BACILLUS PESTIS 397 



of the disease; while if infection occurs via the hands and 

 arms, the buboes appear first in the axillary region. As a 

 rule, the wound through which infection is received shows 

 little or no inflammatory reaction. 



The blood of patients convalescing from plague has an 

 agglutinating action upon fluid cultures of the plague bacillus 

 analogous to that observed when the blood-serum of typhoid 

 or of cholera patients is mixed with similar cultures of the 

 typhoid or the cholera bacillus. (See Agglutinins). 



Protective Inoculation; Vaccination. Active immunization 

 from plague infection by protective inoculation has been 

 variously attempted; by subcutaneous or intramuscular 

 injection of old bouillon cultures of bacillus pestis that had 

 been killed by heat; by similar injections of emulsions made 

 from agar-agar cultures of different ages suspended in 

 isotonic salt solution and likewise killed by heat; by the 

 injection of determined amounts of extractives from plague 

 bacilli; by the injection of mixtures of dead plague bacilli 

 and plague immune serum; by injection of the filtrate from 

 fluid cultures of the organism; by the injections of peri- 

 toneal exudates and organ extracts of animals infected with 

 plague; and by the injection of attenuated living cultures 

 of the organism. For the most part these efforts have been 

 experimental, that is to say, they have been made upon 

 animals susceptible to plague infection, notably guinea-pigs 

 and monkeys. In the problem of protecting human beings 

 from plague, dead cultures have been used practically to 

 the exclusion of all other methods. The method of Haffkine 1 

 has enjoyed more favor than any of the others, though it 

 is difficult to determine its protective value with any degree 

 of exactness. 2 This method consists in the subcutaneous 



1 British Med. Jour., 1897, No. 12. 



2 Bull, de 1'Institut Pasteur, 1906, No. 4, p. 825. 



