278 MICRO-ORGANISMS IN WATER 



It slioulcl be mentioned tliat Dunham ^ found as far 

 back as 1887 that the cholera bacilli multiplied very 

 rapidly in broth containing 1 per cent, of peptone, to 

 which 0*5 per cent, of common salt was added. Koch ^ 

 mentions that no advantage appears to have been taken 

 of this fact in the methods employed for the detection 

 of the cholera bacillus in dejecta, until Dunbar brought 

 it into practical use during the epidemic of cholera, 

 in Hamburg in 1892. Since that time the following 

 method has been employed by Koch and others for the 

 identification of cholera bacilli in water : — 



100 c.c. of the water under examination receives- 

 1 per cent, of peptone and 1 per cent, of common salt, 

 after which the mixture is placed in the incubator- 

 and kept at 37° C. After intervals of ten, fifteen, and 

 twenty hours agar-plates are poured, whilst a careful 

 microscopic examination is also made of the mixture. 

 Any colonies which appear on the agar-plates and 

 resemble those of the cholera bacillus are examined 

 microscopically, and whenever comma-shaped forms are 

 found they are inoculated into fresh tubes so as to 

 enable them to be further tested by means of the indol- 

 reaction, and also by animal inoculations. Koch states 

 that by using the above method he was able to demon- 

 strate the presence of cholera bacilli in the river Elbe at 

 Hamburg, in a well at Altona, in the river Saal, and in 

 other places. 



As is well known, waters of very various origin 

 frequently contain comma-shaped bacteria, which, like* 

 the cholera bacillus, also collect in the upper layers of 

 the liquid, so that every care must be exercised to 



1 ( f 



' Zur cliemischen Reaction der Cholerabacterien,' Zeitschrift /► 

 Hygiene, vol. ii., 1887, p. 337. 



^ ' Der augenblickliche Stand der Choleradiagnose,' Zeitschrift /.. 

 Hygiene, vol. xiv., 1893, pp. 326 and 336. 



