THE BACTERIA OF RIVER WATERS. 



Bv Di;. Joiix S. Billings. 

 (Preseutiug a paper on the bacteria of the Schuylkill River by l>r. .1. H. Wright.) 



The bacteriology of river waters has beeu, for tlie last ten years, a subject of steadily 

 iiiereasiiig interest, and inunerous observations have been made in Europe and in this country 

 upon those streams wliich are used as sources of municipal water supply. These observations in 

 the United States have, however, been, for the most part, made only on occasional samples and 

 by imperfect methods, and there is no river in this country with regard to which we may be 

 said to liave an approximately complete knowledge of what might be called its natural bacte- 

 riological ilora; that is, of the species, and relative proportions of each species, occurring at 

 different seasons of the year, or as aftected by rains, as distinguished from those derived from 

 sewage or waste products of various kinds discharged into the stream. 



Each river will probably be found to differ somewhat from other rivers as to its normal or 

 usual bacteriological flora, and this flora also differs in difl'erent parts of the stream and at 

 different times of the year; nevertheless, there are a few microorganisms of this class which ai-e 

 to be found in almost all such waters at all times. The ordinary river-water bacteria are not 

 patliogenic, and little is known with regard to tlie circumstances whicli influence their growth 

 and development in running streams, or as to the different ett'ects which different species can 

 produce. All that we can say is that these are probably influenced not only by rainfall, but also 

 by the quantity and nature of the organic matters which the stream from time to time contains, 

 by the presence of certain inorganic salts in minute quantities, by temperature, by more or less 

 exposure to light, and by the greater or less aeration of the water, depending upon the depth and 

 smoothness of flow of the stream. A fundamental diliiculty in the way of scientitic observations 

 on these points is the want of accurate knowledge as to the cliaracteristics of different species or 

 varieties of the bacteria, and of means for distinguishing these without the expenditure of much 

 time and labor. While the number of different species of bacteria which have been named is 

 reckoned by hundreds, there are scarcely fifty wliich have been so described that an investigator 

 can identify them by their descriptions. 



We have, in fact, as yet no scientific classification of the bacteria, no agreement as to what 

 kind or degree of difference shouhl be considered as sufficient to determine that a particular form 

 should be recognized as a distinct variety, or species, or genus. The mere morphology of the 

 individual organism gives little aid in this respect, and bacteriologists are relying more and more 

 upon dififereiices in the shape, size, color, etc.. of colonies or masses of the organisms growing on 

 ditiereut media, on their effect on these media, their products, and on tlie effects which they or 

 their products produce in different animals as means of distinguishing one from another. 



Considered from the point of view of the general biologist, or from that of tlie botanist, many 

 of the species admitted on these grounds as distinct by bacteriologists would not be accepted as 

 species, hardly even as varieties, because the differences are differences in function rather thaa 



419 



