Haffkine Prophylactic 597 



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.* 



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 

 it always produces some fever, slight local swellings, and 

 malaise. 



Wyssokowitsch and Zabolotny,f whose studies have al- 

 ready been quoted, used 96 monkeys in the study of the value 

 of the "plague serums," and found that when treatment is 

 begun within two days from the time of inoculation the 

 animals can be saved, even though symptoms of the disease 

 are marked. After the second day the treatment cannot 

 be relied upon. The dose necessary was 20 c.c. of a serum 

 having a potency of i : 10. If too little serum was given, 

 the course of the disease was retarded and the animal im- 

 proved for a time, then suffered a relapse, and died in from 

 thirteen to seventeen days. The serum also produced 

 immunity, but of only ten to fourteen days' duration. Im- 

 munity lasting three weeks was conferred by inoculating 

 a monkey with an agar-agar culture heated to 60 C. If 

 too large a dose of such a culture was given, however, the 

 animal was enfeebled and remained susceptible. 



Of Yersin's serum, which is prepared by immunizing 

 horses against the toxins and cultures of the bacillus in the 

 usual manner, 5 c.c. doses have been found to confer an im- 

 munity lasting for about a fortnight. Larger doses confer a 

 longer immunity. For the treatment of the developed 

 disease in man, doses of 50 and even 100 to 200 c.c. seem 

 necessary to produce the desired effect. 



OTHER MICRO-ORGANISMS OF THE PLAGUE GROUP. 



The Bacillus pestis is a member of a group of organisms 

 collectively known as the bacilli of hemorrhagic septicemia. 

 Two of these organisms are of sufficient interest to deserve 

 special mention. 



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

 t Loc. cit. 



