422 CHOLERA. 



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 con- 

 form closely with Koch's description, though variations un- 

 doubtedly 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 toxines 

 give as 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 Koch's spirillum is the cause of the 

 disease, have been of the greatest value in the diagnosis of 

 the disease. And lastly, the results of Haffkine's method 

 of preventive inoculation in the human subject, which are 

 on the whole favourable, also supply additional evidence. 

 If all these facts are taken together, we consider the con- 

 clusion must be arrived at that the growth of Koch's spirillum 

 in the intestine is the immediate cause of the disease. This 

 does not exclude the probability of an important part being 

 played by conditions of weather and locality, though such 

 are very imperfectly understood. Pettenkofer, for example, 

 recognises two main factors in the causation of epidemics, 

 which he designates x and y, and considers that these two 

 must be present together in order that cholera may spread. 

 The x is the direct cause of the disease an organism 

 which he now admits to be Koch's spirillum ; the y in- 

 cludes climatic and local conditions, e.g., state of ground- 

 water, etc. 



Difficulty does not arise, however, so much with regard 

 to the causal relationship of Koch's spirillum to cholera 

 as in connection with various organisms which have been 



