Kirchner — Bacteriological Examination of River Water. 295 
that erroneous conclusions are drawn from isolated or separate 
tests and insufficient data. We shonld have at hand chemical 
analyses of the water so that we may have information as to 
the mineral and organic constituents. We should have a 
knowledge of the flora and fauna of the water, of the topog- 
raphy and geology of the river-basin, and of certain 
meteorological conditions. The location and influence of 
cities, villages, factories, sewers and tributary streams; the 
effect of river traffic; the variations in the depth of the 
water; the velocity of the stream, and the tendency to sedi- 
mentation; the degree of pollution and the distance of the 
source of pollution; the health statistics of the communities 
along the river; a knowledge of these and many other condi- 
tions may be necessary before an intelligent interpretation of 
bacteriological data of river water as affected by sewage may 
be arrived at. 
When we consider the suffering, the loss of life, and the 
cost which an epidemic entails upon a community, as well as 
the harm done to its commercial interests, we are compelled 
to recognize the importance of a wholesome water supply. It 
is incumbent upon a community to look after the health 
of its inhabitants, and it is important that the water supply 
receive careful and proper attention. The question of the 
pollution of streams and the consequent contamination of 
the water supply by sewage from cities and towns has, 
of late years, received national recognition, but the problems ~ 
involved in arriving at true conclusions are difficult, and 
can be only satisfactorily solved by the most careful and 
scientific inquiry. 
