160 TEAGUE AND BARBER. 



Furthermore, the overcrowded rooms in a warm climate would 

 in reality be thrown open and the moisture of the expired air 

 would be consequently more or less rapidly dissipated, whereas 

 in the cold climate conditions would approximate the hypothe- 

 tical case at 8° C. just cited; hence the difference in the rate 

 of evaporation of droplets in the air due to overcrowding in 

 cold and in warm climates respectively would be, in fact, greater 

 than is indicated by the figures in the hypothetical case just 

 described. 



The surface tension of water at 4° C. is 74.9, and at 30° C. 

 it is 71.03. The surface tension being greater at the lower 

 temperature, with the same amount of water deficit, evaporation 

 would take place more slowly there than at the higher tem- 

 perature. This is, therefore, an additional factor which would 

 tend to cause droplets of pneumonic sputum to persist longer 

 in the air in a cold climate than in a warm one. However, 

 it is a factor of far less influence than the water deficit of the 

 air and hence deserves no further discussion. 



It seems highly probable that plague bacilli in suspended 

 droplets of sputum would survive much longer at a low tem- 

 perature than at a high one, even were the water deficit of the 

 air the same in both cases; or, in other words, that with the 

 same rate of drying, the bacilli would remain alive longer at 

 low temperatures than at higher ones. This would, then, be 

 also an important factor in causing pneumonic plague to spread 

 more rapidly in cold climates than in warm ones. 



It is noteworthy that the only large epidemic of pneumonic 

 plague in India of which we have a record occurred during 

 cold weather in Kashmir in the winter of 1903 to 1904. The 

 epidemic is described by A. Mitra,- who stated that it lasted 

 from November, 1903, to August, 1904, "but the virulence was 

 only from December to March." "In the districts there were 

 altogether 1,443 cases with 20 recoveries. The recoveries being 

 bubonic cases, which were seen at the end of the epidemic." 

 We judge from these statements that the epidemic of pneumonic 

 plague lasted from December till March. Mitra says : 



The conditions of life in these villages during the month of January and 

 February were extremely unfavorable. Everything round was frozen. 



The Indian Weather Review shows that Srinagar, which was 

 the center of the Kashmir epidemic, had, during the month of 

 December, 1903, a mean daily temperature of 36°. 1 F. and a 



'Indian Med. Gaz. (1907), 42, 133. 



