BACTERIA IN WATER. 563 



number, according to Bolton, would be less than one-hundredth 

 of a milligramme, and at least three-fourths of this must consist of 

 water. The organic material represented by this number of bacteria 

 would therefore be so minute that it might be supplied by dust par- 

 ticles accidentally falling into the distilled water. 



Rosenberg has shown that while many of the species which he 

 obtained in pure cultures from the water of the river Main multiplied 

 in sterilized distilled water, other species quickly died out in such 

 water. The growth of certain bacteria depends not only upon the 

 quantity of nutritive material present, but upon its quality, the con- 

 ditions in this regard being widely different for different species. 



In view of the facts heretofore stated bacteriologists are now giv- 

 ing more attention to a careful study of the kinds of bacteria pre- 

 sent in their examinations of water. Rosenberg, in his examinations 

 of the water of the Main in the vicinity of Wiirzburg (1886), found 

 that before the river reached the city the water contained more 

 micrococci than bacilli, but that after receiving the sewage of the 

 city the number of bacilli was greatly in excess. 



Adametz (1888) has described eighty-seven species obtained by 

 him from water in the vicinity of Vienna ; Maschek found fifty-five 

 different species in the drinking water used at Leitmeritz; and Tils 

 (1890) has described fifty-nine species obtained by him from the city 

 water supply at Freiburg. 



Among the pathogenic bacteria which are liable to find their 

 way into water used for drinking purposes, the most important, from 

 a sanitary point of view, are the bacillus of typhoid fever and the 

 spirillum of Asiatic cholera. Both of these microorganisms are pre- 

 sent in great numbers in the excreta of persons suffering from the 

 specific forms of disease to which they give rise, and are consequently 

 liable to contaminate wells and streams which receive surface water, 

 when such excreta are thrown upon the surface or into sewers, etc. 

 Epidemics of these diseases have frequently been traced to the use 

 of such contaminated water, and in a few instances the presence of 

 these specific disease germs in water has been demonstrated by bac- 

 teriological methods. Laboratory experiments indicate, however, 

 that an increase of these pathogenic bacteria in drinking water is not 

 likely to occur, except under special conditions, and that they die 

 out after a time, being at a disadvantage in the struggle for exist- 

 ence constantly going on among the numerous species which have 

 their normal habitat in water. 



Bolton, Frankland, and others have shown that the anthrax ba- 

 cillus, not containing spores, dies out in hydrant water within five or 

 six days. In the experiments of Kraus the anthrax bacillus added 

 to well water, not sterilized, at a temperature of 10.5 C., was still 



