CHAPTER XXIV 



IN the Delta of the Ganges Asiatic cholera has been known for 

 centuries. Not until the nineteenth century, however, did it appear 

 in Europe and America. Traveling along the trade route it reached 

 Europe in 1830, and in 1832 it arrived in America by way of New 

 York and Quebec and spread west as far as the Mississippi. By 

 1849 it had traveled with the searchers for gold as far as California. 



Prior to 1883 nothing was known regarding the causal agent ; 

 in that year Koch discovered in the feces of cholera patients a 

 curved organism now generally 

 known as the "comma bacil- 

 lus " or " cholera spirillum." 

 Soon other observers obtained 

 comma-shaped organisms from 

 many other sources, and a 

 great deal of controversy arose 

 as to their classification. With 

 the advent of serological tests, 

 however, all of these organisms 

 except the vibrio of Koch were 

 shown to be unaffected by the 



. , . , FIG. 35. Cholera Spirilla. 



serum ot animals immunized 



to cholera and hence in no way connected with the disease. 



Morphology and Staining. The cholera spirillum appears in 

 stained preparations as a curved rod about 1.5 fi in length and 

 0.4 /u in width. A single organism may appear slightly curved 

 like a comma. Two organisms remaining attached and curved in 

 an opposite direction may produce a resemblance to the letter S, 

 while adherent in greater numbers they may appear as a long, 

 spiral filament (Fig. 35). The organism is actively motile although 



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