Repo7>t on the Bacteriology of Water. 



199 



A large number of investigators, by means of researches first 

 started by Downes and Blunt in 1877,* in this country, and carried 

 on ever since by others, have shown that the action of the sun's rays 

 has to be taken into consideration when dealing with questions of the 

 vitality or rate of growth, &c, of the spores and rodlets of this and 

 other Schizomycetes. 



The controversy is too long for full treatment in this report, but 

 the upshot of the whole may be summed up as follows. Certain rays 

 of light, apparently more especially those known as the " chemical 

 ra 7 s /'t so affect the germinating spores of certain bacteria (Bacillus 

 typhosus, Bacteria anihracis), in presence of air, that their growth is 

 inhibited. The presumption is that the solar rays enhance certain 

 oxidation processes in the living protoplasm, but questions also arise 

 m some cases as to possible effects on the nutritive media as well, 

 though Janowski certainly seems to have eliminated these in his 

 cultures of the typhoid bacillus. £ 



A second possible view as to the fate of a given species of bacterium 

 when suddenly washed into a stream is that it remains there un- 

 altered, and that the chances are so enormously against its being- 

 detected, or (what, from some points of view, is the same thing) 

 against its finding a suitable nidus in a living animal, that it simply 

 wanders passively in the waste of waters surrounding it for an in- 

 definite period, or until it reaches the sea. 



This view also must be faced as one not altogether unsupported by 

 observations, but only on the understanding that the microbe is in the 

 spore stage, or, at least, passes into that condition soon after reaching 

 the water, for the weight of bacteriological experience is distinctly 

 against the probability of a living Schizomycete, in the simple vege- 

 tative condition, remaining as such for any length of time, at any rate 

 in such a dilute medium as potable water. 



With spores the matter is different. Duclaux found old spores of 

 certain forms which had been kept out of contact with air for several 

 years to be still capable of germination when sown in suitable 



* Downes and Blunt, ' Boy. Soc. Proc.,' 1877, p. 488, and ibid., 1878, p. 199. 



t It should be clearly indicated, however, that the evidence goes rather to show 

 that it is insolation which produces these results, and not diffused light. Insola- 

 tion can have practically no effect in natural waters. 



X For details as to the action of light on bacteria, consult Baum (" Der G-egen- 

 wartige Stand unserer Kenntnisse ii. d. Einfluss des Lichtes auf Baoterien, &c," 

 ' Zeitschr. f. Hyg.,' vol. 6, 1889, pp. 312—368), for full references to literature to 

 date. Then see Pansini ( u Action de la Eumiere Solaire sur les Microorganismes," 

 in ' Bivista d'Igiene,' 1889 ; also ' Ann. de l'lnst. Pasteur,' vol. 3, 1889, p. 686) ; 

 Janowski, (" Zur Biologie der Typhus-bacillen," in ' Centralbl. f. Bakt. u. Paro- 

 sitenk.,' 1890, Nos. 6—8) ; F. Elfving, < Studien uber die Einwirkung des Lichtes 

 auf die Pilze,' Helsingfors, 1890, 139 pp. and 5 plates— deals more especially with 

 fungi proper — and our Appendix A. 



VOL. LT, P 



