SPIRILLA RESEMBLING CHOLERA SPIRILLUM 415 



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

 its toxins 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 conclusion 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, 

 recognised two main factors in the causation of epidemics, which 

 he designated x and y, and considered 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 admitted 

 to be Koch's spirillum ; the y includes climatic and local con- 

 ditions, e.g. state of ground-water, etc. 



Other Spirilla resembling the Cholera Organism. These 

 have been chiefly obtained either from water contaminated by 

 sewage or from the intestinal discharge in cases with choleraic 

 symptoms. Some of them differ so widely in their cultural and 

 other characters (some, for example, are phosphorescent) that no 

 one would hesitate to classify them as distinct species. Others, 

 however, closely resemble the cholera organism. 



The vibrio berolinensis, cultivated by Neisser from Berlin sewage 

 water, differs from the cholera organism only in the appearance of its 

 colonies in gelatin plates, its weak pathogenic action, and its giving a 

 negative result with Pfeiffer's test. It, however, gives the cholera-red 

 reaction. The vibrio Danubicus, cultivated by Heider from canal water, 

 also differs in the appearance of its colonies in plates, and also reacts 

 negatively to Pfeiffer's test ; in most respects it closely resembles the 

 cholera organism. Another spirillum (v. Ivanoff] was cultivated by 

 Ivanoff from the stools of a typhoid patient after these had been diluted 

 with water. The organism differed somewhat in the appearance of its 

 colonies and in its great tendency to grow out in the form of long 

 threads, but Pfeiffer found that it reacted to his test in the same way as 

 the cholera organism, and he considered that it was really a variety of 

 the cholera organism. No spirilla could be found microscopically in the 



