292 BULLETIN No. 161 [November, 



THE DURATION OF LIFE OF TUBERCLE BACILLI IN SUNSHINE AND 

 IN DIFFUSE DAYLIGHT 



INDEX OF Every author consulted, except Weinzirl, used the 



DEATH animal test to determine when tubercle bacilli were 



dead. Weinzirl, using only pure cultures, em- 

 ployed the method of cultivation. No investigator whose work is 

 recorded in Tables 2 and 3 has called attention to the fact that dead 

 cultures produce tuberculosis (for discussion see page 112). Just 

 what error a neglect of attention to this point has introduced into 

 the results given in the following table cannot be definitely known. 

 Tho it is certain that dead tubercle bacilli do produce tuberculosis, 

 yet in no case was it found in my own experimental work that 

 localized tuberculosis was produced by dead organisms. In every 

 case the secondary guinea pigs inoculated from cases of localized 

 tuberculosis became tuberculous and usually severely infected. Cul- 

 tures from diseased tissues produced growth, either from the origi- 

 nal or from the secondary inoculated guinea pigs, or from both. It 

 appears, therefore, that the error arising from not taking into 

 account tuberculosis produced by dead cultures is probably slight. 



TIME REQUIRED P ure cultures of tubercle bacilli when exposed in 

 TO KILL thin layers to the direct sunlight are killed in from 



a few minutes to a few hours. This has been the 

 result obtained by all investigators. To kill these germs in sputum 

 requires only a slightly longer time. The mucoid mass is a slight 

 protection which increases with the thickness and opacity of the 

 material, but even here tubercle bacilli are killed in a very short 

 time. With two exceptions, that of Feltz 38 and of Mitchell and 

 Crouch 98 (see Table 2), no investigator reports these bacilli surely 

 living after twenty-four hours' exposure to the sun. In these two 

 cases the sputum was exposed on soil, and a small layer of soil 

 would afford good protection from the action of the sunlight. 



EFFECT OF Experiments definitely planned to test the killing 



HIGH ALTITUDE power of the sun on tubercle bacilli at different 

 altitudes have been carried out by a Russian, Tres- 

 kinskaja 148 . In our country Mitchell and Crouch 98 have determined 

 the effect of the sun on tuberculous sputum at a height of 1356 

 meters. Treskinskaja used pure cultures emulsified in one-percent 

 peptone solution, spread in thin layers and exposed directly to the 

 sun. These were killed as follows: At a height of 1560 meters, 

 in three hours ; at 903 meters, in four hours ; at sea level, in four 

 hours. The peptone solution when dried gave a thin protective 

 layer covering these organisms. Treskinskaja thought that this 

 protection would be about equal to that of a thin layer of sputum. 



