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 Freudenreich, 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 by Moissan 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 ata 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 adistance 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 
