XL] BACILLUS: PATHOGENIC FORMS. 157 



always thinner than the bacilli cultivated in a neutral fluid 

 medium like pork-broth. 



Cultivation of the blood-bacilli at temperatures varying 

 between 20 and 40 C. in any suitable nourishing material, 

 solid or fluid, however many transferences (new cultivations 

 or so-called new generations) be made, always yields a crop 

 of virulent bacilli. It is absolutely incorrect to say, as 

 Buclmer 1 and Greenfield 2 maintain, that continued transfer- 

 ence weakens the action of the bacilli ; as long as the cultures 

 remain pure, not contaminated and finally suppressed by 

 accidental innocuous bacilli, the anthrax-bacilli retain their 

 full virulence. 



Cultures of the blood-bacilli at 20 to 38 C. in fluid media, 

 e.g. neutral pork-broth, during the first or second week, are 

 virulent to mice, guinea-pigs, and rabbits ; but after that 

 they lose their power on mice, provided the growth takes 

 place only in the depth and no spores are formed ; but they 

 retain it, as regards guinea-pigs and rabbits, as long as they 

 contain good bacilli at all. 3 But fresh cultures made of 

 such bacilli invariably produce a growth which is fatal to all 

 rodents during the first or second week. 



Pasteur has stated that blood-bacilli which have become 

 attenuated in virulence by exposure to 42 or 43 C. for 

 twenty days are capable of starting new cultures of attenu- 

 ated virus. This I question, for I find that such a culture 

 starts new cultures of virulent bacilli ; in the same way the 

 bacilli of a culture that is only " vaccine " for sheep, when it 

 is inoculated into a guinea-pig kills it with anthrax, and then 

 yields bacilli that are fatal to sheep. 



1 Ueber d. Erzeug. dcs Milzbrandes, Munich, 1880. 



2 Proceedings of the Royal Society, June 17, 1880. 



3 Klein, Reports of the Medical Officer of the Local Government Board, 

 1881. 



