io8 Scientific Proceedings (49). 



The results are quite concordant when the dryness of the 

 atmosphere is taken into consideration. Series VI showed a more 

 rapid reduction than the others during the first 7 hours and the 

 relative humidity was 60 per cent. Then came Series V and VIII 

 with a relative humidity of 72 per cent., while in Series IV and 

 VII with an atmospheric humidity of 90 per cent., nearly 70 per 

 cent, of the bacteria were alive after 8 hours. 



The general rate of reduction was directly proportional to the 

 time, during the first 24 hours, and then fell off more and more 

 gradually. As a rule, intestinal bacteria in any foreign medium, 

 colon bacilli in water, for example, decrease rapidly at first and 

 more and more slowly as time goes on, following almost a parabolic 

 curve. Most die at first, but a few persist for a long time. In 

 its general relations the curve for drying is similar. 99 per cent, 

 of the bacteria are gone after 24 hours while 2 out of 10,000 persist 

 after 10 days. The curve for the first 24 hours is however here 

 practically a straight line. 50 per cent, perished after 10 hours, 

 and 99 per cent, after 24 hours. This is to be explained by the 

 fact that during this period the bacteria were not exposed to con- 

 stant conditions, since the originally moist sand was becoming 

 progressively dryer. Determinations made by weighing at inter- 

 vals duplicate samples prepared just like those which were in- 

 oculated with the bacteria showed that nine tenths of the moisture 

 in the sand was gone after 10 hours and practically all of it was 

 gone after 24 hours (with an atmospheric humidity of 80 per cent.). 

 With a constant unfavorable environment, the reduction of 

 bacteria proceeds at a decreasing rate. With an environment 

 growing more and more unfavorable we might expect an approxi- 

 mately even rate of reduction such as is indicated here. 



So far as the absolute reduction is concerned, it appears that 

 drying is highly inimical to the bacteria studied. A uniform 

 reduction of 99 per cent, is indicated after 24 hours. It takes 

 over a week to reach such a point when colon bacilli and similar 

 intestinal forms are stored in water. 



