IMMUNITY AND SUSCEPTIBILITY. 6 1 



with a temperature equally high, readily falls a victim 

 to anthrax without a cold bath. 



(b} By altering the chemistry of the blood by changing 

 the diet or by hypodermic injection. L,eo found that 

 when white rats were injected with or fed upon phlorid- 

 zin an artificial glycosuria resulted which destroyed their 

 natural resistance to anthrax. Hankin found that rats, 

 which possess considerable immunity to anthrax, could 

 be made susceptible by a diet of bread. Platania suc- 

 ceeded in producing anthrax in dogs, frogs, and pigeons, 

 naturally immune, by subjecting them to the influence 

 of curare, chloral, and alcohol. 



(c) By diminishing the strength of the animal. Roger 

 by compelling white rats to turn a revolving wheel until 

 exhausted destroyed their immunity to anthrax. 



(ct) By removing the spleen. Bardach has shown that 

 the chances of recovery from specific diseases are greatly 

 lessened by the removal of the spleen. 



(e) By combining two different species of bacteria, either 

 of which, when injected alone, would be harmless or of 

 slight effect. Roger found that when animals immune 

 to malignant edema were simultaneously injected with 

 i to 2 c. cm. of a culture of Bacillus prodigiosus and the 

 bacillus of malignant edema, they would contract the 

 disease. Pawlowski found that when rabbits, which 

 are very susceptible to anthrax, were simultaneously in- 

 jected with anthrax and prodigiosus, they recovered 

 from the anthrax, as if the harmless microbe possessed 

 the power of neutralizing the products of the patho- 

 genic form. 



Sometimes an apparent immunity depends upon the 

 attenuation of the culture used for inoculation, and the 

 erroneous results to which such a mistake may lead are 

 obvious. Should a culture become attenuated, its viru- 

 lence may sometimes be increased by inoculating it into 

 the most susceptible animal, then from this to a less 

 susceptible, and then to an immune animal. The viru- 

 lence of anthrax is increased by inoculation into pigeons, 



