254 MICRO-ORGANISMS IN WATER 



about 17,000 anthrax colonies per c.c. That the an- 

 thrax spores were practically unaffected by this repeated 

 application of cold was shown by the fact that the 

 first freezing already reduced the number of anthrax 

 colonies to about 3,500, so that the bacilli were pro- 

 bably destroyed in one freezing, and the spores which 

 had survived this first frost did not succumb either to 

 the twenty-eight refrigerations which followed. 



Very different was the behaviour of anthrax bacilli 

 free from spores, taken from a mouse dead of an- 

 thrax, and which were similarly introduced into steam- 

 sterilised Dundee water. This infected water yielded 

 in the first instance about 8,000 anthrax colonies per 

 c.c., and on examination two days subsequently, after 

 having been once frozen, 4 out of 6 plates were entirely 

 sterile, a fifth contained 2, and the sixth 7 anthrax 

 colonies per c.c. ; the control water, which had been 

 kept in the dark at 10-12 C., yielded on the same day 

 6, 10, 135, and 236 anthrax colonies per c.c. On the 

 fifth day the anthrax bacilli had disappeared altogether y 

 both from the water which had now been twice frozen, 

 as well as from the control which had been preserved 

 throughout at 10-12 C. 



As regards the behaviour of cholera bacilli in arti- 

 ficially frozen ice, Eenk : has shown that after five days' 

 uninterrupted exposure to a temperature of 0'5 and 

 7C. in a freezing mixture the bacilli are destroyed, 

 but that if the freezing was interrupted from six to seven 

 days were necessary for their annihilation. In these 

 experiments sterilised river Saale water was infected 

 with cholera broth cultures. In unsterilised Saale 

 water exposed to these low temperatures the cholera 

 bacilli disappeared after three days, and the ordinary 



1 ' Ueber das Verhalten der Cholerabacillen im Else,' Fortscliritte der 

 Med. 1893, No. 10, p. 396. 



