ASIATIC CHOLERA AND THE CHOLERA ORGANISM 841 



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 immunized animals specific 

 bacteriolytic and agglutinating substances are found. The discovery 

 of bacteriolytic immune bodies, in fact, was made by means of 

 cholera spirilla. Both the bacteriolysins and the agglutinins, be- 

 cause of their specificity, are of great importance in making a bac- 

 teriological diagnosis of true cholera organisms. 



Prophylactic Vaccination. Active immunization of cholera was 

 one of the first methods of prophylactic vaccination attempted in 

 the bacteriological era of infectious disease study. The work was 

 done by a Spanish bacteriologist, Ferran, who had been a pupil of 

 Pasteur, and as early as 1884 carried out immunization experiments 

 with cholera on guinea.-pigs. Ferran, 15 in accordance with the 

 methods prevalent at that time, worked with attenuated cholera 

 cultures and developed a method of attenuation which depended 

 upon room-temperature cultivation on gelatin. He tried this method 

 on human beings in Spain in 1885 with results which seemed to him 

 encouraging. Subsequent to this many different vaccines have been 

 developed. Haffkine 16 worked intensely on the subject and observed 

 the results of vaccination on an enormous number of people in 

 India, over a period of more than ten years. Haffkine 's virus has 

 undergone a number of modifications since he first used it. He, 

 too, made use of living cultures, beginning his experiments with 

 attenuation of cholera spirilla by cultivation at temperatures of 

 40 and over, using, at first, a less virulent and next a more virulent 

 strain. Later, it was found that the cultures attenuated by cultiva- 

 tion at increased temperatures were not necessary, and it appears 

 at the present time that in most places only cultures of a virulence 

 enhanced by passage through guinea-pigs are used. The extensive 

 experimental work in India mentioned above seems to have shown 

 that there is a distinct prophylactic value in the use of Haffkine 's 

 virus. 



Other observers have made use chiefly of killed cultures. The 

 French vaccine made at the Pasteur Institute consists of broth 

 cultures killed at 50. Kolle 17 grows his cholera spirilla on agar, 



15 Ferran, Comptes rend, de 1'acad. des sciences, 1885. 



"Haffkine, Bull, med., 1892. 



" Kolle and Schurmann, Kolle and Wassermann Handb., Vol. 4, Second Edition. 



