662 



SCIENCE. 



[N. S. Vol. XVII. No. 434. 



In this experiment the results of the analysis 

 of control tubes left at the ordinary tempera- 

 ture have not been recorded. This appears to 

 the reviewer a serious defect, as the authors 

 seem to have entirely overlooked the fact that 

 the transfer of organisms from one fluid to an- 

 other, especially if these fluids be not isotonic, 

 generally results in the destruction of many 

 of the organisms, and that this fact renders it 

 ■impossible for them to determine the exact 

 part played by the lowered temperature. This 

 defect is somewhat remedied by a comparison 

 with a following independent series of experi- 

 ments on the effect of temperatures slightly 

 above the freezing point. Their conclusion 

 from this series is largely what our knowledge 

 would lead us to expect, namely, that typhoid 

 bacilli behave in water much as they do in 

 ice : " A large proportion of them are killed 

 by a few minutes' exposure to the unfavorable 

 conditions (cold ?) ; during the next few hours 

 the reduction proceeds pari passu with the 

 duration of the experiment; while a few 

 germs persist for some time." The results 

 differ from those obtained by actual freezing 

 in two respects. Freezing for short periods 

 produced varying and uncertain results ; ice 

 over twenty-four hotirs old showed a constant 

 reduction of over ninety per cent. In water 

 the period of uncertainty was much extended; 

 some of the water tubes containing half of 

 their germ contents after a week. Complete 

 sterilization,' however, ensued more often than 

 in frozen tubes. " The reduction in water at 

 10° C. does not seem to be greater than at 

 20° 0." Here, as was surmised above, the tem- 

 perature probably plays a minor part, and the 

 decrease is largely, no doubt, due to other un- 

 favorable conditions. We do not consider, 

 therefore, that the authors have established 

 in a more definite manner than their predeces- 

 sors the exact part played in the destruction 

 of bacteria by freezing and low temperatures. 

 Their experiments may indicate in a fair de- 

 gree the sequences of events when typhoid or 

 other bacilli are suddenly transferred to water 

 from some more favorable environment, but 

 do not establish the behavior of those organ- 

 isms which may have become accustomed to 

 such new surroundings. 



Our" attention has also been attracted by a 

 statement of the authors, that bacteria settling 

 to the bottom ' may soon perish for want of 

 air.' This statement must be born of pure 

 hypothesis, as cultures of typhoid bacilli will 

 in fact live for years anaerobically. 



The result of experiments on the viability of 

 typhoid bacilli in sterilized earth at various 

 temperatures was the following: Typhoid 

 bacilli in dry earth behave just as in water 

 and ice. They die out rapidly at first, and 

 their numbers are progressively reduced as the 

 treatment is prolonged. A fraction of one 

 per cent, persists for some time. Cold alone 

 does not materially effect the reduction of 

 typhoid germs in dry earth. In moist earth 

 the destruction of the bacteria is much less 

 rapid; at times when food supply is plentiful 

 they appear to hold their own. 



In another set of experiments it was found 

 that sedimentation did not produce marked 

 or constant effects on colon and typhoid 

 bacilli in water during as short a period as 

 twenty-four hours. Ice, however, formed on 

 the surface of a quiet body of water contained 

 only about ten per cent, of the bacteria pres- 

 ent in the water. This difference, they con- 

 clude in agreement with various observers, is 

 due to the physical exclusion by the process of 

 crystallization, and not to any germicidal ac- 

 tion, as the temperature of the ice can only 

 differ from that of the adjacent water in a 

 very slight degree. There are two forces at 

 work : low temperature killing off the germs 

 in ice and water nearly equally, and the 

 crystallizing process extruding germs from the 

 ice into the water. 



The general conclusions and applications 

 of the results of the experiments as given 

 by the authors may be summed up somewhat 

 as follows: The main factor determining the 

 reduction of germs in water is time — the time 

 during which the various purifying forces are 

 left to act. Epidemiology shows clearly that 

 disease follows most often a direct, quick 

 transfer of infectious material from patient 

 to victim; and if storage of water for some 

 months could be insured, many sanitarians 

 would consider such storage a sufficient puri- 

 fication. In ice this condition is realized — 



