THE MULTIPLICATION OF MICKO-ORGANISMS 253 



an old and half dried up culture none were found after 

 7 days. The fluorescent bacillus still exhibited as many 

 .as 85,000 per c.c. after 77 days. The typhoid bacillus, 

 "which after 11 days showed 1 million per c.c. to be 

 present, after 77 days 72,000, and after 108 days 7,000. 



In these experiments the organisms were exposed 

 to an uninterrupted low freezing temperature ; but 

 Prudden states that if the temperature is varied, and 

 the ice allowed to thaw and then freeze again, the pro- 

 cess is far more detrimental to the organisms. Thus, 

 typhoid bacilli frozen for 24 hours, interrupted by 3 

 thawings, were reduced in this time from 40,000 at the 

 commencement to 90, and were entirely destroyed by 

 the end of 3 days. 



Eecently experiments have been made by one of us, 

 m conjunction with Dr. Templeman of Dundee, on the 

 ■effect of repeatedly freezing water containing the spores 

 and bacilli of anthrax respectively. A mixture of 

 spores and bacilli was obtained from an agar-agar cul- 

 ture of anthrax, which had been growing for 12 days 

 at 18-20° C, and was introduced into steam-sterilised 

 Dundee water. This infected water at the outset of the 

 experiments yielded about 15,000 colonies to the c.c, 

 and during a period extending over three months it was 

 frozen by means of a mixture of ice and salt no less 

 than twenty-nine times ; on each occasion the tempe- 

 rature was rapidly reduced to — 20° C. by means of 

 the freezing mixture, about twenty-four hours elapsing 

 before the whole of the ice produced in the water had 

 again disappeared, and during the intervals between 

 the successive freezings the infected water was kept in 

 a dark cupboard at 9-15° 0. After being frozen twenty- 

 nine times this water yielded about 3,000 colonies to 

 the c.c, whilst some of the same water, preserved as 

 a control without being subjected to freezing, yielded 



