6o6 



Asiatic Cholera 



about in clothing and upon food-stuffs; how they can be 

 brought to articles of food by flies that have preyed upon 

 cholera excrement ; and other interesting modes of infection. 

 The literature is so vast that it is scarcely possible to men- 

 tion even the most instructive examples. A bacteriologist 

 became infected while experimenting with the cholera spirilla 

 in Koch's laboratory. It is commonly supposed that the 

 cholera organism may remain alive in water for an almost 

 unlimited length of time, but experiments have not shown 

 this to be the case. Thus, Wolffhiigel and Riedel have 

 shown that if the spirilla be planted in sterilized water they 

 grow with great rapidity after a short time, and can be found 

 alive after months have passed. Frankel, however, points 

 out that this ability to grow and remain vital for long peri- 

 ods in sterilized water does not guarantee the same power 

 of growth in unsterilized water, for in the latter the simul- 

 taneous growth of other bacteria serves to extinguish the 

 cholera spirilla in a few days. 



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Fig. 208. Cholera spirilla. 



Morphology. The micro-organism described by Koch, 

 and now generally accepted to be the cause of cholera, is 

 a short rod i to 2 ^ in length and 0.5 ^ in breadth, with rounded 

 ends, and a distinct curve, so that the original name by which 

 it was known, the " comma bacillus," applies very well. One 

 of the most common forms is that in which two short curved 

 individuals are conjoined in an S-shaped curve. 



When the conditions of nutrition are good, multipli- 



