TEXT-BOOK OF BACTERIOLOGY. 265 



blood heat, a multifariously-folded, wrinkled, closely-connected 

 skin almost characteristic of the culture of comma bacilli. The 

 mass of the fluid is only very slightly dimmed; only by shaking 

 the glasses there arise from the bottom a few heaps of baeteria, 

 which are then equally distributed throughout the fluid. 



It is worthy of notice that the cholera bacteria show a particu- 

 larly strong growth in a strongly-diluted bouillon, for instance, if 

 mixed with 6 to 10 parts of water. According to Weibel's exami- 

 nations (mentioned in discussing the Spirillum rubrum), we have to 

 deal in this special case with a quality common to almost all vibri- 

 ones and spirilli, which has been used even for diagnostic purposes. 



The cholera bacteria may also thrive and multiply in sterilized 

 milk without perceptibly changing the fluid a fact to be consid- 

 ered in connection with their transmission to man. In non-sterilized 

 milk they live for only a short period, as Kitasato has shown; 

 acidification soon appearing destroys the cholera bacilli in a rela- 

 tively short time, but so much time usually elapses that milk in 

 most cases would be used before this occurs, and therefore cholera 

 bacteria having entered the fluid would be received alive. 



The thorough examinations by Wolff hiigel and Riedel have 

 finally established the important fact that the comma bacilli sus- 

 tain themselves in sterilized water, no matter whether it is obtained 

 from river, well, or aqueduct. The increase begins some time after 

 the sowing and reaches its highest point on about the seventh day, 

 but the vibriones may be shown in a state capable of development 

 and in considerable number even after months. This state of things 

 is different, indeed, in non-sterilized water, the cholera bacteria 

 being here almost fully dislodged by existing micro-organisms in a 

 few days. 



An observation of Koch shows that the artificial conditions of 

 this experiment do not always correspond to the natural state of 

 things. He succeeded in finding comma bacilli in an Indian tank 

 i.e., in the greatly-polluted water of one of those marshy reser- 

 voirs into which the Hindoos empty their natural offal of any kind 

 and from which they also take their water for drinking and other 

 uses without any hesitation. This significant fact proves that the 

 comma bacilli also thrive in nature outside of the human body, and 

 are able to lead, for a shorter or longer period, a saprophytic mode 

 of life, and are not characterized as genuine parasites, like the 

 tubercle bacilli. 



That the cholera bacteria, while they are growing, change those 

 media on which they develop, is shown by the fact that the gelatin 

 is regularly liquefied under their influence. Brieger has been able 



