1890.] MICROSCOPICAL JOURNAL. 255 



The first disease for which Pasteur obtained attenuated virus was 

 chicken cholera. He found that cultures which had stood for several 

 months exposed to the air, /. c merely plugged with cotton, had 

 weakened in virulence. These old cultures produced on inoculation 

 only a local abscess, which ended in resolution in a few weeks, but the 

 chickens so inoculated were found to be protected from subsequent 

 attacks and also from the disease by inoculations of virulent material. 

 Pasteur attributed the weakened virulence to the action of the air, for 

 he found that in cultures of chicken cholera which were sealed up, the 

 full virulence was retained. 



Pasteur's next successful experiments on attenuation were made with 

 anthrax or malignant pustule. The method of attenuation in this case 

 was different from that for chicken cholera. Cultures of anthrax 

 bacilli were grown at 42° to 43° C, and it was found that these cultures 

 were much less virulent than cultures grown at lower temperatures, 

 and that animals inoculated with them were for the most part pro- 

 tected. Pasteur's inoculations for anthrax have been tested on a very 

 large scale by different experimenters with various results. 



The third disease for which Pasteur obtained vaccines was swine 

 erysipelas {rouget du forc)^ an infectious septicaemia causing great 

 ravages among the hogs of France. The method of attenuation in this 

 case is to inoculate rabbits with virulent cultures. It is found that the 

 micro-organism becomes attenuated after having passed through the 

 body of a rabbit. Cultuies obtained by inoculation from rabbit to rab- 

 bit finally become so attenuated that they will no longer kill. But 

 cultures attenuated in this way protect hogs when inoculated. 



Kitt has put all these methods of inoculation to the test. He found 

 that vaccines for anthrax obtained direct from Pasteur were not capable 

 of protecting the sheep he inoculated. He then inoculated guinea-pigs 

 with the vaccine, and obtained cultures from these guinea-pigs which 

 produced a fatal anthrax in sheep. The organisms had increased in 

 virulence in passing through the guinea-pigs, and, although these 

 cultures were virulent for sheep, they rendered cattle immune. But 

 the fact that Pasteur's vaccines were sufficientlv powerful to protect the 

 sheep which Pasteur inoculated and were not capable of protecting the 

 sheep which Kitt experimented with, shows the practical ditticultv of 

 obtaining cultures of just the right strength. Krajewski's results with 

 the same vaccines were also unfavorable. Hess ol^tained rather more 

 favorable results. Kitt found Pasteur's observations on chicken cholera 

 to be correct, but strongly advises against the use of vaccination. He 

 points out that the excreta from inoculated fowls is virulent for other 

 animals, and, as in the case of anthrax and other bacterial diseases, the 

 organism increases in virulence when passed through the bodv of sus- 

 ceptible animals. 



Kitt's experiments with swine erysipelas gave similar results to those 

 with chicken cholera. He substantiated Pasteur's observation that the 

 virulence of the organism was weakened by its passage through rabbits ; 

 but the faces from hogs inoculated with attenuated cultures were found 

 to be virulent for other domestic animals and for birds. Hess and 

 Guillebeau found protective inoculations for swine erysipelas unsatis- 

 factory. 



\To be conti)nicd.'\ 



