165] FAUNA OF BIG VERMILION RIVER—BAKER 67 
POLLUTION OF SALT FORK BY SEWAGE AND 
MANUFACTURING WASTES 
GENERAL NATURE OF STREAM POLLUTION 
Stream pollution may be broadly divided into two main divisions: 
contamination by organic sewage from cities and towns and by chemical 
wastes from factories and mines. Both are inimical to life but the latter 
is especially fatal to animal life, causing wide stretches of otherwise 
fertile streams to become veritable deserts. Organic sewage, in a crude 
or highly concentrated form, is also very injurious, effectually eliminating 
most forms of life from the polluted body of water. 
The importance and seriousness of the problem of stream pollution in 
its effect on the life of the rivers and streams into which the contaminating 
material is discharged has not until very recently been given the attention 
the subject demands. The diminishing fish supply, and in many places 
the very objectionable physical character of the polluted waters, have 
caused the authorities of several states to pass laws governing the discharge 
of these wastes into streams and the establishment of penalties for dis- 
regarding these laws. New York and Massachusetts have led in the fram- 
ing of these laws and other states are following the good example set by 
these two older commonwealths, where the conditions seem to have reached 
a maximum of harmfulness (see Ward, 1918, 1919). 
During recent years stream pollution has enormously increased and the 
problems arising from this condition have been investigated by many 
biologists and sanitary engineers. The former have studied the problem 
from the viewpoint of its effect on the useful animal life, especially fishes 
and river mussels, and this phase probably bears as close a relation to 
human welfare as any other. Of course, from the standpoint of health, the 
pollution problem is of paramount importance because of its bearing on 
such diseases as typhoid fever which may be caused by a polluted water 
supply. 
Perhaps the worst effect of chemical pollution is to be found in the 
streams of western Pennsylvania, where water heavily loaded with oil or 
acid water from coal mines is permitted to flow into the rivers and streams 
of this part of the state. Studies by Ortmann (1909) show that whole 
stretches of the Allegheny, Ohio, and Monongahela rivers have been made 
into deserts, as far as the animal life is concerned, by the large amount of 
poisonous substances discharged into these streams by the mines, oil indus- 
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