ALLIED ORGANISMS 473 



no organism which gave all the cultural and serum tests 

 (agglutination and Pfeift'er's reaction) of the cholera spirillum. 

 In 1905, however, Gotschlich obtained six different strains of a 

 spirillum which conformed in all these respects. The organisms 

 were obtained at El Tor from the intestines of pilgrims who had 

 died with dysenteric symptoms, and there were no cases of 

 cholera in the vicinity. The organisms in question, however, 

 differ from the cholera organism in having marked hsemolytic 

 action, and also in producing a rapidly acting extracellular toxin. 

 Kraus and others have found, on comparing anti-sera to the 

 cholera and El Tor spirilla, that while the anti-bacterial pro- 

 perties are similar there is a difference in antitoxic action. The 

 El Tor antitoxin neutralises the cholera toxin, but a cholera 

 antitoxin has no effect on the El Tor toxin ; the El Tor spirillum 

 is thus peculiar as regards its toxic products. There is accord- 

 ingly difference of opinion as to whether these organisms are to 

 be regarded as a distinct species or as true cholera spirilla. In 

 view, however, of what we know of variations in the type of the 

 cholera organism, the latter possibility is probably the case. 



Paracholera. — More recent observations have shown that 

 there occur groups of cases with choleraic symptoms or merely 

 diarrhoea, in which the spirilla present differ in certain respects 

 from the cholera spirillum. Such cases have been studied 

 especially in India and Egypt, and the term paracholera has 

 been applied. To speak generally, the symptoms are milder 

 than those of true cholera, fatal results being comparatively rare, 

 and the infection does not tend to spread as an epidemic. In 

 addition to those suffering from the disease, similar organisms have 

 been obtained from the stools of contacts — that is, carriers occur. 

 In those affected, the spirilla are often present in the stools in large 

 numbers, and on isolation are found to have the morphological 

 and cultural characters of the cholera spirillum ; they are also 

 virulent to the guinea-pig on intra-peritoneal injection. They 

 are, however, markedly hsemolytic, when tested both on blood- 

 agar plates and with suspensions of red corpuscles. Further, they 

 differ serologically from the cholera organism — they are not 

 agglutinated by an anti-cholera serum and they react negatively 

 in Pfeiffer's reaction. They also differ serologically amongst 

 themselves, and several varieties may in this way be distinguished 

 (Mackie). In this group of organisms, producing relatively a 

 mild form of disease, we have manifestly a close analogy to the 

 case of the paratyphoid bacilli. 



Anti-Cholera Inoculation. — Haffkine's method for inoculation 

 against cholera exemplifies the above principles. It depends 



