CHAPTER XVII. 



CHOLERA. 



Introductory. It is no exaggeration of the facts to say that 

 previously to 1883 practically nothing of value was known regard- 

 ing the nature of the virus of cholera. In that year Koch was 

 sent to Egypt, where the disease had broken out, in charge of a 

 Commission for the purpose of investigating its nature. In the 

 course of his researches he discovered the organism now generally 

 known as the " comma bacillus " or the " cholera spirillum." 

 He also obtained pure cultures of the organism from a large 

 number of cases of cholera, and described their characters. The 

 results of his researches were given at the first Cholera Conference 

 at Berlin in 1884. 



Since Koch's discovery, and especially during the epidemic in 

 Europe in 1892-93, spirilla have been cultivated from cases of 

 cholera in a great many different localities, and though this 

 extensive investigation has revealed the invariable presence in 

 true cholera of organisms resembling more or less closely Koch's 

 spirillum, certain difficulties have arisen. For it has been found 

 that the cultures obtained from different places have shown con- 

 siderable variations in their characters, and, further, spirilla 

 which closely resemble Koch's cholera spirillum have been 

 cultivated from sources other than cases of true cholera. There 

 has therefore been much controversy, on the one hand, as to the 

 signification of these variations, whether they are to be regarded 

 as indicating distinct species or merely varieties of the same 

 species, and on the other hand, as to the means of distinguishing 

 the cholera spirillum from other species which resemble it. These 

 questions will be discussed below. 



In considering the bacteriology of cholera it is to be borne in 

 mind that in this disease, in addition to the evidence of great 

 intestinal irritation, accompanied by profuse watery discharge, and 



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