440 Chapter XIV 



Previous to these researches on the protective and agglutinative 

 properties, Stern 1 had already put the question : May we not draw 

 gome general conclusion as to the bactericidal power of the blood 

 serum of convalescents from typhoid fever? He found that the 

 typhoid coccobacilli did not thrive so well in the blood serum of 

 persons in good health as in that of convalescents, in which they give 

 abundant cultures. Widal and Sicard (Lc.) subjected this question 

 to a fresh examination, and showed that in this respect there 

 exists no constant or marked difference. Thus, in ten samples of 

 serums from individuals who had never been under the influence of 

 the typhoid infection, four were found to be bactericidal for the 

 typhoid coccobacillus. In twelve other samples, drawn from con- 

 valescents from typhoid fever, five exhibited a bactericidal power 

 against the same micro-organism. 



All the researches made on acquired immunity after recovery from 

 typhoid fever demonstrate clearly that, in this case, it is impossible to 

 attribute it to humoral modifications, which are usually more transi- 

 tory than the immunity. 



The immunity which follows an attack of cholera is far from being 

 either as powerful or as prolonged as that which follows typhoid fever. 

 Certain individuals have contracted cholera twice during the same 

 epidemic, but such cases are exceptional, whilst acquired immunity, 

 temporary at least, may be looked upon as the general rule. Many 

 points in the pathogenesis of intestinal cholera are still obscure ; 

 nevertheless we are justified in affirming that this disease is a real 

 intoxication by the cholera poison manufactured, in the small intestine 

 of man, by Koch's vibrios. The action of the vibrionic toxin is 

 sufficient to set up a grave and often fatal attack of cholera ; but in 

 the majority of cases a secondary infection by the vibrio which pene- 

 [462]trates into the intestinal wall, denuded of its epithelial layer, is 

 associated with the action of the poison. Sometimes this micro- 

 organism becomes generalised in the animal, and is found in the 

 blood and in many of the organs. 



The facts I have here briefly summarised may be utilised to explain 

 certain characters which are found in the fluids of individuals who have 

 recovered from an attack of cholera. Soon after the discovery of the 

 tetanus and diphtheria antitoxins, and almost immediately after the 

 demonstration of the protective power of the blood, taking advantage 

 of the epidemic of Asiatic cholera, which developed in Europe from 

 1 Deutsche med. Wchnschr., Leipzig, 1892, S. 827. 



