330 BACTERIOLOGY. 



The effect of light upon growing bacteria must not 

 be lost sight of, for it has been shown that a surpris- 

 ingly large number of these organisms are robbed of 

 their vitality by a relatively short exposure to the rays 

 of the sun, and it is, therefore, not unlikely that the 

 non-observance of this fact may be, in part at least, 

 accountable for some of the discrepancies that appear in 

 the results of these experiments. 



In his studies upon the behavior of pathogenic and 

 other micro-organisms in the soil, Carl FraenkeF found 

 that the cholera spirillum was not markedly susceptible 

 to those deleterious influences that cause the death of 

 a number of other pathogenic organisms. During the 

 months of August, September, and October, cultures 

 of the comma bacillus that had been buried in the 

 ground at a depth of three metres retained their 

 vitality ; on the other hand, in other months, particu- 

 larly from April to July, they lost their vitality when 

 buried to the depth of only two metres. At a depth 

 of one and a half metres vitality was not destroyed, 

 and there was a regular development in cultures so 

 placed. 



As a result of experiments performed in the Imperial 

 Health Bureau, at Berlin, it was found that the bodies 

 of guinea-pigs that had died of cholera induced by 

 Koch's method of inoculation contained no living 

 cholera spirilla when exhumed after having been buried 

 for nineteen days in wooden boxes, or for twelve days 

 in zinc boxes. In a few that had been buried in moist 

 earth, without having been encased in boxes, when ex- 

 humed after two or three months, the results of exami- 

 nations for cholera spirilla were likewise negative. 



1 Zeitsohrift f. Hygiene, Bd. 11. p. 521. 



