1 68 BACTERIOLOGY. 



be inert in guinea-pigs and rabbits. Bichromate 

 of potash added to a cultivation in the proportion 

 f TTOOO -5-000 ave a f ter three days, a new 

 growth, which killed rabbits, guinea-pigs, and half 

 the sheep inoculated; after ten days, rabbits and 

 guinea-pigs, but not sheep ; and after a longer 

 time even guinea-pigs were unaffected. 



In other diseases similar results have been 

 obtained. 



Arloing, Cornevin, and Thomas found that by 

 inoculating a small quantity of the virus of symp- 

 tomatic anthrax anywhere in the subcutaneous 

 connective tissue, or a moderate quantity at the 

 root of the tail, and even by intravenous injection, 

 immunity was obtained from a virulent dose. 



In swine-erysipelas, Pasteur and Thuillier ob- 

 tained attenuated virus upon quite another principle. 

 They discovered that by passing the virus through 

 pigeons the virulence was increased, but by passing 

 it through rabbits it was progressively diminished. 

 Thus a virus was obtained from the rabbit, which 

 produced only a mild disease in pigs, and after 

 recovery complete immunity. Similarly in rabies 

 Pasteur finds that passage of the virus through 

 various animals considerably modifies its properties. 

 By inoculating a monkey from a rabid dog, and 

 then passing the virus through other monkeys, the 

 virulence is diminished ; but by inoculating a rabbit 

 from the dog, and passing the virus from rabbit 

 to rabbit, the virulence is increased. More recently 



