THE MULTIPLICATION OF MICRO-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 103 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, 

 in 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 9-1 5 C. 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 



