712 DISTRIBUTION AND HABITAT OF THE BACTERIA. 



Behaviour of 

 pathogenic 

 bacteria in 

 water. 



in distilled water which is as pure as possible, as in the 

 so-called bad well water which is contaminated with 

 sewage. Besides these special bacteria we have as 

 inhabitants of the water those forms which are cha- 

 racterised by their more advanced morphological de- 

 velopment, and by the variability of their vegetative 

 forms insisted upon by Zopf, viz., crenothrix, cladothrix, 

 beggiatoa. We require more accurate investigations as 

 to the character of the water which is necessary for the 

 development of these fungi. 



Many of the other saprophytic forms apparently either 

 do not multiply at all in water, or only to a very limited 

 extent. Nor can any of the pathogenic bacteria multiply 

 in water even where the temperature is favourable, 

 because they absolutely require a certain even though a 

 small quantity of the best nutritive materials. Typhoid 

 bacilli require, according to Bolton's experiments, at 

 least 67 milligrammes of organic nutritive materials per 

 litre of water, cholera bacilli require 400 milligrammes 

 per litre. Such an amount of organic materials only 

 occurs extremely rarely in water which is employed for 

 household and drinking purposes ; and besides, in the 

 case of the pathogenic bacteria very much depends on 

 the quality of the nutritive materials, and even the 

 presence of a considerable quantity of the less nutritious 

 organic materials which are usually present in water is 

 unable to replace the necessary but small amount of 

 peptone and albumen. 



On the other hand, the pathogenic bacteria retain their 

 vitality for a comparatively long time in water. Non- 

 spore-bearing anthrax bacilli and micrococcus tetragenus 

 live for about six days, typhoid bacilli free from spores 

 for fourteen to twenty days, spore-bearing bacilli from 

 thirty to ninety days or longer. In the case of cholera 

 bacilli Wolff hiigel and Riedel have made out a duration 

 of vitality of about eighty days, and frequently also a 

 multiplication ; however, in some of their experiments, 

 the results of which are not completely in unison, they 

 have probably sown too many organisms, and have 

 carried over a small amount of nutritive material from 



