420 BACTERIOLOGY. 



Cultures from the different organs or from the oedema- 

 tous fluid about the point of inoculation result in growth 

 of bacillus anthracis. 



The amphibia, dogs, and the majority of birds are 

 not susceptible to this disease. Rats are difficult to 

 infect. Rabbits, guinea-pigs, white mice, gray house- 

 mice, sheep, and cattle are susceptible. Infection may 

 occur either through the circulation, through the air- 

 passages, through the alimentary tract, or, as we have 

 just seen, through the subcutaneous tissues. 



PROTECTIVE INOCULATION. 



The most noteworthy application of artificially pre- 

 pared living vaccines to the protection of animals 

 against infection is seen in connection with anthrax 

 in sheep and in bovines. 



By a variety of procedures the virulent anthrax 

 bacillus may be in part or totally robbed of its patho- 

 genic properties. It is through the very mild consti- 

 tutional disturbance, caused in animals vaccinated with 

 such weakened cultures^ that protection is often afforded 

 against the severer, frequently fatal, form of the infec- 

 tion. 



Without reviewing the various methods that have 

 been employed for attenuating the virulence of this 

 organism to a degree suitable for protective vaccina- 

 tion, it will suffice to say that the most satisfactory 

 results have been obtained by long-continued cultiva- 

 tion (ten to thirty days) at a temperature of from 42 

 to 43 C. In this procedure the spore-free, virulent 

 bacillus anthracis, obtained directly from the blood of 

 a recently dead animal, is brought at once into sterile 



