MEMOIRS UF THE i^ATIONAL ACADEMY OF SCIENCES. 431 



From these results it would appear that the water supi)ly of Philadelphia does uot ditter very 

 radically from the supi)lies of the other two cities. If averages aloue are cousidered, the greatest 

 differeuces are seen in the nitrates and in the " free ammonia," which are comparatively much 

 higher in rhiladelpina water than in the waters of ISlew York and Boston. Considering the 

 extremes alone, it will be observed that both the Schuylkill and the Delaware vary much more 

 than either of the others, and exceed both in all maximal results. If the chemical standards for 

 good or usable water, as given in reliable works on the subject, are applied to the results of the 

 analyses of the water of both rivers the following statements may be made; 



Some of the results for free ammonia, the averages for albuminoid ammonia, and all of the 

 results for nitrates are excessive in both the Schuylkill and the Dtdaware waters, w^hile all of 

 the chlorine determinations and the averages for the free ammonia in both fall within the limits 

 of a good or usable water. The standard given by Park for oxygen consumed is based on determi- 

 nations made under conditions different from those employed in this work, and is therefore not 

 available. 



According to the German authority, in both waters the averages for the albuminoid ammonia 

 and all of the nitrate determinations are not excessive. In the case of the Delawaie the average 

 oxygen consumed exceeds slightly the limit, while the average for the Schuylkill is below it, 

 though some individual determinations are excessive. By the same standards the free ammonia 

 for both is sometimes too high, but the averages are not, and no chlorine determination attains 

 the limits. 



The average number of bacteria per cubic centimeter in both waters is excessive. 

 Of the microorganisms of a bacterial nature met with in the course of the bacteriological 

 work, fifty-two species and varieties are described elsewhere in this report. 



These consist of two species of micrococci, two species of cladothriees, and forty-six .species 

 and two varieties of bacilli. Nearly all of these have been isolated from the plates of the water 

 of the Schuylkill; but it should not be inferred from this that there are only a few species in the 

 water of the Delaware. Many more jilates have been made from Schuylkill water than from the 

 Delaware, and, as many of the organisms described are by no means common, the opportunities 

 to isolate the rare forms in the case of the latter have been comparatively limited. Moreover, the 

 isolations were purposely made for some time from Schuylkill plates exclusively, with the idea of 

 turning later to the Delaware and doing the same, but this was not carried out. The general 

 impression accpiired, liowever, has been that the number of species in the latter is not few, and 

 that practically all of the organisms occurring in the Delaware plates occur also in those of the 

 Schuylkill, but that the bacterial flora of the last named is the richer of the two. 



In the description of the morphology the terms "large," "medium sized," and "small" have 

 been used. In explanation it may be said that by a "large" bacillus is meant one which 

 approaches the dimensions of the bacillus subtilis, while the term "medium sized" may be taken 

 as indicating that the organism is about the size of the typhoid bacillus. 



With the exception of the bacillus subtilis, ramosus exiguus, refractans, nebulosus, and the 

 cladothrix rufula, all of the organisms which grow well at 3G° C. have been inoculated into white 

 mice subcutaneously with no definite results. 



A rabbit was also inoculated subcutaneously with the cladothrix dichotoma, but no abscess 

 formation was observed. In addition to the organisms here described a number of other species 

 have been imperfectly studied and then abandoned for various reasons. Among these was a 

 streptococcus which seemed to be identical in cultural characteristics with the ordinary pyogenic 

 organism. 



It seems very probable that a further study of these waters Avonhl show a number of other 

 species not included in this report. That this number, fifty-two species, is not exceptional will be 

 evident from the statement that Maschek has isolated fifty-five species from the Leitmeritz drinking 

 water, and Tils, from the water supply of Freiburg, fifty-nine species. Only a few of the bacteria 

 isolated in the C(mrse of this work have been identified by the published descriptions at hand 

 with other water bacteria. It is very probable that many of them have been met with in the 

 course of other investigations. Neither the "colon" bacallus nor the bacillus of typhoid fever 

 have been found in tlie water. In regard to microscopic organisms other than bacteria which 

 occur in the water little work has been done. The few examinations which have been made with 



