes to the same thing, a larger 

 quantity of material must be used in order to meet with an 

 active bacillus. 



While there exist any living bacilli in the cultivation it is 

 possible to start new cultivations, which when used in the 

 early stage of the new cultivation or when allowed to form 

 spores kill without fail all rodents. I have made several 

 experiments in this respect, and I have invariably obtained the 

 same results. 



A first cultivation, which promptly killed guinea-pigs during 

 the first fortnight when used in infinitesimal doses, failed to 

 kill a guinea-pig when injected into the subcutaneous tissue 



