GENERAL SUMMARY 461 



other than cholera cases, no organism which gave all the cultural 

 and biological tests (agglutination and Pfeiffer'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 uho had died with dysenteric symptoms, 

 and tliciv \\viv no cases of cholera in the vicinity. The organisms 

 in question, however, differ In mi the cholera organism in having 

 marked ha-niolvtic 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 properties 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 accordingly difference of opinion as to whether these organisms 

 are to be regarded as a distinct species or as true cholera spirilla 

 which had been carried by the patients, though no symptoms 

 resulted from their presence. This instance exemplifies well 

 the great difficulty which may surround the identification of a 

 particular organism obtained from non-cholera cases, and one 

 can hardly doubt that if cholera-like symptoms had been present 

 in the El Tor cases, the spirilla would have been accepted as 

 varieties of the cholera organism. None of the facts ascertained, 

 however, really affect the question as to the causal relationship 

 of Koch's spirillum to cholera, although they indicate the 

 difficulties which may attend the bacteriological diagnosis in 

 isolated cases of disease. 



General Summary. We may briefly summarise as follows 

 the facts in favour of Koch's spirillum being the cause of cholera : 

 First, there is the constant presence of spirilla in true cases of 

 cholera, which on the whole conform closely with Koch's 

 description, though variations undoubtedly occur. Moreover, 

 the facts known with regard to their conditions of growth, etc., 

 are in conformity with the origin and spread of cholera epidemics. 

 Secondly, the experiments on animals with Koch's spirillum or 

 its toxins give ;is definite results as one can reasonably look for 

 in view of the fact that animals do not suffer naturally from the 

 disease. Thirdly, the experiments on the human subject and 

 the results of accidental infection by means of pure cultures are 

 also strongly in favour of this view. Fourthly, the agglutinative 

 and protective properties of the serum of cholera patients and 

 convalescents constitute another point in its favour. Fifthly, 

 bacteriological methods, which proceed on the assumption that 



