560 PATHOGENIC BACTERIA. 



Kitasato found that the bacillus was killed by two 

 hours' exposure to 0.5 per cent, carbolic acid, and also 

 by exposure to a temperature of 8o° C. for five minutes. 

 Ogata found that the bacillus was instantly killed by 5 

 per cent, carbolic acid, and in fifteen minutes by 0.5 per 

 cent, carbolic acid. In o. 1 per cent, sublimate solution 

 it is killed in five minutes. 



According to Wyman, the bacillus is killed by exposure 

 to 55° C. for ten minutes. The German Plague Com- 

 mission found that the bacilli were killed by exposure to 

 direct sunlight for three or four hours ; and Bowhill x 

 found that they are killed by drying at ordinary room 

 temperatures in about four days. 



It seems possible to make a diagnosis of the disease in 

 doubtful cases by examining the blood, but it is admitted 

 that a good deal of bacteriologic practice is necessary for 

 the purpose. 



Abel finds that the blood may yield fallacious results 

 because of the rather variable appearance of the bacilli, 

 which are sometimes long and easily mistaken for other 

 bacteria. He deems the best tests to be the inoculation 

 of broth-cultures and subsequent inoculation into ani- 

 mals, which he advises should have been previously 

 vaccinated against the streptococcus. Plague bacilli 

 persist in the urine a week after convalescence. 



Wilson, of the Hoagland Laboratory, found the thermal 

 death-point of the organism was one or two degrees 

 higher than that of the majority of pathogenic bacteria 

 of the non-sporulating variety, and that, unlike cholera, 

 the influence of sunlight and desiccation cannot be relied 

 upon to limit its viability. 



Kitasato' s experiments first showed that it is possible 

 to bring about immunity to the disease, and Yersin, 

 working in India, and Fitzpatrick, in New York, have 

 successfully immunized large animals (horses, sheep, 

 goats). The serum of these immunized animals con- 

 tains an antitoxin capable not only of preventing the dis- 



1 Manual of Bacteriological Technique and Special Bacteriology, 1899, p. 197. 



