INFLUENCE OF ATMOSPHERIC TEMPERATURE. 



169 



eters showed that the air of the wet hood was nearly saturated 

 with moisture, and hence evaporation of suspended droplets of 

 water must have been reduced almost to the minimum. There- 

 fore, we are justified in concluding that the extremely rapid 

 disappearance of the living cholera vibrios in the dry hood is due 

 to the rapid evaporation of the suspended droplets of saline 

 solution which leads to the death of the contained cholera vibrios 

 from drying. 



The last part of the experiment shows conclusively that the 

 rapid disappearance of living cholera vibrios is not due to 

 settling or removal through air currents, for droplets containing 

 cholera vibrios and those containing sarcina were subjected to 

 identical conditions and yet living sarcinae were present in the 

 air long after the cholera vibrios had disappeared. The sarcina 

 being a larger organism and having a greater tendency to remain 

 in clumps would settle out more rapidly than the cholera vibrio. 

 It remained alive in the air longer than the cholera vibrios 

 because of its greater resistance to drying. A similar experi- 

 ment was performed with B. prodigiosus. 



EXPERIMENT NO. 4. 



A fresh culture was suspended in 0.5 saline solution and passed through 

 filter paper. When plated out this suspension was found to have contained 

 about 100,000,000 organisms per cubic centimeter. 



The same suspension was sprayed for the same length of time into 

 the dry hood, the wet hood, and into a cold storage room the temperature 

 of which was about 18° C. 



The temperature of air in the hood was read as usual through the glass 

 door. 



Time. 



Dry-bulb 

 thermometer. 



Wet-bulb 

 thermometer. 



Difference. 



a. m. 









9. 47j to 9.48. Prodigiosus suspen- 





sion sprayed. 





9.55 



30°. 5 0. 



29°. 2 C. 



1.3 



10.12 



31°. 1 



29°. 



2.1 



11.02 



31°. 2 



29°. 25 



1.95 



p. m. 









12. 05j to 12. 06. Prodigiosus suspen- 





sion sprayed. 





12.20 



31°. 3 C. 



31°. 2 C. 



0.1 



12.60 



31°. 3 



31°. 25 



0.05 



1.50 



31°. 52 



31". 42 



0.1 



2.30 



31°. 7 



31°. 6 



0.1 



3.40 



31°. 8 



31°. 7 



0.1 



