636 Bubonic Plague 



tion against those of one animal not necessarily protecting 

 the organism against those of other animals. 



Bielonovsky * finds that broth, agar, and serum cultures 

 of the plague bacillus possess the property of hemolyzing 

 the blood of normal animals. The hemolytic power of fil- 

 trates of plague cultures increases up to the thirteenth or 

 fourteenth day, then gradually diminishes, but without 

 completely disappearing. The hemolysins are notably 

 resistant to heat, not being destroyed below 100 C. 



Immunity. Kitasato's experiments first showed that it 

 was possible to bring about immunity against the disease, and 

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

 have successfully immunized large animals (horses, sheep, 

 and goats). The serum of the immunized animals contains an 

 antitoxin capable not only of preventing the disease, but also 

 of curing it in mice and guinea-pigs and probably in man. 



Haffkine's Prophylactic. Haffkine f followed his plan 

 of preventive inoculation as employed against cholera, and 

 has invented a mode of prophylaxis based upon the use 

 of devitalized cultures. Bouillon cultures are used, and 

 small floating drops of butter are employed to make the 

 " islands'' of plague bacilli float. The cultures are grown 

 for a month or so, successive crops of the island-stalactite 

 growth being precipitated by agitating the tube. In this 

 manner an "intense extracellular toxin" containing large 

 numbers of the bacilli is prepared. The culture was killed 

 by exposure to 70 C. for one hour, and used in doses of 1-3 

 c.c. as a preventive inoculation. 



An interesting collection of statistics, showing in a con- 

 vincing manner the value of the Haffkine prophylactic, is 

 published of Leumann, of Hubli. The figures, together 

 with a great deal of interesting information upon the subject, 

 can be found in the paper upon "A Visit to the Plague Dis- 

 tricts in India," by Barker and Flint. J 



The immunity conferred by the Haffkine prophylactic 

 lasts about a month. The preparation must never be used 

 if the person has already been exposed to infection, and is 

 in the incubation stage of the disease, as it contains the 

 toxins of the disease, and therefore greatly intensifies the 

 existing condition. When injected into healthy persons, 



* "Arch, des Sci. Biol.," Tome x, No. 4, St. Petersb., 1904. 

 f " Brit. Med. Jour.," June 12, 1897. 

 J " New York Med. Jour.," Feb. 3, 1900. 



