538 APPLICATION OF METHODS OF BACTERIOLOGY 



retained its vitality for 267 days, and in another for 382 days, 

 notwithstanding the fact that many other organisms were 

 present at the same time. There is no ready explanation 

 for these variations, for they depend apparently upon a 

 number of factors which may act singly or together. For 

 example, in general it may be said that the higher the tem- 

 perature of the water in which these organisms are present, 

 up to 20° C, the longer do. they retain their vitality; the 

 purer the water — that is, the poorer in organic matters — the 

 more quickly do the organisms die, whereas the richer it 

 is in organic matter the longer do they retain their vitality. 



The effect of light upon growing bacteria must not be 

 lost sight of, for it has been shown that a surprisingly large 

 number of these organisms are robbed of their vitality by 

 a relatively short exposure to the direct 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 Frankel^ found that micro- 

 spira comma was not markedly susceptible to those dele- 

 terious influences that cause the death of a number of other 

 pathogenic organisms. At a depth of one and a half meters 

 vitality was not destroyed, and there was a regular develop- 

 ment 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 



1 Zeitschrift filr Hygiene, Bd. ii, S. 521. 



