﻿STUDIES IN PLAGUE IMMUNITY. 159 



killed pest cultures in the human inoculations being pursued in this 

 city. Further results obtained by Kolle and his associates in Berlin, 

 and the animal experiments made here, having demonstrated that in 

 very susceptible animals at least, satisfactory immunization could only 

 exceptionally be produced by the methods of human inoculation then in 

 vogue, this laboratory recommended to the Commissioner of Health in 

 Manila the suspension of the human inoculations with killed cultures 

 of the pest bacillus, and has not since recommended to our Government 

 any method of protective inoculation against plague as an efficient pro- 

 cedure against the extension of this disease. However, further experi- 

 mentation, which I have carried on as continuously as was practicable 

 for the past year and a half, has demonstrated that a satisfactory im- 

 munity can be obtained in the guinea pig, an animal even more susceptible 

 to plague infection than is man, by the inoculation of living cultures 

 of plague bacilli of such attenuation that they are no longer dangerous 

 when injected into human beings. Therefore, this laboratory believes 

 that by the method of vaccination 5 against plague with suitable cultures, 

 we have probably an efficient measure for the control of this infectious 

 disease, and we recommend its adoption for this purpose. 



At present there is not sufficient plague in this city to warrant 

 the employment of general vaccination against the malady, but it is hoped 

 that the method may be given a thorough and careful trial in certain 

 districts of India where plague is always present in sufficient amounts 

 to justify its use. A preliminary report on the subject of vaccination 

 against plague was presented to the Manila Medical Society in November, 

 1905, and published in an earlier number of this Journal. In the 

 present article further evidence of the entire safety of vaccination in man 

 against plague with suitable cultures will be presented, together with 

 the experimental work which demonstrates conclusively the efficacy of 

 this procedure and its superiority to other methods of protective inocula- 

 tion, including those in which both natural and artificial plague aggressin, 

 so recently described, are employed. 



5 The term "vaccination" is employed in this article only in the sense in which 

 it was primarily used by Jenner and Pasteur (immunization with the living, 

 attenuated organism) and is not applied to forms of protective inoculation in 

 which the killed organisms or their extracts are employed. See Kolle's previous 

 remarks on this subject. 



"This Journal (1900), 1, 181. 



