INFLUENCE OF ATMOSPHERIC TEMPERATURE. 



171 



Table IV. — Showing growth of colonies. 



Time after 

 sprayiriK. 



B. prodiaiosu9 

 in moist hood. 



B. prodigioaua 

 in cold room. 



Colonies. 



Hrs. min. 



Colonies. 



1 



Innumerable. 



78.000 



G 



260.000 



42.000 



10 



52,000 



30.000 



20 



29.000 



17,000 



30 



13.000 



11,000 



40 



5,000 



6,300 



60 



3.500 



5,000 



1 



350 



8,200 



1 10 



220 



2,100 



1 20 



34 



1,800 



1 30 



17 



1,300 



1 45 



5 



1.200 



2 







870 



2 15 



1 



530 



2 30 







360 



2 45 



3 





380 

 320 







3 15 

 3 30 



3 45 



4 





240 

 160 



130 

 90 











In spite of the fact that the water deficit of the air of the cold 

 room was greater than that of the hood, the bacilli remained 

 alive longer in the cold room. The only interpretation of this 

 result is that B. prodigiosus resists death from drying longer 

 at low temperatures than at high ones, even when the rate 

 of drying is the same in both instances. It seems highly prob- 

 able that this is also true of the plague bacillus; if so, the 

 bearing of the phenomenon is an additional factor in the longer 

 persistence of living plague bacilli in droplets of sputum, and 

 hence upon the more rapid spread of pneumonic plague in cold 

 climates is obvious. 



SUMMARY. 



It is shown that when spread on glass slides and exposed to 

 the air, plague bacilli occupy an intermediate position between 

 the cholera vibrio and B. prodigiosus with regard to resistance 

 to death from drying. Sarcina resists much longer than B. 

 prodigiosus. When suspended in saline solution and sprayed 

 into the air, the living cholera vibrio disappears with surprising 

 rapidity, B. prodigiosus persists for a longer time, and sarcina 

 much longer than B. prodigiosus. The relative length of time 

 that these organisms remain alive when sprayed into the air 

 agrees strikingly with their survival on glass slides. This sug- 

 gests that their disappearance from the air is also due to death 

 from drying. 



