Immunization. Pasteur's Method. ,25 



without injury the second inoculation with the stronger vaccine. 

 Without the first injection the second inoculation would prob- 

 ably prove fatal, while the two inoculations confer the neces- 

 sary immunity upon the animals. 



The results of the vaccination are in general satisfactory 

 in view of the experience obtained from a large number of 

 cases. Some of the immunized animals do not resist an artificial 

 infection by feeding repeated large quantities of spores (in 

 Koch's experiments 2 out of 10 sheep died after feeding them 

 for days wdth virulent spores in quantities of the size of a 

 hazelnut). These are exceptions which have no influence on 

 the practical value of vaccination, inasmuch as under natural 

 conditions the intensity of the infection is far below the amount 

 given in these artificial infections. Where vaccination is prac- 

 ticed in large herds the losses from anthrax in the year follow- 

 ing are in general greatly reduced compared with periods in 

 which the animals were not vaccinated. In numerous localities 

 where the disease raged regularly year after year it has almost 

 entirely vanished as a result of vaccination of the animals. 

 Not infrequently vaccination immediately checks the spread of 

 the disease in a herd. 



The immunity reaches the necessary degree in about 10 

 to 12 days after the second inoculation, and lasts about one 

 year. (In the experiments of Azary vaccinated sheep resisted 

 the artificial infection even after 8 months.) A longer duration 

 of the artificially produced immunity is doubtful, and there- 

 fore a repetition of the vaccination is indicated annually in 

 pronounced anthrax districts. The breed, age and sex of the 

 animals do not appear to influence the results of the vaccination, 

 and young animals which were only shortly weaned may also 

 be vaccinated without danger and with promising results. 



Pasteur's protective vaccination is therefore indicated in 

 all places where the annual losses from anthrax exceed the 

 cost of the vaccination. 



The effectiveness of the vaccination has been proved by Pasteur 

 beyond a doubt through control experiments which he carried out be- 

 fore a commission appointed for this purpose in 1881 at Pouilly-le- 

 Fort. Of 50 sheep 25 were regularly vaccinated with his two vaccines 

 and 14 days after the second vaccination they were inoculated with 

 anthrax material, together with the 25 control animals. The results 

 showed that inside of 2 days all of the 25 control animals died of anthrax, 

 while all of the 25 vaccinated sheep remained alive. 



Up to the end of the year 1899, 708,980 cattle and 4,971,494 sheep had been 

 vaccinated successfully in France, as a result of which the entire annual loss over a 

 period of 12 years dropped to an average of 0.34% in cattle and to 0.94% in sheep. 



In Hungary the first vaccinations were carried out in 1881 on Azary 's initia- 

 tive. Thuillier, Pasteur's assistant, applied them first at the Veterinary Institute 

 at Budapest with very favorable results, while the later ones in Kapuvar were less 

 favorable. As vaccination gave very good results in practice, this protective treat- 

 ment was soon taken up very extensively. During the period of 15 years between 

 1886 and 1900, 53,843 horses, 1,015,700 cattle and 2,279,221 sheep were vaccinated. 



