62 DR. E KLEIN. 



and beautiful anthrax bacilli and threads thereof; and if we 

 find that owing to the absence of sufficient oxygen these bacilli 

 fail to produce spores ; and if we further find that after a 

 certain time the bacilli undergo degeneration, and not being 

 able to form spores owing to the absence of sufficient oxygen, 

 they generally all disappear from the cultivation, I think we 

 are jxistified in concluding that the conditions are exactly the 

 reverse of what is postulated by the theory of Pasteur; in con- 

 cluding, viz. that it is the want of sufficient oxygen which 

 destroys the bacilli. If oxygen had been present in sufficient 

 quantities, the bacilli would have formed spores and the culti- 

 vation would have preserved its full virulence for an indefinite 

 period. 



Pasteur, as mentioned above, maintains that his cultivations, 

 kept without spores, gradually lost all activity. " If we 

 examine the virulence of the culture at the end of two days, 

 four days, six days, eight days, &c., it will be found that long 

 before the death of the culture the microbe has lost all viru- 

 lence, although still cultivable." My observations bear out to 

 a certain extent this statement of Pasteur, inasmuch as the 

 cultivation lost its power to kill mice before it lost its power to 

 kill guinea-pigs and rabbits. But as regards guinea-pigs and 

 rabbits it does not hold good ; for in their case complete want 

 of power to kill has appeared in my experience to be the same 

 thing as want of power to grow in a cultivation. Pasteur 

 further states that the animals inoculated with the mitigated 

 virus remain immune against further attacks of anthrax. It 

 is evident that Pasteur's process of cultivation must in some 

 way have differed from my own, or that his assertion for 

 " animals " generally is too broad, for as regards the mice of 

 my experiments there is no immunity of any kind conferred on 

 them. 



Pasteur in his cultivations, found, that owing to the diminu- 

 tion of virulence, as time went on, he could at will choose for 

 inoculation a fluid of less and less virulent eff"ect, from one that 

 would produce a fatiil eff'ect to one that would have only a 

 slight or local effect. But, says he, sheep inoculated with such 



