590 PATHOGENIC MICROORGANISMS 



Cholera Immunization. — One attack of cholera confers protection 

 against subsequent infection. Active immunization of animals may- 

 be accomplished by inoculation of dead cultures, or of small doses of 

 living bacteria. In the serum of immmiized animals specific bacterio- 

 lytic and agglutinating substances are found. The discovery of bacte- 

 riolytic immune bodies, in fact, was made by means of cholera spirilla. 

 Both the bacteriolysins and the agglutinins, because of their specificity, 

 are of great importance in making a bacteriological diagnosis of true 

 cholera organisms. 



Protective inoculation of man has been variously attempted by 

 Ferran ' and others. Experiments on a large scale were done, more re- 

 cently, by Haffkine,^ who succeeded in producing an apparently dis- 

 tinct prophylactic immunization by the subcutaneous inoculation of 

 dead cholera cultures. Similar immunization with bacterial filtrates 

 has been attempted by Bertarelli.' 



CHOLERA-LIKE SPIRILLA 



The biological group of the vibriones, to which the cholera spirillum 

 belongs, is a large one, numbering probably over a hundred separate 

 species. Most of these are of bacteriological importance chiefly because 

 of the difiiculties which they add to the task of differentiation, for while 

 some of them simply bear a morphological resemblance to the true 

 cholera vibrio, others can be distinguished only by their serum reac- 

 tions and pathogenicity for various animals. Additional difficulty, 

 too, is contributed by the fact that within the group of true cholera 

 organisms occasional variations in agglutinability and bacteriolytic 

 reactions may exist. Certain strains, too, the six El Tor cultures 

 isolated by Gottschlich, while in every respect similar to true cholera 

 spirilla, are considered as a separate sub-species by Kraus,^ because of 

 their ability to produce hemolytic substances, a function lacking in 

 other cholera strains. 



Spirillum Metchnikovi. — This spirillum was discovered by Gamaleia ^ 

 in the feces and blood of domestic fowl, in which it had caused an in- 

 testinal disease. Morphologically and in staining reactions it is identical 



• Ferran, Comptes rend, de I'acad. des sciences, 1885. 

 2 Hafkine, Bull, m^d., 1892. 



5 Bertarelli, Deut. med. Woch., 33, 1904. 



* Kraus, Kraus und Levaditi, "Handbuch,"' vol. i, p. 186. 

 f Gamakia, Ann. de I'inst. Pasteur, 1883. 



