Immunity 599 



The immunity conferred by the Haffkine prophylactic is supposed 

 to last about a year. The preparation must never be used if the 

 person has already been exposed to infection, and is in the incuba- 

 tion stage of the disease, as it contains the toxins of the disease, and 

 therefore greatly intensifies the existing condition. When injected 

 into healtiiy persons it always produces some fever, slight local 

 swellings, and malaise. 



KoUe and Otto* from experimental studies of plague immunity 

 in rats, came to the conclusion that a prophylactic injection con- 

 sisting of a culture of attenuated plague bacilli would have a miuch 

 more powerful and lasting effect than one consisting of killed bacilli. 

 The same conclusion was reached by KoUe and Strongf and the 

 first use of living cultures for preventive inoculation in human beings 

 was by Strong J who found them to be devoid of danger, and is 

 hopeful regarding their efficaay. 



Besredka§ advises the use of a killed culture sensitized by the 

 appUcation of immune serum. Such vaccine seems to be productive 

 of long enduring immunity when tried upon experimental animals. 



Rowland II is under the impression that the essential immunizing 

 antigen is in the bacterial nucleoproteins. These he extracts from 

 the bacterial cells by treating them while moist with anhydrous 

 sodium sulphate, freezing, permitting the water to be absorbed by 

 the chemical, thawing, and then filtering off the fluid at 37°C. The 

 filtrate thus obtained is highly toxic, fatal to rats in minute doses and 

 capable of effecting immunization. 



II. Passive Immunity against plague, through the employment 

 of the serums of experimentally immunized animals for hypo- 

 dermatic injection into man was tried soon after the discovery of 

 the plague bacillus. Kitasato's experiments first showed that it 

 was possible to bring about immimity 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 immimized animals contains specific agglutinins 

 and bacteriolysins as weU as an antitoxin, capable not only of pre- 

 venting the disease, but also of curing it in mice and guinea-pigs 

 and probably in man. 



Study of plague serums has been conducted by Yersin, Calmette 

 and Borrel,** but their value as a prophylactic lacks demonstration. 



Wyssokowitsch and Zabolotny,tt used 96 monkeys in the study 

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



* "Deutsche med. Wochenschrift," 1903, p. 493; "Zeitschrift fiir Hygiene," 

 1903, XLV, S07. 



t "Deutsche med. Wochenschrift," 1906, xxxii, 413. 



I "Jour. Medical Research," N. S., 1908, xviii, 325. 



8 "Bull, de rinst. Pasteur," 1910, viii, 241. 

 A ''Jour, of Hygiene," 1912, xn, 344. 

 * * "Ann. de I'Inst. Pasteur," 1895, ix, 589. 

 IT Loc. cit. 



