Report on the Bacteriology of Water. 197 



It is also clear that pathogenic forms find their access to such 

 waters by the same routes as saprophytic and harmless ones, a point 

 of primary importance when we reflect on the danger of snch being 

 in the air and the drainage of inhabited areas. That the spores of 

 Bacillus aniliracis find their way from the bodies of animals to the 

 surface waters of meadows, and thence into rivers, must be accepted 

 as proved by the researches of Pastenr and Koch,* and our knowledge 

 in this connexion suggests only too plainly what may occur in other 

 cases, thus explaining the observed facts that the microbes of typhoid, 

 cholera, septicaemia, &c, do occur in exposed waters ; and connecting 

 the presence of other pathogenic forms, known to be cast off in secre- 

 tions, dejecta, &c, with the suspicions aroused from the washing of 

 milk vessels, &c, with such waters. 



It is necessary to bear in mind, however, that although the vista of 

 possibilities here opened out is a real one, most of the bacteriological 

 examinations of water support the conclusion that by far the majority 

 of the Schizomycetes met with in natural waters are harmless, or at 

 least are not capable of producing disease directly in those who drink 

 the waters. 



Such conclusions have led to speculations, in different directions, as 

 to why the bacteriological examination of waters has, so far, seldom 

 led to the detection of pathogenic forms, although such waters are 

 exposed to contamination. 



Firstly, it is possible that a Schizomycete should lose its virulence 

 or be weakened, or even die, when transferred from a suitable medium 

 into one so thin and innutritious as any ordinary potable water would 

 be ; secondly, quite apart from the scarcity of food materials, it 

 requires some reflection to thoroughly grasp how great must be the 

 changes in the circumstances which a given pathogenic form — say, the 

 anthrax bacillus, for argument — meets with when it leaves the living 



" Kecent Bacteriological Research in connection with Water Supply," ' Journ. Soc. 

 Chem. Ind.,' 1887 ; " The Applications of Bacteriology to Questions relating to 

 Water Supply," ' Trans. Sanitary Institute of Great Britain,' vol. 9, 188V) ; H. A. 

 Nielsen (" The Bacteria of Drinking Water, in particular as regards the Species in 

 tbe Water Supply of Copenhagen," Copenhagen, 1890 ; see ' Ann. d. l'lnst. Pas- 

 teur,' 1890, p. 41), Bertschinger (' Yierteljahrschr. d. Naturf. G-esellsch.,' vol. 34, 

 1889, also ' Ann. de l'lnst. Pasteur,' vol. 3, 1889, p. 692), Duclaux (" Le Filtrage des 

 Eaux," 'Ann. de l'lnst. Pasteur,' 1889, pp. 41-56; and " Sur les relations du Sol et 

 de l'Eau qui le traverse," ' Ann. de l'lnst. Pasteur,' 1889, pp. 172-184) ; also our 

 Appendix A. 



As to bacteria in ice, snow, and hail, see Prudden (' New York Med. Record,' 

 1887), Bordoni-TJffreduzzi (' Centralbl. f. Bakt. u. Parasitenkunde,' vol. 2, 1887), 

 Janowski (ibid., vol. 4, p. 547), and Schmelck (ibid., vol. 4, p. 545), Fraenkel 

 (' Zeitschr. f . Hyg.' vol. 1, pp. 302—314), and Odo Bujwid (' Ann. de l'lnst. Pasteur,' 

 vol. 1, 1887, p. 592). 



* Pasteur, 'Bull, de l'Acad. de Medecine,' 1880 ; Koch, ' Mittheil. a. d. K. Geeund- 

 heitsamte,' 1881, p. 49. 



