Morphology 



497 



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. 



Fig. 146. Cholera spirilla. 



Morphology. The micro-organism described by Koch, 

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

 a short rod about half the length of a tubercle bacillus, 

 considerably stouter, with rounded ends, and a distinct 

 curve, so that the original name by which it was known, 

 the ''comma bacillus," applies very well (Figs. 146, 14?)- 



A study of the growth of the organism and the forms 

 which it assumes upon different culture media soon con- 

 vinces us that we have to do with an organism in no way 

 related to the bacilli. When the conditions of nutrition 

 are good, multiplication by fission progresses with rapidity ; 

 but when adverse conditions arise, long spiral threads 

 unmistakable spirilla develop. Frankel found that the 

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