BACTERIA IN WATER. 641 



curs it will probably be due to the colon bacillus, but it will be necessary to 

 make plates and pure cultures from single colonies in order to determine 

 this with certainty. The demonstration may be made more quickly, accord- 

 ing to von Freudeiireich, by using a medium containing milk sugar (five per 

 cent) and cultivating at 35 C. If the colon bacillus is present there will be 

 an abundant development of gas in from twelve to twenty -four hours, and 

 the bacillus may then be readily isolated by the plate method. The colon 

 bacillus has been found byMoissan and Gimbert in mineral waters bottled in 

 France. Poncet (1895) has made a careful study of the bacteria found in the 

 various springs at Vichy. The species described are all harmless water bac- 

 teria and have little interest from a sanitary point of view. 



Kruse (1894), as a result of his extended researches and of a critical con- 

 sideration of the experimental data available, arrives at the conclusion that a 

 sanitary inspection of the sources of supply is more important, in determin- 

 ing the safety of the supply from a sanitary point of view, than a chemical 

 or bacteriological examination. The writer has for some years past enter- 

 tained the same opinion. Kruse says, however, that for the control of fil- 

 tering plants bacteriological "counting-methods" are indispensable. He 

 also ascribes a "high scientific value" to investigations relating to the pres- 

 ence of the more important pathogenic bacteria; but says that, notwith- 

 standing the improvements in methods of research, we cannot wait for a 

 demonstration of the presence of the cholera or typhoid bacteria before con- 

 demning a water as probably unsafe, if sources of contamination are dis- 

 covered or, we would add, if cases of cholera or typhoid fever can be traced 

 with a fair degree of certainty to the use of water from a given source. 



Fischer (1894), in his account of the researches made during the Plankton 

 expedition, has given a summary of the experimental evidence relating to the 

 presence of bacteria in the waters of the ocean. The species found were for 

 the most part different from those found in lakes and rivers, and at some 

 distance from the shore none of the previously known species of micrococci 

 and bacilli were encountered. The number of bacteria in samples from the 

 surface at a distance from the shore was comparatively small (usually less 

 than five hundred per cubic centimetre), but in the vicinity of land very 

 large numbers were sometimes found. At a distance of ten metres below the 

 surface the number found was greatly in excess of the number at the surface 

 the difference being probably due to the germicidal action of sunlight. At 

 depths of four hundred metres bacteria were constantly found in great num- 

 bers, and water from a depth of eleven hundred metres was still found to 

 contain them. 



41 



